Treatment Planning in Treatment Planning in FPDFPD

Dr Kaushal Kishor AgrawalAssistant ProfessorDepartmnent of ProsthodonticsKGMU Lucknow

Types of Fixed Types of Fixed Prosthodontic TreatmentProsthodontic Treatment

Conventional tooth supported fixed partial dentureConventional tooth supported fixed partial denture

- - Utilizes an abutment tooth on each end or only one end Utilizes an abutment tooth on each end or only one end (cantilever) of the edentulous space.(cantilever) of the edentulous space.

- If abutment teeth are periodontally sound, the edentulous span - If abutment teeth are periodontally sound, the edentulous span is short and straight and the retainers are well designed and is short and straight and the retainers are well designed and executed, the FPD can be expected to provide a long life and executed, the FPD can be expected to provide a long life and function for the pt.function for the pt.

- there should be : - no gross soft tissue defect in the edentulous - there should be : - no gross soft tissue defect in the edentulous spacespace

- no dry mouth which can create a poor - no dry mouth which can create a poor environment for FPDenvironment for FPD

Resin bonded tooth supported fixed partial dentureResin bonded tooth supported fixed partial denture

- conservative restoration reserved for use on defect free abutments to - conservative restoration reserved for use on defect free abutments to replace single missing tooth usually an incisor or premolar.replace single missing tooth usually an incisor or premolar.

- for molars – replaced only if muscles of mastication are not too - for molars – replaced only if muscles of mastication are not too well developedwell developed

- abutments on both sides of edentulous space, preparation is shallow - abutments on both sides of edentulous space, preparation is shallow and restricted to enameland restricted to enamel

- useful in young pts who have immature teeth with large pulps- useful in young pts who have immature teeth with large pulps - should be used with extreme care and may require additional - should be used with extreme care and may require additional

resistance features (e.g. grooves)resistance features (e.g. grooves) - Abutment Mobility has been shown to be a serious hazard in the - Abutment Mobility has been shown to be a serious hazard in the

successful use of this type of successful use of this type of prosthesis.prosthesis.

Implant supported fixed partial denturesImplant supported fixed partial dentures

-- when there are insufficient abutment teeth, inadequate strength in abutments, no distal when there are insufficient abutment teeth, inadequate strength in abutments, no distal abutment present.abutment present.

- Span length limited by availability of alveolar bone, with satisfactory density and thickness in a - Span length limited by availability of alveolar bone, with satisfactory density and thickness in a broad flat ridgebroad flat ridge

- Single missing tooth – replaced by single implant – therefore no destruction of - Single missing tooth – replaced by single implant – therefore no destruction of

adjacent abutments.adjacent abutments.

- 2-6 missing teeth – replaced by multiple implants either as single units or implant supported - 2-6 missing teeth – replaced by multiple implants either as single units or implant supported FPD’s.FPD’s.

- can be used as pier abutments in a long span … but immovable implant usually not preferred - can be used as pier abutments in a long span … but immovable implant usually not preferred with natural teeth in same rigid prosthesis.with natural teeth in same rigid prosthesis.

- greater degree of abutment alignment precision required than tooth supported FPD’s- greater degree of abutment alignment precision required than tooth supported FPD’s

- occlusal forces should be nearly vertical to the implant as possible to prevent lateral destructive - occlusal forces should be nearly vertical to the implant as possible to prevent lateral destructive forces.forces.

- Implants are better able than natural teeth to survive in a “ Dry Mouth”- Implants are better able than natural teeth to survive in a “ Dry Mouth”

- if tooth abutments require endodontic therapy with or without dowel cores, periodontal surgery - if tooth abutments require endodontic therapy with or without dowel cores, periodontal surgery & even possibly root resection to support a long span complex FPD then, “ Implant may be a & even possibly root resection to support a long span complex FPD then, “ Implant may be a better choice”better choice”

Treatment PlanningTreatment Planning

I - Identification of patients needs a) Correction of existing disease - By identification and reduction of the initiating

factors and improvement of the resistive factors or Both

b) Prevention of future disease - by evaluating the patients disease experience &

knowing the prevalence of the disease in general population. Treatment should

be proposed if future disease seems likely in the absence of such intervention.

c) Restoration of Function – level of the function is assessed during examination

and treatment may be proposed to correct impaired function (e.g. speech &

mastication).

d) Improvement of appearance – listen carefully to the patient’s views and if the

appearance is far outside socially accepted values, the feasibility of corrective

procedures should be brought to the patients attention. Long term dental

health should not be compromised by unwise attempts to improve

appearance and patients should always be made aware of the possible

adverse consequences of treatment.

