INTRODUCTION, TERMINOLOGY, INTRODUCTION, TERMINOLOGY,

CLASSIFICATION,CLASSIFICATION,

INDICATIONS& CONTRAINDICATIONS INDICATIONS& CONTRAINDICATIONS

ADVANTAGES& DISADVANTAGESADVANTAGES& DISADVANTAGES

Seminar by H.SUNILSURESHSeminar by H.SUNILSURESH

FIXED PARTIAL FIXED PARTIAL DENTUREDENTURE

DEFINITION:DEFINITION:

Fixed partial denture is a partial denture Fixed partial denture is a partial denture that is luted or otherwise securely that is luted or otherwise securely retained to natural teeth, tooth roots retained to natural teeth, tooth roots and or dental implant abutments that and or dental implant abutments that furnish the primary support for the furnish the primary support for the prosthesesprostheses

CLASSIFICATION OF CLASSIFICATION OF FPDFPD

Conventional and minimal-Conventional and minimal-preparation bridgespreparation bridges::

Conventional bridges involve Conventional bridges involve removing tooth tissue, or a previous removing tooth tissue, or a previous restoration, and replacing it with a restoration, and replacing it with a retainer. This may be destructive of retainer. This may be destructive of tooth tissue and will certainly be time tooth tissue and will certainly be time consuming and expensive.consuming and expensive.

Minimal- preparation bridge involves Minimal- preparation bridge involves attaching pontics via a metal plate to attaching pontics via a metal plate to the unprepared (or minimally the unprepared (or minimally prepared) lingual surfaces of adjacent prepared) lingual surfaces of adjacent teeth. Attachment is made by a teeth. Attachment is made by a composite resin material, obviously composite resin material, obviously these bridges can be used only when these bridges can be used only when the abutment teeth have sufficient the abutment teeth have sufficient intact enamel.intact enamel.

Classification of Fixed partial denture Classification of Fixed partial denture is basically based on theis basically based on the

1. Design of the bridges, the 1. Design of the bridges, the difference being the type of support difference being the type of support provided at each ends of the pontic.provided at each ends of the pontic.

2. Types of materials used for 2. Types of materials used for bridges.bridges.

DESIGNS:DESIGNS:There are four basic designs of There are four basic designs of

bridge, the difference being the type bridge, the difference being the type of support provided at each end of of support provided at each end of the pontic, namely:the pontic, namely:1. FIXED-FIXED BRIDGE1. FIXED-FIXED BRIDGE2.FIXED- MOVABLE BRIDGE2.FIXED- MOVABLE BRIDGE3.CANTILEVER BRIDGE3.CANTILEVER BRIDGE4.SPRING CANTILEVER BRIDGE 4.SPRING CANTILEVER BRIDGE

The four basic designs are the same The four basic designs are the same whether the bridge is a conventional whether the bridge is a conventional or minimal- preparation type. It is or minimal- preparation type. It is possible to combine 2 or more of the possible to combine 2 or more of the four basic designs and to combine four basic designs and to combine conventional and minimal-preparation conventional and minimal-preparation retainers in the same bridge.retainers in the same bridge.

Of the four designs, the first 3 Of the four designs, the first 3 designs may be either conventional designs may be either conventional or minimal-preparation types. It is or minimal-preparation types. It is unusual to have a minimal-unusual to have a minimal-preparation type in spring cantilever preparation type in spring cantilever bridge. bridge.

FOUR BASIC DESIGNSFOUR BASIC DESIGNS1. 1. FIXED-FIXED BRIDGEFIXED-FIXED BRIDGE : :

A Fixed-Fixed bridge has a rigid A Fixed-Fixed bridge has a rigid connector at both ends of the pontic.connector at both ends of the pontic.

The abutment teeth are therefore rigidly The abutment teeth are therefore rigidly

splinted together, and for a conventional splinted together, and for a conventional bridge, must be prepared parallel to bridge, must be prepared parallel to each other so that the bridge, which is a each other so that the bridge, which is a minimum of 3 units, can be cemented in minimum of 3 units, can be cemented in one piece.one piece.

The retainers should have The retainers should have approximately the same retention as approximately the same retention as each other to reduce the risk that each other to reduce the risk that forces applied to the bridge will forces applied to the bridge will dislodge one retainer from its dislodge one retainer from its abutment, leaving the bridge abutment, leaving the bridge suspended from the other abutment.suspended from the other abutment.

To minimize this risk, it is also To minimize this risk, it is also important for the entire occluding important for the entire occluding surfaces of all the abutment teeth for a surfaces of all the abutment teeth for a conventional bridge to be covered by conventional bridge to be covered by the retainers.the retainers.

The opposing teeth cannot then contact The opposing teeth cannot then contact the surface of an abutment tooth, the surface of an abutment tooth, depress it in its socket and break the depress it in its socket and break the cement lute.cement lute.

If this should happen, the retainer will If this should happen, the retainer will not appear loose since it will be held in not appear loose since it will be held in place by the rest of the bridge. However, place by the rest of the bridge. However, oral fluids will enter the space between oral fluids will enter the space between the retainer and the abutment the retainer and the abutment preparation, and caries will rapidly preparation, and caries will rapidly develop.develop.

This rule does not apply to minimal –This rule does not apply to minimal –preparation bridges in which the preparation bridges in which the bond between the retainer and the bond between the retainer and the abutment tooth is much stronger.abutment tooth is much stronger.

However, it is sometimes not strong However, it is sometimes not strong enough, and debonding sometimes enough, and debonding sometimes occur as a result of a mechanism occur as a result of a mechanism described in conventional type. described in conventional type.

