INDEX

INTRODUCTION

TERMINOLOGY

PRINCIPLES OF CONNECTOR DESIGN

CONNECTORS

I. RIGID CONNECTORS

CAST CONNECTORS

SOLDERED CONNECTORS

WELDED CONNECTORS

LOOP CONNECTORS

II. NON-RIGID CONNECTORS

KEY AND KEYWAY

SPLIT PONTIC

CROSS PIN AND WING

CONNECTORS FOR-

1. TEMPORARY RESTORATIONS

2. ALL METALLIC F.P.DS

3. METAL CERAMIC F.P.DS

4. ALL CERAMIC F.P.DS

5. TOOTH IMPLANT SUPPORTED PROSTHESIS

6. SPECIAL SITUATIONS

-PIER ABUTMENTS

-TILTED MOLARS

-CANTILEVERED BRIDGES

CONNECTOR FAILURES AND REMEDIES

CONCLUSION

REFERENCES

1

2

INTRODUCTION

Connectors basically link different parts of fixed partial dentures

(i.e. pontic and retainers). Thus constitute an important part of F.P.D.

Their designing determines the fate of periodontal ligament under

F.P.D. They may be either rigid /non-rigid type of connectors.

TERMINOLOGY

1. Connector- the portion of fixed partial denture that unites the

retainer’s and pontics.

2. Rigid connector: - a cast, soldered /fused union between the

retainers and pontic.

3. Non-rigid connector: - a connector that permits limited movement

between otherwise independent members of a fixed partial denture.

4. Internal connector: - a non-rigid connector of varying geometric

design’s using a matrix to unite the members of a F.P.D.

5. Sub-occlusal connectors: - an interproximal non-rigid connector

positioned apical to and not in communication with the occlusal plane.

6. Soldering: - to unite, bring into/restore to a firm union, the act of

uniting two pieces of metal by the proper alloy of metals.

PRINCIPLES OF CONNECTOR DESIGN

The connector design determines the success of F.P.D to a

certain extent. The factors to be observed while fabricating a

connector are: -

Type of connector

-Rigid connector

-Non-rigid connector.

Size of connector

Shape of connector

3

Type of connectors

1. Rigid connector-they are the ideal choice of connectors for F.P.D’s.

They provide maximum rigidity and accurately transfer occlusal forces

to abutment teeth.

2. Non rigid connector- they are usually used for pier abutments due to

differences in physiologic tooth movement and difference in arch

position of abutment. It provides a scope for flexing of mandible during

opening and closing movements but it is technically sensitive.

Size of connector

The size of connector is important in maintaining the periodontal

health of the abutment teeth. The recommended occusogingival height

of connector is, ideally 3-4 mm. It should be sufficiently large to

prevent distortion /fracture during function. It should not be too large

which interfere with effective plaque control. Pulp size and crown

height (young teeth) may be a problem in designing non-rigid

connector.

Shape of connector

Connector’s should have a concave shape mesiodistally (appear

as meniscus) and

Convex buccolingually4. In cross section it appears as ellipse. For

effective functioning the long axis of ellipse should be parallel to

direction of force, this leads to encroachment of gingival embrasure, so

usually the long axis of ellipse is placed perpendicular to long axis of

force. It should be highly polished.

For anterior teeth connector should be placed lingual and use of

large connector /inappropriately shaped connector result in display of

metal leading to esthetic failure of F.P.D.

CLASSIFICATION OF CONNECTORS

Connectors are basically classified as: -

4

1. Rigid connectors-

Cast connectors

Soldered connectors

Welded connectors

Loop connectors

2. Non rigid connectors

Key & keyway (dovetail)

Split pontic

Cross pin and wing

RIGID CONNECTORS

Cast Connectors

They are commonly used type of connector,

simple in processing.

They are usually indicated for 3-unit F.P.D, full veneer

preparations.

Contraindications: -

1. F.P.D’s more than 3 units

2. Partial veneer F.P.D’s

Preparation: -

Cast connectors are prepared by waxing the interproximal area

before reflowing the margins and investing the pattern. There should

be 1 mm of gap between connector and gingiva.

Disadvantages: -

1. Difficulty in reflowing proximal margins.

2. Access for proximal margins impeded so removal of patterns from

die is difficult.

3. Simple in fabrication but difficult in seating.

5

4. No opportunity to verify fit of individual retainers in mouth.

Precautions in processing of cast connectors:-

1. Any F.P.D greater than 3 units should be cast in 2 piece and

soldered.

2. Use of bench set with thermal expansion is better than hygroscopic

expansion.

3. It is advisable to use large casting ring (60 mm), which produces

more uniform expansion.

4. Investment expansion and pattern distortion can affect fit of

castings.

5. If F.P.D do not seat properly after routine adjustments then: -

- It is better to cut the connector and resolder.

- Cut the pontic and recast the cut parts 21

(J.Prosthet.dent 55(2), 195-197,1986)

Burno Es et all (1985) 9: - studied the accuracy of different length

of multiunit F.P.D cast in a Ceramo-metal gold alloy. They used 3, 4, 5

unit fpds. Initially were prepared as cast, then sectioned and seated

with duralay resin. The vertical marginal discrepancies and dimension

at gingival axial line angle’s were measure before and after. The

mean vertical discrepancy found with as cast specimens were: -

4 units F.P.D – 176 m highest

3 units F.P.D – 20 m lowest.

The greatest amount of opening was found at mesial finish line of

mesial abutment and distal finish line of distal abutment. So the

distortion is not uniform across the fpd. Increased number of units

caused increased amount of mean marginal opening (54,92,105 m).

They advised use of oval casting ring than cylindrical casting ring. 50%

improvement in seating was found after sectioning. And oval casting

ring preferable (uniform expansion) than round casting ring. With

normal casting procedure the castings are larger facio-lingual

6

dimension, less medio-distal dimension(casting contracted mesio-

distally).

Loop Connectors

They are rarely used and indicated when existing diestema is to

be retained. It contains a lingual loop and designing should include

adequate plaque control. Loop is cast using sprue wax /shaped from

platinum-gold –palladium alloy.

Soldered Connectors

Soldering - is joining of 2 metal parts using a filler metal with melting

point <4500 c.

Brazing - is joining of 2 metal parts using a filler metal with melting

point >4500 c

But for theoretical purposes brazing is regarded as soldering.

The most common connector after cast connectors are soldered

connectors. They are commonly indicated for F.P.D’s more than 3

units; when F.P.D’s with cast connectors are exhibiting high marginal

discrepancy, repair of fractured connectors.

Hong So Yang et al(1999): - studied the stress levels in the teeth and

supporting structures of F.P.D and alteration of stress with addition of

multiple abutments (finite element analysis study)

They found that –

1. Increased number of abutments did not solve the mechanical

problems of long span F.P.D.

2. High stress concentration was found at connector (215.8-298.9

kg /cm 2)

3. The connector material should nave high yield strength and rigidity.

4. Connectors in long span fpd’s should be of greater dimensions.

Dental Solders

They are intermediate filler alloy used to join parent metal parts.