II- Available materials and II- Available materials and techniquestechniques

Clinician shouldClinician should understand the limitationsunderstand the limitations of appropriate materials and procedures & of appropriate materials and procedures &

this will help prevent experimental approach to treatment.this will help prevent experimental approach to treatment.

a)a) Plastic materials (e.g. AgAm & Composite)Plastic materials (e.g. AgAm & Composite)

b)b) Cast Metal – intracoronal restoration & extracoronal restorationCast Metal – intracoronal restoration & extracoronal restoration

c)c) Metal ceramic Metal ceramic

d)d) Resin VeneeredResin Veneered

e)e) Fiber-reinforced resinFiber-reinforced resin

f)f) Complete ceramicComplete ceramic

g)g) Fixed partial dentureFixed partial denture

h)h) Implant supported prosthesisImplant supported prosthesis

i)i) Removable partial denturesRemovable partial dentures

III-Treatment of tooth lossIII-Treatment of tooth loss

Causes-Causes- caries, pdl disease, trauma, neoplasm, congenitally absentcaries, pdl disease, trauma, neoplasm, congenitally absent

a) Decision to remove a tooth –a) Decision to remove a tooth – poor/hopeless teeth should be removed. poor/hopeless teeth should be removed.

A decision about replacing a missing tooth is best made at the time A decision about replacing a missing tooth is best made at the time of of

its removal rather than months or years after the fact.its removal rather than months or years after the fact.

b) Consequences of removal without replacement –b) Consequences of removal without replacement –

- supraclusion/ supraeruption of opposing tooth/teeth.- supraclusion/ supraeruption of opposing tooth/teeth.

- tilting of the adjacent teeth - tilting of the adjacent teeth

- loss of proximal contact- loss of proximal contact

Extended treatment plans like orthodontic repositioning and additional Extended treatment plans like orthodontic repositioning and additional cast restoration may be needed to compensate for the lack of treatment cast restoration may be needed to compensate for the lack of treatment at the time of tooth removalat the time of tooth removal

Fig 1 –Fig 1 –Tooth position and alignment are Tooth position and alignment are maintained, in part by the interaction maintained, in part by the interaction between teeth.between teeth.

Fig 2 –Fig 2 – shows the typical consequences shows the typical consequences 1- supraclusion of opposing teeth1- supraclusion of opposing teeth 2- tilting of adjacent teeth2- tilting of adjacent teeth 3- loss of contact3- loss of contact

IV-Selection of Abutment IV-Selection of Abutment teeth/ Abutment Evaluationteeth/ Abutment Evaluation

--Whenever possible an abutment should be a “VITAL TOOTH”Whenever possible an abutment should be a “VITAL TOOTH”

-The forces that would normally be absorbed by the missing tooth, are transmitted -The forces that would normally be absorbed by the missing tooth, are transmitted through the pontic, connectors and retainers to the abutment teeth therefore the through the pontic, connectors and retainers to the abutment teeth therefore the abutment teeth should be able to withstand the forces normally directed to the abutment teeth should be able to withstand the forces normally directed to the missing teeth in addition to those usually applied to the abutments.missing teeth in addition to those usually applied to the abutments.

-An FPD should be designed as simply as possible-An FPD should be designed as simply as possible

A) REPLACEMENT OF SINGLE MISSING TOOTHA) REPLACEMENT OF SINGLE MISSING TOOTH Unless bone support has been weakened by pdl disease, a single missing tooth can almost Unless bone support has been weakened by pdl disease, a single missing tooth can almost

always be replaced by a 3 unit FPD having one mesial and one distal abutment tooth.always be replaced by a 3 unit FPD having one mesial and one distal abutment tooth.

Factors to be consideredFactors to be considered

i) Cantilever FPD -i) Cantilever FPD - this is a potentially destructive design with the lever arm this is a potentially destructive design with the lever arm created by the pontic.created by the pontic.

Fig AFig A –– the pontic of a cantilever bridge acts as the pontic of a cantilever bridge acts as a lever arm that tends to cause tipping and a lever arm that tends to cause tipping and rotation under strong occlusal vectorrotation under strong occlusal vector..

Fig B –Fig B – the forces that are applied to the pontic the forces that are applied to the pontic of a 3 unit FPD is distributed equally to of a 3 unit FPD is distributed equally to the abutment teeth and less leverage is the abutment teeth and less leverage is applied to the teeth or the retainers than applied to the teeth or the retainers than with the cantilever bridge.with the cantilever bridge.

Uses of Cantilever BridgeUses of Cantilever Bridge

a)a) Replacing Maxillary lateral incisor Replacing Maxillary lateral incisor- There should be no occlusal contact on There should be no occlusal contact on

either centric or lateral excursions.either centric or lateral excursions.- Canine must be the abutment & must Canine must be the abutment & must

have long root and good bone support.have long root and good bone support.- To prevent rotation of pontic and To prevent rotation of pontic and

abutment , a rest can be placed on the abutment , a rest can be placed on the mesial of pontic against a rest mesial of pontic against a rest preparation on the distal of the central preparation on the distal of the central incisor. incisor.

b) b) Replacing Mandibular first premolarReplacing Mandibular first premolar- Occlusal contact should be limited to the Occlusal contact should be limited to the

distal fossa.distal fossa.- Full veneer retainers on both the second Full veneer retainers on both the second

premolar and molar.premolar and molar.- There should be excellent bone support There should be excellent bone support

around the abutment teeth.around the abutment teeth.