2. 2. FIXED- MOVABLE BRIDGE:FIXED- MOVABLE BRIDGE:

A Fixed- movable bridge has a rigid A Fixed- movable bridge has a rigid connector, usually at the distal end of connector, usually at the distal end of the pontic, and a movable connector the pontic, and a movable connector that allows some vertical movement of that allows some vertical movement of the mesial abutment tooth.the mesial abutment tooth.

The movable connector should resist The movable connector should resist both separation of the pontic from the both separation of the pontic from the retainer and lateral movement of the retainer and lateral movement of the pontic.pontic.

Occasionally the fixed and movable Occasionally the fixed and movable connectors are reversed, but this has connectors are reversed, but this has number of disadvantages.number of disadvantages.

The retainer with the movable The retainer with the movable connector (the minor retainer) is connector (the minor retainer) is smaller and less visible and so is better smaller and less visible and so is better in the more anterior abutment tooth. in the more anterior abutment tooth. Posterior teeth commonly tilt mesially, Posterior teeth commonly tilt mesially, and this tends to unseat distal movable and this tends to unseat distal movable connectors, but is resisted by mesial connectors, but is resisted by mesial ones. ones.

The movable connector can be separated The movable connector can be separated before the bridge is cemented, and so the before the bridge is cemented, and so the two parts of the bridge can be cemented two parts of the bridge can be cemented separately.separately.

The abutment teeth do not therefore have The abutment teeth do not therefore have to be prepared parallel to each other and to be prepared parallel to each other and the retention for the minor retainer does not the retention for the minor retainer does not need to be as extensive as for the major need to be as extensive as for the major retainer. Neither does it need full occlusal retainer. Neither does it need full occlusal protection.protection.

Occlusal forces applied to the tooth Occlusal forces applied to the tooth surface not covered by the retainer will surface not covered by the retainer will depress the tooth in its socket, and depress the tooth in its socket, and there will be movement at the movable there will be movement at the movable joint rather than rupturing of the joint rather than rupturing of the cement lute.cement lute.

A fixed- movable minimal- preparation A fixed- movable minimal- preparation bridge cannot have the movable joint bridge cannot have the movable joint within the contour of the original within the contour of the original abutment tooth unless this is prepared abutment tooth unless this is prepared sufficiently for the movable connector, sufficiently for the movable connector, or there is sufficient occlusal clearance, or there is sufficient occlusal clearance, which is sometimes the case following which is sometimes the case following tilting of the minor abutment tooth. tilting of the minor abutment tooth.

The fixed- movable design for The fixed- movable design for minimal- preparation bridges has minimal- preparation bridges has become popular in recent times, and become popular in recent times, and early results suggest that it is more early results suggest that it is more successful than fixed-fixed.successful than fixed-fixed.

This is because it can accommodate This is because it can accommodate individual movement of the individual movement of the abutment teeth and the risk of abutment teeth and the risk of debonding is therefore reduced.debonding is therefore reduced.

3. 3. CANTILEVER BRIDGE:CANTILEVER BRIDGE:

A cantilever bridge provides support for A cantilever bridge provides support for the pontic at one end only. The pontic the pontic at one end only. The pontic may be attached to a single retainer or may be attached to a single retainer or to two or more retainers splinted to two or more retainers splinted together, but has no connection at the together, but has no connection at the other end of the pontic.other end of the pontic.

The abutment tooth or teeth for a The abutment tooth or teeth for a cantilever bridge may be either mesial cantilever bridge may be either mesial or distal to the span, but for small or distal to the span, but for small bridges they are usually distal.bridges they are usually distal.

4.4. SPRING CANTILEVER BRIDGE:SPRING CANTILEVER BRIDGE: Spring cantilever bridges are restricted Spring cantilever bridges are restricted

to the replacement of upper incisor to the replacement of upper incisor teeth. Only one pontic can be supported teeth. Only one pontic can be supported by a spring cantilever bridge.by a spring cantilever bridge.

This is attached to the end of a long This is attached to the end of a long metal arm running high into the palate metal arm running high into the palate and then sweeping down to a rigid and then sweeping down to a rigid connector on the palatal side of a single connector on the palatal side of a single retainer or a pair of splinted retainers.retainer or a pair of splinted retainers.

The arm is made long and fairly thin The arm is made long and fairly thin so that it is springy, but not so thin so that it is springy, but not so thin that it will deform permanently with that it will deform permanently with normal occlusal forces.normal occlusal forces.

Forces applied to the pontic are Forces applied to the pontic are absorbed by the springiness of the absorbed by the springiness of the arm and by displacement of the soft arm and by displacement of the soft tissues of the palate so that tissues of the palate so that excessive leverage forces do not excessive leverage forces do not disturb the abutment teeth.disturb the abutment teeth.

The abutments are usually the two The abutments are usually the two premolar teeth splinted together, or premolar teeth splinted together, or a single premolar or molar tooth.a single premolar or molar tooth.

Spring cantilever bridges are seldom Spring cantilever bridges are seldom made these days and have been made these days and have been replaced either by minimal-preparation replaced either by minimal-preparation bridges or by single-tooth implants.bridges or by single-tooth implants.

The two commonest reasons for The two commonest reasons for making spring cantilever bridges used making spring cantilever bridges used to be to preserve intact anterior teeth to be to preserve intact anterior teeth when posterior teeth needed crowning when posterior teeth needed crowning in any case and also to preserve in any case and also to preserve diastemas between the anterior teeth.diastemas between the anterior teeth.

