This lecture for undergraduate students in fixed prosthodontics division

1. Failure of Crowns and
Fixed Dental Prosthesis
Dr. Hesham I. Othman,
Prof. and Head of Crown and Bridge Dept. Al-Azhar Univ.

2. FACTORS CAUSING FAILURE OF CROWNS AND BRIDGES
COULD BE CLASSIFIED ACCORDING TO THE STAGE IN
WHICH IT OCCURS AS FOLLOWS:
CEMENTATION

3. Failure of
fixed
prosthesis
Biologic
Failure
Mechanical
Failure
Esthetic
Failure
Maintenance
Failure
Classification according to mechanism of
failure

4. Patient complaint may be;
1- Immediate
2- Delayed

5. 1.
2.
3.
4.
5.
6.
7.
Biological Failure

6. Excessive
Pressure on soft
tissues
Retention of food
on the occlusal
surface
Traumatic
occlusion
Torque Cervical
hypersensitivity of
the abutment
Improper pontic/
ridge relationship
Lack of auxiliary
escape grooves
Premature contact Lack of parallism
between abutments
Over displacement
of gingival tissue
during impression
taking
Foreign body
pressing on the
ridge
Improper buccal
and lingual
embrasures
---
Absence of
temporary
protection
Over extended
temporary
protection
Over extension
cervical margins of
retainers or crowns
--- --- ---
Over extended
cervical margins of
restoration
Faulty proximal
contact
--- --- --- Short or open
cervical margins of
restoration
Improper labial or
lingual contour of
retainers or pontics
--- --- ---
Cervical caries
Discomfort, Pain and Sensitivity

8. CARIES
1.
2.
3.
4.
5.
6.

10. PULP INJURY
due to;
1. Improper use of coolant.
2. Over reduction leaving insufficient dentin protective
barrier.
3. Minute pulp exposure.
4. Improper or absence of temporary protection.
5. Use of irritating luting agent.
6. Recurrent caries under the restoration
7. Low grade pulp irritation as a results of traumatic
occlusion

13. PERIODONTAL BREAKDOWN
periodontal breakdown may lead to loss of abutment
Patient suffer from;
- Mobility of abutment
- Periodontal pocket formation
- Periodontal abscess
- Pain which prevent mastication at the side of restoration
- Bad odor and taste

14. Periodontal breakdown may be due to;
1. Inadequate abutment teeth in long span bridge.
2. Periodontally affected abutment teeth.
3. Patient with poor oral hygiene.
4. Poor marginal adaptation.
5. Over or under contour of axial walls
6. Extensively large connectors that restrict the cervical
embrasure.
7. Pontic with large contact area on edentulous ridge.
8. Improper or absence of proximal contact causing
food impaction and periodontal pocket formation.
9. Irregular or rough cervical margin of prosthesis.

16. OCCLUSAL PROBLEMS
Premature contact in centric and eccentric occlusion
excessive tooth mobility.

17. TOOTH PERFORATION
due to;
- Faulty preparation during pinhole preparation.
- Faulty during post space preparation.

19. TOOTH FRACTURE
1- Coronal tooth fracture
Due to;
1. Over reduction of abutment
2. Recurrent caries
3. Un-retained restoration
4. Presence of premature contact or heavy occlusal
force
5. Application of excessive force during seating of
improperly fitting restoration
6. Incorrect removal of cemented restoration

24. 2- Root fracture
Due to;
1. Excessive widening of root canal during endodontic
treatment or during post space preparation
2. Forceful seating of post
3. Caries extended to root surface
4. Trauma

34. MECHANICAL FAILURE
1. Cementation failure; looseness and/or dislodgment of
restoration, it could be due to
a- Cement failure
b- Retention failure
c- Occlusal problems
d- Different degree of abutments mobility
2. Restoration failure ( retainer, pontic, or connector )
3. Occlusal wear or perforation

35. 1- Cementation Failure
a- Cement failure
This could be due to;
1- Cement selection
2- Expired cement
3- Clinician not follow manufacturer’s instructions
4- Incomplete removal of temporary cement
5- Inadequate isolation
6- Inclusion of cotton fibers
7- Incomplete isolation
8- Insufficient pressure seating

36. 1- Cementation Failure
b- Retention failure
This could be due to;
1- Excessive taper
2- Short clinical crown
3- Misfit
4- Misalignment

37. 1- Cementation Failure
c- Occlusal problems
This could be due to;
1- occlusal interference
2- Occlusal perforation
3- Parafunctional activity
4- Loss of occlusal contacts

38. 1- Cementation Failure
d- Different degree of abutments mobility
This induce stresses on the cement which lead to
cementation failure

39. 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

40. 2- Restoration Failure
a- Retainer failure;
- Perforation
- Marginal discrepancy
- Veneering separation, fracture or wearing

43. b- Pontic failure;
- Pontic fracture (Porcelain) with unfavorable occlusal
load
- Limited occlusocervical height due to over eruption

44. c- Connector failure;

47. This could be due to;
1- Improper designing of connector size and position
2- Thin metal at the connector
3- Incorrect selection of solder
4- Porosity

49. Occlusal wear or perforation
Heavy chewing, clenching or Bruxism
wear of restoration
perforation of occlusal surface of
the metal restoration
Leakage, cement dissolution & caries

50. Esthetic Failure
► Improper shade matching
► Insufficient tooth reduction
► Disharmony between restoration and neighboring
teeth
► Improper masking of metal by esthetic material
► Use of improper shade of cement with all ceramic
restoration
► Unnecessary display of metal in case of partial
veneer metal restoration
► Improper marginal adaptation, form, roughness, or
extension which lead to gingival inflammation
causing unnatural soft tissue color

55. Maintenance Failure
Poor oral hygiene and improper maintenance of a well
done restoration may lead to failure of prosthesis.
The patient must be fully informed about his responsibility
in success or failure of restoration
The dentist must recall the patient for periodic clinical and
radiographic examination to detect early any harmful
changes that might occur.