Uses contd…Uses contd…

c) c) Replacing mandibular molars when there is Replacing mandibular molars when there is no distal abutment presentno distal abutment present

- Pontic should be kept as small as Pontic should be kept as small as possible (like a premolar) with light possible (like a premolar) with light occlusal contact in centric and absolutely occlusal contact in centric and absolutely no contacts in any excursions because the no contacts in any excursions because the adjacent abutment acts as a fulcrum with adjacent abutment acts as a fulcrum with a lifting tendency on the farthest retainer.a lifting tendency on the farthest retainer.

- Pontic should possess maximum Pontic should possess maximum occlusogingival height to ensure a rigid occlusogingival height to ensure a rigid prosthesisprosthesis

d) d) Used with implant supported prosthesis Used with implant supported prosthesis - The actual length of cantilever depends The actual length of cantilever depends

on stress factors. on stress factors.

E.g. Parafunction, arch position, masticatory E.g. Parafunction, arch position, masticatory dynamics, opposing arch, crown height, dynamics, opposing arch, crown height, direction of force, bone density, implant direction of force, bone density, implant number, implant width, implant design number, implant width, implant design and A-P distance.and A-P distance.

Factors contd…Factors contd…ii) Assessment of abutmentii) Assessment of abutment teeth teeth

- Thorough investigation of each abutment with radiographic examination- Thorough investigation of each abutment with radiographic examination

- Pulp health should be assessed & if doubtful, endodontic treatment should be carried out- Pulp health should be assessed & if doubtful, endodontic treatment should be carried out- Existing restorations, cavity liners and residual caries should be removed and checked for Existing restorations, cavity liners and residual caries should be removed and checked for

possible pulpal exposurepossible pulpal exposure

iii) Endodontically treated abutmentsiii) Endodontically treated abutments- If properly treated it can serve well as an abutment, with the post and core foundation for If properly treated it can serve well as an abutment, with the post and core foundation for

retention and strength.retention and strength.- Usually failure occurs in teeth with short roots and little coronal tooth structure.Usually failure occurs in teeth with short roots and little coronal tooth structure.- If badly damaged tooth, it is better to remove than to attempt endodontic treatment.If badly damaged tooth, it is better to remove than to attempt endodontic treatment.

iv) Unrestored abutmentsiv) Unrestored abutments- Ideal – Unrestored, caries freeIdeal – Unrestored, caries free- Can be prepared conservatively for a strong retentive restoration with optimum estheticsCan be prepared conservatively for a strong retentive restoration with optimum esthetics- For patients who are reluctant to have a perfectly sound tooth cut down to provide anchorage For patients who are reluctant to have a perfectly sound tooth cut down to provide anchorage

for a FPD , the overall dental health of the patient should be emphasized rather than looking at for a FPD , the overall dental health of the patient should be emphasized rather than looking at each tooth individually.each tooth individually.

Factors contd…Factors contd…

v)v) Tilted molar abutments / Mesially tilted second molarsTilted molar abutments / Mesially tilted second molars- Common problem occurs when the mandibular 2Common problem occurs when the mandibular 2ndnd molar abutment gets tilted into the molar abutment gets tilted into the

space formerly occupied by the first molar. Further complication occurs if the 3space formerly occupied by the first molar. Further complication occurs if the 3 rdrd molar is molar is present and has drifted and tilted with the second molar. In such case the mesial surface of present and has drifted and tilted with the second molar. In such case the mesial surface of the tipped third molar will encroach upon the path of insertion of the FPD. the tipped third molar will encroach upon the path of insertion of the FPD.

If encroachment is slightIf encroachment is slight - - solved by restoring or recontouring solved by restoring or recontouring

the mesial surface of 3the mesial surface of 3rdrd molar molar- - addtion of facial and lingual grooves on 2- addtion of facial and lingual grooves on 2ndnd molar for better retention molar for better retention

If tilting is severeIf tilting is severe – – uprighting of the molar by orthodontic treatment.uprighting of the molar by orthodontic treatment. - also helps in distribution of forces under occlusal loading and even- also helps in distribution of forces under occlusal loading and even helps to eliminate bony defects along the mesial surface of the root.helps to eliminate bony defects along the mesial surface of the root. - usually 3- usually 3rdrd molars are extracted to facilitate movement of 2 molars are extracted to facilitate movement of 2ndnd molar. molar. - Average treatment time – 3 months.- Average treatment time – 3 months. -to prevent post treatment relapse, a temporary FPD is fabricated -to prevent post treatment relapse, a temporary FPD is fabricated immediately after removal of orthodontic appliance.immediately after removal of orthodontic appliance.

If orthodontic correction id not possible , a FPD can still be fabricatedIf orthodontic correction id not possible , a FPD can still be fabricated

Hood, Farah and Craig (1975) and Yang and Thompson (1991) Hood, Farah and Craig (1975) and Yang and Thompson (1991) - A molar which has tipped mesially will actually exhibit less stress in the alveolar bone along the mesial A molar which has tipped mesially will actually exhibit less stress in the alveolar bone along the mesial

surface of its mesial root with a fixed partial denture than without it. However, there will be an increase in surface of its mesial root with a fixed partial denture than without it. However, there will be an increase in stress along the premolar.stress along the premolar.

