Failures in fpd / orthodontics courses in india

COMPLICATIONS IN
FIXED PARTIAL
DENTURE PROSTHESES
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Contents
 Introduction
 Evaluating the quality of existing restorations
 Classification
 Causes of failure
 Biologic failures
 Mechanical failures
 Esthetic failures
 Facing failures
 Removal of restorations
 Repairs
 Review of literature
 Summary
 Conclusion

 Fixed prosthodontic treatment can offer
exceptional satisfaction for both patient and
dentist. It can transform an unhealthy,
unattractive dentition with poor function into a
comfortable, healthy occlusion capable of
giving years of further service while greatly
enhancing esthetics.

The constituents of failure are more
easily interpreted once restorative
care objectives are stated. One can
then define failure as an inability to
meet or satisfy objectives.
Classification system for conventional crown and fixed partial denture failures
John Joy Manappallil, J Prosthet Dent 2008;99:293-

The objectives of fixed prosthodontic
treatment include:
 (1) Preservation or improvement of related hard
and soft tissue structures.
 (2) Preservation or improvement of oral functions.
 (3) Improvement or restoration of esthetics.
 (4) Ensuring restoration retention, resistance, and
stability.
 (5) Providing restorations with mechanical or
structural integrity.
 (6) Preserving or improving patient comfort
 (7) Designing restorations for maximum longevity.
John Joy Manappallil, J Prosthet Dent 2008;99:293-298

 To achieve such success, however,
requires meticulous attention to every
detail from initial patient interview,
through the active treatment phase, to a
planned schedule of follow-up care.
 Failure to achieve the desired
specifications of design for function and
esthetics would result in failure of the
prosthesis

 Looking at a crown or a bridge, it is always
possible to find some minor fault with the fit or
the appearance or some other aspects.
 In many cases it is the matter of degree.
 “There is nothing seriously wrong with the
restoration, only that one dentist, looking at
another’s work, would have applied his or her
skills in different ways; would have introduced
little more incisal translucence or placed the
margin a little more sub-gingivally or supra
gingivally, or finished it better.”
Bernard G.N. Smith PLANNING AND MAKING CROWNS AND BRIDGESwww.indiandentalacademy.com

 “These variations in judgement are to be
expected and need to be encouraged. If
every crown or bridge were standardised,
there would be no room for development and
improvement.”
 At the other extremes there are undisputed
failures for example the fractures PJC or the
loose bridge where extensive caries have
developed.
 Between these extremes lies a large gray
area of partial failures and partial successes.
Bernard G.N. Smith PLANNING AND MAKING CROWNS AND BRIDGESwww.indiandentalacademy.com

 Prostheses cannot be routinely be expected
to last a life time.
 As a matter of fact, when all of the formidable
problems encountered in the oral
environment are considered, it is amazing
that restorations last as long as they do.

What’s the survival rate of
a fixed partial denture
prosthesis??

Meta-analysis of fixed partial denture survival:
Prostheses and abutments
Mark Scurria, James Bader
(J Prosthet Dent 1998;79:459-64.)
 For the aggregate population represented by
the limited longitudinal studies available, this
meta-analysis indicated that:
 less than 15% of fixed partial dentures were
removed or in need of replacement at 10
years;
 whereas, nearly one third were removed or in
need of replacement at 15 years.
 Less than 5% of abutments were removed at
10 years.

Meta-analysis of fixed partial denture
survival: Prostheses and abutments
Mark Scurria, James Bader
(J Prosthet Dent 1998;79:459-64.)
CLINICAL IMPLICATIONS
From the studies included in the meta-
analysis, one might expect
one third of fixed partial dentures to require
replacement by 15 years.

 A complication has been defined as “a
secondary disease or condition developing in
the course of a primary disease or condition.”
Merriam Webster’s Collegiate Dictionary. 10th ed. Springfield, MA: Merriam-
Webster; 1993. p. 236.

Don’t overlook anything !!

 Although complications may be an indication
that clinical failure has occurred, this is not
typically the case.
 It is also possible that complications may
reflect substandard care. But once again, this
is usually not true.
 Most of the time, complications are conditions
that occur during or after appropriately
performed fixed prosthodontic treatment
procedures.
Clinical complications in fixed prosthodontics
Charles J. Goodacre et al (J Prosthet Dent 2003;90:31-41.)

Why to learn about Complications?
 Knowledge regarding the clinical complications
that can occur in fixed prosthodontics:
 Enhances the clinician’s ability to complete a
thorough diagnosis,
 Develop the most appropriate treatment plan,
 Communicate realistic expectations to patients,
and
 Plan the time intervals needed for post-
treatment care.

EVALUATING THE QUALITY OF
EXISTING RESTORATIONS

Donald W. Fisher/William W Morgan
MODIFICATION AND PRESERVATION OF EXISTING
DENTAL RESTORATIONS
An evaluation of existing restoration will lead to
one of the three possible courses:
Leaving the restoration alone, if it is not causing
any serious harm. Although this is the most
common choice by far, it must not be arrived
at by default. Instead a careful examination is
necessary to rule out any defects.
Adjusting or repairing the fault.
Replacing the crown or bridge. The existing
restoration is amenable to modification

 Many failures occur because the dentist does
not take time to do a thorough diagnosis and
plan for success.
 The four major diagnostic aids to making a
dental diagnosis are :
 Taking a history
 Doing a careful clinical examination
 Having a complete set of radiographs
 Having a good set of diagnostic casts
correctly mounted.
MODIFICATION AND PRESERVATION OF EXISTING DENTAL RESTORATIONSwww.indiandentalacademy.com

Abutment tooth selection :
 The selection of an abutment tooth depends
on the length of span of the restoration and
the amount of stress that will be applied to
the abutment .
 The strength of a tooth is directly proportional
to the amount of periodontal ligament that
attaches the tooth to bone.
MODIFICATION AND PRESERVATION OF EXISTING DENTAL RESTORATIONS

 Minimal requirement for an abutment tooth is
a 1:1 crown:root ratio, and the root should not
be mobile or conical shape.
 The optimum crown-root ratio for a fixed
partial denture abutment is 2:3

Although the root surface area of these teeth
is similar, the Root Configuration of the
maxillary premolar (A), with its greater
faciolingual dimension, makes it a superior
abutment to the maxillary central incisor (B),
whose root is essentially circular in cross
section.

Molar with divergent roots (A) will be a better
abutment tooth than one whose roots are
fused (B).

 A simple guide in deciding whether to make a fixed or
a removable partial denture is ante’s rule.
 Ante's Law
 Described way back in the 1926 which still applies
today.
 “In fixed bridges the combined pericemental area of
the abutment teeth should be equal to or greater in
pericemental area than the teeth to be replaced.”

 Exceptions can occasionally be made to this
rule. For instance, longer spans can be used
when the opposing teeth are part of a
removable denture. Removable dentures can
not produce the same biting force as natural
teeth.

Ante's (1926) law revisited: a systematic review on
survival rates and complications of fixed dental
prostheses (FDPs) on severely reduced periodontal
tissue support
Martina Lulic Clinical Oral Implants Research
Volume 18 , Pages 63 - 72,18 Jun 2007
 Conclusions: results showed that
(i) masticatory function could be established
and maintained in subjects receiving FDPs on
abutment teeth with severely reduced but
healthy periodontal tissue support and
(ii) FDPs survival rates compared favourably
with those of FDPs incorporated in subjects
without severely periodontally compromised
dentitions.

Factors such as
Length of time a restoration has been in place
with a minor defect ( a defect that has not
produced untoward results such as caries or
periodontal disease),
Age and Medical history of the patient, and
Severity of the defect need to be considered
before deciding to remake the restoration

 However, whenever an existing restoration is
modified and therefore preserved,
the resulting restoration should be as good if
not better than when it was originally placed.

