biomaterials in orthodontics / orthodontic courses by indian dental academy

BiomaterialsBiomaterials in in

OrthodonticsOrthodonticswww.indiandentalacademy.comwww.indiandentalacademy.com

ContentsContents IntroductionIntroduction Structures and properties of materialsStructures and properties of materials Orthodontic wiresOrthodontic wires Orthodontic bracketsOrthodontic brackets Etching agents, Adhesive resins & CementsEtching agents, Adhesive resins & Cements Elastomeric ligatures & ChainsElastomeric ligatures & Chains Impression materialsImpression materials Prophylactic agentsProphylactic agents & Miscellaneous & Miscellaneous

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Introduction Introduction Knowledge of fundamental principles Knowledge of fundamental principles

governing the relationship between governing the relationship between composition, structure and properties is central composition, structure and properties is central to an understanding of orthodontic materials. to an understanding of orthodontic materials. Because wide array of metallic, ceramic and Because wide array of metallic, ceramic and polymeric materials are used in the profession, polymeric materials are used in the profession, and new materials are continuously being and new materials are continuously being introduced. It is essential that the scientific introduced. It is essential that the scientific basis for selection and proper use of materials basis for selection and proper use of materials for clinical practice be thoroughly understood for clinical practice be thoroughly understood


Structure Structure and and

properties of materialsproperties of materials


MetalsMetalsStainless steel:Stainless steel:

F. Huaptmeyer in 1919F. Huaptmeyer in 1919 These family of steels contain more than 12% of These family of steels contain more than 12% of

chromium which owes for its success chromium which owes for its success Relatively high Chromium content in SSRelatively high Chromium content in SS favors the favors the

stability of BCC unit cells of ferritestability of BCC unit cells of ferrite Ni, Cu, Mn, NNi, Cu, Mn, N favors an FCC structure of austenite favors an FCC structure of austenite Other additives are Other additives are - carbon, Silica, Sulfur, Phosphorus, Manganese - carbon, Silica, Sulfur, Phosphorus, Manganese Heat treatment of these stainless, which promotes the Heat treatment of these stainless, which promotes the

precipitation of some elements addedprecipitation of some elements added..www.indiandentalacademy.comwww.indiandentalacademy.com

Stainless steels are classified Stainless steels are classified according to the American Iron and according to the American Iron and

Steel InstituteSteel Institute Various steels are:Various steels are:

Austenitic steels (300 series)Austenitic steels (300 series) Martensitic steels (400 series)Martensitic steels (400 series) Ferritic steelsFerritic steels Duplex steelsDuplex steels Precipitation-hardenable (PH) steelsPrecipitation-hardenable (PH) steels Cobalt containing alloysCobalt containing alloys Manganese containing steelsManganese containing steels


BCC FCCBCC FCC


MARTENSITIC STEELS (400 SERIES)MARTENSITIC STEELS (400 SERIES)

In Microstructure of these steels is the same as that of iron at In Microstructure of these steels is the same as that of iron at room temperature (BCC).room temperature (BCC).

These steels are stronger but less corrosion resistant alloys These steels are stronger but less corrosion resistant alloys Such stainless steels should be used only for a short contact Such stainless steels should be used only for a short contact

with oral environment with oral environment It is used for sharp instruments and resistant edgesIt is used for sharp instruments and resistant edges

Austenitic FCC structure is unstable at lower temperature.Austenitic FCC structure is unstable at lower temperature. Austenizing elements (Ni, Mn and N) are added, the highly Austenizing elements (Ni, Mn and N) are added, the highly

corrosion resistant solid solution phase can be preserved even at corrosion resistant solid solution phase can be preserved even at room temperature.room temperature.

The 300 series steels are used for most attachments because of The 300 series steels are used for most attachments because of there corrosion resistance.there corrosion resistance.

AUSTENITIC STEELS (300 SERIES )AUSTENITIC STEELS (300 SERIES )


Ferritic steelsFerritic steels Chromium is substituted for some of the iron atoms in the BCC Chromium is substituted for some of the iron atoms in the BCC

unit cells unit cells Modern “Super ferritics” contain 19% to 30 % chromium and are Modern “Super ferritics” contain 19% to 30 % chromium and are

used in several nickel free brackets. These are highly resistant to used in several nickel free brackets. These are highly resistant to chlorides and alloys contain small amounts of aluminum and chlorides and alloys contain small amounts of aluminum and molybdenum and very little carbon.molybdenum and very little carbon.

It consists of an assembly of both austenite and ferrite grains. They It consists of an assembly of both austenite and ferrite grains. They also contain molybdenum and chromium and lower nickel content also contain molybdenum and chromium and lower nickel content The duplex structure results in improved toughness The duplex structure results in improved toughness and ductility.. These steels have been used for the manufacture of and ductility.. These steels have been used for the manufacture of one-piece brackets (Eg: Bioline “low nickel” brackets).one-piece brackets (Eg: Bioline “low nickel” brackets).

Duplex steelDuplex steel


PRECIPITATION-HARDENABLE PRECIPITATION-HARDENABLE STEELSSTEELS

These steels can be hardened by heat These steels can be hardened by heat treatment, which promotes the precipitation of treatment, which promotes the precipitation of some elements added. some elements added.

PH 17-4 stainless steel is widely used for PH 17-4 stainless steel is widely used for “mini” brackets.“mini” brackets.

PH 17-7 stainless steel is used to manufacture PH 17-7 stainless steel is used to manufacture Edgelock brackets (Ormco)Edgelock brackets (Ormco)


TitaniumTitanium The unparalleled tissue tolerance and biocompatibility of titanium The unparalleled tissue tolerance and biocompatibility of titanium

have made it the leading metal for dental implants. . have made it the leading metal for dental implants. . Most alloys used in orthodontics contain potentially toxic nickel, Most alloys used in orthodontics contain potentially toxic nickel,

chromium, and cobalt. . chromium, and cobalt. . Titanium alloy are highly corrosion resistant Titanium alloy are highly corrosion resistant They are strong but not as stiff as stain less steel, hence needed to They are strong but not as stiff as stain less steel, hence needed to

be compensated by over sizebe compensated by over size It exists in alpha and beta forms; beta form is stable above 1620 It exists in alpha and beta forms; beta form is stable above 1620

deg c . But can be stabilized at lower temperaturedeg c . But can be stabilized at lower temperature Titanium oxide film has high affinity which may be the cause for Titanium oxide film has high affinity which may be the cause for

its high frictional resistance.its high frictional resistance. It is used to make intermediate arch wires and can beIt is used to make intermediate arch wires and can be welded .welded .


Beta –titaniumBeta –titanium Introduced BY BURSTONE AND GOLDBERG Introduced BY BURSTONE AND GOLDBERG Commercial name – TMA (Titanium Molybdenum Commercial name – TMA (Titanium Molybdenum

Alloy) Alloy) beta-stabilized titaniumbeta-stabilized titanium Composition Composition

Titanium – 77.8 %Titanium – 77.8 %Molybdenum – 11.3 %Molybdenum – 11.3 %Zirconium – 6.6 %Zirconium – 6.6 %Tin – 4.3 %Tin – 4.3 %

A clinical advantage of A clinical advantage of - titanium is its excellent - titanium is its excellent formability which is due to the BCC structure of beta formability which is due to the BCC structure of beta stabilized titaniumstabilized titanium

Zirconium and zinc - contribute to increased strength Zirconium and zinc - contribute to increased strength and hardness.and hardness. www.indiandentalacademy.comwww.indiandentalacademy.com

CeramicsCeramics The first ceramic used was aluminum oxide or alumina, The first ceramic used was aluminum oxide or alumina,

followed by zirconiafollowed by zirconia alumina and zirconia can be found as tridimensional alumina and zirconia can be found as tridimensional

inorganic macromolecules & are esthetically pleasinginorganic macromolecules & are esthetically pleasing The ionic crystalline structure accounts for its hardness and The ionic crystalline structure accounts for its hardness and

compressive strength which exceeds that of the metals, but compressive strength which exceeds that of the metals, but they have poor flexure strengththey have poor flexure strength

Alumina is quite stable at normal conditions but zirconia Alumina is quite stable at normal conditions but zirconia under goes phase transformation from the tetragonal under goes phase transformation from the tetragonal structure to monoclinic structure when cooled through 1100 structure to monoclinic structure when cooled through 1100 -1200 range. with a volume change of approximately 3 -1200 range. with a volume change of approximately 3 %that can cause fracture of ceramics%that can cause fracture of ceramicswww.indiandentalacademy.comwww.indiandentalacademy.com

Small addition of yttrium oxide and hot isostatic Small addition of yttrium oxide and hot isostatic pressing can be employed to achieve very small grain pressing can be employed to achieve very small grain size yttrium oxide partially stabilized zirconiasize yttrium oxide partially stabilized zirconia

This transformation toughness results in high facture This transformation toughness results in high facture toughness 9- 10mpa.m1/ toughness 9- 10mpa.m1/

A l 3+ A l 3+

A l 3+

A l 3 +

A l 3+ A l 3+

O 2- O 2 -

O 2-

O 2-O 2 -

O 2-

b 2"

b1

b'

b"3

2

1


Organic polymersOrganic polymers Are natural allies of medicine because they enter the Are natural allies of medicine because they enter the

composition of living tissues.composition of living tissues. To be used in the oral cavity these materials must be non-To be used in the oral cavity these materials must be non-

degradable, stable and should not be mutagenic or degradable, stable and should not be mutagenic or carcinogeniccarcinogenic

The first organic polymer to be used in orthodontics were The first organic polymer to be used in orthodontics were rubber and its sulfur cross linked derivatives like vulcaniterubber and its sulfur cross linked derivatives like vulcanite

Polymers truly adequate for dental purpose were only Polymers truly adequate for dental purpose were only discovered in late 1930 s’discovered in late 1930 s’

Polymethy-methacrylates and polyurethanes by Obeyer in Polymethy-methacrylates and polyurethanes by Obeyer in 19371937

Polycarbonates and polysulfones has made possible Polycarbonates and polysulfones has made possible manufacturing esthetic attachment.manufacturing esthetic attachment.

The discovery of epoxies and cyanoacrylates led to the The discovery of epoxies and cyanoacrylates led to the convenient use of adhesives convenient use of adhesives www.indiandentalacademy.comwww.indiandentalacademy.com

Structure and compositionStructure and composition Even though the chemical composition is the Even though the chemical composition is the

same the materials exhibit different properties same the materials exhibit different properties this is basically determined by the polymer this is basically determined by the polymer chain length. small chains and residual chain length. small chains and residual monomer can be detrimental to their propertiesmonomer can be detrimental to their properties

The polymeric chains may be linear branched The polymeric chains may be linear branched or three dimensional or three dimensional

with the increase in the side chains the with the increase in the side chains the polymer becomes stiff polymer becomes stiff

Polymer shrinkage occurs due to excess Polymer shrinkage occurs due to excess monomermonomer


HandlingHandling

The chemical degradation of the polymer and their The chemical degradation of the polymer and their precursor often takes place well in advance of their precursor often takes place well in advance of their deliverydelivery

Among the most sensitive products are polyurethane Among the most sensitive products are polyurethane elastomers.when these materials are subjected to light elastomers.when these materials are subjected to light high temperature, ph variations, solvents, or even air high temperature, ph variations, solvents, or even air polyurethanes degrade and become brownish. polyurethanes degrade and become brownish.

To control these undesirable effects various additives To control these undesirable effects various additives are need, like the initiators, accelerators ,polymerization are need, like the initiators, accelerators ,polymerization inhibitors, plasticizers and uv –stablizers.inhibitors, plasticizers and uv –stablizers.


Poly urethanes are further hydrophilic. water Poly urethanes are further hydrophilic. water and especially saliva hydrolyses themand especially saliva hydrolyses them

The polymer surface may develop crazes an The polymer surface may develop crazes an lodge micro-organism , and become unpleasantlodge micro-organism , and become unpleasant

Biocompatibility Biocompatibility Adhesives, sealants and restorations contain Adhesives, sealants and restorations contain

various additives, aromatic amines , peroxide, various additives, aromatic amines , peroxide, inhibitors and uv –stabilizersinhibitors and uv –stabilizers

Some of them are potentially toxic, Some of them are potentially toxic, carcinogeniccarcinogenic


ImplantsImplants


Implants materials Implants materials

The materials commonly used for implants can The materials commonly used for implants can be divided into 3 categories: be divided into 3 categories:

Biotolerant - stainless steel, chromium-cobalt Biotolerant - stainless steel, chromium-cobalt alloy.alloy.