7

Requirements of dental solders: -

1. Corrosion resistance (minimum 580 fineness)

2. Lower fusion temperature than alloy (600 less)

3. Non –pitting (pitting occur due to over heating which cause

vaporization of components

5. Strength should be similar to a parent metal.

6. It should have free flow

Silver –increases flow

Copper –decreases flow

High fusion solder –show high flow

Low fusing solder show decreased flow

6. It should have same color as parent metal.

Commonly used dental solders are: -

1) Gold solders-

Composition: -Gold –49-73%-corrosion resistance

Silver –17.5 –9%- flow

Copper –23-12.5%

Tin-4.5-2.5 %

Zinc –6.0- 3.0%

Fineness- 490,585,615,650,730.

If solder is indicated as-

585 fine – fineness of solder

180 carat –to be used with 18-carat parent metal

Pre- ceramic soldering.

Fusion temperature of gold solders –780-8300c

They are commonly used with gold alloys.

2) Silver solder: -

Composition –Silver

Copper

Zinc &cadmium-decrease the fusion temperature.

Fusion temperature is 600-7500 c

8

They are commonly used for base metal alloys.

Soldering Flux (Flow)

They are used to provide a clean surface for soldering and increase

wetting of solder they are available as powder, liquid and pastes.

Types of fluxes: -

1. Surface protective – cover metal surface and prevent access to

oxygen.

2. Reducing agent –reduces any oxides present

3. Solvent –dissolves and carry away any surface oxides present.

Commonly used soldering fluxes are

Borax Flux: -(Na2 B4 O7) it is commonly used for pre soldering, as they

are too fluid in nature. They have type I and II function. They are used

with noble metal alloys due to high affinity for copper

Composition; - Borax glass – 55%

Boric acid –35%

Silica-10%

Fluoride Flux: - They are used with base metal alloys. They are

available as powder, liquid and pastes. They dissolve Co,Cr,Ni oxides

Composition: - Borate

Fluoride.

Soldering Antiflux

They limit spread of solder to unwanted areas.

Commonly used antifluxes are:

Graphite –economical & evaporates at high temperature.

Iron oxide (rouge) +turpentine –it is painted on casting with small bristle

brush.

Soldering Investment

9

Composition of soldering investment is similar to routinely used

gypsum and phosphate-bonded investment. But the refractory

component used is fused quartz (it shows least thermal expansion.-

<0.1% at temp >7000 c.

Heat Source

It is needed to melt the filler metal. Different type of heat

source used are: - 1) Flame

2) Oven

3) Infrared light.

Flame

It is commonly used flame is gas-air/gas –oxygen torch.

Flame temperature indicates the temperature.

Heat content –amount of heat /cubic feet of flame (calories /cubic foot).

Lower heat content indicates need of long time to melt the alloy.

Different types of flame torches: -

1) Gas –air

2) Gas –air

3) multi-orifice.

Always melting is to be done with reducing zone. When gas- air torch

is used to melt solder, metal –ceramic restorations are preheated to

avoid porcelain cracking. To prevent uneven heat distribution flame

should never be concentrated in one area.

Type of fuel used

with oxygen

Flame temperature Heat content

Hydrogen gas 2660 275

Natural gas 2680 1000

Propane 2850 2385

Acetylene 3140 1448

10

Oven

Furnace /oven soldering is done under vacuum /air .the soldering

assembly is placed in horizontal muffle with affixed floor, temperature is

raised above fusion point of solder. Then muffle is opened and solder is

fed unto joint space.

Infrared Soldering

It is used with low fusing connectors, preceramic soldered joints. It

needs specially designed apparatus and requires more processing time.

Connector area of soldering assembly must be positioned precisely

relative to the focal point of the reflector that concentrates the heat,

infrared energy from tungsten iodide lamp –34000 c. the operator

observes soldering procedure through protective dark screen and stops

electric supply once solder flows .the joints produced have similar

strength as conventional soldering.

Gerard .b. et all (1992): - compared accuracy of fit of castings (F.P.Ds)

with as cast connectors and infrared soldering. They found that mean

marginal gap was –

65.2(for cast connectors)

18.9(infrared soldered connector)

it was also observed the F.P.Ds with infrared soldered connectors showed

better fit than as cast connectors and to similar to single retainer

castings .

Soldering

Basic steps of soldering involve –

1. Cleaning and preparing the surface (smoothening done using abrasive

discs) to be joined.

2. Assembling the parts to be joined (gap width).

3. Preparation and fluxing the gap surfaces between the parts.

4. Maintain proper position of parts.

5. Control of time to ensure adequate flow of solder.

11

Factors affecting soldering: -

1. Gap width – an average of 0.2 mm wide gap should be present

between adjacent parts with surfaces parallel to each other. With

increase gap width there is decreased capillary action, decreased

strength due to increased amount of solder. With decreased gap width

there is increase flux inclusion, increased porosities.

2. Flame –reducing zone is to be used for soldering.

3. Temperature –50-600c less than melting point of parent metal. If flow

temperature is very near/higher than solidus temperature of parent

mental it causes alloying and decreased strength. If flow temp is very

low it shows low wetting.

4.time –flame should be used till the solder flows and little tome more to

remove flux on parent metal. If soldered for longer duration it causes

alloying .if done for less time it causes incomplete flow.

Selection Of Soldering Technique

Selection of appropriate soldering technique needs a through

understanding of fusion ranges of all materials involved in F.P.D.

Soldering All-Metallic F.P.Ds

Bade metal alloys are difficult to solder due to easy oxidation of its

elements (silver solders). Mid pontic soldering, recasting of cut parts may

be used to increase strength of joint in base metals. Type III & IV gold

retainers are soldered –using gold solders (615 –650 fine) and gas-air

torch /furnace.

Metal-Ceramic F.P.Ds

Soldering of metal –ceramic restorations involves two techniques: -

1) Pre-ceramic soldering

2) Post-ceramic soldering.

Pre-Ceramic Soldering

12

The procedure of soldering before application of porcelain .it mainly

needs gas-oxygen torch. The main advantages are metal try-in can be

done in unglazed state; proximal embrasure in porcelain can be

adjusted. Its main disadvantage is when porcelain is applied to long

structure; the framework should have high sag resistance. High

palladium alloy and base metals have high sag resistance. But gold

alloys have a low sag resistance.

Post-Ceramic Soldering

It involves soldering done after porcelain application and glazing. It is

done using gas-air torch. Its main disadvantages is, if contour

correction of porcelain is needed the joint has to be separated.

Soldering All-Metallic F.P.Ds

Indexing -maintains the relationship between parts of F.P.D till soldering

investment is done. Various materials used are plaster, sticky wax, auto

polymerizing acrylic resin (cause polymerization shrinkage), 4-meta,

ZnO-eugenol, Polyether, polyvinyl siloxane polymer (putty).