Smith (1993)Smith (1993)- Proximal half crowns can be used as a retainer on distal abutment.Proximal half crowns can be used as a retainer on distal abutment. this is simply a three –quarter crown that has been rotated 90 degreesthis is simply a three –quarter crown that has been rotated 90 degreesso that the distal surface is uncovered.so that the distal surface is uncovered.- Possible only if – the distal surface is caries freePossible only if – the distal surface is caries free - the distal surface is not decalcified- the distal surface is not decalcified - there is a very low incidence of proximal caries throughout the mouth- there is a very low incidence of proximal caries throughout the mouth - the patient is able to keep the area exceptionally clean.- the patient is able to keep the area exceptionally clean.- Contraindicated - where there is severe marginal ridge height discrepancy between the distalContraindicated - where there is severe marginal ridge height discrepancy between the distal of the 2of the 2ndnd molar and the mesial of 3 molar and the mesial of 3rdrd molar as a result of tipping. molar as a result of tipping.

Shillingburg HT (1972)Shillingburg HT (1972)- A telescope crown and coping can be used as a retainer on the distal abutment A telescope crown and coping can be used as a retainer on the distal abutment i.e. full crown preparation with heavy reduction is made to follow the long axis of i.e. full crown preparation with heavy reduction is made to follow the long axis of tilted molar. An inner coping is made to fit the tooth preparation and a proximal half tilted molar. An inner coping is made to fit the tooth preparation and a proximal half crown that will serve as a retainer for the FPD is fitted over the coping.crown that will serve as a retainer for the FPD is fitted over the coping.Advantages- allows total coverage of the clinical crown while Advantages- allows total coverage of the clinical crown while - compensating for the discrepancy between the path of insertion of the - compensating for the discrepancy between the path of insertion of the abutmentsabutments - the marginal adaptation is provided by the coping.- the marginal adaptation is provided by the coping.

Another alternative treatment for mesially tilted 2Another alternative treatment for mesially tilted 2ndnd molar molar Use of a Non-rigid connector Use of a Non-rigid connector - A full preparation is done on the molar with its path of insertionA full preparation is done on the molar with its path of insertion

parallel with the long axis of the tilted tooth.parallel with the long axis of the tilted tooth.- A box form is placed on the distal surface of the premolar to A box form is placed on the distal surface of the premolar to

accommodate a keyway in the distal aspect of the premolar.accommodate a keyway in the distal aspect of the premolar.

Reasons for NOT placing the non-rigid connector on the mesialReasons for NOT placing the non-rigid connector on the mesial

aspect of the tipped molar is that it can lead to even greater tipping of the tooth.aspect of the tipped molar is that it can lead to even greater tipping of the tooth.

Uses – when molar exhibits marked lingual as well as mesial inclination because Uses – when molar exhibits marked lingual as well as mesial inclination because

the routine FPD in such cases will lead to drastically overtapered preparation with no retention.the routine FPD in such cases will lead to drastically overtapered preparation with no retention.

Because telescope crowns and non-rigid connectors both require tooth preparations that are more Because telescope crowns and non-rigid connectors both require tooth preparations that are more destructive than normal, the selection of one of these would be influenced by the nature of previous destructive than normal, the selection of one of these would be influenced by the nature of previous

destruction of the prospective abutment toothdestruction of the prospective abutment tooth

for e.g. – the presence of a dowel core or a D.O amalgam on the premolar would favour placement of a for e.g. – the presence of a dowel core or a D.O amalgam on the premolar would favour placement of a

non-rigid connectornon-rigid connector

- while extensive facial and / or lingual restorations on the tilted molar would call for the use of - while extensive facial and / or lingual restorations on the tilted molar would call for the use of

a telescope crown.a telescope crown.

v) Canine replacement FPDv) Canine replacement FPD- FPD’s replacing canine may be difficult because canine often lies outside the interabutment line. FPD’s replacing canine may be difficult because canine often lies outside the interabutment line. - Prospective abutments are - Lateral Incisor ( Weakest tooth in the entire arch)Prospective abutments are - Lateral Incisor ( Weakest tooth in the entire arch)

- First premolar ( Weakest posterior tooth)- First premolar ( Weakest posterior tooth)

FPD’s replacing maxillary canine are subjected to more stresses thanFPD’s replacing maxillary canine are subjected to more stresses than

mandibular canine since the forces are transmitted outward (labially) mandibular canine since the forces are transmitted outward (labially)

on the maxillary arch against the inside of the curve (its weakest point).on the maxillary arch against the inside of the curve (its weakest point).

On the mandibular canine, the forces are directed inward (lingually) On the mandibular canine, the forces are directed inward (lingually)

against the outside of the curve ( its strongest point).against the outside of the curve ( its strongest point).

Any FPD replacing a canine should be regarded as a COMPLEX FPD.Any FPD replacing a canine should be regarded as a COMPLEX FPD.

A FPD replacing a canine should not replace more than one additional A FPD replacing a canine should not replace more than one additional

tooth.tooth.

An edentulous space created by the loss of a canine and any two An edentulous space created by the loss of a canine and any two

contiguous teeth is best restored by a removable partial denture.contiguous teeth is best restored by a removable partial denture.