Bioinert - titanium, carbon and Bioinert - titanium, carbon and Bioactive - vetroceramic apatite hydroxide, Bioactive - vetroceramic apatite hydroxide,

ceramic oxidized aluminum.ceramic oxidized aluminum.


Titanium ImplantsTitanium Implants Advantages of titaniumAdvantages of titanium

Commercially pure titanium is the material Commercially pure titanium is the material most often used in implant logy. most often used in implant logy.

It consists of 99.5% titanium, and the It consists of 99.5% titanium, and the remaining 0.5% is other elements, such as remaining 0.5% is other elements, such as carbon, oxygen, nitrogen, and hydrogen. carbon, oxygen, nitrogen, and hydrogen.

Osseo integrationOsseo integration no allergic or immunological reactions no allergic or immunological reactions Mechanical characteristics -very light weight, Mechanical characteristics -very light weight,

excellent resistance to traction and breakingexcellent resistance to traction and breaking..www.indiandentalacademy.comwww.indiandentalacademy.com

Orthodontic wiresOrthodontic wires


Orthodontic wires , which generate Orthodontic wires , which generate the bio-mechanical forces the bio-mechanical forces

communicate through brackets for communicate through brackets for tooth movement , are central to the tooth movement , are central to the orthodontic practice. In the rational orthodontic practice. In the rational selection of wires for particular selection of wires for particular

treatment, the orthodontist should treatment, the orthodontist should consider a variety of factors.consider a variety of factors.


Low stiffness, good spring back and Low stiffness, good spring back and produce light forcesproduce light forces

highly formable and Ability and ease of highly formable and Ability and ease of joining.joining.

Low coefficient of frictionLow coefficient of friction

Corrosion resistanceCorrosion resistance Cost and biocompatibility Cost and biocompatibility


Stainless steel wires –Stainless steel wires – Austenitic stainless steelAustenitic stainless steel excellent formability & corrosion resistance excellent formability & corrosion resistance Stainless steel alloy used for orthodontic wires are Stainless steel alloy used for orthodontic wires are

18-8 austenitic type, containing approximately 18 18-8 austenitic type, containing approximately 18 % chromium and 8 % nickel and less than 0.20 % chromium and 8 % nickel and less than 0.20 percent carbon.Nickel, percent carbon.Nickel,

Heat treatment of 400 – 500 degree c ……residual Heat treatment of 400 – 500 degree c ……residual stress, heat treatments above 650 degrees c stress, heat treatments above 650 degrees c ……..precipitation of chromium carbide at the ……..precipitation of chromium carbide at the grain boundariesgrain boundaries

The free hand soldering should be done rapidly The free hand soldering should be done rapidly with a well controlled torch and use of flux .with a well controlled torch and use of flux .

spot welding often causes localized loss of wrought spot welding often causes localized loss of wrought microstructuremicrostructure


Cobalt chromium nickel wires Cobalt chromium nickel wires Elgiloy 1950 .Elgiloy 1950 . It is available in four tempers that are color coded –It is available in four tempers that are color coded –

blue (soft) , yellow (ductile) , green (semi resilient) blue (soft) , yellow (ductile) , green (semi resilient) and red (resilent) and red (resilent)

Composition is 40 % Co, 20% Cr, 15 % Ni, 7 % Mo, Composition is 40 % Co, 20% Cr, 15 % Ni, 7 % Mo, and 16% Fe.and 16% Fe.

Corrosion resistance & lower elastic force delivery Corrosion resistance & lower elastic force delivery The eigiloy blue as received wire can easily The eigiloy blue as received wire can easily

manipulated into desired shapes and then heat manipulated into desired shapes and then heat treated to achieve considerable strength and treated to achieve considerable strength and resilience.resilience.

Elgiloy has been used for making fixed lingual quad Elgiloy has been used for making fixed lingual quad helix appliancehelix appliance


Has excellent formability.Has excellent formability.

Spring characteristics are similar to those of Spring characteristics are similar to those of stainless steel. stainless steel.

Can be soldered, but technique is Can be soldered, but technique is demanding.demanding.

Corrosion resistance of the wire is Corrosion resistance of the wire is excellent.excellent.


Beta titaniumBeta titanium TMA by Burstone and GoldbergTMA by Burstone and Goldberg highest friction owing to substantial cold highest friction owing to substantial cold

welding or mechanical abrasion.welding or mechanical abrasion. Ion-implantation - causes surface hardening Ion-implantation - causes surface hardening

and can decrease frictional force by as much and can decrease frictional force by as much as 70% and improve compressive strength, as 70% and improve compressive strength, fatigue resistance and ductility of the wiresfatigue resistance and ductility of the wires

Katherine Kula and proffit in AJO 1998 Katherine Kula and proffit in AJO 1998 concluded that there was no significant concluded that there was no significant difference when ion implanted TMA wire difference when ion implanted TMA wire when compared to unimplanted TMA wire in when compared to unimplanted TMA wire in sliding mechanics clinicallysliding mechanics clinically..


PropertiesProperties Corrosion resistant and biocompatibleCorrosion resistant and biocompatible Deflection 2 ( S.S) = TMADeflection 2 ( S.S) = TMA Beta titanium is ductileBeta titanium is ductile Allows direct welding of auxiliaries to an Allows direct welding of auxiliaries to an

arch wire without reinforcement by arch wire without reinforcement by soldering.soldering.

Beta titanium wires are the most expensive Beta titanium wires are the most expensive of all the orthodontic wire alloys but the of all the orthodontic wire alloys but the increased cost is offset by its combined increased cost is offset by its combined advantageous properties.advantageous properties.


Nickel titanium wiresNickel titanium wires IntroductionIntroduction Andreasen and Hillman in 1971.Andreasen and Hillman in 1971. Nitinol- Buehler.Nitinol- Buehler. Naval Ordinance Laboratory, its place of Naval Ordinance Laboratory, its place of

origin.origin. NiTi, Nitinol, Orthonol, Sentinol and NiTi, Nitinol, Orthonol, Sentinol and

Titanal Titanal Good spring back and flexibilityGood spring back and flexibility large deflections but low forceslarge deflections but low forces


Composition Composition Nitinol is approximately 52 percent nickel, Nitinol is approximately 52 percent nickel,

45 percent titanium, and 3 percent cobalt.45 percent titanium, and 3 percent cobalt. With proper heat treatment, the alloy With proper heat treatment, the alloy

demonstrates significant changes in demonstrates significant changes in mechanical properties and crystallographic mechanical properties and crystallographic arrangement.arrangement.

Have a stabilized martensitic phase formed Have a stabilized martensitic phase formed by cold welding, were the shape memory by cold welding, were the shape memory effect has been suppressed.effect has been suppressed.


Two major NiTi phases are: Two major NiTi phases are: 1. Austenitic Niti - a ordered BCC structure 1. Austenitic Niti - a ordered BCC structure

occurs at high temperatures / low stress. occurs at high temperatures / low stress. 2.Martensitic NiTi- distorted monoclinic, 2.Martensitic NiTi- distorted monoclinic,

triclinic or hexagonal structure and forms at low triclinic or hexagonal structure and forms at low temperatures / high stress. temperatures / high stress.

shape memory effect is associated with a shape memory effect is associated with a reversible martensite to austenite transformation, reversible martensite to austenite transformation, which occurs rapidly by crystallographic twinning which occurs rapidly by crystallographic twinning

When these alloys are subjected to high When these alloys are subjected to high temperatures, detwinning occurs, and the alloy temperatures, detwinning occurs, and the alloy reverts to the original shape or size - shape reverts to the original shape or size - shape memory effect.memory effect.


Kusy has classified nickel titanium wires as Kusy has classified nickel titanium wires as

Martensite stabilised alloys- Nitinol.Martensite stabilised alloys- Nitinol. Martensite active alloys- employ the Martensite active alloys- employ the

thermoelastic effect for shape memory. alloys thermoelastic effect for shape memory. alloys such as Neo-Sentalloy and Copper Ni-Tisuch as Neo-Sentalloy and Copper Ni-Ti

Austenitic active alloys (SIM) These alloys Austenitic active alloys (SIM) These alloys are the super elastic wires that do not possess are the super elastic wires that do not possess thermoelastic shape memory at the thermoelastic shape memory at the temperature of the oral environment such as temperature of the oral environment such as Nitinol SENitinol SE


Shape memory effectShape memory effect Hurst and Nanda in AJO 1990 -specific TTR Hurst and Nanda in AJO 1990 -specific TTR

depends on the chemical composition of the alloy and depends on the chemical composition of the alloy and its processing historyits processing history..

Memory is set in the material by holding it in the Memory is set in the material by holding it in the desired shape while annealing it at 450° F to 500° F desired shape while annealing it at 450° F to 500° F for 10 minutesfor 10 minutes

Once a certain shape is set, the alloy can then be Once a certain shape is set, the alloy can then be plastically deformed at temperatures below its TTR. plastically deformed at temperatures below its TTR. On heating through the TTR, the original shape of On heating through the TTR, the original shape of the alloy is restored. the alloy is restored.

To obtain maximum shape recovery, the deformation To obtain maximum shape recovery, the deformation should be limited to 7% or 8% , below TTR .should be limited to 7% or 8% , below TTR .

Buehler and Cross- shape-memory phenomenon was Buehler and Cross- shape-memory phenomenon was related to the inherent capability of a nickel-titanium related to the inherent capability of a nickel-titanium alloy to alter its atomic bonding as a function of alloy to alter its atomic bonding as a function of temperaturetemperature www.indiandentalacademy.comwww.indiandentalacademy.com

Superelasticity / PseudoelasticitySuperelasticity / Pseudoelasticity

In response to temperature variations, the crystal structure In response to temperature variations, the crystal structure undergoes deformationsundergoes deformations

On activation, the wire undergoes a transformation from On activation, the wire undergoes a transformation from austenitic to martensitic form due to stressaustenitic to martensitic form due to stress

The different loading and unloading curves produce the The different loading and unloading curves produce the remarkable effect the force delivered by the austenitic NiTi remarkable effect the force delivered by the austenitic NiTi wire can be changed during clinical use by merely releasing wire can be changed during clinical use by merely releasing the wire and retying it.the wire and retying it.

Deflection generates a local martensitic transformation and Deflection generates a local martensitic transformation and produces stress-induced martensite (SIM). produces stress-induced martensite (SIM).

In orthodontic clinical applications, SIM forms where the In orthodontic clinical applications, SIM forms where the wire is tied to brackets on malaligned teeth so that the wire wire is tied to brackets on malaligned teeth so that the wire becomes noticeably pliable in the deflected areas, with becomes noticeably pliable in the deflected areas, with seemingly permanent deformationseemingly permanent deformation


Clinical usage Clinical usage The high springback of nitinol is useful in circumstances that The high springback of nitinol is useful in circumstances that

require large deflections but low forces require large deflections but low forces This results in increased clinical efficiency of nitinol wires This results in increased clinical efficiency of nitinol wires

since fewer arch wire changes or activations are required.since fewer arch wire changes or activations are required. for a given amount of activation, wires made of titanium alloys for a given amount of activation, wires made of titanium alloys

produce more constant forces on teeth than stainless steel produce more constant forces on teeth than stainless steel wires. A distinct advantage of nitinol is realized when a wires. A distinct advantage of nitinol is realized when a rectangular wire is inserted early in treatment. This rectangular wire is inserted early in treatment. This accomplishes simultaneous leveling, torquing, and correction accomplishes simultaneous leveling, torquing, and correction of rotations. of rotations.

Andreasen and Morrow - fewer arch wire changes, less Andreasen and Morrow - fewer arch wire changes, less chairside time, reduction in time required to accomplish chairside time, reduction in time required to accomplish rotations and leveling, and less patient discomfort.rotations and leveling, and less patient discomfort.

