in this powerpoint, you will be able to know and understand different kinds of failures experienced in making Fixed partial denture.

1. COMMON PROBLEMS/
FAILURES IN FIXED
PARTIAL DENTURE
 Delgado, Queenie M
 Tamayao, Nicole Kate P.
 Arcueno, Tristan B.
 Bernaldez, Bon Aljune O.
 Pulongbarit, Efraim R.

2. Failures in FPD are common. That is why dentists
must be knowledgeable about the nature of these
failures. Not only for economic purposes but also for
time and energy saving purposes. This presentation
will discuss the common failures in fixed partial
prosthesis, their causes and how to manage them.

3. CLASSIFICATION

4. 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.
Other classification of failures depending the cause: -

5. BENNARD G. N. SMITH
• Loss of retention
• Changes in the abutment tooth
• Periodontal Disease
• Problems with the pulp
• Caries
• Fracture of the prepared natural crown or root
• Movement of the tooth
• Mechanical failure of crowns or bridge components
• Porcelain Fracture
• Failure of Solder Joints
• Distortion
• Occlusal wear and perforation

6. BENNARD G. N. SMITH
• Design Failures
• Under-prescribed FPDs
• Over-prescribed FPDs
• Inadequate clinical or laboratory technique
• Positive ledge
• Negative ledge
• Defect
• Poor shape and color
• Occlusal Problems

7. BENNARD G. N. SMITH
1. LOSS OF RETENTION
Causes:
• Sharp surfaces
• Unequal occlusal loads on different parts of the bridge
• Contaminating cementing procedures
• Increased cement space
• Caries
Clinical Features:
• Looseness
• Sensitivity to temperature and sweetness
• Patient usually complains of recurring bad taste which
should be differentiated from similar symptoms caused by
poor oral hygiene and periodontal problems

8. Detection:
Periodic clinical examination should include, to unseat the
existing prosthesis by lifting the retainers up and down while they are
held between fingers and a curved explorer placed under the
connector
if casting is loose, the occlusal motion causes fluid to be drawn
under casting and when casting is reseated with a cervical force the
fluid is expressed. The examination should be done without drying the
tooth

9. Management:
Re-cementation of old prosthesis
Providing abutment with grooves,
boxes, etc.
Post and core treatment

10. BENNARD G. N. SMITH
2. CHANGES IN THE ABUTMENT TOOTH
A. PERIODONTAL DISEASE
Causes:
• Poor marginal adaptation and proximal contact
• Over contoured axial surfaces
• Excessively large connectors
• Large pontic contacts on edentulous ridge
• Prosthesis with rough surfaces
• Heavy occlusal forces
• Few abutment teeth
• Oversized food table

11. Clinical features:
Gingival recession
Furcation and pocket formation
Mobility (secondary feature)

12. Management:
Proper hygiene
Scaling and proper plaque control
Flap surgery, bone grafts etc.
In case of long span FPD, the FPD must be
removed and remade with multiple terminal
abutments
Narrowing occlusal table

13. B. PROBLEMS WITH THE PULP
Causes:
1. Excess heat generated during preparation
2. Excess tooth reduction
3. Pin point exposure which may go unnoticed
4. Occlusal trauma
5. Poor design
6. Secondary caries

14. Clinical Features:
Pulpal sensitivity
Intense pain
Radiolucencies in the apical
region

15. Management:
Use of varnishes and dentin
bonding agents which forms an
effective barrier and prevents
underlying pulp from toxic effects of
cement and core materials
Endodontic treatment of the
involved tooth by making an excess
opening through the crown, once
obturated, the perforation can be
restored.

16. C. CARIES
Causes:
1. Defective margins
and adaptation
2. Loose retainers
3. Residual ridges
4. Poor design
Detection:
• Visual examination
• Comprehensive
probing of margins
• Radiographs

17. Management:
Fluoride mouth washes
Dental floss
Diet counseling
Professionally applied topical fluoride
Antibacterial cements and anti-microbial should
be used to decrease the caries incidence
Conventional operative dentistry procedures to
restore small lesions
Endodontic treatment incase pulp is involved

18. D. FRACTURE OF THE PREPARED NATURAL
CROWN/ROOT
Causes:
Crown:
1. Caries
2. Excessive tooth reduction
3. Interferences
4. Forcibly seating or removing the fixed partial
prosthesis
5. Preparation mainly containing restorative material
Root:
1. Most often due trauma
2. Forceful seating of post

19. Management:
Crown:
If defect is small it is restored with amalgam
It defect is big/large a new prosthesis fabricated so that it will
cover the fractured area
If fracture causes pulp exposure, endodontic treatment
followed by a post and core is necessary prior to fabrication
of new prosthesis.
Root:
Tooth extraction