 Several clinical factors must be evaluated
when examining any restoration. A
satisfactory restoration must meet the
acceptable criteria in the following areas:
 Function
 Contour
 Esthetics
 Margins
 Occlusion
 Pulpal health
 Periodontal health
 Periapical health

Function
Does the restoration functions as intended??
The patient should be able to chew painlessly,
efficiently and without damaging the teeth or
surrounding tissues
Posterior crowns in proper functional
relationship

Loss of function

Contours
 Poor oral hygiene- should not require a new
restoration unless the crown makes good oral
hygiene difficult
An over-contoured
crown--- inflamed
and swollen gingiva--
that will lead to more
serious periodontal
involvement

An oversized poorly positioned food table

Esthetics

Margins
 A much smaller opening between the tooth
and the crown can be better detected visually,
preferably with magnification, than can be felt
with an explorer.

 Interproximal marginal defects- Bite wings
radiographs; though this not be used
exclusively.
 These are the only options for examining the
already cemented crown, however best time
is to check before cementation.

 During the tooth preparation,
definite, reproducible finish
lines should be created.
 “ There is no substitute for an
accurate impression that
produces all marginal areas”
 Stereomicroscope can be
used to determine whether
all the finish lines are
reproduced, and that they
are accurately trimmed on
the die.

Caries
This is usually perceived by the patient as
 Pain or sensitivity due to hot, cold or sweet
foods and liquids
 Bad taste
 Bad breath
 Loose restoration
 Fractured teeth
 Discolored teeth

 Early detection is possible through comprehensive
probing of the margins of the prosthesis and tooth
surfaces with sharp explorer.
 Radiographs are helpful in detection of caries inter
proximally.
 Conventional operative procedures can be used to
restore small carious lesions with out need to
fabricate new prosthesis.
 Gold foil is the material of choice for restoring
marginal caries.

Occlusion
 Proper occlusion allows for normal function
without leading to any pathology in any areas
related to tooth support, TMJ, or related
tissues.
 Wear facets on occlusal surfaces, widened
periodontal ligament space, or mobility of the
teeth can be caused by malocclusion
 Degeneration of or symptoms in the TMJ may
indicate occlusal problems and must be
investigated by proper patient history and
thorough oral examination

 It may be possible to modify existing
restorations with occlusal problems. If this is
impossible, the defective restoration must be
replaced
 Crowns with severe wear may not be
preservable, and perforations in these
situations would necessitate replacement.
 Small facets, however can be eliminated and
in some cases a perforation can be restored
when the surrounding metal has adequate
thickness.

Extreme wear on occlusal surface of crowns

Pulpal health, Periodontal health,
Periapical health
 While it is impossible to be absolutely certain
the the pulp is healthy, its status should be
determined as accurately as possible.
 A conscientious dentist will not do a crown
without a thorough clinical and radiographic
examination.

CLASSIFICATION
of failures

Bernard G. N. Smith
(PLANNING AND MAKING CROWNS AND BRIDGES)
1. Loss of retention
2. Mechanical failure of
crowns or bridge components
 Porcelain fracture.
 Failure of solder joints.
 Distortion ( Sanitary Pontics too thin; Bridge
removed with too much force)
 Occlusal wear and perforation.
 Lost facings. www.indiandentalacademy.com

 Occlusal wear and perforation (normal with time; if
normal and spotted before caries- can be restored, if
perforation is over Amalgam core- left untreated )
 Lost facings

3. Changes in the abutment tooth
 Periodontal disease ( if diagnose early no treatment
needed)
 Problems with the pulp ( despite taking usual precautions
teeth may become non vital;
it’s sometimes reasonable to attempt endodontic treatment
making an access through the crown;
for coronal pulp removal, large cavity to be done- weaken
the abutment.
crown have been made with rather different anatomy than
natural crown, angulation of root is not apparent
Apicectomy is solution for already RCT treated tooth
 Caries
 Fracture of the prepared
natural crown or root
 Movement of the tooth

Clinical view and radiographs: Failure after
one year due to root perforation, caries and
fractured porcelain

4. Design failures
a. Under-prescribed FPDs
b. Over-prescribed FPDs
4. Inadequate clinical or laboratory technique
a. Positive ledge
b. Negative ledge

Sub pontic red
patch

c. Defect (A gap between crown and preparation margins)
 4 possible causes:
 i) Crown or Retainer did not fit in and gap was present
at try in
 ii) Hydrostatic pressure of the cement particularly if the
cement was beginning to set.
 iii)cement depressed the mobile teeth in its socket.
 iv) no gap at cementatiion but developed following loss
of cement at margins.

 Amalgam is the alternative material because it
produces long term marginal seal.
 Caries in the proximal surfaces may require removal
of the prosthesis to obtain access to caries.
 If the lesion is small the tooth preparation can be
extended to eliminate the caries and new prosthesis
fabricated .
 When larger lesion is present an amalgam restoration
is often required after removal of restoration and
excavation of caries. The abutment preparation is
extended to cover the filling and a new restoration is
fabricated.

 Extensive lesions may encroach the pulp making
endodontic treatment necessary or if it is not possible
then the tooth has to be extracted.
 Marginal caries lesions generally begin at surface
which progress inward .
 They occur internally which are least discernable
externally until extensive destruction . This problem
can be the result of incomplete removal of caries
during a previous treatment or of a loose retainer
casting that allows gross leakage to occur.

d. Poor shape and color
More can be done to adjust the shape of a
crown or bridge in situ than to modify its
colour , although occasionally surface stains
on porcelain can be removed and polished.
Ceramic Finishing & Polishing Kit
designed to finish, polish and
super-polish porcelain restorations.

 PORCELAIN REPAIR (PFM)
With Composite (for optimal results: isolate with rubber dam)
1) Etch porcelain/metal surface with 4% hydrofluoric acid for 4 minutes.
2) Rinse and dry thoroughly.
3) Apply one coat of Porcelain Primer (Silane) to exposed porcelain.
5) Light cure for 10 seconds.
7) Mix equal amounts of dual cure Opaquer Base & Catalyst.
8) Apply thin layer on exposed metal surface to mask out metal shine-
through.
9) Light cure for 10 seconds.
10) Use the composite of choice and light cure in small increments. Use a
microhybrid composite.
11) Proceed with finishing and polishing.
PORCELAIN REPAIR KIT
1 bottle PORCELAIN PRIMER (3ml), 1 bottle 4%
PORCELAIN ETCHANT (3ml), 1 syr. BARRIER GEL
(3ml), 1 bottle OPAQUER catalyst (3ml), 1 bottle
OPAQUER Base Universal (3ml),

LOSS OF RETENTION
 When one retainer – loose – more disastrous.
 Without a seal plaque forms in space
between the retainer and the abutment tooth
and caries develop rapidly across the whole
of the dentin surface of preparation

 Diagnostic test for a loose retainer is to
examine the bridge carefully without drying
the teeth pressing the bridge up and down
and looking for small bubbles in the saliva at
the margins of the retainer.

SOLUTIONS:
 Re-cement the Bridge
 Additional retention by pins
 Abutments made more retentive and bridge
remade
 Additional abutments

Bernard G. N. Smith
(PLANNING AND MAKING CROWNS AND BRIDGES)

TECHNIQUES FOR ADJUSTMENTS,
ADAPTATIONS AND REPAIRS TO CROWNS
AND BRIDGES
 Assessing the seriousness of the problem
 Decision has to made between:
Leaving it alone, if it is not causing any serious
harm.
Adjusting or repairing the fault.
Replacing the crown or bridge.