Since hooks cannot be bent or attached to nitinol, crimpable Since hooks cannot be bent or attached to nitinol, crimpable hooks and stops are recommended for use. hooks and stops are recommended for use.

Cinch-backs distal to molar buccal tubes can be achievedCinch-backs distal to molar buccal tubes can be achievedwww.indiandentalacademy.comwww.indiandentalacademy.com

Chinese Ni Ti wireChinese Ni Ti wire Chinese NiTi wire is applicable in situations Chinese NiTi wire is applicable in situations

where large deflections are required where large deflections are required Used in conditions were teeth are badly Used in conditions were teeth are badly

malaligned and in appliances designed to malaligned and in appliances designed to deliver constant forces.deliver constant forces.

There is a force difference if the appliance is There is a force difference if the appliance is left in place throughout the deactivation or if it left in place throughout the deactivation or if it is removed and retied. If the force levels have is removed and retied. If the force levels have dropped too low for a given type of tooth dropped too low for a given type of tooth movement, then the simple act of untying and movement, then the simple act of untying and retying can increase the magnitude of the retying can increase the magnitude of the force.force.


Copper Ni – Ti wiresCopper Ni – Ti wires

In 1994 copper Ni –Ti wires were introduced by the In 1994 copper Ni –Ti wires were introduced by the ormco corporation. ormco corporation.

It is available in three temperature variants: 270 C, It is available in three temperature variants: 270 C, 350 C and 400 C corresponding to the austenite 350 C and 400 C corresponding to the austenite finish temperatures finish temperatures

Shape memory behaviors is reported to occur for Shape memory behaviors is reported to occur for each variant at temperatures exceeding the specified each variant at temperatures exceeding the specified temperature. temperature.

The addition of copper to nickel titanium enhances The addition of copper to nickel titanium enhances the thermal- reactive properties of the wire, thereby the thermal- reactive properties of the wire, thereby enabling the clinician to provide optimal forces for enabling the clinician to provide optimal forces for consistent toothconsistent tooth movement.movement.


CompositionComposition They are composed of They are composed of Nickel – 44%Nickel – 44% Titanium – 51%Titanium – 51% Copper – less than 5%Copper – less than 5% Chromium – 0.2 – 0.3%Chromium – 0.2 – 0.3% Kusy - wire contains nominally 5-6 wt% of copper Kusy - wire contains nominally 5-6 wt% of copper

and 0.2-0.3 % of chromium. and 0.2-0.3 % of chromium. The 27deg C variant contains 0.5% of chromium to The 27deg C variant contains 0.5% of chromium to

compensate for the effect of copper in raising the Af compensate for the effect of copper in raising the Af above that of the oral environment. above that of the oral environment.

The addition of copper to Ni-Ti not only modifies the The addition of copper to Ni-Ti not only modifies the shape memory , but also increases the stability of shape memory , but also increases the stability of transformation and also helped to control hysteresis transformation and also helped to control hysteresis width and improved corrosion resistance. width and improved corrosion resistance. www.indiandentalacademy.comwww.indiandentalacademy.com

Uses of copper Ni - Ti wires Uses of copper Ni - Ti wires 27°C Copper Ni-Ti generates forces in the high range of 27°C Copper Ni-Ti generates forces in the high range of

physiological force limits and produces constant unloading forces physiological force limits and produces constant unloading forces that can result in rapid tooth movement. Engagement force is that can result in rapid tooth movement. Engagement force is lower than with other superelastic wires. This variant would be lower than with other superelastic wires. This variant would be useful in mouth breathers. useful in mouth breathers.

35°C Copper Ni-Ti generates mid-range constant force levels 35°C Copper Ni-Ti generates mid-range constant force levels when the wire reaches mouth temperature. Early ligation is easier when the wire reaches mouth temperature. Early ligation is easier with full-size archwires due to the lower loading forces. When with full-size archwires due to the lower loading forces. When earlier engagement of full-size wires and sustained unloading earlier engagement of full-size wires and sustained unloading forces at body temperature are desired, 35°C Copper Ni-Ti is the forces at body temperature are desired, 35°C Copper Ni-Ti is the ideal wire. This variant is activated at normal body temperature.ideal wire. This variant is activated at normal body temperature.

40°C Copper Ni-Ti provides intermittent forces that are activated 40°C Copper Ni-Ti provides intermittent forces that are activated when the mouth temperature exceeds 40°C. It is useful as an when the mouth temperature exceeds 40°C. It is useful as an initial wire and can be used to engage severely malaligned teeth initial wire and can be used to engage severely malaligned teeth (such as high cuspids) without creating damaging or painful levels (such as high cuspids) without creating damaging or painful levels of force or unwanted side effects. It is also the wire of choice for of force or unwanted side effects. It is also the wire of choice for patients scheduled for long intervals between visits when control patients scheduled for long intervals between visits when control of tooth movement is a concern. This variant would provide of tooth movement is a concern. This variant would provide activation only after consuming hot food and beverages.activation only after consuming hot food and beverages.


Japanese Ni-Ti wires Japanese Ni-Ti wires Classic NiTi alloy wire used in clinical Classic NiTi alloy wire used in clinical

orthodontics is the work-hardened type wire orthodontics is the work-hardened type wire called Nitinol. called Nitinol.

The Japanese NiTi alloy wire possesses The Japanese NiTi alloy wire possesses excellent springback property, shape memory, excellent springback property, shape memory, and super-elasticity. and super-elasticity.

Super-elasticity is especially desirable because Super-elasticity is especially desirable because it delivers a relatively constant force for a long it delivers a relatively constant force for a long period of time, which is considered a period of time, which is considered a physiologically desirable force for tooth physiologically desirable force for tooth movementmovement


Orthodontic bracketsOrthodontic brackets


Orthodontic brackets bonded to Orthodontic brackets bonded to enamel provide the means to enamel provide the means to transfer the force applied by the transfer the force applied by the activated arch wire to the tooth. activated arch wire to the tooth.


TYPES OF BRACKETS TYPES OF BRACKETS A) METAL BRACKETSA) METAL BRACKETS 1) Stainless steel brackets1) Stainless steel brackets 2) Gold-coated brackets2) Gold-coated brackets 3) Platinum-coated brackets3) Platinum-coated brackets 4) Titanium brackets4) Titanium brackets B) PLASTIC BRACKETSB) PLASTIC BRACKETS 1) Polycarbonate brackets1) Polycarbonate brackets 2) Polyurethane-composite brackets2) Polyurethane-composite brackets 3) Thermoplastic-polyurethane brackets 3) Thermoplastic-polyurethane brackets C) CERAMIC BRACKETSC) CERAMIC BRACKETS 1) Monocrystalline alumina (Sapphire)1) Monocrystalline alumina (Sapphire) 2) Polycrystalline alumina2) Polycrystalline alumina 3) Polycrystalline Zirconia (YPSZ)3) Polycrystalline Zirconia (YPSZ)


Stainless steel bracketsStainless steel brackets The bracket material used for metal brackets is of Aisi type The bracket material used for metal brackets is of Aisi type

316L austentic stainless steel ,to stabilize the austentic 316L austentic stainless steel ,to stabilize the austentic structure at room temperature nickel is addedstructure at room temperature nickel is added

This Ni leaches out in the oral environment leading to This Ni leaches out in the oral environment leading to biocompatibility problems.biocompatibility problems.

These brackets have 16 -18 Cr ,10-14 Ni ,2-3 Mo and a These brackets have 16 -18 Cr ,10-14 Ni ,2-3 Mo and a maximum of 0.03 C. The content of Cr is comparative less and maximum of 0.03 C. The content of Cr is comparative less and Cro does not form that effective film compared to Tio .Cro does not form that effective film compared to Tio .

A 2205 stainless steel alloy than contains half the amount of A 2205 stainless steel alloy than contains half the amount of nickel found in 316L alloy has recently been proposed by nickel found in 316L alloy has recently been proposed by Oshida and colleagues. The 2205 stainless steel alloy has a Oshida and colleagues. The 2205 stainless steel alloy has a duplex microstructure consisting of martensitic and delta-duplex microstructure consisting of martensitic and delta-ferrectic phases, and is harder then the 316L alloy. Moreover, ferrectic phases, and is harder then the 316L alloy. Moreover, the 2205 alloy demonstrates substantially less corrosion then the 2205 alloy demonstrates substantially less corrosion then 316L alloy316L alloy


Titanium bracketsTitanium brackets

Pure titanium bracket (Rematitan-DENTAURUM) is a Pure titanium bracket (Rematitan-DENTAURUM) is a

one-piece construction requires no brazing layer, one-piece construction requires no brazing layer, and thus it is a solder- and nickel-free bracket. and thus it is a solder- and nickel-free bracket.

These brackets appear grey and have greater These brackets appear grey and have greater coefficient of friction then stainless steelcoefficient of friction then stainless steel

According to Hamula et al in JCO 1996, the According to Hamula et al in JCO 1996, the problems of nickel sensitivity, corrosion, and problems of nickel sensitivity, corrosion, and inadequate retention of SS brackets has been solved inadequate retention of SS brackets has been solved with the introduction of new, pure titanium bracket with the introduction of new, pure titanium bracket (Rematitan). (Rematitan).


A computer-aided laser (CAL) cutting A computer-aided laser (CAL) cutting process generates micro- and macro-process generates micro- and macro-undercuts, making it possible to design an undercuts, making it possible to design an “ideal” adhesive pattern for each tooth. “ideal” adhesive pattern for each tooth.

Single-piece construction allows the lowest Single-piece construction allows the lowest possible bracket height, This makes the possible bracket height, This makes the miniaturized appliance even less conspicuousminiaturized appliance even less conspicuous

A low bracket profile can be helpful in A low bracket profile can be helpful in assessing lip balance during treatment, assessing lip balance during treatment, especially in cases of lip insufficiency and especially in cases of lip insufficiency and protrusion. protrusion.


. . Titanium also has low thermal conductivity, Titanium also has low thermal conductivity,

and thus alleviates the sensitivity to extreme and thus alleviates the sensitivity to extreme temperature changes often experienced by temperature changes often experienced by patients wearing metal appliances. patients wearing metal appliances.

It imparts none of the metallic taste of It imparts none of the metallic taste of stainless steel brackets. stainless steel brackets.

Such brackets may provide an alternative to Such brackets may provide an alternative to SS brackets for those who are concerned SS brackets for those who are concerned with nickel toxicitywith nickel toxicity


CompositionComposition A commercially pure (cp) medical grade 4 Ti A commercially pure (cp) medical grade 4 Ti

(designation DIN 17851-German standards) is (designation DIN 17851-German standards) is used as the basis for the manufacture of titanium used as the basis for the manufacture of titanium brackets. brackets.

Composition is Composition is Titanium - over 99% Titanium - over 99% Iron - < 0.30% Iron - < 0.30% Oxygen - < 0.35% Oxygen - < 0.35% Nitrogen - < 0.35% Nitrogen - < 0.35% Carbon - 0.05% Carbon - 0.05% Hydrogen - 0.06%Hydrogen - 0.06%


Surface characteristics Surface characteristics

The surface texture of the Ti brackets is much The surface texture of the Ti brackets is much rougher than that of the SS brackets. rougher than that of the SS brackets.

These are the reasons for significantly more These are the reasons for significantly more plaque accumulation and a more marked change plaque accumulation and a more marked change of color with titanium brackets. of color with titanium brackets.

Titanium brackets are a suitable alternative to Titanium brackets are a suitable alternative to conventional metal brackets in many aspects. conventional metal brackets in many aspects. Their biocompatibility, absence of nickel, good Their biocompatibility, absence of nickel, good corrosion resistance, superior dimensional corrosion resistance, superior dimensional stability, comparable frictional characteristics and stability, comparable frictional characteristics and decreased conspicuousness along with low thermal decreased conspicuousness along with low thermal conductivity make these brackets a suitable conductivity make these brackets a suitable alternative to conventional S.S brackets specially alternative to conventional S.S brackets specially in nickel sensitive patients.in nickel sensitive patients.