20. E. MOVEMENT OF THE TOOTH
Causes:
1. Caries
2. Periodontal disease
3. Crown/Root Fracture
4. Uneven occlusal load
Management:
Proper evaluation of the abutment:
 If there is pathologic mobility – extraction
 If there is periapical lesion accompanied by
movement – extraction
 If there is periapical lesion that is pulpal in origin
with 1st – 2nd degree mobility – RCT, Post and core
then re-evaluate before restoring with a
Crown/bridge
 If there is crown/root fracture – extraction
 If there is minimal movement with absence of
pathologies – relieve all contact areas of occlusal
load

21. 3. Mechanical Failures of
Bridge and Crown
Components

22. Porcelain Fracture
Second most common cause
for FPD replacement
Considered the most common
cause of failure for Porcelain
Fused to Metal (PFM) Crowns
In all ceramic restorations,
veneering porcelain fracture
remains one of the primary
complication affecting longevity

23. Causes of Porcelain Fracture:
1. Incorrect Framework Design
• Thin metal copings (less than 0.2mm) do not support porcelain and allow metal
flexure
• Frameworks that allow centric contacts on or close to metal ceramic junctions
• Improper metal ceramic cutback angle (example: too close to occlusal or proximal
cutback)
• Sharp angles or irregular rough areas over the veneering areas cause stress
concentration
2. Occlusal Interferences
• Caused by heavy forces, eccentric contacts, or parafunctional habits
3. Trauma

24. Opposing cusps must never contact a
junction line between metal and porcelain

26. 4. Debonding
A. separation of the metal and ceramic caused by improper
metal handling such as:
 Contamination
 Excessive oxide formation, which may interfere with bonding
B. Metal porcelain incompatibility
5. Undercut Preparation
• Distorted impression and extended cervical feather edge margins
may cause cracks during forceful prosthesis insertion
• If the prosthesis is otherwise satisfactory, an attempt may be
made to repair the fractured part using a Silane coupling agent or
4-meta to promote bonding. The solution is considered a
temporary one

27. Exposed metal has been roughened with
a diamond high-speed handpiece to
increase mechanical retention
Further mechanical retention is
achieved by sandblasting the exposed
metal and surrounding porcelain
margins

29. Falling 3-unit fixed partial denture

30. Management
Fabrication of new prosthesis
Resin materials are used to rebuild the
porcelain form in area where fracture has
occurred
If fracture is due to heavy occlusal forces,
the contact should be avoided at the
metal ceramic junction and it should be at
least 1.5mm away from the junction
oMore permanent repair is possible when
adequate metal thickness is available
oIf there is any risk of pontic area flexing,
porcelain should be carried on to the
lingual side of the pontic to stiffen them
further
Porcelain Crown Repaired by Composite Resin

31. Sleeve crown
• When a considerable portion of porcelain is
lost from labial/ incisal surface of a retainer or
pontic it is often possible to repair than
replace the entire unit
• The porcelain facing is removed with some of
the underlying metal from the labial surface
and incisal third of the palatal surface
• An impression is taken of this and 2 adjacent
units. The technician is then asked to make
metal ceramic crown that will have two
surfaces instead of usual four. This sleeve
crown is then cemented in usual way. If too
little porcelain is removed from the original
unit, the new sleeve crown will feel slightly
bulky

32. Porcelain Jacket crown failure
Usually caused by faulty reductions or wrong patient selection
(example: presence of excessive forces and parafunctional habits)
1. Vertical Fracture
• Tapered Finishing line (such as chamfer, feather edge or bevel
indefinite finishing line) which results in restorations contacting he
tooth on a sloping surface
• Abutments with unrestored proximal restorations
• Round preparation forms which have no resistance to rotational
forces
• Sharp areas in the reduction producing high stress in the
restoration

33. 2. Facial semilunar cervical fracture
Caused by:
 Short tooth preparations – the OG length of the preparation should be 2/3 to ¾
that of the final restoration
 Incisal forces may tip the restoration facially causing cervical fracture
Metal ceramic crown preparationPorcelain fused to Metal crown
preparation

34. 3. Lingual Fracture
• Semilunar fractures result from occlusion occurring cervical to the
cingulum resulting in shear forces
• Other fractured are caused by inadequate lingual reduction with less
than 1mm porcelain thickness
• Excessive occlusal forces (example: patient with clenching)

35. Management:
Tooth preparation should be adequate but not excessive
Minor defects can be restored with resin
Severely chipped all porcelain crowns must therefore be replaced
by new crowns

36. JOHN F. JOHNSTON
• Discomfort
• LOOSENESS Of FPD
• Recurrence of caries
• Recession of supporting structure
• Degeneration of Pulp
• Fractures od bridge components
• Loss of veneers
• Loss of function
• Loss of tissue tone or form
• Failure to seat