Harper r j et al (1979) 25: - determined the accuracy of different indexing

materials. They reported that ZnO Eugenol indexing system produced a

narrow range and significantly smallest mean distortion than other

indexing system. Mean distortion than other indexing system (in mm): -

ZOE:- 0.033

Polyether –0.052

Plaster 0.061

Stone 0.055

Sticky wax 0.088

Acrylic resin:-0. 052

After wax pattern is prepared and casted, they are finished properly, the

temporary restoration is removed and the parts of F.P.D are checked in

mouth for individual fit and occlusion is corrected. Then using pop as

index material index is prepared.

Indexing

13

A two-piece casting can be used to fabricate a fixed partial denture

with a solid pontic; such as a hygienic .The technique described is used

for soldering three unit posterior fixed partial dentures. The pontic is cast

with the smaller retainer. Then the retainer- pontic unit is soldered to the

larger retainer, utilizing an index of the relationship of the fixed partial

denture components in the patient’s mouth. This provides for the most

accurate relationship between the retainers and between the retainers

and between each retainer and its abutment tooth. The index must

accurately maintain that relationship until the parts if the fixed partial

denture have been embedded in soldering investment. Numerous

materials have been described for transferring the relationship of the

fixed partial denture components from mouth to laboratory bench;

plaster, sticky wax, auto polymerizing acrylic resin (duralay); 4-META

adhesive resin and zinc oxide- Eugenol, which has been shown to be a

highly accurate material for indexing. If plaster is used, the most

accurate and consistent results will be obtained if the castings are not

removed from the index prior to investing. Resin indices are as accurate

as those made of plaster if the components are separated from and

reseated in the plaster. However excess bulk of a resin index will

diminish accuracy because of additional polymerization shrinkage.

Procedure

Remove the provisional restoration from the patient’s mouth and make

certain that there are no traces of temporary cement left on the tooth

preparations. Try in the single retainer first and then the retainer- pontic

combination. On the first try in for each, do not leave the other unit in

place. Verify the marginal fit of each retainer first. Make sure that there

is a small gap between the pontic and the retainer to which it has not yet

been soldered. Adjust the occlusion wit green stones or other

appropriate abrasives. Perform preliminary finishing procedures on the

retainer margins, if they are accessible. Smooth off the occlusal surface

with a rubber sulci disc. The rough surface left on the casting by a

greenstone index. Into polish the castings at this point, since polishing

14

rouge is iron oxide a specific anti-flux for soldering. Mix a small amount

of fast setting impression plaster. Place it on a plastic index tray or a

thoroughly wet tongue depressor. Arrange the index material on the

carrier so that sharp ridge of material runs the length of the depressor or

tray. This ridge facilities getting index material into the central grooves

of the casting. Carefully position the index on the occlusal surface of the

castings, vibrating gently as you seat it. When the material has set

remove the index. If the casings come out with it so much the better. A

plaster index is most accurate when the crowns stay in it. Carefully trims

it with a laboratory knife with a no.25 blade so that all margins are

exposed by at least 1.0 mm. The index should extend at least 3 mm

easily and distally past the crowns being soldered. This guarantees a

symmetric Uniform bulk of investment surrounding the units to be

soldered and should minimize distortion .the plaster index should be

approximately 6mm thick.

If the crowns separate from the index when it is removed from the cast,

trim off excess that might prevent the casting from seating completely

back into the imprints. Trim the area around the imprints enough so that

a substantial part of the axial walls will be covered by investment. Then

clean the index thoroughly with compressed air .the slightest bit of

debris between the index and crown will keep the crown from seating in

the index and will make the relationship inaccurate. Scrub the occlusal

surface of the crowns and clean them in the ultrasonic cleaner before

repositioning them in the index. Place the index on the bench and

carefully try the castings in their respective imprints. If the castings

touch there is a likelihood of increased distortion. For this reason, it has

been suggested that there be a gap of at least .005 inch between the

pontic and the retainer. A conflict arises in determining the proper gap

dimension for a solder joint. The wider the solder joint gap, the stronger

the joint apparently because there is less porosity in the joint. Therefore

a gap width of .012 inch is recommended for strength.

15

In another study, however it was determined that increased gap width

produced an increase in distortion. A gap width of .006 inch is

recommended for some greatest accuracy. Obviously there is a need for

some compromise. A gap width of .008 inch would appear to be optimum

since it is intermediate between the narrow in distorted joint and the

wide string joint. Indeed some investigators have used this distance as a

standard. Furthermore, it can be determined easily by inserting a

business card into the gap , since the average business card is 0.008

inch thick.

The opposing surfaces of the retainer and pontic on either side of the

solder joint should parallel and each other. In these surfaces diverge; the

resulting wedge shape of the solder joint may produce distortion. In

addition wherever there is contact, there will be harder to solder since

capillary action is more difficult to achieve .as a result, solder will be

more likely to stick to one surface or the other, instead of filing the gap

and adhering to both surfaces.

Investing

Pontics and retainers that have come off the index should be luted

back on the index with sticky wax. It is often necessary to use a no.8 bur

to cut small ‘well’ on the facial and lingual edges of each imprint in the

ices. This permits pace for a bulk of sticky wax without forcing it over the

margins. Separate the tongue depressor from the index if they have not

already come apart. Use a cast trimmer to remove excess from the edge

of the index, leaving approximately 3.0mm all around the perimeter.

Allow the index to dry, and apply sticky wax to each casting using the

PKT no.1 instrument. Do not allow the sticky wax to cover occlusal

margins (if any) on the facial surfaces. Flow utility wax into the joint with

a PKT no.2 instrument to prevent the joint area from being filled with

investment. The waxed area should be slightly larger than the solder

joint will be. Any margin covered by wax at this point will not be covered

by soldering investment. This could cause the margin to melt when

heated by the bow pipe during soldering. Run a triangular-shaped

16

extension of utility wax from the lingual side of the solder joint area of

the index. There should be a slightly smaller one on the facial. These wax

wedges will be narrow in the solder joint area than at the edge of the

index. Check again to make sure that the castings are completely

seated.

A separating medium (super-sep, err dental manufacturing co,

Romulus, MI) may be painted over the index outside the castings to

insure easy separation later. Place boxing wax around the index. There

should be 3.0mm of space between the castings and the boxing wax. Mix

a small amount of soldering investment. Paint into the castings and

carefully vibrate it into the castings and carefully vibrate it into the

boxed area. Hold the index so that there is a finger between it and the

vibrator. Overzealous vibrating could jar one of the castings loose.

Allow the investment to set for 1 hr and then remove the boxing wax.

Run hot water over the investment and index to soften the sticky wax.

Separate the index and the investment with a heavy laboratory knife.

Inspect the block of investment containing the fixed partial denture

castings. The investment should measure 2.5cm top to bottom. If it is

more, trim off the excess from the bottom on a cast trimmer. Use of

laboratory knife with ano.25 blade to cut a v- shaped notch buccal and

lingual to the solder joint.

The wax extension placed on the lingual earlier will facilitate this step.