Gold coated bracketsGold coated brackets

Recently gold-coated steel brackets have been Recently gold-coated steel brackets have been introduced and rapidly gained considerable introduced and rapidly gained considerable popularity.popularity.

Brackets are now available with 24 karat gold Brackets are now available with 24 karat gold plating, plated with 300 micro inches of gold.plating, plated with 300 micro inches of gold.

Gold-coated brackets may be regarded as an esthetic Gold-coated brackets may be regarded as an esthetic improvement over stainless steel attachments, and improvement over stainless steel attachments, and they are clean and thus more hygienic than ceramic.they are clean and thus more hygienic than ceramic.

Patient acceptance of gold-coated attachments is Patient acceptance of gold-coated attachments is generally positive. Significant side effects in the form generally positive. Significant side effects in the form of corrosion or allergic reactions have not been of corrosion or allergic reactions have not been observed clinically.observed clinically.


Platinum coated bracketsPlatinum coated brackets

The result is a bracket with greater abrasion The result is a bracket with greater abrasion resistance than gold.resistance than gold.

A smoother, harder surface than stainless steel A smoother, harder surface than stainless steel for reduced friction and improved sliding for reduced friction and improved sliding mechanics is achieved. mechanics is achieved.

By combining platinum metal and an exclusive By combining platinum metal and an exclusive implantation process, a barrier has been created implantation process, a barrier has been created against the diffusion of nickel, cobalt, and against the diffusion of nickel, cobalt, and chromium.chromium.

Platinum has been found to be superior to all Platinum has been found to be superior to all other known metalsother known metals www.indiandentalacademy.comwww.indiandentalacademy.com

Nickel free bracketsNickel free brackets

Made of Cobalt chromium (CoCr) dental Made of Cobalt chromium (CoCr) dental alloyalloy

One-piece construction (without solder) by One-piece construction (without solder) by metal injection molding techniquemetal injection molding technique

Laser structured bracket base for retentionLaser structured bracket base for retention


Plastic bracketsPlastic brackets

Unfilled polycarbonate 1970 s.Unfilled polycarbonate 1970 s. creep deformation, discoloration creep deformation, discoloration ceramic reinforced, fiberglass and metal slot-ceramic reinforced, fiberglass and metal slot-

reinforced polycarbonate brackets were introduced. reinforced polycarbonate brackets were introduced. while metal slot reinforced while metal slot reinforced

polycarbonate brackets reported problems with the polycarbonate brackets reported problems with the integrity of the slot periphery.integrity of the slot periphery.

The beneficial effect of these brackets due to their The beneficial effect of these brackets due to their low modulus of elasticity they tend to peel of during low modulus of elasticity they tend to peel of during debonding like the metal brackets.debonding like the metal brackets.


Various plastic brackets were:Various plastic brackets were:

Polycarbonate brackets (E.g.Elation) Polycarbonate brackets (E.g.Elation) Reinforced polycarbonate brackets ( D B Reinforced polycarbonate brackets ( D B

fibre )fibre ) Polyurethane-composite brackets Polyurethane-composite brackets

(E.g.Envision)(E.g.Envision) Thermoplastic-polyurethane brackets Thermoplastic-polyurethane brackets

(E.g.Value line)(E.g.Value line)


Polycarbonate bracketsPolycarbonate brackets

Various reinforced polycarbonate brackets:Various reinforced polycarbonate brackets:

Polymer fiber reinforced polycarbonate bracketsPolymer fiber reinforced polycarbonate brackets Fiberglass reinforced polycarbonate bracketsFiberglass reinforced polycarbonate brackets Ceramic reinforced polycarbonate bracketsCeramic reinforced polycarbonate brackets Metal slot reinforced polycarbonate bracketsMetal slot reinforced polycarbonate brackets Metal slot and ceramic reinforced polycarbonate Metal slot and ceramic reinforced polycarbonate

bracketsbrackets


Bonding mechanism of plastic brackets is mainly Bonding mechanism of plastic brackets is mainly mechanical retention mechanical retention

DisadvantagesDisadvantages

Polycarbonate brackets undergo creep Polycarbonate brackets undergo creep deformation when transferring torque loads deformation when transferring torque loads generated by arch wires to the teethgenerated by arch wires to the teeth

Discoloration of first generation unfilled Discoloration of first generation unfilled polycarbonate brackets during clinical aging.polycarbonate brackets during clinical aging.

They absorb water to a slight extent and tend to They absorb water to a slight extent and tend to weaken in the course of about one year (Newman weaken in the course of about one year (Newman 1973).1973).


Ceramic bracketsCeramic brackets

Ceramics used for the manufacturing of ceramic Ceramics used for the manufacturing of ceramic brackets were Alumina and Zirconia. Both can be brackets were Alumina and Zirconia. Both can be found as tridimensional inorganic macromolecules.found as tridimensional inorganic macromolecules.

Types of ceramic bracketsTypes of ceramic brackets Monocrystalline (Sapphire)-Inspire ,Starfire TMBMonocrystalline (Sapphire)-Inspire ,Starfire TMB Polycrystalline Alumina-Allure, Mxi, ClarityPolycrystalline Alumina-Allure, Mxi, Clarity Polycrystalline Zirconia (YPSZ) ) Hi-BracePolycrystalline Zirconia (YPSZ) ) Hi-Brace


Bonding mechanisms :Bonding mechanisms :

Mechanical retention employing large Mechanical retention employing large recesses.recesses.

Chemical adhesion facilitated by the use of a Chemical adhesion facilitated by the use of a silane layer.silane layer.

Micromechanical retention through the Micromechanical retention through the utilization of a number of configurations, utilization of a number of configurations, including protruding crystals, grooves, a including protruding crystals, grooves, a porous surface, and spherical glass particlesporous surface, and spherical glass particles


Strength of the brackets can be increased Strength of the brackets can be increased by eliminating the surface flaws that can by eliminating the surface flaws that can serve as the sites of stress concentration and serve as the sites of stress concentration and fracture initiation. Decreasing the grain size fracture initiation. Decreasing the grain size also increases the strength of polycrystalline also increases the strength of polycrystalline brackets. The polycrystalline zirconia brackets. The polycrystalline zirconia brackets manufactured by injection brackets manufactured by injection molding technique followed by isostatic molding technique followed by isostatic pressing in partially stabilized zirconia 5 pressing in partially stabilized zirconia 5 %wt yttrium oxide%wt yttrium oxide


RECYCLING OF ORTHODONTIC RECYCLING OF ORTHODONTIC BRACKETS AND ITS EFFECTSBRACKETS AND ITS EFFECTS

Several in-office bracket-reconditioning methods Several in-office bracket-reconditioning methods have been introduced since 1980, have been introduced since 1980,

Grinding - Wright and Powers (1985)Grinding - Wright and Powers (1985) Sandblasting - Millet et al (1993), Sonis (1996) Sandblasting - Millet et al (1993), Sonis (1996) Direct flamingDirect flaming Buchman method - Buchman (1980)Buchman method - Buchman (1980) BigJane machine method - Buchman (1980BigJane machine method - Buchman (1980))


Buchman (1980) concluded that as Buchman (1980) concluded that as temperatures are increased in thermal temperatures are increased in thermal treatment, the hardness and tensile strength treatment, the hardness and tensile strength are decreased and the microstructures are decreased and the microstructures illustrate corresponding susceptibility to illustrate corresponding susceptibility to metallic intergranular corrosion. metallic intergranular corrosion.

Matasa et al (1989) described that heating Matasa et al (1989) described that heating method used for reconditioning metal brackets method used for reconditioning metal brackets causes intergranular corrosion. He also causes intergranular corrosion. He also enumerated the effects of heat on brackets enumerated the effects of heat on brackets like, structural metal weakening, vertical slot like, structural metal weakening, vertical slot obstruction, steel corrosion and base cloggingobstruction, steel corrosion and base clogging


Enamel Etching


Traditionally slots were welded to the bands and Traditionally slots were welded to the bands and cemented to the crowns, before the introduction of cemented to the crowns, before the introduction of etching agents and adhesive resins, which etching agents and adhesive resins, which demanded extra arch width ,time of the clinician, demanded extra arch width ,time of the clinician, compromised oral hygiene and esthetics compromised oral hygiene and esthetics

With the introduction of acid etching (Bonocore) With the introduction of acid etching (Bonocore) opened new vents for bonding brackets to the opened new vents for bonding brackets to the teeth. Etching of enamel creates microporosities teeth. Etching of enamel creates microporosities with in the enamel and reduces the surface tension with in the enamel and reduces the surface tension that allows resins to penetrate and polymerize that allows resins to penetrate and polymerize with in the etched enamel rods (mechanical with in the etched enamel rods (mechanical bonding)bonding)


Enamel etching with acids Enamel etching with acids Type and concentration of acidType and concentration of acid

Orthodontic bonding of brackets to teeth does not require high bond Orthodontic bonding of brackets to teeth does not require high bond strength (6-8 mpa), as need in restorative dentistry. Various studies have strength (6-8 mpa), as need in restorative dentistry. Various studies have shown that etching with 10%-37% phosphoric acid has provided shown that etching with 10%-37% phosphoric acid has provided adequate bond strength.adequate bond strength.

Some studies have also shown that even treating the enamel with 2% Some studies have also shown that even treating the enamel with 2% phosphoric acid have been able to provide adequate bond strength.phosphoric acid have been able to provide adequate bond strength.

The use of 10% maleic acid for etching results in lower bond strength.The use of 10% maleic acid for etching results in lower bond strength.

Duration of etchingDuration of etching

No difference in bond strength was detected between 15 second and 60 No difference in bond strength was detected between 15 second and 60 second etching with 37% phosphoric acidsecond etching with 37% phosphoric acid

However shorter etching time results in decreased bond strength (0 – 5 However shorter etching time results in decreased bond strength (0 – 5 seconds)seconds)

Scanning electron microscopy showed that etching with 37% phosphoric Scanning electron microscopy showed that etching with 37% phosphoric acid for atleast 30 seconds produces more optimal etchin pattern than acid for atleast 30 seconds produces more optimal etchin pattern than etching for 15 seconds.etching for 15 seconds.


Resin composite does not bond well to un Resin composite does not bond well to un etched enamel; however, hybrid inomer etched enamel; however, hybrid inomer orthodontic cements have a bond strength orthodontic cements have a bond strength ranging from 8 to 25 mpa .ranging from 8 to 25 mpa .

Hybrid inomer cements have better bond Hybrid inomer cements have better bond strength to enamel than sand blasted metal strength to enamel than sand blasted metal bracket base.bracket base.

And these cements lack cohesive strengthAnd these cements lack cohesive strength Use of pumice before etching to clean the Use of pumice before etching to clean the

enamel of surface deposits has shown no enamel of surface deposits has shown no alteration in bond strengthalteration in bond strength


Iatrogenic effect of etching Iatrogenic effect of etching

Fracture or cracking of the enamel during Fracture or cracking of the enamel during debondingdebonding

Porosities caused by etching may cause Porosities caused by etching may cause staining of toothstaining of tooth

Loss of enamel. (10- 20 um)Loss of enamel. (10- 20 um) Resin tags retained in the enamel after Resin tags retained in the enamel after

debonding may get discolored. debonding may get discolored. Alternate methods for etching enamelAlternate methods for etching enamel


Acidic primerAcidic primer

CompositionComposition Acid(phenyl-p) Acid(phenyl-p) HEMAHEMA And dimethacrylateAnd dimethacrylate

Although they are expensive ,comparable Although they are expensive ,comparable bond strength can be attained bond strength can be attained

It also reduces the chair timeIt also reduces the chair time


Air abrasionAir abrasion

Also known as micro etching is a tecnique in Also known as micro etching is a tecnique in

which particles of aluminum oxide are which particles of aluminum oxide are propelled against the surface of enamel propelled against the surface of enamel causes abrasion of the enamel surfacecauses abrasion of the enamel surface

Micro etching metals is an effective way of Micro etching metals is an effective way of increasing bond strength of bracketsincreasing bond strength of brackets

Microetching of enamel produces only 50 % Microetching of enamel produces only 50 % of the bond strength to that of acid etchingof the bond strength to that of acid etching


Laser etchingLaser etching

The application of laser energy on the enamel The application of laser energy on the enamel surface causes localized melting and ablation.surface causes localized melting and ablation.