37. John F. Johnston
1. DISCOMFORT
Causes:
1. Malocclusion or premature contact
2. Oversized or poorly positioned masticating area with retention of
food by pontics or retainers
3. Torque produced by seating of the bridge or from occlusion
4. Excess pressure on tissue
5. Plus or minus contact areas
6. Overprotected or under protected gingival and ridge tissue
7. Sensitive cervical areas
8. Thermal shock

39. Management
Areas of premature contact can be corrected by equilibrium using either a
small knife edge stone or round bur
Oversized or poorly positioned masticating area can be corrected by
reducing the buccolingual measurement at the expense of the lingual cusp
Retention of food may be eliminated by widening the embrasures,
diminishing the lingual cusps and increasing the number of grooves
emptying into embrasures.
Torque can be helped by reduction of buccolingual dimension.
Pressure on tissue has no other cure than removal and reconstruction.
Prepare a small proximo-occlusal cavity in the retainer and cement on inlay
that will bring the strength and location of contact to desired point.
Over contoured areas of crown or pontic may be reduced, reshaped and re-
polished.
For under protection of gingival tissue there is no treatment except
reconstruction of prosthesis.
A cavity preparation can be made at the margin of the restoration and a
restoration is placed.

40. John F. Johnston
2. LOOSENESS OF FPD
Causes:
1. Deformation of metal casting on the
abutment
2. Torque
3. Technique of cementation
4. Solubility of cement
5. Caries
6. Mobility of one or more abutments
7. Lack of full occlusal coverage
8. Insufficient retention in the abutment
preparation
9. Poor initial fit of the casting

41. Management:
Deformed cast retainers must be corrected by reconstruction.
Torque may be eliminated by equilibration by recontouring or reducing
occluding areas, or by construction and insertion of an occluding prosthesis.
If a bridge becomes loose because of the technique cementation, the bridge
maybe removed or recemented.
Cement dissolution cannot be improved except by remaking the bridge.
In case of caries, retainer must be removed and the abutment teeth must be
prepared.
In case in mobility of the abutment, evaluate carefully to
 ascertain whether more abutment teeth and splinting will
 correct the fault or whether the offending abutment must be
 lost.
If there is insufficient retention, a new bridge is mandatory.

42. John F. Johnston
3. RECURRENCE OF CARIES
Causes:
1. Overextension of margins
2. Short castings
3. Open margins
4. Wear
5. Retainer coming loose
6. Pontic form that fill the embrasures
7. Poor oral hygiene
8. Use of wrong type of retainer
9. Uncovered neck of tooth by displacement
of gingiva

43. Management:
For overextended margins it is possible to polish off the excess
casting, prepare a cavity and place a restoration.
In short castings, the caries may be removed and the area can be
restored with a casting or a resin restoration.
Open margins require remaking of a prosthesis.
If the cause of the caries is wear, a plastic restoration or an inlay may
be sufficient.
When cleaning embrasures is not possible due to pontic form, the only
remedy is to remove the bridge and build one with a correct design.
If the neck of the tooth is uncovered, re-preparing the abutment tooth
and extending the cervical margin of the preparation to a less
susceptible point should be considered.

44. John F. Johnston
4. RECESSION OF SUPPORTING STRUCTURE
Causes:
May result from overloading due to:
1. Length of the span
2. Size of the occlusion table
3. Embrasure form
4. Contour of the retainers
5. Too few abutment teeth or it may be developed
because of overextended margins

45. Management:
Often the size of the occlusion table can be
reduced, embrasure form can be changed or contour of
the retainers can be altered to decrease the load during
mastication.
If too few abutment teeth have been used, the
bridge must be removed and remade with multiple
terminal abutments.
An overextended margin must be ground and polished
to contour.

46. John F. Johnston
5.DEGENERATION OF PULP
Causes:
1. Excess heat generated during
preparation
2. Excess tooth reduction
3. Pinpoint exposure which may go
unnoticed
4. Occlusal Trauma
5. Poor design
6. Secondary caries

47. Management:
Use of varnishes and dentin bonding
agents which forms as an effective barrier and
prevents underlying pulp from toxic effects of
cement and core materials.
Endodontic treatment of the involved tooth by
making an access opening through the crowns,
once obturated the perforation can be restored.