Adjusting by grinding and polishing in situ.
 Porcelain finishing instruments
 Reciprocating Hand-piece
(for removing overhangs)
Repairs by restoring in situ
 Occlusal repairs
( In metal can be done with
Amalgam. In porcelain,
Composite can be used) Reciprocating
disposable pophy
angles
Endo-Express™
Reciprocating
Handpiece

 Repairs at margins:
 Secondary caries that is identified at an early
stage can or early erosions/ abrasions can be
repaired by class V restorations using
amalgam, Composites, Glass ionomer
Cement.

 Although repairs are justified to extend the life
of an established crown or bridge, they
should never be used to adapt the margins of
a poorly fitting bridge on insertion.
 In some cases raising a full gingival flap may
be justified.

A bridge with defective
margins and extensive
gingival inflammation
The same bridge after a
periodontal flap has been
raised, the retainer
margins adjusted by
grinding and polishing, and
the flap then apically re-
positioned. The gingival
condition is now healthy

 The causes of FPD failures were summarized as
early as in 1920 when Tinker wrote -
 “ Chief among the causes for such disappointing
results have been:
 First : Faulty, and in some cases, no attempt at
diagnosis and prognosis.
 Second: Failure to remove foci of infection in
attention to treatment and care of the investing
tissues and mouth sanitation.
 Third: Disregard for tooth form
 Fourth: Absence of proper embrasures
 Fifth: Inter-proximal spaces
 Sixth: Faulty occlusion and articulation”

Clinical complications in fixed
prosthodontics
Charles J. Goodacre et al
(J Prosthet Dent 2003;90:31-41.)

Table I. Most common single crown
complications
Number crowns
studied/affected
Mean incidence
Need for endodontic
treatment
823/27 3%
Porcelain fracture 199/6 3%
Loss of retention 1,061/19 2%
Periodontal disease 986/6 0.6%
Caries 1,105/4 0.4%www.indiandentalacademy.com

Complications associated with fixed
partial dentures with a loose retainer
 Clinical findings recorded prior to FPD removal
showed that 41% of patients were unaware they had
a loose FPD retainer.
 82% reported no discomfort associated with the loose
retainer.
 Caries were noted on 50% of the teeth with a loose
retainer.
 Damage resulting from attempted removal of the
cemented retainer included minor porcelain fracture
(9%), minor core chipping (14%), minor incisal edge
chipping of tooth preparations (27%), and major
damage to the abutment tooth (4%).
Complications associated with fixed partial dentures with a loose retainer
Donald A. Curtis (J Prosthet Dent 2006;96:245-51.)

Charles J. Goodacre et al (J Prosthet Dent 2003;90:31-41.)www.indiandentalacademy.com

Classification system for conventional crown
and fixed partial denture failures
John Joy Manappallil,
J Prosthet Dent 2008;99:293-298

 A system for classifying fixed prosthodontic
failures is important for a variety of reasons.
For example, thorough assessment of the
cause and severity of failure is valuable for
patient education and retreatment planning.
 Also, a comprehensive classification system
would facilitate interoperator discussions and
offer an improved method for standardizing
studies and surveys concerned with failures.
298

 Simple classification system applicable to all
conventional fixed prosthodontic failures.
 Failures can be grouped into 6 categories,
with severity increasing from Class I to Class
VI

 Class I Cause of failure is correctable without
replacing restoration.
 Class II Cause of failure is correctable without
replacing restoration; however, supporting tooth
structure or foundation requires repair or
reconstruction.
 Class III Failure requiring restoration replacement
only. Supporting tooth structure and/or foundation
acceptable.
 Class IV Failure requiring restoration replacement
in addition to repair or reconstruction of
supporting tooth structure and/or foundation.

 Class V Severe failure with loss of supporting
tooth or inability to reconstruct using original
tooth support. Fixed prosthodontic
replacement remains possible through use of
other or additional support for redesigned
restoration.
 Class VI Severe failure with loss of supporting
tooth or inability to reconstruct using original
tooth support. Conventional fixed
prosthodontic replacement is not possible.

 Class I failures are correctable through
occlusal adjustment or composite resin
repairs without requiring replacement of the
restoration.
 The loss of a cement bond (not related to a
design flaw) is a Class I failure corrected by
re-cementing the restoration. Other Class I
problems are correctable if it is possible to
remove the restoration.
 If the restoration resists removal attempts and
has to be sectioned for removal, or if either
the restoration or tooth support is damaged
during the process, the problem would be
reclassified into a higher order of failure.

Class I failure. A, Mandibular
first molar metal ceramic
crown lacking occlusal
contact. Crown replacement
was not required since it was
possible to remove and
improve existing crown.
B, Crown in place with
improved occlusal contact.

 In a Class II failure, the restoration itself is
acceptable; however, the supporting tooth
structure or foundation (core restoration, or
post and core) requires repair or
reconstruction.
 Examples of Class II failures are foundation
failures and loss of supporting tooth structure
resulting from caries or fracture.
 Fractures can also occur during attempts to
remove a restoration.

B, Acrylic resin post-and-core
pattern custom made to fit existing
crown
Class II failure. A, Fracture
involving endodontically treated
lateral incisor restored with
complete crown.

.
C, Cast post and core
cemented into remaining
tooth structure.
D, Original crown cemented
in place.

Class III failure
 Restoration replacement is required however,
the supporting tooth structure or foundation
remains intact and would provide acceptable
support for a replacement restoration
 This classification would include
unserviceable restorations due to defective
margins, technical failures, or esthetic
considerations.

Class III failure. Maxillary incisor
complete all-ceramic crowns
required replacement because of
gingival inflammation and patient
dissatisfaction with crown
esthetics. Condition of supporting
tooth preparations was satisfactory
without additional treatment.
Replacement all-ceramic crowns
with improved gingival health and
esthetics.

 Class IV - the restoration requires
replacement, and the supporting tooth
structure or foundation is deficient.
 Examples in this category include failures
associated with caries, fracture of supporting
tooth structure, or a defective foundation.
 Before making a new restoration, the tooth
structure must be reinforced, reconstructed,
or replaced.
 Various means can be used, including cores
and post-and-core foundations

Class IV failure. A, Failed
maxillary central incisor
restorations requiring
replacement.
B, Prepared teeth were
carious and lacked
sufficient support for
crown reconstruction.

C, After periodontal health
improvement, cast posts and
cores were fabricated and
cemented in place.
D, New metal ceramic crowns.

 In a Class V failure, support structures can no longer
provide adequate support for the existing restoration
due to extensive fracture, carious destruction,
periodontal problems, or other complications. A
damaged tooth may require extraction.
 Even though the failure may involve tooth loss,
restoration of the site with a conventional fixed
prosthesis remains a reasonable option when other
available teeth can be incorporated into aredesigned
restoration.
 Class V failures can also include FPDs for which
abutment teeth provide inadequate tooth and/or
periodontal support. These abutment teeth can be
treated and restored to function in a redesigned FPD,
if additional abutment teeth are used to improve
support.

Class V failure. A, Restored
maxillary right central incisor
tooth was extracted following
periodontal complications.
B, Subsequently, with adjacent
teeth suitable for abutment
service, conventional FPD was
fabricated to replace
extracted incisor tooth.

 A Class VI failure is the most severe failure;
in this situation, a conventional fixed
replacement is no longer possible because of
supporting tooth failure and the lack of
additional support for use in a redesigned
restoration.
 An example of a Class VI FPD failure would
be the loss of the terminal abutment of an
FPD replacing a first molar, assuming the
third molar is missing or unsuitable for
abutment service (Fig. 6).