The four basic designs can be combined The four basic designs can be combined in a variety of ways in particular the fixed-in a variety of ways in particular the fixed-fixed and cantilever designs are often fixed and cantilever designs are often combined. In larger bridges additional combined. In larger bridges additional cantilever pontics may be suspended cantilever pontics may be suspended from the end of a large fixed-fixed from the end of a large fixed-fixed section. Similarly, it is possible to section. Similarly, it is possible to combine fixed-fixed and fixed-movable combine fixed-fixed and fixed-movable designs. designs.

It is possible to combine a bridge with a It is possible to combine a bridge with a removable buccal flange that replaces removable buccal flange that replaces lost alveolar tissue. lost alveolar tissue.

Combination Designs:Combination Designs:

Hybrid designHybrid design This term refers to a bridge with a This term refers to a bridge with a

combination of conventional and combination of conventional and minimal-preparation retainers. minimal-preparation retainers.

There are three different hybrid designs:There are three different hybrid designs: Fixed-fixed with one conventional and Fixed-fixed with one conventional and

one minimal-preparation retainer.one minimal-preparation retainer. Fixed-movable with a minimal-Fixed-movable with a minimal-

preparation retainer carrying the preparation retainer carrying the movable connector.movable connector.

Fixed-movable with the conventional Fixed-movable with the conventional retainer carrying the movable connector.retainer carrying the movable connector.

The first design should not be used and the The first design should not be used and the second only rarely. In either case, if the minimal second only rarely. In either case, if the minimal preparation retainer becomes debonded then it preparation retainer becomes debonded then it will not be possible to re-cement it without will not be possible to re-cement it without removing the conventional retainer, which may removing the conventional retainer, which may well involve destroying the bridge.well involve destroying the bridge.

The third design is acceptable and may well be The third design is acceptable and may well be the one of choice given circumstances in which the one of choice given circumstances in which one of the abutment teeth (usually the mesial one of the abutment teeth (usually the mesial one) already has a restoration that could be one) already has a restoration that could be replaced by means of an inlay or other replaced by means of an inlay or other conventional retainer and the other abutment conventional retainer and the other abutment tooth is unrestored or the restoration does not tooth is unrestored or the restoration does not involve the surfaces to be covered by a involve the surfaces to be covered by a minimal-preparation retainer. These minimal-preparation retainer. These circumstances occur surprisingly often, and so circumstances occur surprisingly often, and so this design of bridge is increasingly being used.this design of bridge is increasingly being used.

Variations:Variations:Removable bridgesRemovable bridges

All the designs described so far are All the designs described so far are permanently cemented in the patient's permanently cemented in the patient's mouth. With large bridges there are mouth. With large bridges there are disadvantages in permanent cementation disadvantages in permanent cementation in that the maintenance and further in that the maintenance and further endoclontic or periodontal treatment of endoclontic or periodontal treatment of abutment teeth is difficult, and if abutment teeth is difficult, and if something goes wrong with one part of something goes wrong with one part of the bridge or with one of the abutment the bridge or with one of the abutment teeth, usually the whole bridge has to be teeth, usually the whole bridge has to be sacrificed. sacrificed.

For this reason, larger bridges, including For this reason, larger bridges, including full arch bridges, are sometimes made so full arch bridges, are sometimes made so that they can be removed by the patient. that they can be removed by the patient. The advantage of this is that cleaning The advantage of this is that cleaning around the abutment teeth and under around the abutment teeth and under the pontics is much easier. The bridge the pontics is much easier. The bridge has to withstand handling by the patient, has to withstand handling by the patient, and so it is usually made with acrylic and so it is usually made with acrylic facings. The acrylic facings are less liable facings. The acrylic facings are less liable to chip if the bridge is dropped. They can to chip if the bridge is dropped. They can also be replaced without the risk of also be replaced without the risk of distorting the framework as would be the distorting the framework as would be the case with porcelain.case with porcelain.

Based On MaterialsBased On Materials

Metal onlyMetal only Many posterior bridges, both conventional Many posterior bridges, both conventional

and minimal-preparation can be made and minimal-preparation can be made entirely of cast metal, whether they are entirely of cast metal, whether they are fixed-fixed, fixed-movable or cantilever.fixed-fixed, fixed-movable or cantilever.

If the retainers or pontics do not show If the retainers or pontics do not show when the patient smiles and speaks then when the patient smiles and speaks then an all-metal bridge is the best choice with an all-metal bridge is the best choice with conventional bridges - the material conventional bridges - the material necessitates the least destruction of tooth necessitates the least destruction of tooth tissue and depending on the choice of tissue and depending on the choice of metal, may be the least costly. Margins metal, may be the least costly. Margins are also easier to adapt to the are also easier to adapt to the preparations.preparations.

Metal-ceramicMetal-ceramic

When the strength of metal is required When the strength of metal is required together with a tooth-coloured retainer together with a tooth-coloured retainer or pontic, metal-ceramic is the best or pontic, metal-ceramic is the best material. material.

A range of composite crown and bridge A range of composite crown and bridge facing materials is also available.facing materials is also available.

Ceramic onlyCeramic only

The all-ceramic bridge is limited by its The all-ceramic bridge is limited by its relatively poor strength to two-unit relatively poor strength to two-unit cantilever bridges or three-unit fixed-fixed cantilever bridges or three-unit fixed-fixed bridges. All-porcelain bridges made from bridges. All-porcelain bridges made from conventional feldspathic porcelain can conventional feldspathic porcelain can have a very satisfactory appearance. With have a very satisfactory appearance. With improvements, All-ceramic materials have improvements, All-ceramic materials have produced a new generation of all-ceramic produced a new generation of all-ceramic bridges.bridges.