48. John F. Johnston
6. FRACTURE OF BRIDGE COMPONENTS
a. Faulty solder joint
b. incorrect casting technique
c. overwork of the metal due to length of the span or parts that are too small
7. LOST OF VENEERS
a. little retention
b. badly design metal protection
c. deformation of the protecting metal
d. malocclusion
e. improper fusing or technique
8. LOSS OF FUNCTION
a. they don’t function in occlusion
b. they have no contact with opposing teeth
c. they have permanent contact
d. over carved or under carved occlusal surface may impair efficiency
e. Loss of opposing or approximating teeth

49. 9. LOSS OF TEETH TONE OR FORM
a. pontic design
b. position and size of joints
c. Embrasure form
d. over contouring or under contouring of the retainers
e. oral hygiene practice of the patient
10. FAILURE TO SEAT
a. abutment preparation are not parallel
b. soldering assembly may have been incorrect, or relationship
of the retainers may have been altered during soldering

50. Types of Bridge Failures
I. Cementation Failure
II. Mechanical Failure
III. Gingival and Periodontal Breakdown
IV. Caries
V. Necrosis of Pulp
VI. Biomechanical Failure
VII. Esthetic Failure

51. Cementation Failure
Broadly divided into:
1.Cement failure
2.Retention Failure
3.Occlusal Problems
4.Distortion of FPD

52. Cement Failure
Primary function of 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
i. Adequate working time Properties of Ideal Luting Agent:
ii. Adhere well to both tooth structure and metal surface
iii. Provides good seal
iv. Non toxic to the pulp
v. Have adequate strength properties
vi. Be compressible into thin layers
vii. Have low viscosity and solubility
viii. Exhibit good working time and setting properties

53. An inadequate retainer, failure can also occur because of a poor
cementation technique
This may be due to the wrong choice of material, failure to observe the
manufacturer’s mixing instructions, the use of old or contaminated material,
and inadequate powder/liquid ration, or the insertion of the prosthesis when
the cement has started to set
Inadequate cemented restoration may cause:
i. Increase vertical dimension of occlusion
ii. Loosening of the crown or FPD after a relatively short time
iii. Leakage and decay under the abutment
iv. Unsightly appearance of a metal margin where originally the metal was
concealed under the gingiva
v. Sensitivity to sweets or brushing due to exposure of the cervical end of
the tooth

54. Causes:
1. Cement selection
2. Expired cement
3. Clinician not following manufacturer’s instruction
4. Incomplete removal of temporary cement
5. Inadequate isolation
6. Inclusion of cotton fibers
7. Incomplete isolation
8. Insufficient pressure seating

55. How to confirm cementation failure:
1. Pull the restoration margin and see for movement of it
2. Bubbles come out of the margin or perforation (if present)
when the restoration pushed by occlusal pressure

56. Retention Failure
For restoration to accomplish its purpose, it must stay in place on the
tooth
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 necessary retention and resistance
Cause for retention failure:
1. Excessive taper
2. Short clinical crowns
3. Mis-fitting
4. Misalignment

57. Excessive Taper
• As a cast metal or ceramic restoration is placed on or in the
preparation after the restoration has been fabricated in its final form,
the axial walls of the preparation must taper slightly to permit the
restoration to seat
• Theoretically, the more nearly parallel the opposing walls of the
preparation are, the greater should be the retention
• Recommendations for optimal axial wall taper of tooth preparations
for cast restorations ranged from 10-12˚
• Tooth preparation taper should be kept minimal because of its
adverse effect on retention, but Mock estimates that a minimum taper
of 12˚ is necessary just to ensure the absence of undercuts

59. 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 its
retention
• 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 restorations 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

60. Virginia Type
• Moon and Hudgins et al produced particle roughened retainers by
incorporating salt crystals into the retainer patterns to produce
roughness on the inner surfaces
• This method is also known as Lost Salt Technique
• The framework is outlined on the die with a wax pencil and the area
to be bonded is coated first with model spray and then with lubricant
• Sieved cubic salt crystal (NaCl), ranging in size from 149 to 250 µm
are sprinkled over the outlined area

61. Clinical conditions with excessive taper and short clinical crown
should be treated with:
a. In case of excessive taper:
I. Incorporation of proximal grooves
II. Additional retentive grooves (should be along with the path of insertion)
III. Additional pins
B. In case of short crowns:
I. Crown lengthening procedure
II. Modification of supra-gingival margin to sub-gingival margin
III. Additional retentive grooves and proximal box
IV. Incorporation of pins
V. Addition of extra abutments

63. MIS FITTING
• The fit of casting can be defined best in terms of the “misfit” measure at
various points between the casting surface and the tooth
Measurement of misfit at different locations and geometrically related
to each other and defined as:
i. Internal gap
ii. Marginal gap
iii. Vertical marginal discrepancy
iv. Horizontal marginal discrepancy
v. Over-extended margin
vi. Under-extended margin

64. Causes for Mis Fitting
1. Expansion of the metal substructure
2. Improper water/powder ration
3. Improper mixing time
4. Improper burnout temperature
5. Distortion of the margins (towards the tooth surface)
6. Distortion of the metal substructure
7. Metal bubbles in occlusal or marginal regions
i. Inadequate vacuum during investing
ii. Improper brush technique
iii. No surfactant
8. Porcelain flowed inside the retainer
9. Excessive oxide layer formation in inner side of the retainer (due to contaminated
metal or repeated firing of porcelain)
10. Tight contact points
11. Thick cement space
12. Insufficient pressure during cementation procedure