Class VI failure. Distal abutment for mandibular 3-unit FPD, compromised by
severe carious and large periapical lesion, was not restorable. Extraction
resulted in Class VI failure; conventional FPD replacement was no longer
possible.

By John F. Johnston
A. Biologic failures
 Caries
 Pulp degeneration
 Periodontal breakdown
 Occlusal problems
 Tooth perforation
B. Mechanical failures
 Loss of retention
 Connector failure
 Occlusal wear
 Tooth fracture
 Acrylic veneer wear / loss
 Porcelain fracture
C. Esthetic failures
D. Facing failures

By Roberts D H
 Cementation failure
 Mechanical breakdown
Flexion, tearing or fracture of the gold
Solder joint failure
Pontic fracture
Bonded porcelain failure
 Gingival irritation or recession
 Periodontal breakdown
 Caries
 Necrosis of the pulp

Barreto M T – JPD 1984; 51, 186-89
 Biologic - caries, fractures, generalized periodontal
disturbances
 Esthetics - shapes, contours, surface characteristics
 Biophysical - physical properties and chemical
composition of porcelain and metal
 Biomechanical - faulty designs, misplaced finish
lines, rough or sharp surfaces, undercuts on the
bonding surface cause porcelain to be dislodged.

Contents
 Introduction
 Evaluating the quality of existing restorations
 Classification
 Causes of failure
 Biologic failures
 Mechanical failures
 Esthetic failures
 Facing failures
 Repairs
 Review of literature
 Summary
 Conclusion

TYPES OF BRIDGE FAILURE
I. Cementation failure
II. Mechanical failure
III. Gingival and periodontal
breakdown
IV. Caries
V. Necrosis of pulp
VI. Biomechanical failure
VII.Esthetic failure

CEMENTATION
FAILURE

Cementation failures can be broadly divided into:
1. CEMENT FAILURE
2. RETENTION FAILURE
3. OCCLUSAL PROBLEMS
4. DISTORTION OF FPD

CEMENT
FAILURE

1. CEMENT FAILURE
The primary function of the luting agent is to provide a
seal preventing marginal leakage and pulp irritation. The
luting agent should not be used to provide significant retentive
and resistive forces.
An ideal luting agent would have the following properties:
1. Adequate working time
2. Adhere well to both tooth structure and metal surface
3. Provides a good seal
4. Non toxic to the pulp
5. Have adequate strength properties
6. Be compressible into thin layers
7. Have low viscosity and solubility
8. Exhibit good working time and setting properties

Besides an inadequate retainer, failure can
also occur because of a poor cementation
technique.
This maybe due to the:
• wrong choice of material,
• failure to observe the manufacturer’s
mixing instructions,
• old or contaminated material,
• inadequate powder/liquid ratio,
• insertion of the prosthesis when the
cement has started to set.

An inadequately cemented restoration
may cause
 An increased vertical dimension of occlusion
 A loosening of the crown or FPD after a
relatively short time
 Leakage and decay under the abutment
 The unsightly appearance of a metal margin
where originally the metal was concealed
under the gingiva
 Sensitivity to sweets or brushing due to
exposure of the cervical end of the tooth

Causes of cement failure
1) Cement selection
2) Old cement
3) Prolonged mixing time
4) Thin mix
5) Cement setting prior to seating
6) Inadequate isolation
7) Incomplete removal of temporary cement
8) Thick cement space
9) Inclusion of cotton fibers
10) Insufficient pressure

Dental luting agents: A review of the current
literature
Stephen F. Rosenstiel (J Prosthet Dent 1998;80:280-301.)

Cements for Use in Esthetic Dentistry
Pegoraro et al Dent Clin N Am 51 (2007) 453–471

Dislodgement of luted post.
(A) Clinical view of dislodgement
of resin cement (Panavia)
(B) Radiographic view
(C,D) Closer view of the post
(E) SEM image of the dislodged
post. Note the massive
presence of bubbles,
especially on the middle and
apical thirds.
(F) Closer view of (E), the
presence of bubbles, which
could be attributed to the
water that migrated through
the adhesive layer
(G) Higher magnification of (F).
The water droplets are kept
trapped in the poorly
polymerized cement (black
circle), leading to degrdation
and crack spots along the
adhesive-cement interface.

SEM images showing surface
topographies of different cements
after mixing and curing.
entrapped bubbles due to mixing.
Huge amount of particles (white
asterisks) without matrix in
between can be seen even inside
the enormous entrapped bubble

 The material should have a glossy surface
when the restoration is placed, and should
flow easily to allow complete seating without
the firm, sustained pressure required for the
other luting agents.
 A dull finish on the surface of the excess
occurs rapidly with the material achieving a
sudden ‘‘snap set’’.
 Because of the snap set, quickness must be
exercised to insure complete seating for all
restorations. Prior to cementation, the tooth
surface should be clean and dry but not
dehydrated, with the smear layer retained.

 To reduce potential postoperative sensitivity,
the use of a resin-based sealer, which also
enhances retention, has been recommended
 Applying petroleum jelly to the exposed glass-
ionomer cement margin after bulk removal
has been suggested as a simple solution to
maintain water balance.
 Dehydration remains a problem, so isolation
from the oral environment for longer than 10
minutes is not recommended.

Dental Cements for Definitive Luting:A Review and Practical
Clinical Considerations
Edward E. Hill Dent Clin N Am 51 (2007) 643–658
 Post-cementation sensitivity with GIC:multifactorial
in origin, although studies concerning pulpal
reactions to these materials are highly variable in
results.
As with all AB cements, the dentist should take care
to insure that
 at least 1 mm of sound dentin surrounds the pulp
for any preparation,
 avoid dessication and bacterial contamination,and
 use proper cementation technique to optimize
pulpal health

RETENTION
FAILURE

2. RETENTION FAILURE
No cements that are compatible with living tooth
structure and the biologic environment of the oral
cavity possess adequate adhesive properties to hold a
restoration in place solely through adhesion. The
geometric configuration of the tooth preparation must
place the cement in compression to provide the
necessary retention and resistance.
CAUSES FOR RETENTION FAILURE
1) Excessive taper
2) Short clinical crowns
3) Mis-fit
4) Misalignment www.indiandentalacademy.com

Excessive taper :
Axial walls of the preparation must taper slightly to
permit the restoration to seat
Theoretically, opposing walls of the preparation :
nearly parallel
Recommendations for optimal axial wall taper of
tooth preparations for cast restorations ranged from 10
to 12 degrees.
Tooth preparation taper should be kept minimal
because of its adverse effect on retention, but
Mock estimates that a minimum taper of 12 degrees is
necessary just to insure the absence of undercuts.

Short clinical crown : Cement creates a
weak bond largely by mechanical interlocks
between the inner surface of the restoration
and the axial wall of the preparation.
Therefore, the greater the surface area of the
preparation the greater is its retention. The
preparations on large teeth are more retentive
than preparations on small teeth.

 A short, over-tapered or short clinical crown
would be without retention as there would be
many paths of removal.
 For the restoration to succeed, the length
must be great enough to interfere with the arc
of the casting pivoting about a point on the
margin on the opposite side of the
restoration. A shorter wall cannot afford this
resistance. The walls of short preparations
should have as little taper as possible.

