Download - Connectors.ppt
Connectors For Fixed Partial Denture
DefinitionIt is a part of fixed partial denture that joins its individual
units together.
Types1-Rigid :
-The rigid connector is a solid one- It may be casted, welded or soldered.
2-Nonrigid: limited movement between pontic and retainer, stress breaker on the weak abutment
1.Rigid connectors
A- The cast connector the entire bridge cast as one
piece, i.e. a single piece casting. N.B. -disadvantage of single piece casting.-cannot verify individual retainers.-as length of a single piece bridge increases, its inaccuracy also increased
B-The welded connector
depends on melting and fusion
of the adjacent surfaces to be
joined.
N.B-laser welding
•Advantages
•disadvantages
C- The Solder connector
-any bridge larger than three units should be casted in two pieces and then soldered.
Requirements of the dental solder :1- tarnish and corrosion resistance.2- Lower fusing temperature than alloy to be soldered.3- Free flowing through narrow gaps.4-The same color as the alloy to be soldered.
Requirements of an ideal solder joint
The soldering uses:1-Adding proximal contact.2-Repairing casting voids.3-Joining of fixed partial denture units (Bridge assemblage).
Steps of assembly
1.Indexing,
2. Investing.
3. Soldering.
• Factors affecting success of soldering procedure
1- the gap distance between the assembled units.
2- solder alloy selection
3- soldering flux and anti flux
4- soldering investment
5- mode of heat application
1-The gap distance between the assembled units.
-Compensation for solidification shrinkage.
-Capillary attraction for the solder alloy.
• The factors which may be expected to affect the width of solder gap are
- setting expansion of the soldering investment.- Thermal expansion of investment during pre-heating.- Expansion of pontic and retainers during heating and
expansion of these parts when exposed to soldering temperature.
-Type of the alloy used (The space for gold alloy 0.1-0.2mm, for non-precious 0.7mm).
2-Solder alloy selection• Gold solders are classified by fineness and by
carat.• Fineness. • carat.• Solders are also classified into pre-ceramic (used
before application of porcelain) and post ceramic solders (used after application of porcelain).
3- Soldering flux and anti fluxSoldering Flux • Borax glass (Na2B4O7 ).
• All fluxes should be kept from contacting porcelain- veneered surfaces.
Soldering anti flux- placed on a casting before the flux application. -Graphite (from a pencil) ,iron oxide (rouge) in a
suitable solvent.
4-soldering investment• Soldering investments are similar in composition to
casting investments.• Casting investments, both gypsum and phosphate
bonded, mixed with water only, have been used for soldering.
• Soldering investments should ideally contain fused quartz (the lowest thermally expanding form of silica) as their refractory component.
5-Mode of heat application
• Torch soldering “soldering flam”
• Oven soldering.
• Infra red soldering.
• Soldering technique1- building up of deficient proximal contacts or
contours or to repair casting voids in single unit restoration.
2- Investing soldering technique.It used for assembling components of FPD
• 1-adding proximal contacts.
2- Investing soldering technique
•soldering index.• Different materials
could be used for such purpose e.g. plaster, autopolymerizing resin and zinc oxide eugenol impression material.
• C:\Documents and Settings\Home\My Documents\Downloads\Video\investing soldering.flv
II. Non-rigid connectors.
Indications 1-Fixed partial denture with pier abutment
2-When a common path of insertion can't be obtained(Mesial drift of teeth).
3-Complex FPD, where it is easier to replace and repair it, if divided into shorter components, especially in questionable prognosis.
Contraindications:
1-short clinical crown.
2-the teeth that are narrow
bucco-lingual.
3-large pulp horn (young
patient).
4-Unequally distributed
occluding force on all parts
of the fixed-supported
bridge.
Requirements of non rigid connector.I-It should be as small as possible and strong
enough to resist all the forces of mastication without
fracture.
2-It should not impair esthetics.
3-easily cleaned.
4-It should have a high wear resistance .
5-It should apply a minimum amount of stress and
strain on the abutment teeth.
Types of non rigid Connector:According to the shape, the connectors may be:a. Dove tail(key and key-way).b. Split pontic (connector inside the pontic).c. Cross pin and wing.d. Sub occlusal, occlusal in posterior teeth and lingual rest in anterior teeth.
Dove tail connector:
-Components (Key, Key way).
-Location.
-Types:
1-Prefabricated (precision). 2-Laboratory made (semi precision).
1-prefabricated(precision attachment).
2-laboratory made (Semi precision Attachment):
b.Split Pontic:
c- Cross pin and Wing:(Two pieces pontic system)
d.Sub-occlusal Rest
Advantage:-
-normal embrasures
-No interference with occlusion
Disadvantages:– retainers must be placed simultaneously.
Occlusal rest:
Lingual rest:
Advantages of non rigid Connectors.1- Stress breaking of the applied occlusal force.2- Overcoming problems of alignment of two or more abutment teeth have not common path of insertion.
Disadvantages of non rigid connector:
1-excessive reduction of tooth structure
2- The excessive cost.
3-The clinical and laboratory procedures need qualified dentist and technician.
Thank you