65. 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

66. Causes of Misalignment:
1. Abutment displacement due to improper temporization
2. Distortion of wax pattern while sprueing and investing
3. Casting defects
4. Distortion of metal frameworks in porcelain firing
5. Porcelain flow inside the retainers
6. Misalignment of soldering points
7. Insufficient pressure in cementation
8. Thick cement film
9. 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

67. Occlusal Problems
Following the placement of a dental restorations, a patient might
report discomfort ranging from a feeling of “lameness” to “sever 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

68. Causes in Occlusal Problems:
a. Immediate Problems
1. Occlusal interference
2. Marginal ridges ate different levels
3. Supra eruption of the opposing tooth
4. Parafunctional Habits
b. Delayed Problems
1. Wearing of occlusal surface
2. Loss of occlusal contacts
3. Perforation of occlusal surface
4. Food lodgment due to plunger cusp
5. Fracture of facing due to defective occlusal contact
6. Periodontal or gingival breakdown due to improper occlusal contacts
7. Tenderness due to food lodgement

69. Occlusal Wear and Perforation
With normal attrition the metal occlusal surface may wear down over
2-3 decades. This maybe accelerated in thin castings in case of
insufficient reduction Perforations allow leakage and caries
In case of metal castings this eventually develops into a perforation
which allows leakage resulting in caries and prosthesis failure. Early
detection maybe sealed by gold or amalgam prolonging the service of
the restoration
In case of ceramic restorations opposing natural teeth, enamel wears
occurs that may even reach dentin
Ceramic restorations opposing metal restorations also cause their
wear
In case of heavy bite, it is better to make castings with metal occlusal
surfaces to preserve integrity of the opposing surfaces
At times deliberate occlusal perforations may be made for root canal
therapy and then sealed

70. Insufficient occlusal preparation lead to less thickness of the metal and this
may lead to perforation, which may occur in the finishing and polishing
Even with normal attrition, the occlusal surfaces of teeth wear down
substantially over a lifetime
Causes:
1. Heavy occlusal forces
2. Clenching, bruxism lead to accelerated occlusal wear
3. Inadequate clearance
Clinical Features
1. Attrition of opposing teeth
2. Polished facets of the retainers or pontics
3. Gingival recession
4. Perforation of the prosthesis

72. Management:
If perforation is detected early a restoration can be placed to seal the
area
If metal surrounding perforation is extremely than a new prosthesis
should be fabricated
If occlusal surfaces are covered with porcelain, opposing natural
teeth shows dramatic wear of enamel, so go for metal crowns to
minimize the wear

73. Distortion
Marginal Integrity
Completed restoration should go into place without binding of its
internal aspect against the occlusal surface or the axial walls of the
preparation
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
Distortion of all metal bridges may occur, for example: Hygienic pontics are
made too thin or if a bridge removed using to much force when this happens
the bridge has to be remade
In metal ceramic bridges, distortion of the framework can occur during
function, or a result of trauma. This is likely if the framework is too small in
cross section for the length of span and the material used

75. Causes of Failure in Marginal Integrity:
1. Bending of FPD (wax patterns and metal substructure)
 in waxing stage
oRemoval from the die
oSpruing Stage
oInvesting Stage (thick mix of investment distort or displace the wax
pattern)
Incomplete casting
oWax patterns too thin
oIncomplete wax elimination
oCold mod/ melt
oInadequate metal

76. Rough Casting
oImproper finishing of wax pattern
oExcess surfactant
oImproper water powder ratio
oExcessive burnout temperature
oImproper divesting (direct hit on the metal framework)
Bending of long span FPDs
oThin crown
oSoft metal
oHeat treatment not being done
oPorosity in the metal
oDistortion of the metal substructure during porcelain firing
oContaminated metal

77. Inadequate FPD Design
Designing bridges is difficult, it is neither a precise science nor creative form
of art. It needs knowledge, experiencing judgement, which take years to
accumulate
A. Under-Prescribed FPDs
Includes designs that are unstable or have too few abutment teeth
Examples: Cantilever FPD carrying pontics that cover too long a span or a
fixed movable FPD where again the span is too long or where abutment
teeth with too little support has been selected
Another “under-design” fault is to be too conservative in selecting retainers
Examples: intra-coronal inlays for fixed FPDs
With this design faults, little can be done other than to remove the FPD and
use another type of replacement

79. B. Over-Prescribed FPDs
Dentists sometimes include more abutment teeth than are necessary
retainer which fails:
The 1st lower premolar might be included as well as the 2nd premolar
and 2nd molar in a bridge to replace the lower 1st molar, this is not
necessary
Upper canines and both premolars on each side are replacing the
four incisors.
As well as being destructive, or this gives rise to unnecessary practical
difficulties in making bridge
The retainers themselves may be over prescribed with complete
crowns being used where partial crowns or intra-coronal retainers
would have been quite adequate, or metal ceramic crowns might be
used where all metal crowns would have been sufficient

