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