The lingual notch is larger than the facial, because the solder will be fed

into the joint area from the lingual. The facial notch is necessary to gain

access for heating the castings during soldering. If either of these

notches is not placed, an incomplete solder joint is likely to result. Flush

out the remaining wax with boiling water from a boil-out tank. Use a

nop.2 pencil to draw heavy line across the marginal ridges adjacent to

the solder joint area. This will act as an antiflux and will prevent solder

from flowing onto the occlusal surfaces. While the castings are still

warm, add flux paste with an explorer. It will melt, and capillary action

will draw it through the entire solder joint. If flux is applied later when

17

the castings are hot, it will bubble up and stick where it is applied rather

than flowing into the joint where it is needed. Also, surface oxidation

may occur before the protective flux is applied.

Soldering -

the invested castings should be preheated to insure even heating. If

the castings are not preheated, the uneven heat distribution that will

occur when the blowpipe is applied to a cold block may produce

distortion of the finished joint. The investment block can be placed in an

oven and brought from room temperature to 8150c. In an alternative

method of preheating the invested castings, they are set on a tripod and

screen over a fisher burner. Continue to preheat the castings for 10-15

min.

Begin heating with the blowpipe, and brush the flame over the entire

investment block repeatedly until it is so hot that the castings glow red

when the flame is held on throughout this process. Wedge two or three

pieces of solder 2*3mm, covered with flux, into the lingual embrasure of

the joint area. They will be milted by the heat of the castings, and not by

the blowpipe. If too much solder is used, it may run onto the occlusal

surface, and a larger bulk of solder is more likely to produce distortion.

If the blowpipe is used to melt the solder directly the following

difficulties can be expected; the solder will “ball up” and not flow at all,

or it will not flow through the entire joint.

Aim the blowpipe obliquely at the investment, since an obliquely

directed flame results in more even heating and less distortion.

Concentrate the tip of the blue cone on the buccal side of the block near

the open space between retainer and pontic. The solder on the lingual

side of the casting will flow toward the source of heat on the facial. When

the solder starts to flow, direct the torch into the buccal notch and keep

it there while the solder flows through the joint. Leave the flame there a

few seconds longer while the solder shimmers and appears to “ roll” in

the joint. Turn off the flame.

18

Remove the investment block from the tripod with casting tongs and

place it someplace where there is no chance or someone picking it up

and getting burned. The bottom of a casting well is good for this

purpose. If you must place it on a bench top , select an area where there

is little traffic and be sure the surface is heat resistant. Leave a

conspicuous sign to earn off “ lab lizards” who wander around picking up

other people’s work. Do not quench immediately. Quenching shortly

after soldering will produce thermal stresses that will result in distortion.

On the other hand, allowing the investment block to cool slowly to

room temperature may produce excessively recrystallization and grain

growth. The resulting solder joint will be weaker. If the invested fixed

partial denture is allowed to bench cool for 5 minutes and is then

quenched, distortion should be minimized. This allows time for the gold

and solder to respond to an ordering heat treatment, which will increase

hardness and strength while reducing elongation. Place the invested

block in water and remove the investment. That which does not flake off

should be picked off with a sharp instrument and an old toothbrush.

Examine the solder joint to make sure that it is pit free. Evaluate the

size. If it is too bulky, it can be trimmed down with a carborundum disc.

Inadequate bulk or the presence of pits requires reinvestment and

resoldering. Air abrade the castings with 50m aluminum oxide. The

fixed partial denture is ready to be finished and tried in the patient’s

mouth.

Soldering Metal –Ceramic Alloys

Although an effort is made to fabricate metal-ceramic fixed partial

dentures as a single unit. It is sometimes necessary to solder the units

together. This may occur is; 1) there is distortion in a single –piece fixed

partial denture castings; 2) one retainer has inadequate margins and

must be redone; 3) the fixed partial denture length is too great for an

accurate single- piece casting; or 4) type III partial veneer retainers are

used in an other wise metal- ceramic fixed partial denture.

19

If all units of the fixed partial denture requiring soldering are of a

metal- ceramic alloy, the fixed partial denture may be assembled in one

of two ways. Pre-veneer soldering uses a high-fusing solder that is

melted by torch before porcelain is added. Pre-ceramic pontic soldering

allows a diagonal joint through the middle of a pontic, which produces

stronger joints than soldering in the interproximal connector area, and it

is technically easier. In post-veneer soldering, a low-fusing solder is

molted in the oven after porcelain has been baked on the fixed partial

denture. Post-ceramic soldering compensates for any tooth movement in

the mouth between final impression and restoration and it eliminates the

significance of any distortion that might occur during porcelain firing.

If the fixed partial denture includes a type III gold alloy retainer, it can

be assembled only by post-veneer soldering. The high temperatures

reached during the porcelain firing cycle would melt the type III gold

alloy if it were soldered to the fixed partial denture before the porcelain

and been added.

For many years, soldering was done with a gas- air blowpipe. With the

development metal-ceramic restorations, a need for oven soldering

developed. Oven soldered post-veneer solder joints are at least as strong

as torch-soldered pre-veneer solder joints, and several investigators

found that post-veneer joints to be stronger. Certainly, post-veneer

soldering does present special problems. Soldering investment, flux, and

solder just be kept from contacting the porcelain to prevent discoloration

or fracture of the porcelain.

In recent years a third method of soldering has been developed that

utilized as infrared soldering machine. The device focuses a

concentrated beam of infrared energy from a tungsten iodine lamp that

operates at 3,4000 c in a closed chamber in porosity and strength have

been found between torch-soldered and infrared-soldered joints although

infrared soldering has been found to require more time than torch

soldering.

Pre-veneer Metal-Ceramic Alloy Soldering

20

Although some investigators have found post-veneer to be stronger

than pre-veneer solder joints. Pre-veneer soldering remains more

popular with ceramists. This is because post-veneer soldering takes more

time, skill and attention to detail to keep the investment, flux and solder

from touching porcelain, which in turn can require the reapplication of

porcelain and resoldering. The apparent superiority of the post-veneer

solder joints also may be offset by the fact that unlike the standardized

joint size in the laboratory studies clinical post-veneer joints frequently

are smaller because of the ceramist’s fear of causing damage to the

ceramic by contacting it with solder.

The example demonstrated her is of a six-unit metal-ceramic fixed

partial denture with two retainers at one end, fabricated as a five-unit

FPD’S (canine to lateral incisor ) with the second retainer, a canine,

made separately to facilitate margination of the proximal surfaces of the

contiguous retainers. These restorations should be fabricated so that

there will be parallel surface in the solder joint area, with adequate

separation for a solder joint with optimum strength and minimum

distortion.

To accurately transfer the segments to be joined to the laboratory

bench, tack them together with an auto polymerizing acrylic resin index.

Place monomer and polymer in separate dappen dishes or medicine

cups. Make sure that the segments of the fpd are completely seated and

stable in the mouth, if one is not stable; hold it down with a finger. Dry

the area with compressed air and isolate it with cotton rolls. Use a

disposable brush to apply a few drops of monomer between the two

retainers. Then dip the brush in polymer and apply a small amount of

powder to the joint. Continue alternating small quantities of liquid and

powder, making sure that the material between the retainers is always

wet. Build the index as that it extends onto adjacent surfaces of the two

retainers.