Removal of enamel results primarily by micro Removal of enamel results primarily by micro explosion of entrapped water in the enamelexplosion of entrapped water in the enamel

Laser etching is done by neodymium-yttrium-Laser etching is done by neodymium-yttrium-aluminum garnetaluminum garnet

Laser typically produces low bond strength Laser typically produces low bond strength compared to acid etchingcompared to acid etching


Crystal growing solutionCrystal growing solution A proposed alternative to etching for retention of A proposed alternative to etching for retention of

adhesive is to grow crystals on the enamel surfaceadhesive is to grow crystals on the enamel surface This technique is called crystal bondingThis technique is called crystal bonding The potential advantages of crystal bonding The potential advantages of crystal bonding

include easy debonding, less residual adhesive left include easy debonding, less residual adhesive left on the tooth, and less enamel damage.on the tooth, and less enamel damage.

It includes application of poly(acrylic acid) It includes application of poly(acrylic acid) solution containing sulfate ions,which cause solution containing sulfate ions,which cause growth of calcium sulfate dehydrate crystals on growth of calcium sulfate dehydrate crystals on the enamelthe enamel

It produces 60-80 %0f bond strength compared to It produces 60-80 %0f bond strength compared to acid etching Acidic primersacid etching Acidic primers


Bonding agentsBonding agents


Based on the polymerization initiation Based on the polymerization initiation mechanism:mechanism:

Chemically activated (self cured ) :two paste Chemically activated (self cured ) :two paste or one pasteor one paste

Light cured ( photo cured )Light cured ( photo cured ) Dual cured (chemically activated and light Dual cured (chemically activated and light

curedcured Thermo curedThermo cured


Chemically activated orthodontic Chemically activated orthodontic adhesive systemsadhesive systems

These adhesives employ benzoyl as an initiator and tertiary These adhesives employ benzoyl as an initiator and tertiary aromatic amine such as dimethy-p-toluidene as activatoraromatic amine such as dimethy-p-toluidene as activator

Initiation occurs from the mixing of the paste and liquid Initiation occurs from the mixing of the paste and liquid components of these systems and free radicals are formed by components of these systems and free radicals are formed by multi step processesmulti step processes

Chemically cured two phase systems:Chemically cured two phase systems: Polymerization is initiated by mixing of liquid and paste Polymerization is initiated by mixing of liquid and paste Clinical handling is laborious; time consumingClinical handling is laborious; time consuming PropertiesProperties Increased exposure of the components to the air induces Increased exposure of the components to the air induces

oxygen inhibition oxygen inhibition Mixing introduces defects due to trapping of air and formation Mixing introduces defects due to trapping of air and formation

of voids of voids Concise (3M)Concise (3M) www.indiandentalacademy.comwww.indiandentalacademy.com

Chemically cured one phase systemChemically cured one phase system Application of the liquid component on the enamel and on the Application of the liquid component on the enamel and on the

bracket base.bracket base. No mixing is involvedNo mixing is involved Clinical handling: - efficient application ;limitation in time Clinical handling: - efficient application ;limitation in time

requirements requirements

Properties Properties Limited data is available on the bond strength and degree of Limited data is available on the bond strength and degree of

curing curing Inhomogeneous Patten of curing due to the sandwich involvedInhomogeneous Patten of curing due to the sandwich involved Enamel bracket sides of the polymer is more polymerized than Enamel bracket sides of the polymer is more polymerized than

the middle of the bracketthe middle of the bracket System 1(ormco)System 1(ormco) Unite (3M)Unite (3M)


Visible light curedVisible light cured The photo initiator in these systems is The photo initiator in these systems is

camphoroquinone and a reducing aminecamphoroquinone and a reducing amine Polymerization is initated by exposure to light Polymerization is initated by exposure to light

curing sourcecuring sourceClinical handlingClinical handling Provides increased working time and bracket Provides increased working time and bracket

placement time.placement time. Curing should be done from the incisal and cervical Curing should be done from the incisal and cervical

marginsmarginsPropertiesProperties The degree of cure of a stain less steel brackets The degree of cure of a stain less steel brackets

bonded with light cured adhesive is comparable to bonded with light cured adhesive is comparable to that of a transparent aesthetic bracketthat of a transparent aesthetic bracket


Dual cureDual cure

Polymerization is initiation is achieved by through Polymerization is initiation is achieved by through exposure to light and the reaction progress following exposure to light and the reaction progress following a chemically cured patterna chemically cured pattern

Clinical handling Clinical handling Combines the disadvantages of handling both light Combines the disadvantages of handling both light

cured and chemical cured materials.cured and chemical cured materials. Most time consuming applicationMost time consuming applicationPropertiesProperties Increased degree of cure and bond strength ,but of Increased degree of cure and bond strength ,but of

questionable clinical significancequestionable clinical significance Ideal for bonding molar tubesIdeal for bonding molar tubes


Moisture activeMoisture active

Polymerization – cyanoacrylate, no liquid Polymerization – cyanoacrylate, no liquid component is involved. Polymerization is component is involved. Polymerization is initiated on exposure to waterinitiated on exposure to water

Clinical handling Clinical handling One step procedure-intentionally the surface One step procedure-intentionally the surface

of the tooth must be wettedof the tooth must be wetted One of the study has shown acceptable bond One of the study has shown acceptable bond

strengthstrength Smart bond (Gestenco)Smart bond (Gestenco)


Moisture resistantMoisture resistant

Primer compatible with the use of the Primer compatible with the use of the adhesive adhesive

Clinical handlingClinical handling Application of primer on wet enamel Application of primer on wet enamel

surface surface Trans bond MIP(3M)Trans bond MIP(3M)


Microbial alteration and caries Microbial alteration and caries prophylaxisprophylaxis


Individuals with malocclution have many Individuals with malocclution have many retion site owing to the irregularities of retion site owing to the irregularities of teeth .more retion sites are introduced when teeth .more retion sites are introduced when orthodontic appliances are bonded and orthodontic appliances are bonded and banded to teeth. Oral hygine is thus banded to teeth. Oral hygine is thus markedly more difficult to maintain for markedly more difficult to maintain for orthodontic patientsorthodontic patients


Table 6.1Table 6.1


Caries prophylaxis aspect of orthodontic treatmentCaries prophylaxis aspect of orthodontic treatment Fluoride is the most caristatic agent know Fluoride is the most caristatic agent know The mechanism of action of fluoride is generally The mechanism of action of fluoride is generally

believed to be due to its effect in plaque film believed to be due to its effect in plaque film around the mineral crystallites, by inhibiting around the mineral crystallites, by inhibiting demineralizing and increasing remineralizing of demineralizing and increasing remineralizing of mineral lost during the caries processes mineral lost during the caries processes

Rationale caries prophylactic measures for Rationale caries prophylactic measures for orthodontic patient is prevention of caries lesion orthodontic patient is prevention of caries lesion developed during orthodontic treatmentdeveloped during orthodontic treatment


Fluoride tooth pastesFluoride tooth pastes Fluoride toothpaste is the basis for all caries Fluoride toothpaste is the basis for all caries

prevention. Most tooth pastes contain sodium prevention. Most tooth pastes contain sodium fluoride, monofluorophosphate, stannous fluoridefluoride, monofluorophosphate, stannous fluoride

The fluoride concentration may vary, but the The fluoride concentration may vary, but the maximum concentration allowed is 0.15 %.fluoride maximum concentration allowed is 0.15 %.fluoride concentration less than 0.1 % should not be concentration less than 0.1 % should not be recommended for orthodontic patients recommended for orthodontic patients

The cariostatic effect of fluoride will improved The cariostatic effect of fluoride will improved significantly if oral hygiene is improved significantly if oral hygiene is improved

The anionic agent sodium lauryl sulphate is a The anionic agent sodium lauryl sulphate is a popular detergent popular detergent

It increases the permeability of the oral mucosa and It increases the permeability of the oral mucosa and increases the nickel sensitivity and has been reported increases the nickel sensitivity and has been reported for helping in development of ulcersfor helping in development of ulcers


Stannous fluoride has a plaque inhibiting effect in Stannous fluoride has a plaque inhibiting effect in addition to the anticaries action. the stannous ion addition to the anticaries action. the stannous ion is responsible for the plaque inhibiting effect. is responsible for the plaque inhibiting effect. Stannous inhibit the adsorption of plaque bacteria Stannous inhibit the adsorption of plaque bacteria to the enamel by bonding to the phosphate to the enamel by bonding to the phosphate polymer lipoteichoic acid present on the surface of polymer lipoteichoic acid present on the surface of gram positive bacteria. Stannous fluoride also gram positive bacteria. Stannous fluoride also interferes with the acidogenicity of the plaque. It is interferes with the acidogenicity of the plaque. It is possible that tin atoms bound to the surface of the possible that tin atoms bound to the surface of the bacteria also block the sucrose from entering the bacteria also block the sucrose from entering the cell and there by preventing acid formationcell and there by preventing acid formation

Detergents and surface active agents are Detergents and surface active agents are incorporated in to the tooth paste and mouth incorporated in to the tooth paste and mouth rinses to lower the surface tension and loosen and rinses to lower the surface tension and loosen and penetrate the deposits and emulsify and suspend penetrate the deposits and emulsify and suspend the debristhe debris


Fluoride supplementsFluoride supplements High and long lasting cariogenic challengeHigh and long lasting cariogenic challenge For average orthodontic patient it was found that tooth pastes For average orthodontic patient it was found that tooth pastes

alone were inadequate to stop caries and there fore alone were inadequate to stop caries and there fore recommended the use of fluoride mouth rinses (0.05 % NaF ) recommended the use of fluoride mouth rinses (0.05 % NaF ) dailydaily

An improved cariostatic effect can be achieved by use of An improved cariostatic effect can be achieved by use of fluoride in combination with antibacterial agents like fluoride in combination with antibacterial agents like chlorhexidine, triclosan and zincchlorhexidine, triclosan and zinc

Topical fluoride in the form of varnishes or gels may be Topical fluoride in the form of varnishes or gels may be recommendedrecommended

Solution of titanium tetra fluoride inhibits the development of Solution of titanium tetra fluoride inhibits the development of lesions associated with fixed appliances more efficiently than lesions associated with fixed appliances more efficiently than other conventional preparation ,its mechanism of action is other conventional preparation ,its mechanism of action is probably due to retentive, titanium rich. Glaze like coating probably due to retentive, titanium rich. Glaze like coating formed on the treated enamelformed on the treated enamel


Fluoride releasing bonding agentsFluoride releasing bonding agents

Fluoride reservoir that does not depend on patient co Fluoride reservoir that does not depend on patient co operation .and fluoride is deposited in an area immediately operation .and fluoride is deposited in an area immediately adjacent to the caries susceptible areas.adjacent to the caries susceptible areas.

Gass inomer cements, and resin modified glass inomer cements Gass inomer cements, and resin modified glass inomer cements In studies simulating oral environment, it was found that the In studies simulating oral environment, it was found that the

fluoride availability from glass inomer cements is PH-controlled.fluoride availability from glass inomer cements is PH-controlled. glass inomer cements take up fluoride from the oral environment glass inomer cements take up fluoride from the oral environment

and released .and released . It is seen that much fluoride is released during the first few days It is seen that much fluoride is released during the first few days

to weeks. Short term studies have shown that here is reduction in to weeks. Short term studies have shown that here is reduction in incidence of caries but long term effect shows there was a incidence of caries but long term effect shows there was a significant reduction in the release of fluoridesignificant reduction in the release of fluoride

Fluoride releasing sealants are also available sFluoride releasing sealants are also available swww.indiandentalacademy.comwww.indiandentalacademy.com

Elastomeric ligatures and chainsElastomeric ligatures and chains


Elastomeric products are used in Elastomeric products are used in orthodontics as ligatures and as continuous orthodontics as ligatures and as continuous modules for the engagement and the modules for the engagement and the retraction.retraction.

