Treatment Planning in
FPD
Dr Kaushal Kishor Agrawal
Assistant Professor
Departmnent of Prosthodontics
KGMU Lucknow
Types of Fixed Prosthodontic
Treatment

-
Conventional tooth supported fixed partial denture
Utilizes an abutment tooth on each end or only one end
(cantilever) of the edentulous space.
- If abutment teeth are periodontally sound, the edentulous span
is short and straight and the retainers are well designed and
executed, the FPD can be expected to provide a long life and
function for the pt.
- there should be : - no gross soft tissue defect in the edentulous
space
- no dry mouth which can create a poor
environment for FPD

Resin bonded tooth supported fixed partial denture
- conservative restoration reserved for use on defect free
abutments to replace single missing tooth usually an incisor or
premolar.
- for molars – replaced only if muscles of mastication are not
too well developed
- abutments on both sides of edentulous space, preparation is
shallow and restricted to enamel
- useful in young pts who have immature teeth with large pulps
- should be used with extreme care and may require additional
resistance features (e.g. grooves)
- Abutment Mobility has been shown to be a serious hazard in
the successful use of this type of
prosthesis.

Implant supported fixed partial dentures
- when there are insufficient abutment teeth, inadequate strength in abutments, no distal
abutment present.
- Span length limited by availability of alveolar bone, with satisfactory density and thickness in
a broad flat ridge
- Single missing tooth – replaced by single implant – therefore no destruction of
adjacent abutments.
- 2-6 missing teeth – replaced by multiple implants either as single units or implant supported
FPD’s.
- can be used as pier abutments in a long span … but immovable implant usually not preferred
with natural teeth in same rigid prosthesis.
- 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 forces.
- 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
& even possibly root resection to support a long span complex FPD then, “ Implant may be a
better choice”
Treatment 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 techniques
Clinician should understand the limitations of appropriate materials and procedures &
this will help prevent experimental approach to treatment.
a)
Plastic materials (e.g. AgAm & Composite)
b)
Cast Metal – intracoronal restoration & extracoronal restoration
c)
Metal ceramic
d)
Resin Veneered
e)
Fiber-reinforced resin
f)
Complete ceramic
g)
Fixed partial denture
h)
Implant supported prosthesis
i)
Removable partial dentures
III-Treatment of tooth loss
Causes- caries, pdl disease, trauma, neoplasm, congenitally absent
a) Decision to remove a tooth – poor/hopeless teeth should be removed.
A decision about replacing a missing tooth is best made at the time of
its removal rather than months or years after the fact.
b) Consequences of removal without replacement –
- supraclusion/ supraeruption of opposing tooth/teeth.
- tilting of the adjacent teeth
- loss of proximal contact
Extended treatment plans like orthodontic repositioning and additional
cast restoration may be needed to compensate for the lack of treatment at
the time of tooth removal
Fig 1 –Tooth position and alignment are
maintained, in part by the interaction
between teeth.
Fig 2 – shows the typical consequences
1- supraclusion of opposing teeth
2- tilting of adjacent teeth
3- loss of contact
IV-Selection of Abutment teeth/
Abutment Evaluation
-Whenever possible an abutment should be a “VITAL TOOTH”
-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
abutment teeth should be able to withstand the forces normally directed to the
missing teeth in addition to those usually applied to the abutments.
-An FPD should be designed as simply as possible
A)
REPLACEMENT OF SINGLE MISSING TOOTH
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.
Factors to be considered
i) Cantilever FPD - this is a potentially destructive design with the lever arm
created by the pontic.
Fig A – the pontic of a cantilever bridge acts
as a lever arm that tends to cause tipping
and rotation under strong occlusal vector.
Fig B – the forces that are applied to the pontic
of a 3 unit FPD is distributed equally to
the abutment teeth and less leverage is
applied to the teeth or the retainers than
with the cantilever bridge.
Uses of Cantilever Bridge
a) Replacing Maxillary lateral incisor
There should be no occlusal contact on
either centric or lateral excursions.
Canine must be the abutment & must
have long root and good bone support.
To prevent rotation of pontic and
abutment , a rest can be placed on the
mesial of pontic against a rest
preparation on the distal of the central
incisor.
b) Replacing Mandibular first premolar
Occlusal contact should be limited to
the distal fossa.
Full veneer retainers on both the second
premolar and molar.
There should be excellent bone support
around the abutment teeth.
Uses contd…
c) Replacing mandibular molars when there is
no distal abutment present
Pontic should be kept as small as
possible (like a premolar) with light
occlusal contact in centric and absolutely
no contacts in any excursions because the
adjacent abutment acts as a fulcrum with
a lifting tendency on the farthest retainer.
Pontic should possess maximum
occlusogingival height to ensure a rigid
prosthesis
d) Used with implant supported prosthesis
The actual length of cantilever depends
on stress factors.
E.g. Parafunction, arch position, masticatory
dynamics, opposing arch, crown height,
direction of force, bone density, implant
number, implant width, implant design