Make a backup plaster index on a tongue depressor. Mix quick-setting

plaster and place it on wet depressor, creating a ridge of plaster that

21

extends the length of the tongue depressor. Apply it to the teeth while

plaster is still fluid. If any cracks appear in the plaster, remove the

material, wash the FPD thoroughly, and remake the index. Hold the index

until the plaster is completely set index. Hold the index until the plaster

is completely set. If left untended, it could shift or slip, necessitating a

remake. Remove the index along the path of insertion of the abutment

preparations. Examine it thoroughly to see if the components are

securely embedded.

Carve the surface of the index surrounding the fpd exposing the

pontics and retainers. Very carefully expose each pontic and retainer.

Cut around, but do not disturb the resin. If the components are still firmly

embedded in the plaster, they can be left there and invested from the

plaster index using the technique previously described. The resin will

serve as filler in the solder joint.

Those who are more experienced at soldering may prefer to lift the

components from the plaster. If the resin remains intact, mix some

investment and gently vibrate it into the retainers. Use your fingers as a

cushion between the vibrator and the fpd components. Place a quantity

of investment large enough to contain the fpd on a ceramic or hard resin

tile.

Invert the framework, whose retainers and filled with investment, and

place it into the top of the soft mound of the investment. With light finger

pressure, partially submerge the luted- together castings into the

investment; the incisal half of the castings (approximately) should

protrude from the investment. Add a little investment over the units that

will not be directly involved in soldering. Allow the investment to set

hard. When it does, trim the periphery to produce a near-even bulk of

investment around the castings. Preheat the invested castings in a

burnout furnace at 650-8150c. When the invested block has reached the

desired temperature, use casting tongs to transfer it to the mesh or

some other area that will not be damaged by flame. Several 2*3 mm

pieces of solder in a hemostat can be fed into the embrasure after it gets

22

hot. The solder used should have melting range within 1,050-1,1500c.

Brush the investment with a gas-oxygen flame until the block glows if

the flame is held in one spot for a few seconds. Hold the flame on the

lingual surface of the block of investment. Then direct the torch into the

lingual notch, as solder is red into the facial notch. Heat will draw the

solder through joint area.

Remove the soldered FPD from the tripod and place it in a casting well

or some other safe place where someone will not be able to touch it and

be burned, when it has cooled to room temperature, break the

investment by pickling it up with casting tongs and tapping it on the

bottom of the casting well or a heat resistant bench top. Retrieve the fpd

from among the bits of soldering investment and clean it up. Air abrade

the surface 50m aluminum oxide.

When the restoration is tried in all margins should be closed without

any special force needing to be applied anywhere. Check for any

encroachment on the interdental papilla on the facial or especially on the

lingual; aspect. If there is any, remove the restoration from the mouth

and relieve the affected area.

Post-veneer Metal-Ceramic Alloy Soldering

The technique that follows is for the soldering of a gold-palladium

alloy. All phases of the porcelain addition, including glazing, must be

completed before the soldering process. The solder has a melting range

of 710-7400c and it is used with flux.

Try the units in the mouth and make whatever adjustments are

necessary. This technique is often employed without prior intent; i.e. a

fixed partial denture is carried to completion in expectation of cementing

it without any type of try-in, only to find that it does not seat. The best

joint esthetically, strength wise, or both, is selected for separation, using

a very thin (0.009 in 0r 0.23 mm) disk.

Remove the fpd from the mouth, cut the joint using the disk on a lathe.

This allows the use of both hands to hold the fpd, and the disks are very

easily broken. After separation of the two parts of the prosthesis, try the

23

retainers in the mouth to see if they fit individually. If they do, continue

with the soldering procedure. A soldering index can be made of quick-

setting impression plaster, resin, or zinc oxide-Eugenol bite registration

paste as previously described.

Finish those areas of the crown that are to be soldered with extra-fine

sandpaper discs. Use no rouge or polishing compounds. Outline the area

to be soldered with ano.2 pencil, which will serve as an antiflux. Reseat

the components of the fixed partial denture in the mouth. With the two

parts of the fpd firmly seated, pour monomer and polymer into separate

containers. Dry the area with compressed air and isolate it with cotton

rolls. Use a disposable brush to apply monomer between the retainer and

the pontic.

Next dip the brush in polymer and apply a small amount to the joint.

Continue alternating small quantities of liquid and powder, making sure

that the material between the retainer and the pontic is always wet.

Build the index so that it extends onto adjacent surfaces of the two

castings.

Fabricate a secondary plaster index on a tongue depressor. Arrange

quick –setting plaster on a wet depressor, making a ridge of plaster that

extends the length of the length of the tongue depressor. Apply it to the

teeth while the plaster is fluid. Stabilize the index until the plaster is

completely set. Remove the index along the path of insertion of the

abutment preparations.

Carve the surface of the index around the fpd components, creating a

flat surface with shallow imprints. Rearrange the parts of the fpd on the

plaster index. if the resin index has come loose, make sure that it is back

in place between segments of the fpd, without any spaces. Squeeze a

cyanoacrylate liquid resin in and around the joint while holding the parts

securely. Then spray the zapit accelerator over the joint. Zapit is the

material of choice when indexing on a cast in the laboratory, but it

should not be used in oral cavity because it’s safety has not been

proven. Duralay is the material of choice for use in the mouth.

24

To prevent investment from contaminating the ceramic veneer

covering mush of the fixed partial denture, place a 1.0mm thick layer of

ivory wax over the gingival one half to two-thirds of the facial surfaces of

the retainers and pontic. The wax for this step and those following should

overlap the metal by 1.0mm. Turn the restoration over and apply a coat

of wax to the gingival and lingual aspects of the pontic. Be sure to apply

wax to any exposed ceramic that is part of a porcelain shoulder , add

wax to the joint area to insure access for the solder after the restoration

has been invested.

Mix a small amount of soldering investment and carefully vibrate it into

the crowns are filled completely with investment. Since this is the major

support for the crowns in the block, avoid vibrating the castings directly

to prevent the cr0wn from being loosened. Build a mound of investment

on a flat surface and set the inverted margins first, into the investment.

Push up a ridge of investment with a spatula to cover most of the lingual

surfaces of the retainers and pontic,

When the investment has set, trim it to within 30.mm of the castings.

Create a wide bevel around the entire periphery of the invested block

with a laboratory knife equipped with a no.25 blade. Then carve a v-

shaped notch on the lingual aspect to insure adequate access to the

solder joint. Flush out the wax with boiling water. When the fps was

embedded in investment, the wax prevented contact between

investment and porcelain. After the wax has been removed, there is a

space surrounding the porcelain, including any all-porcelain shoulders.

Place the invested castings in front of a porcelain oven to warm slowly

for 10 minutes. Open the muffle of the oven and warm the castings for 5/

or more minutes.

Add a couple of 2*3mm pieces of fluxed solder to the solder joint,

making surf that they contact only the metal framework of the fixed

partial denture. Place the castings in the oven, turn on the vacuum, and

raise the temperature to 8150c at the rate of 420c/min. check the castings

for completion of soldering. If the solder has not yet fused, continue

25

raising the temperature in the oven until it reaches 8700c. The final

temperature used will vary with different solders. Be sure to use the

solder recommended by the manufactures for the specific ally being

used.