B) REPLACEMENT OF SEVERAL MISSING TEETHB) REPLACEMENT OF SEVERAL MISSING TEETHFPD becomes more difficult when several teeth must be replaced, and underestimation FPD becomes more difficult when several teeth must be replaced, and underestimation

of the problems involved in extensive prosthodontics can lead to failure.of the problems involved in extensive prosthodontics can lead to failure.

Factors to be consideredFactors to be considered

i) i) Overloading of abutment teethOverloading of abutment teeth

the ability of the abutment teeth to accept applied forces without drifting or becoming mobile the ability of the abutment teeth to accept applied forces without drifting or becoming mobile

must be estimated.must be estimated.

The forces are particularly severe during parafunctional grinding and clenching and need toThe forces are particularly severe during parafunctional grinding and clenching and need to

eliminate them becomes obvious.eliminate them becomes obvious.

a) Direction of Forcesa) Direction of Forces. .

- - a well fabricated FPD can distribute applied force in the most favorable way by directing them in a well fabricated FPD can distribute applied force in the most favorable way by directing them in

the long axis of the abutment teeth.the long axis of the abutment teeth.

- The dislodging forces on a FPD retainer tend to act in a mesiodistal direction as opposes to the- The dislodging forces on a FPD retainer tend to act in a mesiodistal direction as opposes to the

more common buccolingual direction of forces in a single restoration.more common buccolingual direction of forces in a single restoration.

- Preparations should be modified accordingly to produce greater resistance & structural durability- Preparations should be modified accordingly to produce greater resistance & structural durability

- Multiple grooves, including some on the buccal and lingual surfaces are commonly employed- Multiple grooves, including some on the buccal and lingual surfaces are commonly employed

for this purpose.for this purpose.

b) Root surface area / Area of periodontal attachment of the root to the boneb) Root surface area / Area of periodontal attachment of the root to the bone

- When supporting bone is lost , the involved teeth have lessened capacity to serve as abutments, - When supporting bone is lost , the involved teeth have lessened capacity to serve as abutments,

Jepsen (1963)Jepsen (1963) reported the areas of the root surfaces of various teeth.reported the areas of the root surfaces of various teeth.

Tylman (1970)Tylman (1970) - stated that two abutment teeth could support two pontics. - stated that two abutment teeth could support two pontics.

Irvin H Ante (1926)Irvin H Ante (1926) – suggested that in fixed partial prosthodontics for the observation that, the – suggested that in fixed partial prosthodontics for the observation that, the

combined pericemental area of the abutment teeth supporting a fixed partialcombined pericemental area of the abutment teeth supporting a fixed partial

denture should be equal or greater in pericemental area than the tooth or teeth to denture should be equal or greater in pericemental area than the tooth or teeth to

be replaced.be replaced.

Johnson et al (1974)Johnson et al (1974) – designated “ ANTE’S LAW “ which states that the root surface area of – designated “ ANTE’S LAW “ which states that the root surface area of the the

abutment teeth had to equal or surpass that of the teeth being replaced with ponticsabutment teeth had to equal or surpass that of the teeth being replaced with pontics

Therefore according to this premise :Therefore according to this premise :

One missing tooth can be successfully replaced One missing tooth can be successfully replaced

if abutment teeth are healthy .if abutment teeth are healthy .

If two teeth are missing, a FPD can probably replace If two teeth are missing, a FPD can probably replace

the missing teeth but the limit is being approached.the missing teeth but the limit is being approached.

When the root surface area of the teeth to be replacedWhen the root surface area of the teeth to be replaced

by pontics surpass that of the abutment teeth ,then a by pontics surpass that of the abutment teeth ,then a

high risk or an unacceptable situation exists.high risk or an unacceptable situation exists.

As a clinical guideline there is some validity in the concept of “Ante’s Law”.As a clinical guideline there is some validity in the concept of “Ante’s Law”.

- i.e. FPD’s with short pontic spans have a better prognosis than do those with extremely long spans.i.e. FPD’s with short pontic spans have a better prognosis than do those with extremely long spans.However,However,

Nyman and EricssonNyman and Ericsson - - have demonstrated that even teeth with very poor periodontal support have demonstrated that even teeth with very poor periodontal support

can serve successfully as FPD abutments in carefully selected cases.can serve successfully as FPD abutments in carefully selected cases.

ii)ii) Root shape and angulation / Root configuration.Root shape and angulation / Root configuration. Roots that are broader labiolingually than mesiodistally or elliptical Roots that are broader labiolingually than mesiodistally or elliptical cross-section roots will offer better support than circular cross section cross-section roots will offer better support than circular cross section roots. A single rooted tooth with evidence of irregular configurationroots. A single rooted tooth with evidence of irregular configuration or with some curvature in the apical third of the root is preferred or with some curvature in the apical third of the root is preferred to the tooth that has nearly perfect taper.to the tooth that has nearly perfect taper.