80. Several suggestions have been proposed scientifically to explain distortion
resulting in metal framework after the various stages of the porcelain firing
schedule, these include:
a) Contraction of the porcelain with subsequent metal deformation
b) Contamination of the casting, reducing its melting temperature
c) Grain growth of the allow, 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
** Shillinburg stated that ceramic metals require certain amount of bulk in the
cervical area to resist distortion when subjected to the repeated firing cycles of
porcelain

81. INADEQUATE CLINICAL AND LABORATORY
TECHNIQUES
Marginal Deficiency
Positive ledge (overhang):-it is an excess of
crown material protruding beyond the margin
of preparation. These are common with
porcelain. However, it is often possible to
correct them without otherwise disturbing the
restoration by grinding and polishing in situ.
Negative Ledges:- In a deficiency of crown
material that leaves the margin of preparation
exposed with no major gaps between the
crown and the tooth. It is fairly common fault
particularly with the metal margins. But one
that is difficult or impossible to correct at try in
stage.

82. PONTIC DESIGN
Tissue contact of Pontic
Extensive area of the tissue contact is
cited as major cause of failure. Area
of contact should be small and
convex. Mesial, Distal, lingual gingival
embrasures should be wide open to
allow easy cleaning. Contact between
the pontic tissue should allow floss to
be passed from one retainer to the
another.

83. DOWEL DESIGN
• If a dowel is used its extension into the root is must at least
equal the length of the crown.
• A minimum of 4mm gutta percha and more if possible should
remain to prevent dislodgement and subsequent leakage.
• To prevent fracture, encirclement, of 1-2mm vertical axial tooth
should be done.

84. Mechanical Failure

85. In the design of fixed partial denture pontics, if insufficient
attention is given to mechanical principle, the prognosis will be
compromised
Mechanical problems might be due to poor diagnosis and
treatment plan, improper choice of materials, poor framework
design, poor tooth preparation, or poor occlusion
The following mechanical problems could lead to fracture of the
prosthesis or displacement of the retainers
Therefore, it is important to evaluate the likely forces on a pontic
and to design it accordingly.

86. Classifications of Mechanical
Failure
1.Retainer Failure
2.Pontic Failure
3.Connector Failure

87. Retainer Failure
1. Perforation
2. Marginal Discrepancy
3. Facing Failure
•Fracture
•Wearing
•Discoloration

88. Perforation
Causes:
1. Insufficient occlusal reduction
2. Insufficient occlusal material
3. High points in opposing dentition (plunger cusp)
4. Premature contacts
5. Contaminated metal
6. Porosity in metal work (subsurface, back pressure, suck back)
7. Due to improper melting temperature
8. Improper pattern position
9. Improper sprue (too thin)
10. Improper location
11. Parafunctional habits

89. Marginal discrepancy
Causes:
1. Selection of margin
2. Improper preparation and failure to establish the margin properly
3. Failure to do gingival retraction prevents definite margin location and
subsequently in impression
4. Selection of the impression material:
i. Shrinkage in material (condensation silicone)
ii. Distortion of material (alginate)
5. Improper impression procedures
6. Voids in the impression
7. Variation in pressure application in wash technique
8. Delayed pouring of die material
9. Distortion of wax patterns at margins

90. 10. Insufficient flow of metal
11. Shrinkage of metal
12. Nodules in margins and inner side of coping
i. Due to inadequate vacuum during investing
ii. Improper brushing technique
iii. No surfactant
13. Excessive sand blasting
14. Distortion due to degassing procedure
15. Open margins due to porcelain shrinkage (opaque porcelain)
16. Thick cement
17. Cement setting prior to seating
18. Insufficient pressure application during cementation

91. Lost Facings/ Facing Failure
Laboratory made ceramic or acrylic facing, may be entirely lost
With acrylic facing, wear and discoloration are also common
Causes of veneer fracture:
1. Poor retention
2. Heavy occlusion on the facing
3. The facing is not protected by the metal completely
4. Deformation of the protecting metal
5. Malocclusion
6. Micro-leakage between metal and facing
7. Improper curing or fusing technique
8. Excessive oxide layer formation

92. Cause of Wearing of Facing:
1. Improper curing or fusing technique
2. Deep bite (decreased overbite in lower anteriors)
3. Acrylic veneering opposing porcelain teeth
4. Faulty brushing techniques and flossing
5. Parafunctional habits
Causes of Discoloration:
1. Absorption of oral fluids
2. Absorption of artificial food coloring agents through micro-cracks or
microleakage in metal and facing interfaces
3. Tarnish and underlying metal and facing (greening of porcelain in silver
alloys)
4. micro-cracks due to malocclusion