Break the vacuum and remove the invested fixed partial denture from

the oven. Allow the casting to cool to room temperature. The castings

cannot be quenched, as the porcelain may fracture. When the fixed

partial denture has cooled, remove the investment. Cover the porcelain

with masking tape and air abrade the fpd.

Soldering can be done on abase metal fixed partial denture with gold

solder n a manner similar to that used for gold-palladium metal-ceramic

alloys. While restorations of base metal alloys can be soldered, they tend

to be quite technique sensitive, with variable results. Overheating of the

metal substrate and excessive flux have been faults, while others have

blamed surface oxides. Closed vacuum furnaces were suggested as a

solution for this problem and testing by lima verds and stein confirmed

that soldering under vacuum resulted in mean tensile strengths that

were as much as 40% greater than those soldered in air. High and low-

temperature solders are capable of producing joints with adequate

tensile strength that will not lose that strength in a corrosive

environment. Gold solder use with high resistance nickel-chromium alloy

prevents corrosion. While silver solder use on the same alloy permits

corrosion. Silver solder joints become porous from corrosion along the

interface between the solder and the nickel-chromium substrate. This

does not occur with gold solder.

Welded connectors

In 1967 orange memorial hospital was started at Florida, 1970 Gordon

te28 1st demonstrated use of laser welding form fpd’s, using neodymium

lasers. They found that the results were satisfactory.

26

CPTI: - Forms an o2 layer at higher temperature. So soldering is

ineffective. Laser welding has low thermal influence on parts and is

effective. High power neodymium laser with very high power is used.

Parts:-

Glove-hax –laser tip.

Argon gas source.

Stereomicroscope with lens cross hairs for precise alignment of laser

beam.

They have a maximum penetration depth of 2.5mm. They do not cause

damage to ceramic /polymer material.

J d Preston et al (1975) 18: - studied the laser fusion of selected dental

casting alloys. He evaluated the optimum energy levels needed for

fusing ceramic compatible alloys

Precious alloys- (C) a

Non-precious alloy - (U) a

Type III gold alloy – (F) a

They found that laser fusion of non-precious alloys could yield union that

is superior to those in a conventional manner. The tensile strength of

joints by laser > conventional soldering. The laser used was neodymium

glass laser unit.

The energy values were-

(C) a- 4 joules / 6msec.

(U) a- 4jooules / 4msec.

Sjogren g et al (1980) 9: - studied effect of laser on titanium properties

and found decrease in % elongation and increase in tensile strength.

NON RIGID CONNECTORS

There are several situations when rigid connectors are not suitable. Then

non-rigid connectors are to be used. They are mainly indicated when two

abutments cannot be prepared for common path of insertion, for 5-unit

fpd with a pier abutment and if one of designated abutment has good

27

gold cast restoration and key and can be used. But are mainly

contraindicated when the abutment tooth show significant mobility.

Douglas Clark et al (1989) 15 advised the use of non-rigid connectors

following periodontal therapy. The loss of attachment increase crown:

root ratio and tooth mobility due to bone loss. Anterior teeth show

increase movement in buccolingual movement than mesiodistal

direction. Maxillary canine have shown good prognosis after periodontal

treatment. And can be use as abutment using non-rigid connectors.

Goodkind r j et al (1973) 17: - “mandibular flexure in opening and

closing movements”.

Studied the amount of mandibular flexural that occurs during

mandibular movement. It was found that mandible width decreased

during wide opening movements. The mean amount of flexure was

0.0768mm in 2nd molar region and 0.0316 mm in 1st bicuspid region. This

defines the need to use non-rigid connector in FPD connecting anterior

and posterior mandibualr segments.

There are different types of non-rigid connectors: -

1. Key and keyway- precision attachment.

- Semi-precious attachment.

2. Split pontic.

3. Cross pin and wing.

Key and keyway

When a fixed partial denture is fabricated with a non-rigid connector, it is

necessary to align the path of insertion of the keyway with that of the

distal abutment. This technique is best suited for relieving stress at mid

span on long pontics.

The wax pattern for the retainer on the pier abutment is fabricated on

the working cast. When a plastic pattern is used for the key and keyway,

a deep box form is carved into the distal surface of the wax pattern to

28

create space for the placement of the plastic keyway pattern. Adequate

depth and a parallel path of insertion are essential when preparing the

box form in the distal of this abutment.

Place the working cast, with the wax pattern seated, on the table of a

surveyor. Assemble the key and keyway portions of the connector, and

lock the mandrel that extends from the top of the key portion of the

pattern into the vertical spindle of the surveying instrument. Manipulate

the surveying instrument. Manipulate the surveyor table until the

mandrel and attachments are parallel with the path of insertion of the

distal preparation. Then lower the plastic pattern to the middle retainer

wax pattern and lute it in place with sticky was. Remove the key portion

and complete the middle retainer wax pattern by blending the distal

surface with the keyway.

The pattern is then invested, burned out, and cast. After the casting has

been cleaned and air abraded, carefully cut off any part of the keyway

portion of the attachment that protrudes above the occlusal surface.

Place the casting on the working cast, and place the prefabricated plastic

pattern for the key into the keyway. T this point the pontic wax pattern is

attached to the pontic key. The pontic pattern is completed, removed

from the working cast, invested, burned out and cast. After the casting is

recovered from the investment, the mandrel and any excess on the top

portion of the key are carefully reduced so the key and keyway are flush.

For a semiprecious attachment, the wax pattern for the middle retainer

is first completed. Cut a keyway or t- shaped preparation in the distal

surface of the wax pattern with a no-170l bur. The path of insertion of

the keyway can be checked against the path of insertion of the tooth

preparation for the distal retainer by use of a surveyor or by visual

examination. After the prepared wax pattern has been cast in gold,

return it to the working cast. Refine and finish the tapered keyway

preparation in the casting with and no.169 l or no.170 l bur. lubricate the

casting and form the key by placing acrylic resin in the keyway. After the

acrylic key has polymerized, attach it to the wax pontic. The pontic wax

29

pattern, incorporating the resin key, is then removed, invested, burned

out, and cast. Because a precise fit is essential to prevent undue

movement and stress in this ling-span fixed partial denture, the rigid

three-unit anterior segment is joined before try-in.

At the time of try-in verify the fir of each individual unit. Then trial set all

of the units; the three-unit anterior combination with the distal pontic

keyed into it, the pier abutment retainer, and the distal retainer. Make a

soldering index of all the units with zinc oxide –Eugenol bite registration

paste or fast-setting impression plaster. Place the distal two units in their

respective imprints and invest for soldering.

Try in the finished soldering components in the mouth again at a

subsequent appointment and make occlusal adjustments if necessary.

When the restoration is cemented, place the mesial three-unit portion

immediately afterward. No cement should be placed in the keyway.

Moulding m b (1992) 10: - “An alternate orientation of non-rigid

connector in FPD”.