and A-P distance.
Factors contd…
ii) Assessment of abutment teeth
-
Thorough investigation of each abutment with radiographic examination
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
possible pulpal exposure
iii) Endodontically treated abutments
-
-
If properly treated it can serve well as an abutment, with the post and core foundation for
retention and strength.
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.
iv) Unrestored abutments
-
Ideal – Unrestored, caries free
Can 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 a FPD , the overall dental health of the patient should be emphasized rather than looking at
each tooth individually.
Factors contd…
v)
Tilted molar abutments / Mesially tilted second molars
-
Common problem occurs when the mandibular 2nd molar abutment gets tilted into the
space formerly occupied by the first molar. Further complication occurs if the 3 rd molar is
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.
-
If encroachment is slight - solved by restoring or recontouring
the mesial surface of 3rd molar
- addtion of facial and lingual grooves on 2nd molar for better retention
If tilting is severe – uprighting of the molar by orthodontic treatment.
- also helps in distribution of forces under occlusal loading and even
helps to eliminate bony defects along the mesial surface of the root.
- usually 3rd molars are extracted to facilitate movement of 2nd molar.
- Average treatment time – 3 months.
-to prevent post treatment relapse, a temporary FPD is fabricated
immediately after removal of orthodontic appliance.
If orthodontic correction id not possible , a FPD can still be fabricated
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
surface of its mesial root with a fixed partial denture than without it. However, there will be an increase in
stress along the premolar.
Smith (1993)
Proximal half crowns can be used as a retainer on distal abutment.
this is simply a three –quarter crown that has been rotated 90 degrees
so that the distal surface is uncovered.
Possible only if – the distal surface is caries free
- the distal surface is not decalcified
- there is a very low incidence of proximal caries throughout the mouth
- the patient is able to keep the area exceptionally clean.
Contraindicated - where there is severe marginal ridge height discrepancy between the distal
of the 2nd molar and the mesial of 3rd molar as a result of tipping.
-
Shillingburg HT (1972)
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
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.
Advantages- allows total coverage of the clinical crown while
- compensating for the discrepancy between the path of insertion of the
abutments
- the marginal adaptation is provided by the coping.
-
Another alternative treatment for mesially tilted 2nd molar
Use of a Non-rigid connector
-
-
A full preparation is done on the molar with its path of insertion
parallel with the long axis of the tilted tooth.
A box form is placed on the distal surface of the premolar to
accommodate a keyway in the distal aspect of the premolar.
Reasons 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.
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.
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
destruction 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
non-rigid connector
- while extensive facial and / or lingual restorations on the tilted molar would call for the use of
a telescope crown.
v) Canine replacement FPD
-
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)
- First premolar ( Weakest posterior tooth)
FPD’s replacing maxillary canine are subjected to more stresses than
mandibular canine since the forces are transmitted outward (labially)
on the maxillary arch against the inside of the curve (its weakest point).
On the mandibular canine, the forces are directed inward (lingually)
against the outside of the curve ( its strongest point).
Any FPD replacing a canine should be regarded as a COMPLEX FPD.
A FPD replacing a canine should not replace more than one additional
tooth.
An edentulous space created by the loss of a canine and any two
contiguous teeth is best restored by a removable partial denture.
B) REPLACEMENT OF SEVERAL MISSING TEETH
FPD becomes more difficult when several teeth must be replaced, and underestimation
of the problems involved in extensive prosthodontics can lead to failure.
Factors to be considered
i) Overloading of abutment teeth
the ability of the abutment teeth to accept applied forces without drifting or becoming mobile
must be estimated.
The forces are particularly severe during parafunctional grinding and clenching and need to
eliminate them becomes obvious.
a) Direction of Forces.
- 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 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.
- Preparations should be modified accordingly to produce greater resistance & structural durability
- Multiple grooves, including some on the buccal and lingual surfaces are commonly employed
for this purpose.
b) 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,
Jepsen (1963) reported the areas of the root surfaces of various teeth.
Tylman (1970) - stated that two abutment teeth could support two pontics.
Irvin H Ante (1926) – suggested that in fixed partial prosthodontics for the observation that, the
combined 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
be replaced.
Johnson et al (1974) – designated “ ANTE’S LAW “ which states that the root surface area of the
abutment teeth had to equal or surpass that of the teeth being replaced with pontics
Therefore according to this premise :



