varnishes liners bases

Varnish, LinersVarnish, Liners AndAnd

BasesBases

Introduction

Pulp is a specialized connective tissue that occupies the pulp chamber .It comprises of nerves ,vessels ,lymph channels etc.

Mainly 4 functions- Formative/Developmental- Nutritive- Sensory- Defensive/Reparative

Knowledge of the size and contour of the pulp cavity is essential during tooth preparation.

If leakage of chemical irritants from biomaterials or bacteria occurs , there causes irritation to pulp.

VARIOUS TYPES OF IRRITANTS-Microbial irritation-Mechanical irritation-Thermal irritation-Chemical irritation-Radiant irritation

• MICROBIAL IRRITATION

Bacteria that survive drying under the filling material remain viable for many years .Such dormant bacteria can become active when moisture is reintroduced as a result of marginal percolation of various filling materials , poor marginal seals improper condensation of fillings etc.

• MECHANICAL AND THERMAL IRRITATION

It depends on

- Speed of rotation

- Size & Shape of bur

- Amount of moisture / water

- Coolant

• CHEMICAL IRRITANTS

They are

- Various filling materials

- Various medicaments used for desensitization or dehydration of dentin

- Dentin sterilizing agents such as phenol, silver nitrate, eugenol etc.

• RADIANT IRRITANTS

X ray radiation, laser beam, uptake of radium containing water cause radiant irritation.

• INFLAMMATION

Is the complex vascular and lymphatic reaction as well as local tissue destruction. Involve macrophages , plasma cells & lymphocytes.

Pulpal irritation leads to pulp inflammation.

INFECTION

Invasion of micro organisms in to the region of injury is called infection.

PULP PROTECTION

• To protect the pulp against those irritants we give

- chemical protection - electrical protection - thermal protection - mechanical protection - pulp medication

OVERVIEWOVERVIEWOF PULPAL PROTECTIONOF PULPAL PROTECTION

PROBLEM = No perfect replacement for missing enamel and dentin.PROBLEM = No perfect replacement for missing enamel and dentin.

NORMAL

1.1. CHEMICAL ProtectionCHEMICAL Protection 2.2. PULPAL MedicationPULPAL Medication

3.3. THERMAL / ELECT ProtectionTHERMAL / ELECT Protection

4.4. MECHANICAL ProtectionMECHANICAL Protection1.1. SOLUTION LINER = thin film (varnish, bonding system, dentin sealer)SOLUTION LINER = thin film (varnish, bonding system, dentin sealer)2.2. Suspension Liner (20-25 Suspension Liner (20-25 m)m)3.3. CEMENT LINER = medium thickness (100-500 CEMENT LINER = medium thickness (100-500 m)m)4.4. CEMENT BASE = thick (500-1000 CEMENT BASE = thick (500-1000 m)m)

PROCEDURE SUMMARYPROCEDURE SUMMARYforfor Medicament, Liner/Base, Varnish/Sealer/DBSMedicament, Liner/Base, Varnish/Sealer/DBS

Restoration

Base

Liner

Cavity Varnish • Cavity varnish is a liner used to seal the dentinal tubules to

help prevent micro leakage and is placed in a cavity to receive amalgam alloy after any bases have been placed.

• Cavity varnish is being used less and less with amalgam restorations, and dentin bonding agents are replacing cavity varnish as the liner of choice.

• Cavity varnish has an organic solvent of ether or chloroform that quickly evaporates, leaving the resin as a thin film over the preparation. This varnish should be slightly thicker than water. If it becomes very thick, discard it.

Cavity VarnishAdvantages :

» Reduces Microleakage around newly placed amalgam restoration

» Reduces passage of irritants into dentinal tubules from overlying restoration or base

» In case of amgm prevents penetration of corrosion products into dentinal tubule thus reduces tooth discoloration

» Used as surface coating over certain restoration to protect from dehydration or contact with oral fluids

» Can be applied over metallic restorations to reduce galvanic shock

COMPOSITION:» Natural gum like copal, rosin or synthetic resin

dissolved in organic solvent such as alcohol, acetone or ether.

» Chlorbutanol, Thymol & eugenol, some contains fluorides

Properties:» Film thickness – 2 to 40 um» They neither provide mechanical strength nor

thermal insulation

» Nearly insoluble in oral fluids

Manipulation

• A small cotton pellet held by cotton forceps is dipped into the varnish just enough to wet the pellet.

• The cavity varnish is applied to the pulpal area, walls of the cavity preparation, and onto the edge of the margins of the preparation. Any excess varnish can be removed from the enamel with a fresh cotton pellet.

• A second application of cavity varnish is placed over the first to thoroughly coat the surfaces of the dentin and fill any voids from bubbles created when the first application dries. After liners and bases are placed into the cavity preparation, the tooth may be restored with materials, such as amalgam, composite resin, or glass ionomer.

Contraindications:» Cavity varnish is not used with composites

since the varnish retards the set of composites and interferes with the bonding of composites.