Multirooted posterior teeth with widely separated roots will offer betterMultirooted posterior teeth with widely separated roots will offer better periodontal support than roots that converge, fuse or generally present aperiodontal support than roots that converge, fuse or generally present a conical configuration. Teeth with conical roots can be used as an conical configuration. Teeth with conical roots can be used as an abutment for a short span FPD if all other factors are optimal.abutment for a short span FPD if all other factors are optimal.

iii) Crown - root ratio.iii) Crown - root ratio.- This ratio is a measure of the length of the tooth occlusal to This ratio is a measure of the length of the tooth occlusal to

the alveolar crest of bone compared with the length of the alveolar crest of bone compared with the length of

root embedded in the bone.root embedded in the bone.- Optimum crown-root ratio for a tooth to be utilized as Optimum crown-root ratio for a tooth to be utilized as

a FPD abutment is a FPD abutment is 2:32:3

-- A ratio of A ratio of 1:11:1 is the minimum ratio that is acceptable is the minimum ratio that is acceptable

for a prospective abutment under normal circumstances.for a prospective abutment under normal circumstances.

If the occlusion opposing a proposed fixed partial denture is composed of artificial teeth, the If the occlusion opposing a proposed fixed partial denture is composed of artificial teeth, the

occlusal force will be diminished with less stress on the abutment teeth.occlusal force will be diminished with less stress on the abutment teeth.

Kaffenbach (1936)Kaffenbach (1936) - - showed that the occlusal force exerted against prosthetic appliance has showed that the occlusal force exerted against prosthetic appliance has

been shown to be considerably less than against natural teeth.been shown to be considerably less than against natural teeth.

i.e. 26.0 lbs for removeable partial dentures,i.e. 26.0 lbs for removeable partial dentures,

54.5 lbs for fixed partial dentures versus54.5 lbs for fixed partial dentures versus

150 lbs for naural teeth.150 lbs for naural teeth.

After a horizontal bone loss from periodontal disease the pdl supported root surface areas can be After a horizontal bone loss from periodontal disease the pdl supported root surface areas can be dramatically reduced.dramatically reduced.

Because of the conical shape of most roots, when one third of theBecause of the conical shape of most roots, when one third of the

root length has been exposed half of the supporting area is lost. root length has been exposed half of the supporting area is lost.

In addition, the forces applied to the supporting bone are magnified becauseIn addition, the forces applied to the supporting bone are magnified because

of the greater leverage associated with the lengthened clinical crown.of the greater leverage associated with the lengthened clinical crown.

However, However, Nyman et al (1975) & Laurell et al (1991)Nyman et al (1975) & Laurell et al (1991) – said that – said that

successful FPD can be fabricated on teeth with severely reduced periodontalsuccessful FPD can be fabricated on teeth with severely reduced periodontal

support, provided the periodontal tissues have been returned to excellentsupport, provided the periodontal tissues have been returned to excellent

health and long term maintenance has been ensured.health and long term maintenance has been ensured.

Healthy periodontal tissues are prerequisites for all FPD’s and it is important that excellent plaque Healthy periodontal tissues are prerequisites for all FPD’s and it is important that excellent plaque

removal techniques be implemented and maintained at all times.removal techniques be implemented and maintained at all times.

iv) Span Lengthiv) Span Length- All FPD’s flex slightly when subjected to load.All FPD’s flex slightly when subjected to load.- In addition to the increased load placed on the periodontal ligament by a long span FPD , longer In addition to the increased load placed on the periodontal ligament by a long span FPD , longer

spans are less rigid and therefore flex more.spans are less rigid and therefore flex more.

Bending or deflection varies :Bending or deflection varies :

Directly with the cube of the length andDirectly with the cube of the length and Inversely with the cube of the occlusogingival thickness of the ponticInversely with the cube of the occlusogingival thickness of the pontic..

Smyth (1952)Smyth (1952)

Compared a FPD having a single tooth pontic span with aCompared a FPD having a single tooth pontic span with a

two tooth pontic span and a three tooth pontic span and two tooth pontic span and a three tooth pontic span and

stated that stated that

- A two tooth pontic will bend 8 times as much and A two tooth pontic will bend 8 times as much and

- A three tooth pontic will bend 27 times as much as A three tooth pontic will bend 27 times as much as

a single tooth pontica single tooth pontic

- A pontic with a given occluso-gingival dimension will bend 8 times as much if the pontic thickness A pontic with a given occluso-gingival dimension will bend 8 times as much if the pontic thickness is halved.is halved.

- Therefore, a long span FPD on short mandibular teeth can have disappointing results.- Therefore, a long span FPD on short mandibular teeth can have disappointing results.

- Longer pontic spans also have the potential for producing more torquing forces on the FPD.- Longer pontic spans also have the potential for producing more torquing forces on the FPD.