93. Facing Failure Types of Veneer Failures:
a) Fracture
b) Wearing of facing (resin veneers)
c) discoloration

94. 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 support

95. 1. Pontic Space
• One function of an FPD is to prevent tilting or drifting of the adjacent
teeth into the edentulous space
• If such unwanted movement has already occurred, the space available
for the pontic may be reduced and its fabrication may be competed.
• Under these circumstances, it is often impossible to create an
acceptable appearance without repositioning the abutment teeth
orthodontically where aesthetics is important
• With a less aesthetic requirement, as for posterior teeth, overly small
pontics are unacceptable because they trap food and are difficult to
clean
• When orthodontic repositioning is not possible, it may be better to
increase the proximal contours of adjacent teeth than to make and FPD
with undersized pontics

96. 2. Residual Ridge Contour
• Contour texture of the edentulous ridge should be carefully evaluated
during the treatment planning phase
• Ideally shaped ridge is smooth and is the easiest to maintain plaque
free
• Unfortunately, many patients present with irregular hypoplastic tissue.
Under these circumstances, surgical removal of the excess fibrous
tissue may be recommended
• Patients who suffer sever bone resorption following tooth loss can
present a significant aesthetic challenge. Surgical ridge augmentation
may be one solution

97. 3. Biological Considerations
• Biologic principles of pontic design pertain to the maintenance and
preservation of the residual ridge, abutment and opposing teeth and
supporting tissues:
a. Pontic Ridge contact
• Pressure free contact between the pontic and the underlying tissue 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
b. Dental Plaque
• Chief cause of ridge irritation is the toxins released from the plaque
• It accumulates between the gingival surface of the pontic and the residual ridge
causing tissue inflammation and calculus formation
• To enhance plaque control, patient must be taught to perform efficient oral hygiene
techniques, with emphasis on cleaning the gingival surface of the pontic
• Shape of gingival surface, its relation to the ridge, and materials used in fabrication
will influence the success of these measures

98. c. Gingival surface of pontic
Where aesthetics is of concern in the anterior region of the mouth, the
pontic should contact the gingival tissue on the labial or buccal aspect
to give an appearance of immerging the tissue.
- In the posterior region, like the mandibular premolar and molar areas
more attention should be given to occlusion, function and hygiene.
- Pontic contacts maybe classified into different groups: mucosal and
non-mucosal contacts.
- Normally, where tissue contacts occurs, the gingival surface of the
pontic is inaccessible for cleaning with a toothbrush. Therefore, the
patient must develop excellent hygiene habit's and the use of devices
such as proxa-brushes, pipe cleaners and dental floss.

99. Oral Hygiene Aids

100. A pontic with a concave fitting surface
that overlaps the residual ridge buccally
and lingually is called a saddle shape.
This is avoided because the gingival
surface cannot be easily cleaned.
An egg shaped or bullet shaped
pontic is the easiest for the patient to keep
clean. It should be made as convex as
possible, with only one point of contact at
the center of residual ridge. This design is
recommended for the replacement of the
mandibular posterior teeth because
aesthetics is of less concern here.

101. 4. Pontic Ridge relationship
Hygienic or sanitary pontic-
tissue surface of a mandibular
posterior pontic should be left
well clear of the residual ridge.
The hygienic design permits
easier plaque control by allowing
gauze strips and other cleaning
device to be passed under the
pontic and seesawed in
shoeshine fashion

102. 5. Pontic material
Any material chosen to fabricate should provide aesthetics
results where needed, biocompatibility, rigidity, and strength to
withstand occlusal forces, and. the desired longevity.
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.

103. 6. Biocompatibility
• Glazed porcelain is considered to be the
most biocompatible of the available
pontic materials
• Highly glazed porcelain is relatively easy
to clean
• 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

104. 7. Occlusal Forces
• Reducing the buccolingual width of the pontic by as much as possible as 30% has long
been suggested as a means of lessening occlusal forces on the abutment tooth
• Narrowing the occlusal table may impede or preclude the development of a harmonious
and stable occlusal relationship
• Mechanical failure of the pontic may occur because of inadequate strength.
• Thus, an all-porcelain pontic should never be used unless the bite is favorable
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. Framework must provide a uniform veneer of porcelain (approx. 1.2mm), excessive
thickness of porcelain contributes to inadequate support and predisposes to eventual
fracture
b. 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 reduced bond strength and increases the possibility of mechanical
failure

105. c. Sharp angles on the veneering surfaces should be rounded. They
provide increased stress concentration that could cause mechanical
failure
d. 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

106. COLOR MISMATCH
This could be the result of:
• Inability to match the patient natural
teeth with available porcelain colors.
• Shade selection may have been
inadequate.
• Metamerism also leads to poor color
match.
• Insufficient tooth reduction / failure to
properly apply and fire the porcelain
may have been created a restoration
that does not match the shade guide
or surrounding teeth.