Conventional orientation: - keyway within distal surface of anterior

retainer of mesial segment. Keyway opening on occlusal surface with

taper diverging occlusally. The mesial segment is delivered 1st and then

distal segment is seated with the key sliding in the keyway of the

anterior retainer.

The main disadvantage of this system is need of increased tooth

reduction on distal surface of anterior abutment/ leads to over

contouring of distal surface of mesial retainer.

The author described an alternative orientation by reversing key and

keyway. Key is attached to distal surface of anterior retainer and is

inverted so that it taper converges occlusaly. The keyway is also inverted

and incorporated in the mesial surface of the pontic, with the pontic; the

mesial segment is seated first at delivery followed by distal segment,

with the keyway sliding over the key of the anterior retainer.

Advantages: -

30

1) Conservative tooth preparation: - as key is place extracoronally,

improves retention, stability and maintain pulpal integrity.

2) Physiologic axial contour: - prevents over contouring of distalaxial

surface of anterior retain. A flat emergence profile and physiologic

contour of gingival 1/3rd can be developed.

3) Flexibility of angulations: - the problem of paralleling the non-rigid

connector to a mesially inclined posterior abutment can be resulted with

the inverted orientation. The key is cantilevered distally on a structure of

metal that becomes the connector and the keyway is positioned more

distally within the pontic. This inverted orientation allows more flexibility

in positioning the angled connector while maintaining the desired

embrasure facially, lingually and gingivally. The principles of biologic

contours are then realized with physiologic emergence angles.

4) Esthetic potential- inverted orientation of non-rigid connection can

be more esthetically pleasing in PFM FPD’S. Since the keyway opening is

open the tissue surface of pontic the only visual evidence do the

connector is the interface between the metal guiding planes of the two

segments. This surface can be concealed by placing the guide planes at

occlusal embrasure between the retainer and pontic. However, with

porcelain coverage. Caution must be exercised to ensure that no contact

occurs between the porcelain of the 2 segments. The porcelain can

fracture as a result of shear stresses because of the slight unavoidable

movement of the non-rigid connector

Moulding (1998) demonstrated no significant difference exists in stress

patterns with reverse orientation of key and keyway with photoelastic

analysis study.

Disadvantage- the opening of key and key-way, the porcelain metal

junction are positioned on tissue surface of pontic with tissue- containing

pontics the sprue between the key and the keyway is an area for plaque

retention and resultant tissue irritation. This can be avoided b use non

tissue-contacting pontic.

Pier abutments: -

31

Moulding m b et al (1988) 8: - “photo elastic analysis of supporting

alveolar bone as modified by non-rigid connector”

The study was done to qualitively compare the stress induced in

periodontium of abutment teeth of 5-unit pier abutment fps with non-

rigid connector on stress pattern loading conditions.

The rigid fpd distributed stress vertically and evenly. The non-rigid

distal on canines and non-rigid mesial of molar designs distributed stress

almost similar to rigid fpd. They also resisted rotational movements and

resultant horizontal stress better than other non-rigid designed. The non-

rigid connector at pier abutment showed greater apical and horizontal

stress especially with 1-point loading on the pier.

The pattern of non-rigid connector orientation at distal aspect of pier

abutment has no effect on stress pattern. The placement of non-rigid

connector on least desirable on mesial aspect of pier abutment.

Split pontic

This is an attachment that in placed entirely within the pontic. it is

particularly useful in tilted abutment cases, where the use of a

conventional dovetail would necessitate the preparation of a very drastic

box in the distal aspect of the pier abutment. The wax pattern of the

anterior three-unit segment (mesial retainer-pontic –pier retainer) is

fabricated first, with a distal arm attached to the tissue-contacting area

of a pontic. A surveyor is used to position either the key or the keyway

segment of fpd pattern, pointing occlusally. This segment must align

with the distal abutment preparation.

Invest, burnout and cast the mesial three-and –a-half –unit segment.

After preliminary finishing, seat the cast segment on the working cast.

Place the plastic pattern down into it (if the keyway is in the casting), or

down onto it (if the key was left facing upward on the pontic base). Wax

the distal retainer and the disto-occlusal two-thirds of the pontic pattern.

The pontic can be meta-ceramic, periphery of the ceramic section. Try it

on the prepared teeth I the mouth, making adjustments as necessary.

32

Cement the mesial segment first, followed immediately by the distal

segment. No cement should be placed between the two segments of the

pontic.

Cross-pin and wing

The cross pin and wing are the working elements of a two-piece pontic

system that allows two segments to be rigidly fixed after the retainers

nave been cemented on their respective abutment preparations. The

design will find use primarily in accommodating abutment teeth with

disparate long axes. The path of insertion of each tooth preparation is

made to parallel the long axis of that tooth.

Attach a vertical wing, cut out of a piece of base plate wax, to the

mesial surface of the distal retainer wax pattern. The wing should

parallel the path of insertion of the mesial abutment preparation, extend

out 3.0mm mesially from the distal retainer, have a 1.0mm thickness

faciolingually, be 1.0mm short of the occlusal surface, and have an

undersurface that follows the intended contour of the underside of the

pontic.

Invest, burnout, and cast the distal retainer, with wing. Seat the

retainer on the cast, and drill a 0.7mm hole through the wing with a twist

drill in a hand piece. Place a 0.7mm diameter pencil lead through the

hole and build the wax pattern around the lead and the wing. Remove

the lead, with draw the retainer-pontic wax pattern, and replace the

0.7mm lead in the pontic pattern to maintain the patency of the hole

during investing and casting.

Assemble the two parts of the fixed partial denture on the working

cast. Use a tapered8/0 machinist reamer to ream a smooth, tapered hole

through pontic and wing, following he pilot hole produced by the 0.7mm

pencil lead.Fabricate a pin of the same alloy used for the fixed partial

denture casting. A mold can be made by drilling a hole in apiece of

aluminum with the machinist reamer and filling the hole with auto

polymerizing resin. An impression of the reamer can be made with

polyvinylsiloxane impression material and filled with resin or molten wax.

33

Invest, burnout, and cast it. It must be long enough to extend all the way

through the pontic –wing assembly. Try the pin for fit in the components

on the cast.Cement the retainer with the wing first followed by the

retainer-pontic segment. Seat the pin in the hole with a punch and

mallet. Remove excess length from the pin both facially and lingually. If

it is ever necessary to remove part of this fixed partial denture, the pin

can be taped out and the parts dealt with separately. This technique

requires no special patterns and does allow for a completely rigid

prosthesis when completed.

Connectors for provisional restorations: -

The connectors for provisional restorations should be carefully

fabricated due to the low strength of the material usually used. They

should be slightly overcontoured for increasing strengthening. Decrease

the sharpness at the junction this relieves the stress concentration which

may lead to fatigue failure of restoration. Use high strength materials

such cast metals, heat-processed resin fiber reinforced.

Connectors for all ceramic fpd’s: -

Failure of all ceramic fpd’s was analyzed on model (1995) 12 it was found

that the fracture commonly occurred at core veneer interface (70-78%).

This is mainly due to Hertzian stress state, which is the propagation of

localized contact damage crack system.