One missing tooth can be successfully replaced
if abutment teeth are healthy .
If two teeth are missing, a FPD can probably replace
the missing teeth but the limit is being approached.
When the root surface area of the teeth to be replaced
by pontics surpass that of the abutment teeth ,then a
high risk or an unacceptable situation exists.
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.
However,
Nyman and Ericsson - have demonstrated that even teeth with very poor periodontal support
can serve successfully as FPD abutments in carefully selected cases.
-
ii)
Root shape and angulation / Root configuration.
Roots that are broader labiolingually than mesiodistally or elliptical
cross-section roots will offer better support than circular cross section
roots. A single rooted tooth with evidence of irregular configuration
or with some curvature in the apical third of the root is preferred
to the tooth that has nearly perfect taper.
Multirooted posterior teeth with widely separated roots will offer better
periodontal support than roots that converge, fuse or generally present a
conical configuration. Teeth with conical roots can be used as an
abutment for a short span FPD if all other factors are optimal.
iii) Crown - root ratio.
-
This ratio is a measure of the length of the tooth occlusal to
the alveolar crest of bone compared with the length of
root embedded in the bone.
Optimum crown-root ratio for a tooth to be utilized as
a FPD abutment is 2:3
- A ratio of 1:1 is the minimum ratio that is acceptable
for a prospective abutment under normal circumstances.
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.
Kaffenbach (1936) -
showed that the occlusal force exerted against prosthetic appliance has
been shown to be considerably less than against natural teeth.
i.e. 26.0 lbs for removeable partial dentures,
54.5 lbs for fixed partial dentures versus
150 lbs for naural teeth.
After a horizontal bone loss from periodontal disease the pdl supported root surface areas can be
dramatically reduced.
Because of the conical shape of most roots, when one third of the
root length has been exposed half of the supporting area is lost.
In addition, the forces applied to the supporting bone are magnified because
of the greater leverage associated with the lengthened clinical crown.

However,
Nyman et al (1975) & Laurell et al (1991) – said that
successful FPD can be fabricated on teeth with severely reduced periodontal
support, provided the periodontal tissues have been returned to excellent
health and long term maintenance has been ensured.
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.
iv) Span Length
-
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
spans are less rigid and therefore flex more.
Bending or deflection varies :


Directly with the cube of the length and
Inversely with the cube of the occlusogingival thickness of the pontic.