All-ceramic bridges, if properly designed All-ceramic bridges, if properly designed and constructed, have sufficient strength and constructed, have sufficient strength to survive normal functional forces. to survive normal functional forces.

Combinations of materialsCombinations of materials

Many combinations are possible, but Many combinations are possible, but three deserve special mention. The first three deserve special mention. The first two are common.two are common.

A metal-ceramic retainer and pontic A metal-ceramic retainer and pontic with a movable connector to a gold with a movable connector to a gold inlay or other minor retainer.inlay or other minor retainer.

An all-metal retainer (a full or partial An all-metal retainer (a full or partial crown) towards the posterior end of the crown) towards the posterior end of the bridge with anterior metal-ceramic bridge with anterior metal-ceramic units.units.

A framework of standard casting alloy A framework of standard casting alloy and separately constructed porcelain and separately constructed porcelain crowns cemented to them; this type of crowns cemented to them; this type of construction is now uncommon, but construction is now uncommon, but they are still seen in a number of they are still seen in a number of patients and need to be maintained, patients and need to be maintained, sometimes by the replacement of sometimes by the replacement of fractured crowns fractured crowns

MINIMAL PREPARATION MINIMAL PREPARATION BRIDGES BRIDGES DIRECTDIRECT

INDIRECTINDIRECT1.1. Macro Mechanical Retention Macro Mechanical Retention

1.1. e.g. Rochettee.g. Rochette

2.2. Medium Mechanical RetentionMedium Mechanical Retention1.1. e.g. Virginia Salt Mesh Crystal Bond e.g. Virginia Salt Mesh Crystal Bond

3.3. Micro Mechanical Retention Micro Mechanical Retention 1.1. e.g. Marylande.g. Maryland

4.4. Chemically Adhesive Chemically Adhesive 1.1. e.g. Panavia -exe.g. Panavia -ex

Direct bridgesDirect bridges Direct bridges may be made using the Direct bridges may be made using the

crown of the patient's own tooth. This crown of the patient's own tooth. This can often be done as a simple and rapid can often be done as a simple and rapid way of replacing a tooth lost through way of replacing a tooth lost through injury (which cannot re reimplanted) or injury (which cannot re reimplanted) or which has to be extracted urgently. which has to be extracted urgently.

Sometimes metal mesh or wire is added Sometimes metal mesh or wire is added to the lingual surface to increase to the lingual surface to increase strength, but this is not always strength, but this is not always necessary. If the natural crown of the necessary. If the natural crown of the tooth is not available or is not suitable, tooth is not available or is not suitable, an acrylic denture tooth can be used in an acrylic denture tooth can be used in the same way the same way

Macro-mechanically retentive Macro-mechanically retentive bridgesbridges

Macro-mechanically retentive bridges Macro-mechanically retentive bridges (Rochette) have large undercut (Rochette) have large undercut perforations through the cast-metal perforations through the cast-metal plate, through which the composite plate, through which the composite flows. These holes are cut in the wax flows. These holes are cut in the wax or acrylic pattern with a bur and are or acrylic pattern with a bur and are then countersunk.then countersunk.

Medium-mechanical retentive Medium-mechanical retentive systemssystems

Involve retentive features cast as part of the Involve retentive features cast as part of the metal framework. They all add significantly to the metal framework. They all add significantly to the cement-film thickness in some areas, at least, of cement-film thickness in some areas, at least, of the retainer and they all produce large, non-the retainer and they all produce large, non-undercut lumps of metal on the fit surface that do undercut lumps of metal on the fit surface that do not contribute to retention but necessitate a not contribute to retention but necessitate a relatively thick retainer. They are therefore no relatively thick retainer. They are therefore no longer used, but patients with this type of bridge longer used, but patients with this type of bridge may present with the bridge debonded. It is may present with the bridge debonded. It is usually not worth trying to re-attach it.usually not worth trying to re-attach it.

The size of the retentive features is intermediate The size of the retentive features is intermediate between those of macro- and micromechanical between those of macro- and micromechanical retentive systems.retentive systems.

Micro-mechanical retentionMicro-mechanical retention

Micro-mechanical retention is produced Micro-mechanical retention is produced by casting the metal retainer and then by casting the metal retainer and then etching the fit surface by one of two etching the fit surface by one of two methods:methods:

Electrolytic etching in acid in the Electrolytic etching in acid in the laboratorylaboratory

Chemical etching with a hydrofluoric Chemical etching with a hydrofluoric acid gel either in the laboratory or at the acid gel either in the laboratory or at the chairside. chairside.

Although these two systems produce Although these two systems produce different etch patterns, they are all very different etch patterns, they are all very retentive. The size of the retentive retentive. The size of the retentive features is approximately one-tenth that features is approximately one-tenth that of the medium-mechanical retentive of the medium-mechanical retentive systems, and the retentive features are systems, and the retentive features are undercut from the surface. The smaller undercut from the surface. The smaller size of these etch pits and the absence size of these etch pits and the absence of any unnecessary non-retentive of any unnecessary non-retentive features (as in the medium-mechanical features (as in the medium-mechanical retentive systems) allow thinner metal retentive systems) allow thinner metal retainers and a thinner cement film retainers and a thinner cement film thickness.thickness.

Chemically retentiveChemically retentive

Chemically retentive resins are now Chemically retentive resins are now available. Several have been marketed, available. Several have been marketed, and some (e.g. Panavia 21) have and some (e.g. Panavia 21) have performed well in laboratory and short-performed well in laboratory and short-term clinical trials. They adhere term clinical trials. They adhere chemically to recently sandblasted chemically to recently sandblasted metal surfaces and are retained on the metal surfaces and are retained on the tooth by conventional acid-etching of tooth by conventional acid-etching of the enamel. the enamel.