Despite the popularity, there has been some Despite the popularity, there has been some concern about the force degradation concern about the force degradation exhibited by the elastomeric chainsexhibited by the elastomeric chains

Efforts have also been directed to minimize Efforts have also been directed to minimize plaque retention capacity of elastomeric plaque retention capacity of elastomeric chains. Fluoride releasing elastomeric chains. Fluoride releasing elastomeric ligatures has been introduced to minimize ligatures has been introduced to minimize the risk of demineralization of enamel the risk of demineralization of enamel marginsmargins


Composition and structureComposition and structure

The elastomeric ligature and chains are The elastomeric ligature and chains are polyurethanes, which are thermosetting polymers polyurethanes, which are thermosetting polymers possessing a –(NH)-(C=O)-O-stural unit formed by possessing a –(NH)-(C=O)-O-stural unit formed by condensation polymerization.condensation polymerization.

The cross linking between the chains must be The cross linking between the chains must be relatively few to facilate large extension with the relatively few to facilate large extension with the failure of primary bonds. failure of primary bonds.

The glass transition temperature of biomedical The glass transition temperature of biomedical polyurethanes range from -50 to -80 deg. C polyurethanes range from -50 to -80 deg. C

The difference in energy between the rigid and The difference in energy between the rigid and rubber states corresponds to increase in the amount rubber states corresponds to increase in the amount of molecular motion experienced by the polymer of molecular motion experienced by the polymer after undergoing the glass transition temperature after undergoing the glass transition temperature


Greater the glass transition temperature more rigid Greater the glass transition temperature more rigid is the polymer and generates more force.is the polymer and generates more force.

The two main methods of processing the modules The two main methods of processing the modules are injection molding technique and die stamping. are injection molding technique and die stamping. The die stamping polymers are found to be more The die stamping polymers are found to be more consistent in physical properties.consistent in physical properties.

It is said that pigments added to the elastomers also It is said that pigments added to the elastomers also effect the physical properties of polymer, however effect the physical properties of polymer, however the general studies has shown that there is no the general studies has shown that there is no difference between the conventional and the colored difference between the conventional and the colored elastomeric materials.elastomeric materials.


Fluoride releasing polyurethanesFluoride releasing polyurethanes Advances in the field of elastomerics include the Advances in the field of elastomerics include the

introduction of products withintroduction of products with fluoride releasing features fluoride releasing features It was thought a reliable means of long term It was thought a reliable means of long term

fluoride releasing areas adjacent to the bracket fluoride releasing areas adjacent to the bracket margins would be paramount significance.margins would be paramount significance.

Though it was thought such fluoride release is Though it was thought such fluoride release is beneficial it is said to hamper the properties of beneficial it is said to hamper the properties of elastomers and early degrading of elastomerelastomers and early degrading of elastomer


Elastomeric chains Elastomeric chains Significant differences in their force decay Significant differences in their force decay

characteristics have been reported. These characteristics have been reported. These differences may be attributed to several factors , differences may be attributed to several factors , variation in manufacturing techniques, variations variation in manufacturing techniques, variations in additives incorporated in the basic in additives incorporated in the basic polyurethane polymer, variation in morphology or polyurethane polymer, variation in morphology or dimensional characteristics .dimensional characteristics .

Many in vitro studies that have measures the Many in vitro studies that have measures the force degradation rate of he elastomerics modules force degradation rate of he elastomerics modules ……the census of these studies is that elastomerics ……the census of these studies is that elastomerics modules experience a steeps decline in force , modules experience a steeps decline in force , ranging from 40 to 50 % during the first 24 hrs ranging from 40 to 50 % during the first 24 hrs which continues at a lower rate for nest 2 to 3 which continues at a lower rate for nest 2 to 3 weeks. weeks.


Traditionally these modules have been used for Traditionally these modules have been used for retraction of anterior teeth to close extraction spaces retraction of anterior teeth to close extraction spaces as well as midline diastemas as well as midline diastemas

with the advent of Super elastic ni ti coil springs with the advent of Super elastic ni ti coil springs which can deliver low constant forces , use of which can deliver low constant forces , use of elastomerics has diminished significantlyelastomerics has diminished significantly

Then there has been a criticism related to lack of Then there has been a criticism related to lack of mechanical control of teeth Engaged with mechanical control of teeth Engaged with elastomerics chains , because loss of directional elastomerics chains , because loss of directional control of moments leads occasionally to undesirable control of moments leads occasionally to undesirable mesio-distal or bucco-lingual rotations as describes mesio-distal or bucco-lingual rotations as describes previously that the elastometic chains loose almost previously that the elastometic chains loose almost half the applied force half the applied force


very early , some investigators have proposed that very early , some investigators have proposed that this deficiency can be counteracted by application of this deficiency can be counteracted by application of higher initial force of 3 to 4 times the desired force higher initial force of 3 to 4 times the desired force level .Some other investigators felt that the level .Some other investigators felt that the application of orthodontic force up to 4 times the application of orthodontic force up to 4 times the optimal level for tooth moment may have optimal level for tooth moment may have unpredictable outcomes on biological processes unpredictable outcomes on biological processes

Several studies have also dealt with the use of Several studies have also dealt with the use of prestreaching to eliminate the force loss by prestreaching to eliminate the force loss by elastomerics modules . 2 methods have been elastomerics modules . 2 methods have been suggested , one is instantaneous pre stretching suggested , one is instantaneous pre stretching technique by young and et el other is the extended technique by young and et el other is the extended time technique by Brantley et al but evidence has time technique by Brantley et al but evidence has also shown that it only eliminates about 10 % of also shown that it only eliminates about 10 % of force decayforce decay


Cements in orthodonticsCements in orthodontics


In orthodontics application of cements is In orthodontics application of cements is limited to luting of appliances,limited to luting of appliances,

for acceptable performance the luting agent for acceptable performance the luting agent should have a variety of properties :should have a variety of properties :

Adequate working time and setting time.Adequate working time and setting time. high tensile high tensile CompressiveCompressive Shear strengthShear strength Resistance to dissolution Resistance to dissolution Clinically acceptable bond strength low Clinically acceptable bond strength low

adhesive remnant index score on debonding, adhesive remnant index score on debonding, and anti carigenic potentialand anti carigenic potential


Zinc phosphate cementZinc phosphate cement

Once zinc phosphate cements were widely Once zinc phosphate cements were widely used for cementation of orthodontic bands.used for cementation of orthodontic bands.

These cements are available as hand mixed These cements are available as hand mixed powder and liquid system although some powder and liquid system although some encapsulated products are marketedencapsulated products are marketed


CompositionComposition The principal constituent of cement powder is zinc The principal constituent of cement powder is zinc

oxide.oxide. A small quantity of Magnesium oxide which A small quantity of Magnesium oxide which

improves mechanical properties and color stability. improves mechanical properties and color stability. Small amounts of additives such as Silica or alumina Small amounts of additives such as Silica or alumina which also improves mechanical properties.which also improves mechanical properties.

Approximately 10% fluoride in the form of stannous Approximately 10% fluoride in the form of stannous fluoride for anti cariogenic effect.fluoride for anti cariogenic effect.

The liquid is an aqueous solution of phosphoric acid The liquid is an aqueous solution of phosphoric acid in concentrations from 45% to 64% buffered by 2 to in concentrations from 45% to 64% buffered by 2 to 3% of aluminum phosphate and 1 to 9% of zinc 3% of aluminum phosphate and 1 to 9% of zinc phosphate.phosphate.

Buffered by a small quaintly of 2-3% of aluminum Buffered by a small quaintly of 2-3% of aluminum phosphate .phosphate . www.indiandentalacademy.comwww.indiandentalacademy.com

Properties. Properties. The powder to liquid ratio for the cement strongly The powder to liquid ratio for the cement strongly

affects the working and setting times.affects the working and setting times. A thin consistency (low viscosity)is essential when A thin consistency (low viscosity)is essential when

the cement is used as a luting agent, to ensure the cement is used as a luting agent, to ensure adequate flow during cementation of orthodontic adequate flow during cementation of orthodontic bands.bands.

A reasonable working time for zinc phosphate A reasonable working time for zinc phosphate cements ranges between 3 and 6 minutes, and the cements ranges between 3 and 6 minutes, and the setting time should be between 5 and 9 minutes.setting time should be between 5 and 9 minutes.

For optimum results the powder should be For optimum results the powder should be incorporated into the liquid in small Proportions incorporated into the liquid in small Proportions and a relatively slow rate to achieve the desired and a relatively slow rate to achieve the desired consistency, the exothermic setting reaction is consistency, the exothermic setting reaction is retardedretarded www.indiandentalacademy.comwww.indiandentalacademy.com

In contrast, rapid mixing of the cement powder and In contrast, rapid mixing of the cement powder and liquid causes substantial heat evolution, with liquid causes substantial heat evolution, with considerable decrease in working and setting time.considerable decrease in working and setting time.

Mixing over a large area of the glass slab also results Mixing over a large area of the glass slab also results in a lower temperature increase from the setting in a lower temperature increase from the setting reactionreaction

Cooled and dried mixing slab retards the reaction Cooled and dried mixing slab retards the reaction rate.rate.

Care must be taken not to cool the slab below dew Care must be taken not to cool the slab below dew point, since condensation from the air can cause point, since condensation from the air can cause contamination by water. contamination by water.

The film thickness should be around 20 um Since The film thickness should be around 20 um Since adhesion has not been documented to develop adhesion has not been documented to develop between zinc phosphate cements and orthodontic between zinc phosphate cements and orthodontic bands, retention of the bands is attained by bands, retention of the bands is attained by mechanical interlocking.mechanical interlocking.


PropertiesProperties Initial setting takes place at 4-7 minutes it attains up to 50 %of Initial setting takes place at 4-7 minutes it attains up to 50 %of

the final strength which is attained at 24 hours. Exhibits the final strength which is attained at 24 hours. Exhibits compressive strength of 80 – 140 mpa tensile strength of less compressive strength of 80 – 140 mpa tensile strength of less than 5 mpathan 5 mpa

Solubility Solubility During the first 24 hours of cementation significant solubility During the first 24 hours of cementation significant solubility

of the cement has been reported as much as 0.04 -3.3 %by of the cement has been reported as much as 0.04 -3.3 %by weight and decreases due time .weight and decreases due time .

High powder liquid ratio decreases the solubility of the cement High powder liquid ratio decreases the solubility of the cement

Draw backsDraw backs Zinc phosphate is brittle.Zinc phosphate is brittle. It has a relatively high solubility in the mouth and it does not It has a relatively high solubility in the mouth and it does not

adhere to tooth substance.adhere to tooth substance. Zinc phosphate relies on mechanical interlocking for its Zinc phosphate relies on mechanical interlocking for its

retentive effect. retentive effect. It does not provide any chemical bonding to tooth or metal It does not provide any chemical bonding to tooth or metal

surfaces.surfaces. www.indiandentalacademy.comwww.indiandentalacademy.com

Zinc polycarboxylate cements:Zinc polycarboxylate cements:

These cement were introduced by smith in These cement were introduced by smith in 1968 and these cements were the 1 st dental 1968 and these cements were the 1 st dental materials developed with an adhesive materials developed with an adhesive potential to enamel and dentin and it has potential to enamel and dentin and it has the desirable properties of zinc phosphate the desirable properties of zinc phosphate and zinc oxide eugenoland zinc oxide eugenol


CompositionComposition The zinc polycarboxylate is available in powder liquid The zinc polycarboxylate is available in powder liquid

formations, the powder consists of zinc oxide with 10 % of formations, the powder consists of zinc oxide with 10 % of magnesium oxide or tin oxide , silica , alumina , or bismuth magnesium oxide or tin oxide , silica , alumina , or bismuth salts and small quantities of stannous fluoride may be salts and small quantities of stannous fluoride may be incorporated in some brandsincorporated in some brands

The presence of fluoride in these cements also increases the The presence of fluoride in these cements also increases the strength while controlling the setting time,strength while controlling the setting time,

The liquid is an aqueous solution of a homopolimer o acrylic The liquid is an aqueous solution of a homopolimer o acrylic acid or co polymers acrylic with other unsaturated carboxylic acid or co polymers acrylic with other unsaturated carboxylic acids such as etaconic and maelic acid .acids such as etaconic and maelic acid .