Clinical conditions with excessive taper and short clinical
crowns should be treated with :-
1. In case of excessive taper:
a. Incorporation of proximal grooves.
b. Additional retentive grooves (should be along with the path
of insertion).
c. Additional pins
2. In case of short crowns:
a. Crown lengthening procedure
b. Modification of supra-gingival margin to sub-gingival
margin
c. Additional retentive grooves and proximal box
d. Incorporation of pins
e. Addition of extra abutmentswww.indiandentalacademy.com

Misfit : The fit of casting can be defined best in terms of the
“misfit” measured at various points between the casting surface
and the tooth.
The measurement of misfit at different locations and geometrically
related to each other and defined as :
1. Internal gap
2. Marginal gap
3. Vertical marginal discrepancy
4. Horizontal marginal discrepancy
5. Over-extended margin
6. Under-extended margin

Causes for misfit :
a. Expansion of the metal substructure
b. Improper water / powder ratio
c. Improper mixing time
d. Improper burnout temperature
e. Distortion of the margins (towards the tooth surface)
f. Distortion of the metal substructure
g. Metal bubbles in occlusal or marginal regions
i. Inadequate vacuum during investing
ii. Improper brush technique
iii. No surfactant
h. Porcelain flowed inside the retainer
i. Excessive oxide layer formation in inner side of the retainer (due
to contaminated metal or repeated firing of porcelain)
j. Tight contact points
k. Thick cement space
l. Insufficient pressure during cementation procedurewww.indiandentalacademy.com

Misalignment : In case of the fixed FPD, it is
more difficult to differentiate whether a FPD is
not seating because of a faulty fit, or the
alignment of the retainers relative to each other is
incorrect. The only difference which may
sometimes be apparent is that, in the case of
misalignment the FPD will have some ‘spring’ in
it and tend to seat further on pressure due to the
abutment teeth moving slightly, whereas in the
case of a defective fit, the resistance felt will be
solid.

Causes for misalignment
a. Abutment displacement due to improper temporization.
b. Distortion of wax pattern while spruing and investing.
c. Casting defects.
d. Distortion of metal frameworks in porcelain firing.
e. Porcelain flow inside the retainers.
f. Misalignment of soldering points.
g. Insufficient pressure in cementation.
h. Thick cement film.
i. Excessive metal or porcelain in tissue surface (ridge lap) of
pontic prevents the proper seating of FPD and open margin
(can be detected by observing the blanching of the tissue or
patient may complain of pressure on the pontic region).

OCCLUSAL
PROBLEMS

3. OCCLUSAL PROBLEMS
Following the placement of a dental restoration,
a patient might report discomfort ranging from a
feeling of ‘lameness’ to ‘severe and constant pain’.
Sensitivity, in most cases, is due to pulp irritation from
traumatic contact or greater leverages. When the
occlusion has been adjusted, each type of discomfort
may be relieved almost instantly and should disappear
shortly.

Causes in occlusal problems
1. Immediate problems
 Occlusal interference
 Marginal ridges at different levels
 Supra eruption of the opposing tooth
 Parafunctional habits
2. Delayed problems
 Wearing of occlusal surface
 Loss of occlusal contacts
 Perforation of occlusal surface due to
• Porcelain Vs resin
• Porcelain Vs gold
 Food lodgment due to plunger cusp
 Fracture of facing due to defective occlusal contact
 Periodontal or gingival breakdown due to improper occlusal
contacts
 Tenderness due to food lodgmentwww.indiandentalacademy.com

DISTORTION
OF FPD

4. DISTORTION OF FPD
Margin Integrity
The completed restoration should go into
place without binding of its internal aspect against
the occlusal surface or the axial walls of the tooth
preparation. In other words, the best adaptation
should be at the margins. If the indirect procedure
is handled properly, there should be no noticeable
difference between the fit of a restoration on the
die and that in the mouth.

Causes for failure in marginal integrity:
1) Bending of FPD (wax patterns and metal substructure)
• In waxing stage
• Removal from the die
• Spruing stage
• Investing stage (thick mix of investment distort or displace
the wax pattern)
1) Incomplete casting
• Wax patterns too thin
• Incomplete wax elimination
• Cold mold or melt
• Inadequate metal

3) Rough casting
• Improper finishing of wax pattern
• Excess surfactant
• Improper water powder ratio
• Excessive burnout temperature
• Improper divesting (direct hit on the metal framework)
3) Bending of long span FPDs
• Thin crown
• Soft metal
• Heat treatment not being done
• Porosity in the metal
• Distortion of the metal substructure during the porcelain
firing
• Contaminated metal

distortion resulting in metal frameworks after the various stages of the
porcelain firing schedule causes include:
a) Contraction of the porcelain with subsequent metal deformation
b) Contamination of the casting, reducing its melting temperature
c) Grain growth of the alloy, constricting the diameter of the crown
d) Plastic flow and creep of the porcelain gold alloy at high
temperatures
e) Reduction in the resiliency of the metal due to the rigidity of
porcelain
f) Improper support of the framework during firing
g) Inadequate framework design at the gingival level
h) inadequate design of the framework as a whole

Shillingburg stated that ceramic metals
require a certain amount of bulk in the
cervical area to resist distortion when
subjected to the repeated firing cycles
of porcelain

MECHANICAL
FAILURES

Due to:
• poor diagnosis and treatment plan,
• improper choice of materials,
• poor framework design,
• poor tooth preparation,
• poor occlusion.
These could lead to fracture of the prosthesis or
displacement of the retainers.
It is therefore important to evaluate the
likely forces on a pontic and to design it
accordingly.
For example, a strong all metal pontic may be needed
in situations of high stress rather than a metal ceramic
pontic which could be more susceptible to fracture.www.indiandentalacademy.com

Classification of mechanical failure
1. Retainer failure
2. Pontic failure
3. Connector failure

1. RETAINER FAILURE
1) Perforation
2) Marginal discrepancy
3) Facing failure
Fracture
Wearing
Discoloration

1) Perforation
Causes
a) Insufficient occlusal reduction
b) Insufficient occlusal material
c) High points in opposing dentition (plunger cusp)
d) Premature contacts
e) Contaminated metal
f) Porosity in metal work (subsurface, back pressure, suck
back)
g) Due to improper melting temperature
h) Improper pattern position
i) Improper sprue (too thin)
j) Improper location
k) Parafunctional habits

2) Marginal discrepancy
Causes
a) Selection of margin
b) Improper preparation and failure to establish the margin
properly
c) Failure to do gingival retraction prevents definite margin
location and subsequently in impression
d) Selection of the impression material
i. Shrinkage in material (condensation silicon)
ii. Distortion of material (alginate)
e) Improper impression procedures
f) Voids in the impression
g) Variation in pressure application in wash technique
h) Delayed pouring of die material
i) Distortion of wax patterns at marginswww.indiandentalacademy.com

j) Insufficient flow of metal
k) Shrinkage of metal
l) Nodules in margins and inner side of coping
i. Due to inadequate vacuum during investing
ii. Improper brushing technique
iii. No surfactant
l) Excessive sand blasting
m) Distortion due to degassing procedure
n) Open margins due to porcelain shrinkage (opaque porcelain)
o) Thick cement
p) Cement setting prior to seating
q) Insufficient pressure application during cementation

3. Facing failure
Types of veneer failures
a) Fracture
b) Wearing of facing (resin veneers)
c) Discoloration

Causes for veneer fracture:
i. Too little retention (mechanical)
ii. Badly designed metal protection
iii. Deformation of the protecting metal
iv. Malocclusion
v. Micro-leakage between metal and facing
vi. Improper curing or fusing technique
vii.Excessive oxide layer formation

Cause of wearing of facing:
i. Improper curing or fusing technique
ii. Deep bite (decreased overbite in lower anteriors)
iii. Acrylic veneering opposing porcelain teeth
iv. Faulty brushing techniques and flossing
v. Parafunctional habits

Causes of discoloration:
i. Absorption of oral fluids
ii. Absorption of artificial food colouring agents through
micro-cracks or microleakage in metal and facing
interfaces
iii. Tarnish of underlying metal and facing (greening of
porcelain in silver alloys)
iv. Micro-cracks due to malocclusion