A number of laboratory studies and A number of laboratory studies and clinical trials have shown that micro-clinical trials have shown that micro-mechanical and chemical adhesive mechanical and chemical adhesive systems are the most retentive. The systems are the most retentive. The chemical adhesive systems have been chemical adhesive systems have been available for a number of years and are available for a number of years and are proving the most successful of the proving the most successful of the systems. However, longer-term clinical systems. However, longer-term clinical trials are still necessary. The more trials are still necessary. The more recently introduced materials are recently introduced materials are claimed to have better retentive claimed to have better retentive properties than earlier materials, but properties than earlier materials, but time will tell. time will tell.

An advantage of using the chemical An advantage of using the chemical adhesive materials is that the laboratory adhesive materials is that the laboratory only needs a sandblaster rather than only needs a sandblaster rather than etching equipment, and the health and etching equipment, and the health and safety hazards of etching in an acid safety hazards of etching in an acid solution or using hydrofluoric acid gel are solution or using hydrofluoric acid gel are avoided. The adhesive cement is easy to avoided. The adhesive cement is easy to mix and use and has a good working mix and use and has a good working time, so that the bridge can be fully time, so that the bridge can be fully seated without too much hurry. Rubber seated without too much hurry. Rubber dam should always be used and the dam should always be used and the margins of the restoration coated with a margins of the restoration coated with a gel material to prevent air contacting the gel material to prevent air contacting the setting cement, since its setting is setting cement, since its setting is inhibited by oxygen.inhibited by oxygen.

A disadvantage of the micro-mechanical A disadvantage of the micro-mechanical retention system is that the metal retention system is that the metal framework should not be tried in the framework should not be tried in the mouth after the surface has been mouth after the surface has been etched. This is because the very delicate etched. This is because the very delicate etch pattern may well be damaged or etch pattern may well be damaged or clogged by deposits from saliva. This clogged by deposits from saliva. This means that the ideal is to try-in the means that the ideal is to try-in the unetched framework and then either unetched framework and then either return it to the laboratory for etching or return it to the laboratory for etching or etch it at the chairside. This takes time etch it at the chairside. This takes time and therefore adds to the cost.and therefore adds to the cost.

The macro-mechanical retentive design The macro-mechanical retentive design (Rochette) overcomes this problem but (Rochette) overcomes this problem but is less retentive in most cases, and, is less retentive in most cases, and, because it is cemented with a because it is cemented with a conventional composite (rather than conventional composite (rather than one specifically designed for cementing one specifically designed for cementing minimal-preparation retainers) and the minimal-preparation retainers) and the composite comes through the composite comes through the perforations to the mouth, it is prone to perforations to the mouth, it is prone to degradation over a period of years. degradation over a period of years.

However, the main advantage of the However, the main advantage of the Rochette bridge is that it can be Rochette bridge is that it can be removed from the mouth fairly easily. removed from the mouth fairly easily. The composite is drilled out from the The composite is drilled out from the holes, and the bridge can usually be holes, and the bridge can usually be removed without too much force. removed without too much force.

For this reason, the Rochette bridge is For this reason, the Rochette bridge is still used when the abutment teeth still used when the abutment teeth have a poor prognosis and when further have a poor prognosis and when further modifications are likely to be necessary modifications are likely to be necessary - for example when one lower incisor is - for example when one lower incisor is being replaced for periodontal reasons being replaced for periodontal reasons and the other teeth are still receiving and the other teeth are still receiving periodontal treatment. periodontal treatment.

The Rochette design is also used for The Rochette design is also used for immediate insertion bridges so that the immediate insertion bridges so that the bridge can be removed when the tissues bridge can be removed when the tissues have healed and the pontic adapted to have healed and the pontic adapted to the ridge or the bridge remade.the ridge or the bridge remade.

Historically, the medium-mechanical Historically, the medium-mechanical retentive systems were developed after retentive systems were developed after the Rochette and Maryland designs in an the Rochette and Maryland designs in an attempt to overcome the disadvantages attempt to overcome the disadvantages of these described above. However, they of these described above. However, they have disadvantages of their own in being have disadvantages of their own in being less retentive than the micro-mechanical less retentive than the micro-mechanical system and yet having thicker metal system and yet having thicker metal retainers and a thicker cement film. retainers and a thicker cement film.

Disadvantages of Disadvantages of Minimal-preparation bridgesMinimal-preparation bridges

As the metal plate is added to the surface of the As the metal plate is added to the surface of the tooth or only replaces part of it, the thickness of tooth or only replaces part of it, the thickness of the tooth is increased, and may interfere with the tooth is increased, and may interfere with the occlusion unless space is created the occlusion unless space is created orthodontically or by grinding the opposing orthodontically or by grinding the opposing teeth.teeth.

The margin of the retainer inevitably produces a The margin of the retainer inevitably produces a ledge where plaque can collect. This is a ledge where plaque can collect. This is a problem, especially in the replacement of lower problem, especially in the replacement of lower incisors. Here plaque and calculus deposits are incisors. Here plaque and calculus deposits are common on the lingual surface towards the common on the lingual surface towards the gingival margin, and the presence of such a gingival margin, and the presence of such a ledge can only make it more difficult for the ledge can only make it more difficult for the patient to clean in this area. patient to clean in this area.