To minimize flexingTo minimize flexing - - select pontic design with greater occlusogingival directionselect pontic design with greater occlusogingival direction

- make bulky connectors to ensure optimum rigidity- make bulky connectors to ensure optimum rigidity

- if long span or unfavorable crown –root ratio then use double abutments- if long span or unfavorable crown –root ratio then use double abutments ..- Criteria for double Abutments.Criteria for double Abutments.- Secondary abutments (remote from edentulous space) must have – as much root surface area and Secondary abutments (remote from edentulous space) must have – as much root surface area and

as favorable a crown root ratio as the primary abutment ( adjacent to the edentulous space).as favorable a crown root ratio as the primary abutment ( adjacent to the edentulous space).- The retainers on secondary abutments must be at least as retentive as on primary abutments because The retainers on secondary abutments must be at least as retentive as on primary abutments because

when the pontic flexes tensile forces will be applied on the retainers on the secondary abutments. when the pontic flexes tensile forces will be applied on the retainers on the secondary abutments.- There must also be sufficient crown length and space between adjacent abutments to prevent There must also be sufficient crown length and space between adjacent abutments to prevent

impingement on the gingiva under the connectorimpingement on the gingiva under the connector

v) Pier Abutmentsv) Pier Abutments

An edentulous space can occur on both sides of a tooth creating a lone , free standing pier abutment.An edentulous space can occur on both sides of a tooth creating a lone , free standing pier abutment.

Shillingburg and Fisher (1973)Shillingburg and Fisher (1973) – forces are transmitted to the terminal retainers as – forces are transmitted to the terminal retainers as

a result of the middle abutment acting as a fulcrum causing failure of the weaker a result of the middle abutment acting as a fulcrum causing failure of the weaker

retainer.retainer.

However, photoelastic stress analysis and displacement measurement indicate that However, photoelastic stress analysis and displacement measurement indicate that

the prosthesis bends rather than rocks and the prosthesis bends rather than rocks and Standlee & Caputo (1988)Standlee & Caputo (1988) suggested that suggested that

tension between the terminal retainers and their respective abutments rather than tension between the terminal retainers and their respective abutments rather than

pier fulcrum, as the mechanism of failure.pier fulcrum, as the mechanism of failure.

Because of the forces :-Because of the forces :-

- the retainers or the casting will get loosened- the retainers or the casting will get loosened- Leakage will be caused around the margin leading to extensive caries.Leakage will be caused around the margin leading to extensive caries.

Since there are limits to increase a retainers capacity to withstand displacing forces, some Since there are limits to increase a retainers capacity to withstand displacing forces, some means must be used to neutralize the effects of those factors.means must be used to neutralize the effects of those factors.

Shillingburg and Fisher (1973)Shillingburg and Fisher (1973) recommended the use of a NON-RIGID recommended the use of a NON-RIGID CONNECTOR CONNECTOR to reduce this hazard. to reduce this hazard. It has an apparently close fit It has an apparently close fit Enough movement to prevent the transfer of stress from the Enough movement to prevent the transfer of stress from the segment being loaded to the rest of the FPD. segment being loaded to the rest of the FPD.- It is a broken stress mechanical union of retainer and ponticIt is a broken stress mechanical union of retainer and pontic- It transfers shear stress to supporting bone rather than It transfers shear stress to supporting bone rather than

concentrating it in the connectors concentrating it in the connectors - It appears to minimize mesiodistal torquing of the abutment,It appears to minimize mesiodistal torquing of the abutment,

while permitting them to move independently while permitting them to move independently - most commonly used non-rigid design -------- T- shaped key that is attached to the pontic & a dovetail most commonly used non-rigid design -------- T- shaped key that is attached to the pontic & a dovetail

keyway placed in the retainerkeyway placed in the retainer

A rigid FPD distributes the load more evenly than a non-rigid design, making it preferable for teeth with A rigid FPD distributes the load more evenly than a non-rigid design, making it preferable for teeth with decreased periodontal attachment where as ,decreased periodontal attachment where as ,

A non rigid FPD should not be used if prospective abutment teeth exhibit significant mobility.A non rigid FPD should not be used if prospective abutment teeth exhibit significant mobility.

LocationLocation:: should be placed in the middle abutmentshould be placed in the middle abutment

- placement on either of the terminal abutments can lead to pontic acting as a lever arm- placement on either of the terminal abutments can lead to pontic acting as a lever arm

Keyway - should be placed within the normal distal contours of pier abutmentKeyway - should be placed within the normal distal contours of pier abutment

Key - should be placed on the mesial side of the distal pontic.Key - should be placed on the mesial side of the distal pontic.

Long axes of posterior teeth usually lean slightly in a mesial direction and about 98% posterior Long axes of posterior teeth usually lean slightly in a mesial direction and about 98% posterior teeth tilt more mesially when subjected to occlusal forces. teeth tilt more mesially when subjected to occlusal forces. Therefore, Therefore,

ShillingburgShillingburg - if keyway is placed on the distal of pier abutment - if keyway is placed on the distal of pier abutment

Then the mesial movement seats the key into the keyway more solidly.Then the mesial movement seats the key into the keyway more solidly.

Standlee & Caputo (1988Standlee & Caputo (1988)) If placement of the keyway is on the If placement of the keyway is on the

mesial side then it causes the key to be unseated during the mesialmesial side then it causes the key to be unseated during the mesial

movement which in time can cause a pathologic mobility in the movement which in time can cause a pathologic mobility in the

canine or failure of the canine retainer.canine or failure of the canine retainer.