Kamposiora p et al (1996) 11 studied the stress concentration of all ceramic posterior fpd’s

maximum stress found was

Material Diameter of connector Maximum stress

Gold 3mm 20.5

4mm 12.7

Dicor 3mm 19.4

4mm 12.5

Inceram 3mm 12.5

4mm 7.0

34

It was found that stress concentration was found more in region of

force applied and at connector region. And stress levels were higher in

3.0mm than in 4.00 mm at connector. Higher stress was found in the

apical region of connector & least in middle part of connector. So they

advised to increase the height of connector to increase the bulk and

have good stress distribution, and have smooth geometry as compared

to angulated geometry in short connectors. It was recommended to use

4*4mm connector size for ceramic 2*3mm for metal.

Connectors for metal ceramic: -

Berger Robert (1989) 16 described the esthetic and physiologic

consideration in metal framework design

The amount of beam distortion 1

L2 * D3

There should be no beam distortion to prevent porcelain fracture. So for

long span fpd’s connectors size should be increased. The interproximal

zone should have adequate span for porcelain and connector placed

lingually.

Connectors for cantilever bridges: -

Hong so yand et al (1996) 13: - stress analysis of a cantilevered fps with

normal and reduced bone support.

Studied the mechanical behavior of a cantilever fpd with normal and

reduced bone support. They found high stress concentrations were found

around the connector of fpd. Design of fpd should be such that occlusal

forces are limited to the connector’s ability to accept them. Greatest

stress was seen in distal cantilevered prosthesis and stress was seen

distal to the most distal retainer and fracture may occur at this location.

Cantilevered fpds should limit to replacement single tooth only and also

use splinting of abutments.

Connectors for tooth implant supported fpd’s: -

Mahamoud h et al (2000) 7 performed a 14 yr comparison of connected

and non-connected tooth-implant fpd’s. The difference in mobility of

tooth (50-200m) and implant (10m). This difference can lead to

35

intrusion of abutment, fracture of abutment teeth, fracture of implant

component, increased marginal bone loss and loss of Osseo integration.

Rangert et al (1997) stated that implant connected to tooth will act as

cantilever.

Cohen s r et al (1994) advocate use of non-rigid connection between

teeth and implants. To limit cantilever forces and direct occlusal loads

axially to the implant.

Modifications of implant system to combat mobility difference:-

1) Imz implants- intra-mobile zylender of polyoxymethelene.

2) Complaint keeper systems with silicon ‘o’ ring.

The study resulted in a finding with no difference between rigid and

non-rigid connection with respect to long-term outcome.

Benefits of connecting teeth to implant: -

1) Some occlusal support and relief of the tooth load on the teeth.

2) Input of periodontal ligament mechanoreceptors.

3) Reduction of the number of implant abutment needed for restoration.

4) Assistance in splinting of teeth.

James v altieri(1995)14 – proposed augmentation of popular tooth –

numbering system addressing pontic, implants and restoration

connector. He described modification in nomenclature of tooth

numbering system to include, tooth supported connected fpd, pontic

implants, implant supported crown. For implant supported fpd

i. i endosseous implant

ii. p pontic`

iii. - (hypen) denotes the connector

CONNECTOR FAILURES

A connector between an abutment retainer and a pontic or between

two pontics can fracture under occlusal forces, failures of both cast and

soldered connections have been observed and are generally caused by

internal porosity that has weakened the metal.

36

When fracture occurs, pontics are placed in a cantilevered relationship

with the retainer casting, and this can allow excessive forces to be

developed on the abutment tooth. For this reason, the prosthesis should

be removed and remade as soon as possible. Occasionally, an inlay like

dovetailed preparation can be developed in the metal to span the

fracture site, and a casting can be cemented to stabilize the prosthesis.

If this is not possible, and a remake cannot be removed by cutting

through the intact connectors. A temporary removable partial denture

can then be inserted to maintain the existing space and satisfy esthetic

requirements.

Modified sanitary pontic design gives optimum connector design with

least gingival irritation. The main causes of connector failure:-

- Improper design

- Weak framework

- Incomplete flow /crystallization of the soldered joints.

- Porosities can result in either soldered/ cast connectors that may

lead to failures.

If abutment castings can be removed, they can be indexed, resoldered

and recemented. If removal is unsuccessful it may be necessary to be

remade some/ all of the units of the restoration. In special situations /

where extensive restorations are involved an innovative techniques may

be used with good results.

David c Appleby(2001)6 : - “repair of fractured connectors in provisional

fpd”.

Fracture connectors cause dislodgement of retainer, occlusal

disharmony, food impaction, esthetic embrassement, and violation all

the stated goals.

Preventive care of fracture:-

1) Increase dimension of connector( rosensteil)

2) Reinforce connector with metal wire/plate

3) Fabricate connector with heat polymerized acrylic resin

4) Acrylic resin reinforce with cast metal substrate.

37

5) Auto polymerizing acrylic resin with cast metal

Common methods for repair broken provision fps connector.

1) Brush paint on technique (bead –brush technique).

2) Slot technique- remove fractured provisional restoration and traces of

provisional cement. Return then back in mouth, mark the location of

adjacent contact on either side of fracture. Remove the provisional

components and prepare a class II preparation in each toot adjacent

to the fracture in the marked area of contact (done extra orally).

Place the parts of restoration back in mouth and fill both cavities

simultaneously with auto polymerizing resin. Then do the finishing

and polishing.

Thaxter k miller, Keith e Thayer (1971) 20: - “described the intraoral

repair of complex cast restorations fracture”

A case report was published who had a fracture between 11 and 21

(pontics) of a complex restoration. The following innovative idea was wth

the following steps.

A special impression tray was fabricated. The area pontic was prepared

for parallel pin repair. Porcelain and gold was removed from gingival 1/3 rd

of lingual surface of fractured area. The depression created 4mm wide,

concave occluso-gingivally extending two teeth on either side of

fractured joint. Depth of 1.5- 1mm in center of concave area no pinholes

are placed at this time.

Secondary impression was made covering prepared area and fractured

joint. Jaw relation record was made and articulation of master cast was

done.

Pin location was determined with 4 pins planned for pontic and on

abutment care was taken to prevent pulp exposure.

A matrix with sleeves / brushings parallel to each other are placed

using mandrel to position than (cold cure matrix) with sticky wax. Drill

holes with hand in master cast with chips of stone dust frequently

cleaned. Matrix is removed. Pins are inserted in master cast holes and

38

resin is poured over all pins and a matrix + pin assembly is recovered

and checked for parallelism. The margins are refined with inlay wax. The

matrix + pin + inlay wax is sprued, casted and finished.

The matrix containing the paralleling sleeve is placed in-patient.

Drilling on pontic and abutment done using Ney’s parallel pin drive

assembly at slow speed. After completely pinholes are made the casted

repair is cemented using zinc phosphate cement.

CONCLUSION

Every part of the prosthesis has its own role in the long-term success.

The connector also plays a vital role in the success of the prosthesis. The

design features of the connector are to be kept in mind while fabricating

the prosthesis. This helps in avoiding long-term complications and

embrassement before the patient.

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41