2. PONTIC FAILURE
Factors affecting selection and failure of pontics
1) Pontic space
2) Residual ridge contour
3) Biological consideration
a. Ridge relation
b. Dental plaque
c. Gingival surface of pontic (Contact with mucosa)
i. Mucosal contact
ii. Non mucosal contact
4) Pontic ridge relationship
5) Pontic material
6) Biocompatibility
7) Occlusal forces
8) Metal substructure supportwww.indiandentalacademy.com

3) Biological consideration
The biologic principles of pontic design
pertain to the maintenance and
preservation of the residual ridge,
abutment and opposing teeth and
supporting tissues.
Factors of specific influence are:
a) Pontic ridge contact
b) Removal of dental plaque
c) Gingival surface of the pontic

a)Pontic ridge contact
Pressure free contact between the
pontic and the underlying tissues is
indicated to prevent ulceration and
inflammation of the soft tissues. If any
blanching of the soft tissue is observed at
try in, the pressure areas should be
identified with pressure indicating paste
and the pontic re-contoured until tissue
contact is entirely passive.www.indiandentalacademy.com

b)Dental plaque
 The chief cause of ridge irritation is the
toxins that are released from microbial
plaque, which accumulates between the
gingival surface of the pontic and the residual
ridge causing tissue inflammation and
calculus formation.
 Patient must be taught to perform efficient
oral hygiene techniques, with particular
emphasis on cleaning the gingival surface of
the pontic. The shape of the gingival surface,
its relation to the ridge, and the materials
used in its fabrication will influence the
success of these measures.

c) Gingival surface of the pontic
anterior region aesthetics - pontic should
contact the gingival tissue on the labial or buccal aspect
to give an appearance of ‘emerging from the tissue’.
posterior region, like the mandibular premolar and
molar areas more attention should be given to occlusion,
function and hygiene.

 Considering these aspects, pontic contacts
may be classified into different groups:
mucosal and non mucosal contacts based on
the shape of the gingival surface and its
relationship with the underlying tissue.

Normally, where tissue contact occurs, the
gingival surface of a pontic is inaccessible for
cleaning with a tooth brush. Therefore, the
patient must develop excellent hygiene habits
and the use of devices such as proxibrushes,
pipe cleaners and dental floss.

A pontic with a concave fitting surface
that overlaps the residual ridge bucally and
lingually is called a saddle. This is avoided
because the gingival surface cannot be easily
cleaned.

4) Pontic ridge relationship
Since 1918 it has been a popular concept
that the tissue surface of a mandibular posterior
pontic should sometimes be left well clear of the
residual ridge. This design was often called
‘hygienic’ or ‘sanitary’.
The hygienic design permits easier plaque
control by allowing gauze strips and other
cleaning devices to be passed under the pontic
and seesawed in shoeshine fashion.

There are disadvantages to the design as well.
Food particles tend to become trapped, which
may lead to tongue habits that are annoying
to the patient. The hygienic design also is
contraindicated if minimum vertical space
exists and where esthetics is important; tissue
proliferation can occur when the pontic is too
close to the residual ridge, forgoing the
originally intended advantages.

5) Pontic material
Any material chosen to fabricate the pontic should
provide good aesthetic results where needed, biocompatibility,
rigidity and strength to withstand occlusal forces, and the
desired longevity. FPDs, during mastication or parafunction,
may impinge upon the gingiva and also the veneering material
may fracture. In the fabrication of metal-ceramic FPDs, the
porcelain on the occlusal surfaces should be carefully
evaluation. Porcelain is a brittle material and may fracture
easily.
When a metal-ceramic restoration is chosen, it is of
paramount importance to design the metal substructure properly
if flexure and porcelain fracture is to be avoided. Occlusal
contacts should not fall on the junction between metal and
porcelain during centric and eccentric contacts.

6) Biocompatibility
Glazed porcelain is generally considered to be the most
biocompatible of the available pontic materials and clinical data
tends to support this opinion, although the critical factor seems
to be the material’s ability to resist accumulation of plaque
rather than the material itself. Highly glazed porcelain is
relatively easy to clean, making plaque removal from it easier
than from other materials. For ease of plaque removal, it is
recommended that the tissue surface of the pontic be made in
glazed porcelain whenever possible.
Well-polished gold is smoother, less prone to corrosion, and
less retentive of plaque than an unpolished or porous casting.

7) Occlusal forces
Reducing the buccolingual width of the pontic by
as much as 30% has long been suggested as a means of
lessening occlusal forces on abutment teeth. Narrowing
the occlusal table may actually impede or even preclude
the development of a harmonious and stable occlusal
relationship. Like a malposed tooth, it may cause
difficulties in plaque control as well as fail to provide
proper cheek support. For these reasons, pontics with
normal occlusal widths are generally recommended.
Mechanical failure of the pontic may occur
because of inadequate strength. Thus an all-porcelain
occlusal pontic should never be used unless the bite is
favourable. www.indiandentalacademy.com

8) Compromised metallic substructure
Causes
a. Limited edentulous space occluso-cervically
due to supra-eruption of opposing tooth.
b. Limited space mesiodistally due to migration
or drifting of adjacent tooth.

How to avoid:
a. The framework must provide a uniform veneer of porcelain
(approx 1.2mm). excessive thickness of porcelain
contributes to inadequate support and predisposes to
eventual fracture. This is often true in the cervical portion of
an anterior pontic. A reliable technique for ensuring uniform
thickness of porcelain is to wax the fixed prosthesis to
complete anatomic contour and then accurately cut back the
wax to a pre-determined depth.
b. The metal surfaces to be veneered must be smooth and free
of pits. Surface irregularities will cause incomplete wetting
by the porcelain slurry, leading to voids at the porcelain
metal interface that reduces bond strength and increases the
possibility of mechanical failure.

c. Sharp angles on the veneering surface should be rounded.
They produce increased stress concentrations that could cause
mechanical failure.
d. The location and design of external metal porcelain junctions
need particular attention. Any deformation of the framework at
the junction can lead to chipping of the porcelain. For this
reason occlusal centric contacts must be placed at least 1.5mm
away from the junctions. Attention must be paid to excursive
eccentric contacts that might deform the metal ceramic
interface.

3. CONNECTOR FAILURE
The connector is that part of the FPD or splint that joins the
individual components (retainers and pontics) together.
Requirements of solders are their ability to resist tarnish and
corrosion, to be free flowing, to match the colour of the units to be
joined and to be strong. These factors also depend on the chemical
composition of the solder.
Casting can make a rigid connection as part of a multi unit
wax pattern or by soldering which involves the use of an
intermediate metal whose melting temperature is lower than that of
the parent metal. The parts being joined are not melted during
soldering, but they must be thoroughly wettable by liquefied solder.
Dirt or surface oxide can reduce wetting and impede successful
soldering.

Causes for connector failure
a. Improper selection of connector
b. Thin metal at the connector
c. Incorrect selection of solder
d. Solder gap – narrow or wide
e. Porosity
f. Insufficient metal around
g. Defective occlusal contacts over thin connectors

GINGIVAL AND
PERIODONTAL
PROBLEMS

Margins are one of the most important and weakest
links in the success of FPD restorations. One of the prime goals
of restorative therapy is to establish a physiologic periodontal
health.
A successful prosthesis depends on a healthy
periodontal environment and periodontal health depends on the
continued integrity of the prosthodontic restoration.
All displacement techniques have the potential damage
gingiva, attachment apparatus and bone, especially if anatomic
forms are weak or if disease is present.
In healthy patients, properly used cord displacement or
copper band methods have proved to be atraumatic.

