2. INTRODUCTION
• The fixed prosthesis is a branch of the dental prosthesis that concerns the replacement
and / or restoration of teeth by artificial substitutes that cannot be removed or
removed from the mouth. The fixed prosthesis can be cemented, or securely retained
in natural teeth, dental roots and / or pillars of dental implants
3. CLASSIFICATION BENNARD G.N. SMITH
• 1. Loss of retention
• 2. Mechanical failure of crowns or bridge components
a. Porcelain fracture
b. Failure of solder joints
c. Distortion
d. Occlusal wear and perforation
e. Lost facings
4. • 3. Changes in the abutment tooth
• a. Periodontal disease
• b. Problems with the pulp
• c. Caries
• d. Fracture of the prepared natural crown or root
• e. Movement of the tooth
5. DESIGN FAILURES
• A. Under-prescribed FPDs
• b. Over-prescribed FPDs
5. Inadequate clinical or laboratory technique
a. Positive ledge
b. Negative ledge
c. Defect
d. Poor shape and color
6. Occlusal problems
6. JOHN.F.JOHNSTON
a. Malocclusion or premature contact
b. An oversized or poorly positioned mastication area, with retention of food by
pontics or retainers.
c. Torque produced from the seating of the bridge or from occlusion
d. An excess of pressure on the tissue
e. Plus or minus contact area
f. Over protected or under protected gingival and ridge tissue.
7. 2. Looseness of FPD
a.Deformation of the metal casting on the abutment
b. Torque
c. Technique of cementation
d. Solubility of cement
e. Caries
f. Mobility of one or more abutments
g. Lack of full occlusal coverage
h. Insufficient retention in the abutment preparation
i. Poor initial fit of the casting.
8. 3. RECURRENCE OF CARIES
a.Over extension of margins
b. Short castings
c. Open margins
d. Wear
e. A retainer becoming loose
f. Pontic form that fills the embrasure
g. Poor oral hygiene
h. Use of wrong type of retainer, which will promote caries susceptibility
i. Permanent displacement of the gingiva due to temporary protection
9. 4. RECESSION OF SUPPORTING STRUCTURE
a.Length of the span
b. Size of the occlusal table
c. Embrasure form
d. Few extensions of the cervical margins
e. Impression technique can also stimulate recession of the gingiva.
10. 5. Degeneration of Pulp
6. Fractures of bridge components
a. 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. Loss of veneers
a. Little retention
b. Badly designed metal protection
c. Deformation of the protecting metal
d. Malocclusion
e. Improper fusing or technique
11. 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
12. 9. Loss of teeth tone or form
a. Pontic design
b. Position and size of the joints
c. Embrasure form
d. Over contouring or under contouring of retainers
e. Oral hygiene practiced by the patient
13. 10. FAILURE TO SEAT
a. The abutment preparations may not be near parallel
b. Soldering assembly may have been incorrect, or relationship of the
retainers may have been altered during soldering.
14. 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
16. AN INADEQUATELY CEMENTED
RESTORATION MAY CAUSE:
1.An increased vertical dimension of occlusion
2. A loosening of the crown or FPD after a relatively short time
3. Leakage and decay under the abutment
4. The unsightly appearance of a metal margin where originally the
metal was concealed under the gingiva 5. Sensitivity to sweets or
brushing due to exposure of the cervical end of the tooth
17. CAUSES OF CEMENT FAILURE:
1. Cement selection – poor shelf life
2. Prolonged mixing time
3. Thin mix Cement
4. setting prior to seating
5. nadequate isolation
6. Incomplete removal of temporary cement
7. Thick cement space
8. Inclusion of cotton fibers
9. Insufficient pressure
18. CAUSES FOR RETENTION FAILURE
1) Excessive taper : 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
to 12 degrees. Tooth preparation taper should be kept minimal because of its
adverse effect on retention, a minimum taper of 12 degrees is necessary just to
insure the absence of undercuts
19. 2) Short clinical crowns: the greater the surface area of thepreparation 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.
20. 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
21. METAL BUBBLES IN OCCLUSAL OR
MARGINAL REGIONS
i. Inadequate vacuum during investing
ii. Improper brush technique
ii. 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 procedure
22. RETAINER FAILURE
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
23. CONCLUSION :
Failures in FPD construction for the most part is due to a 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. 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.