Smyth (1952)
Compared a FPD having a single tooth pontic span with a
two tooth pontic span and a three tooth pontic span and
stated that
-
A two tooth pontic will bend 8 times as much and
-
A three tooth pontic will bend 27 times as much as
a single tooth pontic
A pontic with a given occluso-gingival dimension will bend 8 times as much if the pontic thickness
is halved.
- 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.
To minimize flexing - select pontic design with greater occlusogingival direction
- make bulky connectors to ensure optimum rigidity
- if long span or unfavorable crown –root ratio then use double abutments.
Criteria for double Abutments.
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).
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.
There must also be sufficient crown length and space between adjacent abutments to prevent
impingement on the gingiva under the connector
-
v) Pier Abutments
An edentulous space can occur on both sides of a tooth creating a lone , free standing pier abutment.
Shillingburg and Fisher (1973) – forces are transmitted to the terminal retainers as
a result of the middle abutment acting as a fulcrum causing failure of the weaker
retainer.
However, photoelastic stress analysis and displacement measurement indicate that
the prosthesis bends rather than rocks and Standlee
& Caputo (1988) suggested that
tension between the terminal retainers and their respective abutments rather than
pier fulcrum, as the mechanism of failure.
Because of the forces :- the retainers or the casting will get loosened
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
means must be used to neutralize the effects of those factors.
Shillingburg and Fisher (1973) recommended the use of a NON-RIGID CONNECTOR
-
-
-
to reduce this hazard.
It has an apparently close fit
Enough movement to prevent the transfer of stress from the
segment being loaded to the rest of the FPD.
It is a broken stress mechanical union of retainer and pontic
It transfers shear stress to supporting bone rather than
concentrating it in the connectors
It appears to minimize mesiodistal torquing of the abutment,
while permitting them to move independently
most commonly used non-rigid design -------- T- shaped key that is attached to the pontic & a dovetail
keyway placed in the retainer
A rigid FPD distributes the load more evenly than a non-rigid design, making it preferable for teeth with
decreased periodontal attachment where as ,
A non rigid FPD should not be used if prospective abutment teeth exhibit significant mobility.
Location: should be placed in the middle abutment
- 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 abutment
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
teeth tilt more mesially when subjected to occlusal forces.
Therefore,
Shillingburg
- if keyway is placed on the distal of pier abutment
Then the mesial movement seats the key into the keyway more solidly.
Standlee & Caputo (1988) If placement of the keyway is on the
mesial side then it causes the key to be unseated during the mesial
movement which in time can cause a pathologic mobility in the
canine or failure of the canine retainer.
Another complication/ problem
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 have
little or no occlusal forces will SUPRAERUPT.
iii) Replacing multiple anterior teeth
Special considerations - problems with appearance
- 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)
This is a common problem while Replacing four maxillary incisors
* solved by - gaining additional retention in the opposite direction from
the lever arm and at a distance from the interabutment axis
equal to the length of the lever arm. Therefore the first
premolars are sometimes used a secondary abutments for
better retention because the tensile forces will be applied to
the premolar retainers.
Replacing four madibular incisors
Can be replaced by simple FPD with retainers on each canine
Not usually necessary to include the first premolars
Lone standing incisors should be removed because its retention can complicate & further jeopardize
long term results
Mandibular 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 veneer
ii) pulpal exposure during tooth preparation or
iii) selective tooth removal.
C) INDICATIONS FOR REMOVEABLE PARTIAL DENTURE
Whenever possible edentulous spaces will should be restored with FPD than RPD,
however under the following circumstances RPD is indicated.

Where vertical support from the edentulous ridge is needed .
E.g. in the absence of a distal abutment.

Where resistance to lateral movement is needed from contra-lateral teeth and
soft tissues.
E.g. to ensure stability with a long edentulous space

When there is a considerable bone loss in the visible anterior region and an FPD
would have an unacceptable appearance.
V) Sequence of treatment
Includes :
a) Treatment of symptoms
Relief of discomfort accompanying acute conditions
Urgent treatment of non-acute problems
b) Stabilization of deteriorating factors
Dental caries
Periodontal disease
c) Definitive therapy
Oral surgery, Periodontics, Endodontics, Orthodontics,
Fixed Prosthodontics – Occlusal adjustments
- Anterior restorations
- Posterior Restorations
- Complex Prosthodontics
d) Follow up specific program of follow up care & regular recall visits.
References
1) Contemporary Fixed Prosthodontics – Rosenstiel, Land & Fujimoto
2) Fundamentals of Fixed Prosthodontics – Shillingburg
3) A preliminary diagnostic and treatment protocol – J Bowley et al
DCNA.July 1992,36(3) 551-567.
4) Decision making in Dental treatment planning – Hall, Roberts and
LaBarre
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