The margin is one of the components of the cast restoration
most susceptible to failure, both biologically and mechanically.
Most of the investigative proof shows that supragingival margins
are kinder to the gingiva than are subgingival margins. However,
practicality dictates that supragingival margins are not always
usable
There are three locations in which to prepare crown margins:
 Supragingival
 At the crest of the gingiva
 Subgingival

SUPRAGINGIVAL Vs SUBGINGIVAL
MARGINS:
Whenever possible, the margin of the preparation should
be supragingival.
Subgingival margins of cemented restorations have been
identified as a major factor in periodontal diseases, particularly
where they encroach on the epithelial attachment.
Supragingival margins are easier to prepare accurately without
trauma of the soft tissues. They can usually also be situated on
hard enamel, whereas subgingival margins are often on dentin or
cementum.

SUPRAGINGIVAL MARGINS
ADVANTAGES:
 They can be easily finished
 They are more easily cleaned
 Impressions are more easily made, with less potential for soft
tissue damage
 Restorations can be easily evaluated at recall appointments
DISADVANTAGE:
 Aesthetically not indicated for anterior region
 Metal can be seen
 Not indicated in short clinical crowns
 The proximal contacts extend to the gingival crest
 In case of root sensitivity

SUBGINGIVAL MARGINS
SPECIFIC DEMANDS FOR SUBGINGIVAL MARGINS:
 Aesthetic demands
 Caries removal
To cover existing subgingival restorations
 To gain needed crown length
 To provide more favourable crown contour
DISADVANTAGES:
 Difficult for preparation
 Gingival management should be perfect
 Prone for soft tissue trauma
 More prone for gingival and periodontal pathosis
 Difficult to maintain oral hygiene
 Metal margins can be seen through the gingivawww.indiandentalacademy.com

SOFT TISSUE PROBLEMS: GENERALIZED (Not due to bridge)
LOCALISED (May be due to
bridge)
Causes for soft tissue problems:
 Over / under contouring
 Narrow embrasures
 Over / under extended crowns
 Pressure of pontic over tissue
 Loss of contact
 Horizontal food impaction due to plunger cusp in the opposing
arch
 Marginal ridges at different levels
 Wide occlusal table
 Trauma from occlusion
 Parafunctional habits
 Acrylic facing in contact with gingivawww.indiandentalacademy.com

RESULTS OF IMPROPER CONTACT AREAS
 Cause displacement of teeth bucally, lingually, mesially and
distally.
 Exert a lifting force on the tooth when placed too high occlusally.
 Disturb the axial relation of the teeth, resulting in trauma.
 Cause rotation of the teeth.
 Cause injury to the investing structures by excessively opening or
closing the contact and interproximal embrasures.
 Disturb the coordination of the inclined planes and cusps causing
deflective occlusal contacts.
 Cause vertical or horizontal food impaction.

OVER EXTENDED CROWN
The over extended crown usually encroaches beyond the cut
of the preparation on the tooth and the excess beyond the margin of
the preparation is usually not in contact with the tooth surface. This
overhang impinges the gingival tissue, irritates and often causes
edema and proliferation of the gingival tissue, destruction of the
marginal alveolar bone and ultimate loss of the tooth. The over-
extension of the crown is usually due to inaccurate technique and /
or the dentists desire to ‘play safe’ by making it long enough to
cover the preparation or to extend beneath the gingival margin.

SHORT CROWN
The short crown fails to cover the cut surface of the prepared
tooth and often does not extend below the gingival margin. This
uncovered ground tooth surface is often sensitive to sweets and to
temperature changes and invites development of caries and causes
gingival irritation. Also, it is usually due to inadequate technique
and a willingness of the dentist to accept impressions that are
incomplete.
CONTOUR
The poorly contoured crown is one which may have an
excess contour that impinges on the gingival tissue and deflects food
over and away from this tissue, thereby depriving it of its normal
stimulation; or it may be under contoured and permit the impaction
of food into the gingival crevice, thereby stripping the gingival
tissue away from the tooth. Either will cause irritation of the
surrounding tissue and may lead to the loss of the tooth.www.indiandentalacademy.com

CARIES

CAUSES
Iatrogenic (dentists role)
 Failure to identify caries
 Incomplete removal of caries
 Rough abutment finishing margins
 Subgingival marginal placement in inaccessible areas or regions
 Burning of root dentin or cementum in electro surgical technique
(leads to damage or rough surface and causes plaque retention)
 Overhanging margins
 Rough margins of crowns or bridges
 Over contouring of the cervical thirds of crowns or bridges
prevents the physiologic too cleaning by tongue or muscles
 Marginal discrepancy
 Thick cement space in margins leads to cement dissolution.
 Narrow embrasures (inaccessibility to maintain hygiene)
 Wide connector
 Failure to motivate or educate the patient about oral hygienewww.indiandentalacademy.com

Patient role
 Systemic factors
 Xerostomia
 Due to radiation therapy
 Drug induced
 Endocrine disorders
 Epilepsy (difficult to maintain the oral hygiene)
 Rheumatoid arthritis
 Local factors
 Improper brushing and flossing
 Dietary habits
 Failure to understand importance of oral hygiene.

PULP
DEGENERATION

Pulp reactions to various procedures
Each step in full crown preparation presents
hazards, which may injure the pulp. The result
may be pulpitis or even necrosis. Among the
many essential procedures that may cause pulp
injury are tooth preparation, impression making,
temporization and cementation. In general, heat
desiccation and / or chemical injury cause the
insult.

BIOMECHANICAL
FAILURE

Every restoration must be able to withstand the constant
occlusal forces to which it is subjected. This is of particular
significance when designing and fabricating an FPD, since the forces
that would normally be absorbed by the missing tooth are transmitted
through the pontic, connectors and retainers to the abutment teeth.
The abutment teeth are therefore called upon to withstand forces
directly to the missing teeth in addition to those usually applied to
them.
In addition to increased load placed on the periodontal
ligament by a long span FPD, longer spans are less rigid. Bending or
deflection varies directly with the cube of the length and inversely
with the cube of the occluso-gingival height of the pontic. Compared
with the FPD having a single tooth span, a two-toothed pontic span
will bend eight times as much, and a three-toothed pontic will bend
27 times as much.

ESTHETIC
FAILURES

REASONS FOR ESTHETIC FAILURE
 Failure to identify patient expectations regarding esthetics
 Improper shade selection
 Excessive metal thickness at incisal and cervical regions
 Thick opaque layer application
 Surface blistering (chalky appearance)
 Over glazing or too smooth a surface
 Metal exposure in connector, cervical and incisal regions
 Dark space in cervical third due to improper pontic selection
(anteriors)
 Failure to produce incisal and proximal translucency
 Improper contouring
 Failure to harmonize contra lateral tooth morphology
 Contour
 Color
 Position
 Angulation
 Discoloration of facing

REVIEW OF LITERATURE

1. I. Gerson (1957) – stated that inadequately cemented
restorations may cause an increased vertical dimension,
loosening of the crown or FPD after a relatively short time,
microleakage and decay under the abutments, exposure of metal
margins and sensitivity.
2. Kenneth C. Pruden (1957) – stated that the multiple abutments
should be resorted to only where the added support or root
length is needed, and only periodontally sound teeth should be
included.
3. Leonard I. Linkow (1962) – gave the importance of form, type,
shape and position of contact areas. He stated that the contacts
which are flat, open, improperly placed, rough, or poorly
polished will lead to displacement of teeth and exert a lifting
force, disturb, the axial relationship, injure supporting tissues,
produce a deflective occlusal contact and vertical or horizontal
food impaction. www.indiandentalacademy.com