COMPARISON COMPARISON OF VARIOUS OF VARIOUS

BRIDGE BRIDGE DESIGNDESIGN

Fixed-fixedFixed-fixedAdvantages:Advantages:CONVENTIONAL BRIDGE CONVENTIONAL BRIDGE Robust design with maximum retention Robust design with maximum retention

and strengthand strength Abutment teeth are splinted together; Abutment teeth are splinted together;

this may be an advantage, particularly this may be an advantage, particularly when teeth are uncomfortably mobile when teeth are uncomfortably mobile following bone loss through periodontal following bone loss through periodontal diseasedisease

The design is the most practical for The design is the most practical for larger bridges, particularly when there larger bridges, particularly when there has been periodontal diseasehas been periodontal disease

The construction is relatively The construction is relatively straightforward in the laboratory straightforward in the laboratory because there are no movable joints because there are no movable joints to maketo make

Can be used for long spansCan be used for long spans

MINIMAL-PREPARATION BRIDGE MINIMAL-PREPARATION BRIDGE A large retentive surface areaA large retentive surface area A single casting and so relatively A single casting and so relatively

simple in the laboratorysimple in the laboratory

Disadvantages:Disadvantages:

CONVENTIONAL BRIDGE CONVENTIONAL BRIDGE Requires preparations to be parallel, and this Requires preparations to be parallel, and this

may mean more tooth reduction than normal, may mean more tooth reduction than normal, endangering the pulp and reducing retention; endangering the pulp and reducing retention; the strength of the prepared tooth may also the strength of the prepared tooth may also be reducedbe reduced

Preparations are difficult to carry out, Preparations are difficult to carry out, particularly if several widely separated teeth particularly if several widely separated teeth are involved; the preparation is slow and the are involved; the preparation is slow and the parallelism has to be constantly checked, or parallelism has to be constantly checked, or alternatively (and wrongly) the preparations alternatively (and wrongly) the preparations are over-tapered to ensure that there are no are over-tapered to ensure that there are no undercuts and so retention is lostundercuts and so retention is lost

All the retainers are major retainers and All the retainers are major retainers and require extensive, destructive preparations of require extensive, destructive preparations of the abutment teeththe abutment teeth

Has to be cemented in one piece, so Has to be cemented in one piece, so cementation is difficult.cementation is difficult.

MINIMAL-PREPARATION BRIDGEMINIMAL-PREPARATION BRIDGE Because part of the occlusal surfaces of both Because part of the occlusal surfaces of both

abutment teeth are usually opposed by teeth abutment teeth are usually opposed by teeth in the opposing jaw, there is a tendency for in the opposing jaw, there is a tendency for them to be dislodged from the retainer, thus them to be dislodged from the retainer, thus debonding the bridgedebonding the bridge

With tilted abutments it is sometimes difficult With tilted abutments it is sometimes difficult to achieve an adequate retentive surface to achieve an adequate retentive surface without substantial tooth preparation The without substantial tooth preparation The retention of both retainers should be retention of both retainers should be approximately equal. This is difficult to achieve approximately equal. This is difficult to achieve when one retainer is a molar tooth and the when one retainer is a molar tooth and the other a premolarother a premolar

Fixed-movableFixed-movable Advantages: Advantages: CONVENTIONAL BRIDGE CONVENTIONAL BRIDGE Preparations do not need to be parallel to each Preparations do not need to be parallel to each

other, so divergent abutment teeth can be used.other, so divergent abutment teeth can be used. Because preparations do not need to be parallel, Because preparations do not need to be parallel,

each preparation can be designed to be retentive each preparation can be designed to be retentive independently of the other preparations.independently of the other preparations.

More conservative of tooth tissue because More conservative of tooth tissue because preparations for minor retainers are less preparations for minor retainers are less destructive than preparations for major retainers.destructive than preparations for major retainers.

Allows minor movements of teeth.Allows minor movements of teeth. Parts can be cemented separately, so Parts can be cemented separately, so

cementation is easy.cementation is easy.

MINIMAL-PREPARATION BRIDGEMINIMAL-PREPARATION BRIDGE Independent tooth movement is possible, Independent tooth movement is possible,

particularly for the minor abutment tooth particularly for the minor abutment tooth (with the movable joint). The major (with the movable joint). The major retainer can be designed for optimum retainer can be designed for optimum retention, sometimes incorporating intra- retention, sometimes incorporating intra- coronal as well as extra-coronal elements coronal as well as extra-coronal elements replacing restorations.replacing restorations.

The retention of the minor retainer need The retention of the minor retainer need not be substantial, particularly if the not be substantial, particularly if the movable joint consists only of a rest movable joint consists only of a rest seated in a seat on the minor retainer In seated in a seat on the minor retainer In this case there are few displacing forces this case there are few displacing forces on the minor retainer. on the minor retainer.

The retention of the two retainers can The retention of the two retainers can be very different, usually with the major be very different, usually with the major retainer distally and the smaller, minor retainer distally and the smaller, minor retainer attached to a premolar tooth. retainer attached to a premolar tooth. The retainer can be made very small, The retainer can be made very small, and its appearance is similar to a small and its appearance is similar to a small amalgam restoration.amalgam restoration.