The acid concentration is 40 %by wt. it has a relatively high The acid concentration is 40 %by wt. it has a relatively high molecular wt which may increase the strength of the material .molecular wt which may increase the strength of the material .

undesirable effects such as short shelf life and difficulties in undesirable effects such as short shelf life and difficulties in manipulation occur because of high viscositymanipulation occur because of high viscosity


Mixing of the polycarboxylate cements should be Mixing of the polycarboxylate cements should be completed rapidly within 30 to 40 seconds.completed rapidly within 30 to 40 seconds.

The working time varies from 2 to 5 minutes at The working time varies from 2 to 5 minutes at room temperature and setting time ranges from 6 room temperature and setting time ranges from 6 to 9 minutes at 37 degree centigrade.to 9 minutes at 37 degree centigrade.

The powder should be rapidly incorporated into The powder should be rapidly incorporated into the liquid in large quantities to optimise the the liquid in large quantities to optimise the working and setting time.working and setting time.

The working time of polycarboxylate cement can The working time of polycarboxylate cement can be extended by lowering the temperature of the be extended by lowering the temperature of the mixing slab and storing the powder in a mixing slab and storing the powder in a refrigerator.refrigerator.


Refrigeration of liquid is avoided because gelation Refrigeration of liquid is avoided because gelation may occur from formation of hydrogen bonds.may occur from formation of hydrogen bonds.

The cement mixture should be used while it still The cement mixture should be used while it still has a glossy surface appearance.has a glossy surface appearance.

Although the polycarboxylate cement mixture has Although the polycarboxylate cement mixture has a thicker consistency than that for zinc phosphate a thicker consistency than that for zinc phosphate cement its flows readily when loaded, yielding an cement its flows readily when loaded, yielding an appropriate film thickness of 20 μm. appropriate film thickness of 20 μm.

The fully set cement at 24 hours after mixing has The fully set cement at 24 hours after mixing has compressive strength ranging from 48 to 80 Mpa. compressive strength ranging from 48 to 80 Mpa.

Tensile strength ranging from 8 to 12 MPa. Tensile strength ranging from 8 to 12 MPa. Modulus of elasticity of zinc polycarboxylate Modulus of elasticity of zinc polycarboxylate cement is between 3 to 6 GPa.cement is between 3 to 6 GPa.


Solubility Solubility The solubility of these cements in water is low , The solubility of these cements in water is low ,

ranging between .1 % to .6%by wt. ranging between .1 % to .6%by wt. some products incorporating stannous fluoride some products incorporating stannous fluoride

exhibit higher solubility because of fluoride exhibit higher solubility because of fluoride release .release .

These cements have low resistance to These cements have low resistance to dissolution under acidic conditions such as dissolution under acidic conditions such as lactic acid citric acid.depending upon the pH lactic acid citric acid.depending upon the pH of the environment.of the environment.


BondingBonding These cements are capable of bonding with These cements are capable of bonding with

surfaces of metallic restorations, prostheses surfaces of metallic restorations, prostheses and appliances particularly nickel-and appliances particularly nickel-chromium, silver-palladium and stainless chromium, silver-palladium and stainless steel alloyssteel alloys

DisadvantagesDisadvantages High viscosity.High viscosity. High intraoral solubilityHigh intraoral solubility Short setting time.Short setting time.


Glass inomer cementGlass inomer cement

HistoryHistory Glass ionomer cements was first introduced Glass ionomer cements was first introduced

by Wilson and kent in 1972by Wilson and kent in 1972 It is referred to as polyalkenoate It is referred to as polyalkenoate

cement ,also known as ASPA(Alumino-cement ,also known as ASPA(Alumino-silicate poly acrylate)silicate poly acrylate)


Glass ionomer cements can be classified based Glass ionomer cements can be classified based on use as:on use as:

Type I or luting cements.Glass particle size Type I or luting cements.Glass particle size is 13 to 19 microns.Powder to liquid ratio is is 13 to 19 microns.Powder to liquid ratio is approximately 1.5:1.approximately 1.5:1.

Type II or restorative cements.Particle size Type II or restorative cements.Particle size of upto 50 microns.Powder to liquid ratio is of upto 50 microns.Powder to liquid ratio is approximately 3:1approximately 3:1

Type III. Chemically set liners/bases or pit Type III. Chemically set liners/bases or pit and fissure forms.and fissure forms.

Type IV.Visible light activated liners/basesType IV.Visible light activated liners/baseswww.indiandentalacademy.comwww.indiandentalacademy.com

Glass ionomer cement was introduced to orthodontics in 1986.Glass ionomer cement was introduced to orthodontics in 1986.CompositionComposition GIC powder is an acid soluble Calcium flouroalumino silicate GIC powder is an acid soluble Calcium flouroalumino silicate

glass.glass. Main constituents include silicon dioxide, aluminium Main constituents include silicon dioxide, aluminium

oxide,calcium flouride, aluminium phosphate, aluminium oxide,calcium flouride, aluminium phosphate, aluminium flouride and sodium flouride.flouride and sodium flouride.

The liquid for GIC is an aqueous solutions of polyacrylic acid The liquid for GIC is an aqueous solutions of polyacrylic acid in a concentration of about 50%.in a concentration of about 50%.

The liquid was quite viscous and tended to gel over time.The liquid was quite viscous and tended to gel over time. The other acids were in the form of itaconic acid, maleic acid The other acids were in the form of itaconic acid, maleic acid

and tartaric acid.These acids tend to increase the reactivity of and tartaric acid.These acids tend to increase the reactivity of the liquid, decrease the viscosity and reduce the tendency for the liquid, decrease the viscosity and reduce the tendency for gelation.gelation.

These acids can be freeze dried into powder and added to glass These acids can be freeze dried into powder and added to glass powder or water, to extend the working time.powder or water, to extend the working time.


PropertiesProperties The luting glass ionomer cements have working The luting glass ionomer cements have working

times 3 to 5 minutes and setting time 5 to 9 minutes.times 3 to 5 minutes and setting time 5 to 9 minutes. The water based glass ionomer cements have longer The water based glass ionomer cements have longer

working and setting times compared to polyacid working and setting times compared to polyacid containing cements.containing cements.

The margins of setting cement should be protected The margins of setting cement should be protected from moisture contamination with a varnishfrom moisture contamination with a varnish

Compressive strength ranges between 90 and 140 Compressive strength ranges between 90 and 140 MPa. MPa.

Tensile strength is 6 to 8 MPa. Tensile strength is 6 to 8 MPa. Modulus of elasticity is 3.5 to 4 GPa.Modulus of elasticity is 3.5 to 4 GPa. The flexural strength (9 to 20 MPa) and fracture The flexural strength (9 to 20 MPa) and fracture

toughness are higher for glass ionomer cements than toughness are higher for glass ionomer cements than for all other types of luting cementsfor all other types of luting cements


The solubility in water of the fully set cement is The solubility in water of the fully set cement is considerably lower than that of zinc polycarboxylate considerably lower than that of zinc polycarboxylate and zinc phosphate.and zinc phosphate.

Their early susceptibility to moisture within 4 to 10 Their early susceptibility to moisture within 4 to 10 minutes after the start of mixing is very high.minutes after the start of mixing is very high.

Prior to application of glass ionomer ,the enamel Prior to application of glass ionomer ,the enamel surface for bonding may be conditioned with an surface for bonding may be conditioned with an aqueous solution of polyacrylic acid having a aqueous solution of polyacrylic acid having a concentration in the range of 10 to 40%.concentration in the range of 10 to 40%.

GlC act as a reservoir of fluoride,providing a GlC act as a reservoir of fluoride,providing a possible means to minimise the potential of possible means to minimise the potential of subsurface enamel demineralisation.subsurface enamel demineralisation.

The initially elevated level of fluoride release is The initially elevated level of fluoride release is attributed to higher elution occuring before the attributed to higher elution occuring before the cement has set. the cement,finally attaining a low cement has set. the cement,finally attaining a low constant levelconstant level


Hybrid resin inomersHybrid resin inomers

Since the early 1990's,hybrid resin/glass Since the early 1990's,hybrid resin/glass ionomer products have been introduced for ionomer products have been introduced for clinical purposes.clinical purposes.

They may be categorised as:They may be categorised as: Resin modified glass ionomersResin modified glass ionomers Compomers (polyacid modified resin Compomers (polyacid modified resin

composites)composites) Ionomer modified compositeIonomer modified composite


RESINMODIFIED GLASS IONOMERSRESINMODIFIED GLASS IONOMERS

COMPOSITIONCOMPOSITION

The powder of resin modified glass ionomer cements, consists The powder of resin modified glass ionomer cements, consists of either the glass composition used for conventional glass of either the glass composition used for conventional glass ionomer cements barium aluminosilicate glass is also ionomer cements barium aluminosilicate glass is also incorporated in some products.incorporated in some products.

Significant alteration have been made in the liquid Significant alteration have been made in the liquid component of RMGIC'scomponent of RMGIC's

The most prominent changes are the replacement of water by The most prominent changes are the replacement of water by a water-HEMA (Hydroxyethyl methacrylate)mixture and the a water-HEMA (Hydroxyethyl methacrylate)mixture and the incorporation of photoinitiators or chemical initiators for free incorporation of photoinitiators or chemical initiators for free radical polymerisation.radical polymerisation.

In some products,methacrylate based monomers BisGMA, In some products,methacrylate based monomers BisGMA, TEGDMA and UDMA are added to the polyacrylic acid TEGDMA and UDMA are added to the polyacrylic acid solution ; The final hardening and strengthening is enhanced solution ; The final hardening and strengthening is enhanced by the formation of polycarboxylate salt matrix.by the formation of polycarboxylate salt matrix.


PropertiesProperties Resin modified glass ionomer cements have longer Resin modified glass ionomer cements have longer

working time and undergo rapid setting after light curing.working time and undergo rapid setting after light curing. The desirable film thickness for luting applications may be The desirable film thickness for luting applications may be

obtained with a lower powder to liquid ratio.obtained with a lower powder to liquid ratio. The enamel surface should first be pumiced,rinced and The enamel surface should first be pumiced,rinced and

dried without desiccation taking place.dried without desiccation taking place. The powder should be incorporated into liquid in large The powder should be incorporated into liquid in large

portions and rapid spatulation for 10 seconds is suggested; portions and rapid spatulation for 10 seconds is suggested; the usual working time is upto 20 seconds. the usual working time is upto 20 seconds.

A more rapid rate of strength development for these A more rapid rate of strength development for these materials may be attained by photopolymerisation, which materials may be attained by photopolymerisation, which presumably accelerates the setting process.presumably accelerates the setting process.

RMGIC appear to provide significantly higher bond RMGIC appear to provide significantly higher bond strength than the conventional GIC and a decreased strength than the conventional GIC and a decreased probability for bond failure.probability for bond failure.


The fluoride release from RMGIC has a relatively constant The fluoride release from RMGIC has a relatively constant rate, characterized by a substantially lower initial ion elution rate, characterized by a substantially lower initial ion elution compared to other types of glass ionomer cements.compared to other types of glass ionomer cements.

Resin modified glass ionomer cement demonstrate superior Resin modified glass ionomer cement demonstrate superior compressive and tensile strength, fracture toughness and are compressive and tensile strength, fracture toughness and are more resistant to permanent deformation and dissolution in more resistant to permanent deformation and dissolution in wet environment, even during the early setting stage.wet environment, even during the early setting stage.

A more rapid rate of strength development for these materials A more rapid rate of strength development for these materials may be attained by photopolymerisation, which presumably may be attained by photopolymerisation, which presumably accelerates the setting process.accelerates the setting process.

RMGIC appear to provide significantly higher bond strength RMGIC appear to provide significantly higher bond strength than the conventional GIC and a decreased probability for than the conventional GIC and a decreased probability for bond failure.bond failure.