4. Marvin Reynolds (1964) – reviewed the properties of porcelain,
acrylic resin and gold as related to their use in pontics. He stated
that acrylic resin does not permit the precise control of color and
light refraction as it absorbs oral fluids and is less resistant to wear
and abrasion. Gold alloys provide the best strength to withstand the
stresses of occlusion and resistance to wear. Porcelain is superior to
other materials as it maintains the color, is resistant to abrasion and
is dimensionally stable and insoluble to oral fluids.
5. Richter et al (1970) – studied the tensile strength and compressive
strength of cements. The results showed the tensile strength of zinc
phosphate, hydrophosphate and ZnOE cements are equal,
carboxylate cements had less strength properties. Compressive
strength is lowest with carboxylate and highest with zinc phosphate.
6. Guy M Newcomb (1974) – investigated the location of subgingival
margins and related that to gingival inflammation. The results
showed that the least inflammation is observed when subgingival
crown margins are placed at the gingival crest or just into the
gingival crevice. www.indiandentalacademy.com

7. Brule et al (1981) – conducted a study on placement of margins in
anterior veneer crowns. He concluded that the subgingival margin
placement of anterior crown for esthetics might be unnecessary
except in some cases like in short clinical crowns.
8. Abraham Revah et al (1985) – discussed the problems with tilted
posterior tooth in relation with path of insertion. He advised the
mesial half of the crown be with parallel seating grooves for better
seating and retention.
9. Aaron H Wilson et al (1994) – examined the relationship between
degree of convergence or a machined metal die and retention of its
casting. The retention was found to increase from 0 degree
convergence to a peak between 6 -12 degree convergences.
Convergence angles of less than 6 degrees are not advisable as it
causes incomplete seating of the crown due to increase in
hydraulic pressure in between the crown and cement.

10. Paulo Baldissara et al (1998) – conducted a comparative
study about the marginal microleakage of six cements in
fixed provisional crowns. Results showed Zinc phosphate
and cavity bas compound cements had the best sealing
properties than other cements.

CONCLUSION

Failures in FPD construction for the most
part is due to attempted short cuts or positive
indifference and inexcusable ignorance on the
part of those concerned with building the
prosthesis. Also a FPD can just wear out and
this cannot be called as failure and no lifetime
guarantee can be given.
Failures most often occur because of
violation of principles either collectively or
individually. This may be due to reactions of
the soft tissue and reactions of the abutment.www.indiandentalacademy.com

It is better to speak of the level of
acceptability to the patient and the dentist
and consider what needs to be done to
improve the treatment. The fundamentals
of fixed prosthodontic therapy modality
have to be followed strictly, failure of
which will lead to the failure of the
prosthesis itself.

 This clinical report describes the catastrophic failure
of an FPD. The etiology was severe periodontal
disease localized to the maxillary second molar that
permitted excessive forces on the second premolar
abutment.
 A biomechanical challenge was created when the
excessively mobile distal abutment was rigidly
connected to an abutment with only limited
physiologic mobility.
 When an excessively mobile FPD abutment is
subjected to an occlusal force, a torquing force is
created on the other abutment that may result in
cement failure or fracture of the abutment. The forces
transmitted to the anterior abutment in this instance
are similar to the forces that occur on a cantilever
FPD abutment adjacent to the cantilever section
when the cantilever is subjected to occlusal loading
Ronald G. Verrett (J Prosthet Dent 2005;93:21-3.)www.indiandentalacademy.com

Maxillary right posterior FPD at time of
insertion (12 years previous).
FPD at time of patient presentation with
distal abutment exhibiting 8 to 9 mm
periodontal probing depths
and Class III mobility.

Removal of FPD revealed horizontal
fracture through anterior abutment.
Maxillary right second premolar
received endodontic treatment and
prefabricated dowel with core
foundation. FPD was sectioned
and premolar crown was
recemented

Increased mobility of distal abutment (A), combined
with occlusal forces (B), created shear forces between
abutment anterior abutment and axial walls of retainer.
These forces may result in fracture of abutment (C).www.indiandentalacademy.com

Suggested devices and techniques include use of
 Matrix band,
 Hemostat,
 Richwil crown remover (Richwil Laboratories,
Orange, Calif),
 Acrylic resin mold compressed with a curved
 Hemostat,
 Ultrasonics,
 Prepared slot for a purchase point
 Pneumatic crown remover.
These techniques for casting removal have been
reported to result in fractured porcelain margins or
damage to preparation finish lines

 Techniques advanced specifically for FPD
removal have included the use of a wire and
loop as a class 1 lever to elevate and remove
an FPD
Simplified technique for the removal of a fixed partial denture.
Conny et al. J Prosthet Dent 1981;46:505-8.www.indiandentalacademy.com

Dentco crown removal instrument Wire loop held by hemostats

Wire loop was passed under retainer and held by hemostats
with J-shaped hook attachment used to engage wire loopwww.indiandentalacademy.com

Successful removal of cemented retainer

Radiograph of FPD with large post in abutment tooth with
cemented retainer. Due to large post, intact FPD removal was
not attempted. Cemented FPD retainer was sectioned and
removed.

Easy Pneumatic Crown and Bridge
Remover II
 Slimmer, pneumatic crown and bridge remover saves
time, expense, aggravation every time.
 No drilling or anesthesia necessary.
 No spring calibration or resetting needed.
 Saves chair time — no assistant needed.
 Fully sterilizable including dry heat.
 Simply attach the Easy Pneumatic to your low or high
speed air line and touch the button. The rapid,
repeatable action breaks the seal on any type of
cement and prevents it from reseating. A dial at the
hose connection makes force adjustment easy.
Quiet, non-invasive operation ensures patient
acceptance. Operates on 30 to 60psi.

KNOERNSCHILD AND CAMPBELL
(J Prosthet Dent 2000;84:492-8.)
Evidence suggests that restoration factors such as
 poor margin adaptation,
 intracrevicular margin placement,
 rough surfaces, and
 overcontouring
couldcontribute to localized gingival inflammation,
increased probing depths, and bone resorption.
Crown insertion increased the incidence of advanced
gingival inflammation adjacent to restorations.

The retention of complete crowns
prepared with three different tapers and
luted with four different cements Omar Zidan, (J Prosthet Dent 2003;89:565-71.)
 the retentive values of the adhesive resins at 24-
degree taper
 were 20% higher than the retentive values of the
conventional cements at 6-degree taper. The use of
resin luting
 agents yielded retention values that were double the
values of zinc phosphate or conventional glass
ionomer
 cement.

Figs. 1–4: Pre-treatment lower facial view (Fig. 1). Poor aesthetic of the existing fixed
partial denture (Fig. 2). Pre-treatment panoramic radiograph. Note the radiolucency over
the maxillary right central incisor (Fig. 3). Placement of Replace Select tapered implant
(Fig. 4).

Figs. 5–10_Post-surgical panoramic radiograph. Note the excellent bone healing subseque
removal (Fig. 5). Provisional restorations with good soft tissue health and contour (Fig. 6).
impression coping connected and soft tissue retracted with retraction cord in preparation o
making (Fig. 7). Procera Esthetic Abutment and ceramic foundation seated on the maxillar
8). Completed extra-coronal restoration (Procera Crown Zirconia) seated on the maxillary s
9). Completed Procera Crown Zirconia (Fig. 10).www.indiandentalacademy.com

Figs. 11–14: Procera Esthetic Abutment connected to the implant
(Fig. 11). Ceramic post fitted (Fig. 12). Completed restorations
(Fig. 13). Panoramic radiograph showing the completed prosthesis
(Fig. 14).

Post-operative lower facial view

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