Prevents a posterior abutment tooth Prevents a posterior abutment tooth tilting as is sometimes the case with a tilting as is sometimes the case with a cantilever bridge. The movable joint cantilever bridge. The movable joint merely acts to prevent this rather than merely acts to prevent this rather than to provide any retention for the bridgeto provide any retention for the bridge

Disadvantages: Disadvantages: CONVENTIONAL BRIDGE CONVENTIONAL BRIDGE Length of span limited, particularly with mobile Length of span limited, particularly with mobile

abutment teethabutment teeth More complicated to construct in the More complicated to construct in the

laboratory than fixed-fixedlaboratory than fixed-fixed Difficult to make temporary bridgesDifficult to make temporary bridgesMINIMAL-PREPARATION BRIDGEMINIMAL-PREPARATION BRIDGE Not suitable for anterior bridgesNot suitable for anterior bridges More difficult to make in the laboratory, More difficult to make in the laboratory,

requiring two separate castingsrequiring two separate castings Not suitable for longer-span bridges, where a Not suitable for longer-span bridges, where a

conventional fixed-movable bridge would be conventional fixed-movable bridge would be satisfactory. This is because the movable joint satisfactory. This is because the movable joint is seldom large enough to resist lateral forces is seldom large enough to resist lateral forces on the pontic, but will only resist axial forces on the pontic, but will only resist axial forces by means of the rest on the minor retainerby means of the rest on the minor retainer

CantileverCantilever Advantages:Advantages:CONVENTIONAL BRIDGE CONVENTIONAL BRIDGE The most conservative design when only one The most conservative design when only one

abutment tooth is neededabutment tooth is needed If one abutment tooth is used, there is no need If one abutment tooth is used, there is no need

to make preparations parallel to each other; if to make preparations parallel to each other; if two or more abutment teeth are used, they are two or more abutment teeth are used, they are adjacent to each other, so it is easier to make adjacent to each other, so it is easier to make the preparations parallel Construction in the the preparations parallel Construction in the laboratory is relatively straightforwardlaboratory is relatively straightforward

Most suitable in replacing anterior teeth Most suitable in replacing anterior teeth where, if the occlusion is favourable, there is where, if the occlusion is favourable, there is little risk of the abutment tooth tilting.little risk of the abutment tooth tilting.

MINIMAL-PREPARATION BRIDGEMINIMAL-PREPARATION BRIDGE The most conservative of all designs, The most conservative of all designs,

usually only involving a single minimal-usually only involving a single minimal-preparation retainer.preparation retainer.

Ideal for replacing upper lateral incisors, Ideal for replacing upper lateral incisors, using the canine tooth as the abutment, using the canine tooth as the abutment, provided the occlusion is favorable.provided the occlusion is favorable.

Suitable posteriorly when the span is short.Suitable posteriorly when the span is short. Easy for the patient to clean with floss Easy for the patient to clean with floss

passed through the contact point between passed through the contact point between the pontic and the unrestored adjacent the pontic and the unrestored adjacent toothtooth

No need to align preparations.No need to align preparations. Easy laboratory construction.Easy laboratory construction.

Disadvantages: Disadvantages:

CONVENTIONAL BRIDGE CONVENTIONAL BRIDGE With small bridges the length of span is limited With small bridges the length of span is limited

to one pontic because of the leverage forces to one pontic because of the leverage forces on the abutment teeth; if more teeth are to be on the abutment teeth; if more teeth are to be replaced with a cantilever bridge, a large replaced with a cantilever bridge, a large number of abutments widely spaced round the number of abutments widely spaced round the arch must be usedarch must be used

The construction of the bridge must be rigid to The construction of the bridge must be rigid to avoid distortionavoid distortion

Occlusal forces on the pontic of small posterior Occlusal forces on the pontic of small posterior bridges encourage tilting of the abutment bridges encourage tilting of the abutment tooth, particularly if the abutment tooth is tooth, particularly if the abutment tooth is distal to the pontic and is already predisposed distal to the pontic and is already predisposed to tilting mesially.to tilting mesially.

MINIMAL-PREPARATION BRIDGEMINIMAL-PREPARATION BRIDGE Relatively small retentive area, and Relatively small retentive area, and

vulnerable to debonding through vulnerable to debonding through torquing forces torquing forces

General General considerationsconsiderations

Patient attitudePatient attitude Patients show different degrees of Patients show different degrees of

enthusiasm for fixed and removable enthusiasm for fixed and removable prostheses. Unless the patient is prostheses. Unless the patient is particularly anxious to have a bridge or particularly anxious to have a bridge or implant- retained prosthesis and fully implant- retained prosthesis and fully understands the implications, it is often understands the implications, it is often better, particularly when a number of teeth better, particularly when a number of teeth are missing, to make a partial denture first are missing, to make a partial denture first to see how the patient responds. It may be to see how the patient responds. It may be that the denture is satisfactory, both that the denture is satisfactory, both aesthetically and functionally. aesthetically and functionally.

If so, the destructive and irreversible tooth If so, the destructive and irreversible tooth preparations that may be necessary for a preparations that may be necessary for a bridge or surgical procedures for implants bridge or surgical procedures for implants can be avoided, or atleast deferred. can be avoided, or atleast deferred. Alternatively, if the patient is unhappy with Alternatively, if the patient is unhappy with the partial denture, he or she will enter the partial denture, he or she will enter into the arrangements for making a bridge into the arrangements for making a bridge or implant retained prostheses with or implant retained prostheses with greater enthusiasm and commitment. greater enthusiasm and commitment. Patients should never be persuaded to Patients should never be persuaded to have bridges or implants against their have bridges or implants against their wishes, and they must give fully informed wishes, and they must give fully informed consent, including, in most cases, time to consent, including, in most cases, time to reflect.reflect.

Age and sexAge and sex Similar arguments apply to bridges as to Similar arguments apply to bridges as to

crowns. Sports players and wind-crowns. Sports players and wind-instrument players have However, instrument players have However, whereas there may be no satisfactory whereas there may be no satisfactory alternative to a crown for an old or young alternative to a crown for an old or young patient, a partial denture may make a patient, a partial denture may make a very satisfactory alternative to a bridge or very satisfactory alternative to a bridge or implant-retained prostheses. This is implant-retained prostheses. This is particularly true for very young patients, particularly true for very young patients, who may not fully appreciate the lifelong who may not fully appreciate the lifelong implications of bridges or implants. implications of bridges or implants.