The fluoride release from RMGIC has a relatively constant The fluoride release from RMGIC has a relatively constant rate, characterized by a substantially lower initial ion elution rate, characterized by a substantially lower initial ion elution compared to other types of glass ionomer cements.compared to other types of glass ionomer cements.


CompomersCompomers These are supplied as anhydrous single pastes and contain These are supplied as anhydrous single pastes and contain

major ingredients of both resin composites and glass major ingredients of both resin composites and glass ionomers,except for water.ionomers,except for water.

Exclusion of water ensures that initial setting occurs only by Exclusion of water ensures that initial setting occurs only by polymerisation and is essential in preventing premature polymerisation and is essential in preventing premature setting of the material in the containersetting of the material in the container

An acid base reaction may occur later as the material absorbs An acid base reaction may occur later as the material absorbs water invivo.This cannot take place without appreciable water invivo.This cannot take place without appreciable water diffusion.water diffusion.

By the time this has occured,the self limiting visible light cure By the time this has occured,the self limiting visible light cure generated network will have a sufficient cross link density to generated network will have a sufficient cross link density to suppress extensive reaction, although the water does provide suppress extensive reaction, although the water does provide a measure of plasticization.a measure of plasticization.

Flouride release is minimal.However strength and ease of Flouride release is minimal.However strength and ease of handling are superiorhandling are superiorwww.indiandentalacademy.comwww.indiandentalacademy.com

IONOMER MODIFIED COMPOSITESIONOMER MODIFIED COMPOSITES These set only by a polymerisation mechanism but These set only by a polymerisation mechanism but

contain ion leachable glasses in an attempt to contain ion leachable glasses in an attempt to achieve flouride release.achieve flouride release.

Developments involving the use of glass ionomers Developments involving the use of glass ionomers as luting agents has been the introduction of self-as luting agents has been the introduction of self-cured hybrid resin/glass ionomer products cured hybrid resin/glass ionomer products

These cements have several advantages compared These cements have several advantages compared to traditional glass ionomer luting agents to traditional glass ionomer luting agents

They have greater tensile strength and are less They have greater tensile strength and are less brittle.brittle.

In addition,they release at least as much flouride In addition,they release at least as much flouride as traditional glass ionomers,are less soluble and as traditional glass ionomers,are less soluble and are less sensitive to moisture contamination and are less sensitive to moisture contamination and desiccation.desiccation.


IONOMER MODIFIED COMPOSITESIONOMER MODIFIED COMPOSITES These set only by a polymerisation mechanism but These set only by a polymerisation mechanism but

contain ion leachable glasses in an attempt to achieve contain ion leachable glasses in an attempt to achieve flouride release.flouride release.

Developments involving the use of glass ionomers as Developments involving the use of glass ionomers as luting agents has been the introduction of self-cured luting agents has been the introduction of self-cured hybrid resin/glass ionomer products hybrid resin/glass ionomer products

These cements have several advantages compared to These cements have several advantages compared to traditional glass ionomer luting agents traditional glass ionomer luting agents

They have greater tensile strength and are less They have greater tensile strength and are less brittle.brittle.

In addition,they release at least as much flouride as In addition,they release at least as much flouride as traditional glass ionomers,are less soluble and are traditional glass ionomers,are less soluble and are less sensitive to moisture contamination and less sensitive to moisture contamination and desiccation.desiccation. www.indiandentalacademy.comwww.indiandentalacademy.com

Impression materialsImpression materials


There are a variety of impression materials There are a variety of impression materials for general dentistry but orthodontic for general dentistry but orthodontic purposespurposes

the routinely used impression materials are the routinely used impression materials are alginate less commonly polyvinylsiloxanesalginate less commonly polyvinylsiloxanes


Alginate hydrocolloidAlginate hydrocolloid

Components:Components:Diatomaceous earthDiatomaceous earthK alginate or Ca alginateK alginate or Ca alginateK sulfateK sulfateNa phosphateNa phosphateAmmonium salts & CLXAmmonium salts & CLXGlycolGlycolOthers Others

FunctionsFunctions FillerFiller Alginate gelAlginate gel Plaster settingPlaster setting RetarderRetarder DisinfectantsDisinfectants Render the powder dust Render the powder dust

lessless Provide taste and colorProvide taste and color


Properties of the impression materials and Properties of the impression materials and relation ship to clinical use relation ship to clinical use

Properties before insertion into the patient Properties before insertion into the patient mouthmouth

Material cost and shelf lifeMaterial cost and shelf life Ease of preparation and use Ease of preparation and use


Properties while in the patients mouthProperties while in the patients mouth

BiocompatibilityBiocompatibility Patient acceptance Patient acceptance Flow Flow Wetting of oral structures Wetting of oral structures Setting dimensional change Setting dimensional change Setting timeSetting time


Properties during the removal from patient Properties during the removal from patient mouth mouth

Flexibility Flexibility Tear strengthTear strength Creep compliance Creep compliance


Properties after removal mouthProperties after removal mouth

Dimensional stability Dimensional stability

Immunity and disinfectionImmunity and disinfection

Compatibility with die materialCompatibility with die material


PolyvinysiloxanePolyvinysiloxane Component FunctionComponent Function Siloxane oligomer Mech & chem. Siloxane oligomer Mech & chem. inertnessinertness Oligomer with for cross linkingOligomer with for cross linking terminal vinyl groupterminal vinyl group

+ Platinum acid crystal Catalyst + Platinum acid crystal Catalyst + Filler Improve the + Filler Improve the handlinghandling


Bonding to non conventional Bonding to non conventional surfacessurfaces


With the ever increasing adult patients With the ever increasing adult patients undergoing orthodontic treatment situations undergoing orthodontic treatment situations arise were many of these patients have arise were many of these patients have restored teeth. Although banding can one restored teeth. Although banding can one alternative for bonding these teeth but alternative for bonding these teeth but sometimes it may become necessary to bond sometimes it may become necessary to bond these teeth for esthetics and better hygiene. these teeth for esthetics and better hygiene. The materials commonly used for restoration The materials commonly used for restoration teeth are ceramics, cast alloys, composites, teeth are ceramics, cast alloys, composites, amalgam restoration, acrylic resins amalgam restoration, acrylic resins


Bonding to ceramicsBonding to ceramics

A variety of ceramic materials are used to restore A variety of ceramic materials are used to restore teeth, it becomes extremely difficult for the teeth, it becomes extremely difficult for the clinician to identify the chemical composition but clinician to identify the chemical composition but what becomes important is the external what becomes important is the external restoration of the ceramic. The principal restoration of the ceramic. The principal veneering material used is leucite containing veneering material used is leucite containing feldspar.. How ever there are other materials like feldspar.. How ever there are other materials like fluorine mica silicate in dicor castable alloy fluorine mica silicate in dicor castable alloy systems .these type of ceramics all the color is systems .these type of ceramics all the color is obtained from the external layer hence can be obtained from the external layer hence can be problematic. All other ceramic achieve there color problematic. All other ceramic achieve there color from the internal ceramic layer.from the internal ceramic layer.


The protocol for bonding the ceramic surfaces is as followsThe protocol for bonding the ceramic surfaces is as follows

The glaze is first removed by sand blasting , using 50 um The glaze is first removed by sand blasting , using 50 um aluminum oxide for 2 to 4 seconds aluminum oxide for 2 to 4 seconds

The ceramic surface is then etched with 9.6% HF acid for two The ceramic surface is then etched with 9.6% HF acid for two minutesminutes

Subsequently followed by two to three layers of silane Subsequently followed by two to three layers of silane coupling agent on the etched surface and followed by drying.coupling agent on the etched surface and followed by drying.

Then two layers of unfilled resins are applied as thin coatingThen two layers of unfilled resins are applied as thin coating Then the bracket is finally bonded to the prepared ceramic Then the bracket is finally bonded to the prepared ceramic

surface with highly filled bisGMA resin.surface with highly filled bisGMA resin. It is said that if the color of ceramic and integrity of the It is said that if the color of ceramic and integrity of the

restorations not to be altered and further chances of restorations not to be altered and further chances of rebonding are there then it is advised not to follow the above rebonding are there then it is advised not to follow the above protocolprotocol


Alternative surface preparation that have Alternative surface preparation that have been found to achieve satisfactory resultsbeen found to achieve satisfactory results

mechanical roughening with stones and mechanical roughening with stones and diamonddiamond

sand blastingsand blasting chemical roughening with hydro fluoric chemical roughening with hydro fluoric

acid acid and chemical coupling with the use of salineand chemical coupling with the use of saline


Bonding to casting alloysBonding to casting alloys A proper surface preparation and special A proper surface preparation and special

adhesives are required for acceptable bonding to adhesives are required for acceptable bonding to the casting alloys. although roughening the surface the casting alloys. although roughening the surface of the alloy with stone increases the bond strength.of the alloy with stone increases the bond strength.

intaoral sand blasters provide better resultsintaoral sand blasters provide better results Research has shown that tin plating the noble Research has shown that tin plating the noble

alloys increases the bond strengthalloys increases the bond strength In the recent years adhesives that chemically bond In the recent years adhesives that chemically bond

to metal surface have been developed. The to metal surface have been developed. The commercial products superbond C & B and C & commercial products superbond C & B and C & B metabond .B metabond .

Other commercial products like panavia EX and Other commercial products like panavia EX and panavia21 and bis-GMApanavia21 and bis-GMA

Intermediate resins are also usedIntermediate resins are also usedwww.indiandentalacademy.comwww.indiandentalacademy.com

Bonding to dental amalgamBonding to dental amalgam Sand blasting of the surface the restoration Sand blasting of the surface the restoration

followed by use of adhesives4-metabis-followed by use of adhesives4-metabis-GMAand intermediate resins improves the GMAand intermediate resins improves the bonding to the dental amalgambonding to the dental amalgam

Bonding to composite resinsBonding to composite resins The uppermost resin composite has to be The uppermost resin composite has to be

removed with a diamond bur then the surface removed with a diamond bur then the surface is etched with37% phosphoric acid.silination is etched with37% phosphoric acid.silination follows before the application of an unfilled follows before the application of an unfilled resin and bondingresin and bonding


Bonding of acrylic resinsBonding of acrylic resins

The surface is first wetted with methyl The surface is first wetted with methyl methacrylate for three minutes then the methacrylate for three minutes then the brackets then can be bonded using a brackets then can be bonded using a bonding agent and resin compositebonding agent and resin composite

Or it can be embedded in a Pmma Or it can be embedded in a Pmma restoration+ Glass ionomer cementsrestoration+ Glass ionomer cements


Dental SolderDental Solder Brazing : it is the joining of metal parts by a Brazing : it is the joining of metal parts by a

filler metal at temperature below the solidus filler metal at temperature below the solidus temparature of the metals being joined and temparature of the metals being joined and above 450 deg cabove 450 deg c

Soldering :it is the joining of metal parts by a Soldering :it is the joining of metal parts by a filler metal at temparature below the solidus filler metal at temparature below the solidus temparature of metals being joined and below temparature of metals being joined and below 450 deg c450 deg c


SolderSolder

Soft solderSoft solder hard solderhard solder

Lead tin alloysLead tin alloys

Not usedNot used

Gold solderGold solder Silver solderSilver solder


Composition Composition Gold solderGold solder Gold:-45 to 81%Gold:-45 to 81% Silver:- 8 to 30 %Silver:- 8 to 30 % Copper :- 7 to 20 %Copper :- 7 to 20 % Tin:- 2 to 4 %Tin:- 2 to 4 %

Silver solder Silver solder Silver:- 10 to 80 %Silver:- 10 to 80 % Copper :- 15 to 50 %Copper :- 15 to 50 % Zinc :- 4 to 32%Zinc :- 4 to 32%


PropertiesProperties These have high melting temperatureThese have high melting temperature Greater strength and hardness Greater strength and hardness


ConclusionConclusionWhether to surrender to the Whether to surrender to the

manufacturer manufacturer

or drive away the bull…..or drive away the bull…..www.indiandentalacademy.comwww.indiandentalacademy.com


www.indiandentalacademy.comwww.indiandentalacademy.comLeader in continuing dental educationLeader in continuing dental education

biomaterials in orthodontics / orthodontic courses by indian dental academy

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