» Glass Ionomer restorations» Therapeutic action is expected from the

overlying cement. eg: ZOE & Ca(OH)2

Cavity linersCavity liners are aqueous or volatile organic liquid

suspensions or dispersions of zinc oxide or calcium hydroxide liquids that are thinly applied to a cavity surface.

They usually do not have sufficient thickness, hardness or strength to be used alone in a deep cavity.

Liners are formulated to provide - Relief of pulpal inflammation -Facilitation of dentinal bridging for physiologic protection

Types of liners: 1.thin film liners: A . Solution liners: varnishes, 2 - 5 µm thick. B . Suspension liners: 20-25 µm.2.thicker liners: also known as Cement liners: 200-1000 µm (0.2-1mm) used for thermal protection, pulpal medication.

Cavity liners» Used to provide barrier against the passage of irritants from

cement or other restorative materials» To reduce sensitivity of freshly cut dentineCOMPOSITION:» GI or suspension of Ca(OH)2 in an organic liquid such as methyl

ethyl ketone or ethyl alcohol» Calcium hydroxide can be used in extremely deep areas as an

antibacterial agent and/or as a pulp capping material. » They are fluid in consistency can be easily painted over dentinal

surface» The solvent evaporates to leave a thin film residue that protect

the pulp» Ca(OH)2 liners are soluble & should not be applied at the

margins of restorations

• OTHER LINERS

- Type III GIC

- Type IV ZOE

Glass ionomer cavity liner

Fast setting radio opaque versions of conventional GIAdv:» Chemically bond to dentine» Release of F – Anticariogenic» Nearly insoluble in oral fluids» High compressive strength» Injectable liners are available

Disadv:» Sensitive to moisture during application & hardening

process» Time consuming

BASE

A base is a material that is used beneath permanent restorations to encourage recovery of the injured pulp or to protect the pulp from thermal shock, mechanical trauma, toxic ingredients of some restorative materials, galvanic shock and microleakage.

• Bases must have sufficient strength to withstand the forces of mastication and condensation of the permanent restorative material.

• TYPES

- High Strength Bases

Provide thermal protection for pulp & mechanical support for the restoration. Eg:Zn phosphate,Zn poly carboxylate,Glass ionomer,RMGI

Low Strength Bases

Have min strength & rigidity

Act as a barrier to irritating chemicals and to provide therapeutic effect to pulp.

eg: Ca Hydroxide, ZnOE

In case of deep excavation its necessary to overlay CaOH with RMGI or a srong base.

Bases

Materials used

• ZOE

• ZnPolycarboxylate

• Zn PO4

• Glass ionomer cements

Zinc oxideTreatment Restoration. • The most frequent use of zinc oxide and eugenol is as a treatment restoration.

Eugenol is an obtundent (pain-relieving agent)It helps prevent pulpal irritation when set in place for treatment of fractured teeth, lost restorations, advanced caries, or pulpitis. This dental material also exerts a palliative effect on the pulp.

Intermediate Base. • It is used as an intermediate base. This material provides insulation between

metallic restorations and vital tooth structure. Because of the low crushing strength, its use is sometimes contraindicated.

Pulp Capping.

• This material is used in pulp capping for near and direct exposures of the pulp, but this use is declining. Calcium hydroxide is now preferred for pulp capping.

Zinc phosphate

• Film thickness:

• Working time:

»

• Setting time:»

• < 25 microns (um)

• 1.5 - 2 minutes • (each increment 15-20

secs)

• 2.5- 8 minutes» ANSI/ADA NO: 96

Thermal properties:» Good thermal insulator & effective in reducing galvanic

effect

Adhesive properties:» Do not form any chemical bond with enamel or dentine

Biological properties» Initially acidity of cement is quite high due to the

presence of phosphoric acid » Three min after start of mixing pH 3.5 and later rapidly

comes to neutral in 24 to 48 hrs

Optical properties» Set cement is opaque

Zinc phosphate

• Disadvantages:

– pulpal irritation (initial acidity)

– lack of antibacterial action

– brittleness

– lack of adhesion– solubility in oral fluids

Zinc polycarboxylate cement

• 1.5 parts powder to 1 part liquid• Working time approx 2.5 minutes• Film thickness 25 µm• pH of Lqd is 1.5 which rapidly gets neutralized as mix

progresses– Large particle size

Less irritant than ZP

Zn Polycarboxylate Cement

• Advantages– low irritancy (neutral pH)– adhesion to tooth– easy manipulation

• strength tensile 2.4- 4.4 MPa

• solubility (sim zp)– film thickness (sim zp)

• Disadvantages– accurate proportioning– lower compressive

strength 55-67 MPa zp– greater viscoelasticity

6 GPa than zp

Glass Ionomer cements

Properties. • Glass Ionomer cement is free from phosphoric acid and has

very low solubility. • It adheres chemically to enamel and dentin and, readily, to

wet tooth structure, leaving minimal film thickness. • It is well tolerated by the pulp and remains rigid under a load,

exhibiting no creep.• Glass Ionomer possesses high compressive strength.• It releases fluoride ions to tooth structure. It is simple to

proportion, mix, apply, and clean up.