It is often better to make a minimal It is often better to make a minimal preparation bridge or partial denture preparation bridge or partial denture until the patient is mature enough to until the patient is mature enough to assess the relative merits of the assess the relative merits of the alternatives. But a teenager with a alternatives. But a teenager with a missing incisor who cannot be fitted missing incisor who cannot be fitted with a minimal-preparation bridge may with a minimal-preparation bridge may be desperately unhappy about wearing be desperately unhappy about wearing a partial denture. In this case, the a partial denture. In this case, the provision of a conventional bridge or provision of a conventional bridge or single tooth implant as early as possible single tooth implant as early as possible may make a remarkable psychological may make a remarkable psychological difference At the other end of the age difference At the other end of the age scale, no patient, however old, should scale, no patient, however old, should be written off as being past bridgework.be written off as being past bridgework.

Confidence Confidence Many patients feel more confident with a bridge Many patients feel more confident with a bridge

than with any form of removable appliance.than with any form of removable appliance. However retentive a partial denture, some However retentive a partial denture, some

patients never lose the anxiety that it will patients never lose the anxiety that it will become dislodged during speaking or eating. become dislodged during speaking or eating. Others are not prepared to remove partial Others are not prepared to remove partial dentures at night.dentures at night.

Many patients do tolerate partial dentures very Many patients do tolerate partial dentures very well, however, and it is often difficult to tell well, however, and it is often difficult to tell beforehand what the response will be to either beforehand what the response will be to either form of treatment. The majority of patients who form of treatment. The majority of patients who have had both partial dentures and bridges have had both partial dentures and bridges prefer the latter.prefer the latter.

Occupation Occupation Although sports players should be provided with Although sports players should be provided with

crowns when necessary, it may be better to defer crowns when necessary, it may be better to defer making an anterior bridge or implant-retained making an anterior bridge or implant-retained prostheses until the patient gives up the more prostheses until the patient gives up the more violent sports, and meanwhile to provide a partial violent sports, and meanwhile to provide a partial denture.denture.

Although wind-instrument players usually need a Although wind-instrument players usually need a bridge replacement for their missing anterior bridge replacement for their missing anterior teeth, there are some who find that air escapes teeth, there are some who find that air escapes beneath and between the teeth of a bridge. They beneath and between the teeth of a bridge. They are better able to maintain a seal with a partial are better able to maintain a seal with a partial denture carrying a buccal flange.denture carrying a buccal flange.

Public speakers and singers who make more Public speakers and singers who make more extreme movements of the mouth often need the extreme movements of the mouth often need the confidence that comes from wearing a bridge.confidence that comes from wearing a bridge.

General health General health Both bridges and partial dentures are Both bridges and partial dentures are

elective forms of treatment, and need not elective forms of treatment, and need not be provided for people who are ill. When be provided for people who are ill. When tooth replacement is necessary for tooth replacement is necessary for someone who will have difficulty tolerating someone who will have difficulty tolerating it because of poor health, or when there it because of poor health, or when there are medical complications such as with are medical complications such as with patients who require antibiotic cover for patients who require antibiotic cover for every appointment, it is better to consider every appointment, it is better to consider the simpler, less time-consuming form of the simpler, less time-consuming form of treatment first.treatment first.

AppearanceAppearance When a tooth is lost, alveolar bone and When a tooth is lost, alveolar bone and

gingival contour are also lost, and it is gingival contour are also lost, and it is never possible to disguise this fact never possible to disguise this fact entirely. Thus no artificial replacements entirely. Thus no artificial replacements ever look exactly like the natural teeth, ever look exactly like the natural teeth, although some may be sufficiently although some may be sufficiently realistic to deceive all except the dentist realistic to deceive all except the dentist with his bright light and mouth mirror. In with his bright light and mouth mirror. In some cases dentures with flanges achieve some cases dentures with flanges achieve this object better than bridges; in others this object better than bridges; in others bridges have the better appearance. bridges have the better appearance.

When a substantial amount of alveolar When a substantial amount of alveolar bone is lost in one area, the bone is lost in one area, the combination of a bridge with a separate combination of a bridge with a separate removable buccal flange sometimes removable buccal flange sometimes gives the best appearance. gives the best appearance.

When the loss of alveolar bone is When the loss of alveolar bone is significant and the lipline is such that it significant and the lipline is such that it shows and is difficult to disguise easily, shows and is difficult to disguise easily, the ridge may be augmented surgically the ridge may be augmented surgically and the tooth or teeth replaced by a and the tooth or teeth replaced by a bridge or implant.bridge or implant.

Indications:Indications:

TOOTH -BOUNDED EDENTULOUS TOOTH -BOUNDED EDENTULOUS REGIONSREGIONS

MODIFICATION SPACES MODIFICATION SPACES Class lll modification 1 Class lll modification 1

ANTERIOR MODIFICATION SPACESANTERIOR MODIFICATION SPACES

Contraindications:Contraindications: Youth or advanced age of patient.Youth or advanced age of patient.

Youth- large dental pulps and lack of Youth- large dental pulps and lack of clinical crown height (under age clinical crown height (under age 17years)17years)

Aged- reduced life expectancy and Aged- reduced life expectancy and frequently failing general health.frequently failing general health.

Great length of edentulous span.Great length of edentulous span. Excessive bone loss of residual ridge.Excessive bone loss of residual ridge. Psychological problems.Psychological problems. Economic considerations.Economic considerations.