107. PRINCIPLE OF SHADE SELECTION
1) Teeth to be matched must be clean
2) Remove bright colors from the field
of view
• Make up / tinted eye glasses
• Bright gloves
• Neutral operator walls
1. View patient at eye level
2. Evaluate shade under multiple light
sources
3. Make shade comparisons at the
beginning of appointment
4. Shade comparisons should be
made quickly to avoid eye fatigue

108. REPAIRING PORCELAIN-METAL
RESTORATIONS WITH COMPOSITE RESIN
1. Pre-operative view of fractured
porcelain on pontic of 3-unit
bridges
2. Preparation of the exposed
metal creating undercuts in the
metal.
3. Application of metal bonding
agent.
4. Application of resin more opaque

109. 5. Matrix is placed on gingival
area of pontic to shape
the composite resin repair.
6. Placement of composite resin.
7. Complete composite resin repair
of the lateral incisor.

110. Connector / Solder Joint Failure
Connector is the part of FPD or splint that joins the individual
components (retainers and pontics) together
Requirements of solder:
Ability to resist tarnish and corrosion
To be free flowing
To match the color of the units to be joined
Strong
Casting can make rigid joint 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 must be thoroughly wet by liquified solder. Dirt or
surface oxide can reduced wetting and impede successful soldering

111. Causes of Failure:
1. Improper/ incorrect selection of connector
2. Thin metal at the connector
3. Flaw or inclusion in the solder itself
4. Solder gap – narrow or wide
5. Porosity
6. Insufficient metal around
7. Defective occlusal contacts over thin connector
8. Failure to bond to surface of the metal
9. The solder joint not being sufficiently large for conditions in which
it is placed

112. A problem, particularly with metal-ceramic bridge work, is that too
much restriction of the solder connectors, buccally, gingivally and
incisally can lead to inadequate area of solder failure
It is better to join multiple unit bridges by solder joints in the middle
of pontics before the porcelain is added, strengthened by porcelain
covering

114. Detection:
Wedges are placed beneath the connector to separate the Fixed
Partial component to confirm diagnosis

115. Management:
*There are NO satisfactory intraoral repair methods, and it is not
possible to re-solder (whole bridge has to be remade) *
Fabrication of new prosthesis
Occasionally an inlay dovetailed preparation can be made on
metal and this casting can be cemented to stabilized prosthesis

116. Loss of Veneers
Common reasons for loss of veneers:
1. Little retention
2. Badly designed metal protection
3. Deformation of the protecting
metal
4. Malocclusion
5. improper fusing or technique

117. Common reasons for loss or failure of
veneers:
Mechanical:
• Fracture
• poor positioning of incisal margin
• Less incisal thickness
• Margin too subgingival
• Debonding
• Use of expired cement
• Faulty veneer/ tooth preparation during luting

118. Biological:
• Post-operative sensitivity
• Improper curing of cement
• Poor marginal adaptation
• Marginal microleakage
• Poor fit and extension
Aesthetic:
• Improper shade selection
• Gingival recession
• Over contour
• Improper subgingival placement

119. Oral manifestation of loss veneers
you may notice that your tooth is sensitive to hot
and cold foods and beverages after you lose a veneer,
although it won’t affect your ability to chew or eat. The
tooth may also feel rough. This us usually just a
cosmetic issue, but if the roughness irritates your mouth,
cover the front of the tooth with dental wax

120. Management:
 your dentist will examine the veneer that is
detached if you still have it, determine why it is
detached, and decide if it can be successfully
re-attached. If it can’t, the dentist will order a
new veneer.

121. Loss of Function
• Don’t function in occlusion
• Have no contact with opposing teeth
• Have permanent contact
• Over carved and under carved occlusal surface may impair
efficiently
• Loss of opposing or approximating teeth

122. Loss of teeth tone or form
Cause:
1. Pontic design
2. Position and size of the joints
3. Embrasure form
4. Over contouring or under contouring of retainers
5. Oral hygiene practice by the patient

123. CONTACTS PLACED TOO GINGIVALLY
- It will increase the depth of the occlusal embrasure.
- Impingement on interdental areas
LOOSE (OPEN) CONTACT AREAS
- Leading to food impaction
- Accumulation of bacterial plaque
- Periodontal and caries problem

124. Management:
1. Tissue contact of point, extensive area of tissue contact is major cause of
failure. Area of contact should be small and convex. Mesial, distal, lingual
gingival embrasures should be wide open to allow easy clean, contact
between pontic and tissue should allow floss to be passed from one
retainer to other
2. If you chose to extend the contact area between anterior teeth from the
incisal embrasures, the lingual embrasure must be wide enough for the
access to gingival tissue under the contact areas from the lingual surface
3. Proper re-contoured embrasure space in gingival papilla for effective oral
hygiene
4. Good selection of pontic design and re-contouring also for effective oral
hygiene