Another complication/ problemAnother complication/ problem- If the posterior abutment and pontic are either unopposed or opposed by a removable partial denture, If the posterior abutment and pontic are either unopposed or opposed by a removable partial denture,

and if the three anterior units are opposed by natural teeth ------ then the key and the posterior units that haveand if the three anterior units are opposed by natural teeth ------ then the key and the posterior units that have

little or no occlusal forces will SUPRAERUPT.little or no occlusal forces will SUPRAERUPT.

iii) Replacing multiple anterior teethiii) Replacing multiple anterior teeth Special considerationsSpecial considerations - problems with appearance - problems with appearance

- need to resist laterally directed tipping forces when pontics lie outside the - need to resist laterally directed tipping forces when pontics lie outside the

intrabutment line axis (pontics acts as a lever arm which can produce torquing movement)intrabutment line axis (pontics acts as a lever arm which can produce torquing movement)

This is a common problem while This is a common problem while Replacing four maxillary incisorsReplacing four maxillary incisors

* * solved by - gaining additional retention in the opposite direction from solved by - gaining additional retention in the opposite direction from

the lever arm and at a distance from the interabutment axisthe lever arm and at a distance from the interabutment axis

equal to the length of the lever arm. Therefore the first equal to the length of the lever arm. Therefore the first

premolars are sometimes used a secondary abutments for premolars are sometimes used a secondary abutments for

better retention because the tensile forces will be applied tobetter retention because the tensile forces will be applied to

the premolar retainers.the premolar retainers.

Replacing four madibular incisors Replacing four madibular incisors - Can be replaced by simple FPD with retainers on each canineCan be replaced by simple FPD with retainers on each canine- Not usually necessary to include the first premolarsNot usually necessary to include the first premolars- Lone standing incisors should be removed because its retention can complicate & further jeopardizeLone standing incisors should be removed because its retention can complicate & further jeopardize

long term results long term results

Mandibular incisors because of small size make poor abutment teeth & plaque control difficultMandibular incisors because of small size make poor abutment teeth & plaque control difficult

Therefore, a clinician must make a choice between i) compromised esthetics from too thin a ceramic veneerTherefore, a clinician must make a choice between i) compromised esthetics from too thin a ceramic veneer

ii) pulpal exposure during tooth preparation or ii) pulpal exposure during tooth preparation or

iii) selective tooth removal.iii) selective tooth removal.

C) INDICATIONS FOR REMOVEABLE PARTIAL C) INDICATIONS FOR REMOVEABLE PARTIAL DENTUREDENTURE

Whenever possible edentulous spaces will should be restored with FPD than RPD, Whenever possible edentulous spaces will should be restored with FPD than RPD,

however under the following circumstances RPD is indicated.however under the following circumstances RPD is indicated. Where vertical support from the edentulous ridge is needed . Where vertical support from the edentulous ridge is needed .

E.g. in the absence of a distal abutment.E.g. in the absence of a distal abutment. Where resistance to lateral movement is needed from contra-lateral teeth and Where resistance to lateral movement is needed from contra-lateral teeth and

soft tissues.soft tissues.

E.g. to ensure stability with a long edentulous spaceE.g. to ensure stability with a long edentulous space When there is a considerable bone loss in the visible anterior region and an FPDWhen there is a considerable bone loss in the visible anterior region and an FPD

would have an unacceptable appearance.would have an unacceptable appearance.

V) Sequence of treatmentV) Sequence of treatmentIncludes : Includes :

a) Treatment of symptomsa) Treatment of symptoms Relief of discomfort accompanying acute conditionsRelief of discomfort accompanying acute conditions

Urgent treatment of non-acute problemsUrgent treatment of non-acute problems

b) Stabilization of deteriorating factorsb) Stabilization of deteriorating factors

Dental cariesDental caries

Periodontal diseasePeriodontal disease

c) Definitive therapy c) Definitive therapy

Oral surgery, Periodontics, Endodontics, Orthodontics, Oral surgery, Periodontics, Endodontics, Orthodontics,

Fixed Prosthodontics – Occlusal adjustmentsFixed Prosthodontics – Occlusal adjustments

- Anterior restorations- Anterior restorations

- Posterior Restorations- Posterior Restorations

- Complex Prosthodontics- Complex Prosthodontics

d) Follow up d) Follow up specific program of follow up care & regular recall visits.specific program of follow up care & regular recall visits.

ReferencesReferences

1)1) Contemporary Fixed Prosthodontics – Contemporary Fixed Prosthodontics – Rosenstiel, Rosenstiel, Land & FujimotoLand & Fujimoto

2)2) Fundamentals of Fixed Prosthodontics – Fundamentals of Fixed Prosthodontics – ShillingburgShillingburg

3)3) A preliminary diagnostic and treatment protocol A preliminary diagnostic and treatment protocol – – J Bowley et al J Bowley et al

DCNA.July DCNA.July 1992,36(3) 551-567.1992,36(3) 551-567.

4) Decision making in Dental treatment planning – 4) Decision making in Dental treatment planning – Hall, Roberts andHall, Roberts and

LaBarreLaBarre

THANK YOU !THANK YOU !