Introduction

Fixed prosthodontic treatment does not last a life time.Patients often ask how long the bridge will last. This is an impossible question to answer, since most bridges do not wear out, neither do the supporting teeth.Failure is the result of an isolated incident, a progressive disease process, or bad planning or execution.

Types of failures

Biological failures

Mechanical failures

Esthetic failures

BIOLOGICAL FAILURES

Biological failures are mainly due to

Caries

Pulp degeneration

Gingival & periodontal diseases.

Occlusal problems

Tooth perforation

CARIES: It is one of the most common biological failures.

Causes:

patients with high caries index.

Improper excavation of caries.

cementation failure leading to marginal leakage.

Carious abutment teeth revealed by removing aBridge that was firmly attached to the sound abutment Teeth.

Diagnosis:

Comprehensive probing of the margins of the prosthesis and tooth surfaces with a sharp explorer.

Radiographs are also helpful, especially for interproximal lesions.

TREATMENT

Small lesions can be restored with gold foil amalgam, composite. In case of large lesions a new prosthesis have to be made.Prevention of Caries in FPD patients requires meticulous oral hygiene procedures.Fluoride containing dentifrices, mouth rinses and professionally applied topical fluoride will prevent caries.

PULP- DEGENERATION

Post insertion pulpal sensitivity on abutment teeth that does not subside with time, intense pain, or periapical abnormalities that are detected radiographically often indicates the need for an endodontic intervention.

Treatment:

If the bridge abutment becomes non-vital and the tooth involved is an anterior one, it can often be treated by apicectomy.When little sound tooth structure remains, a post and core can be placed and a new prosthesis can be fabricated.

GINGIVAL DISEASE

The main cause of gingival disease is mainly due to poor oral hygiene maintenance by the patient. Irritation of mucosa by the pontic may be due to the wrong choice of material for its fit surface. Gingival irritation caused by acrylic may be further aggravated by the deposition of calculus on it.

Treatment:

If the gingival disease is localized the reason should be assessed and if possible eliminated.

If generalized, a periodontal therapy may be indicated.

PERIODONTAL PROBLEMS

Periodontal disease can produce extensive bone-loss that in time results in the loss of abutment teeth.

Localized breakdown around prosthesis occurs as a result of

Inadequate oral hygiene maintenance

Effective plaque removal around prostheses may be hindered due to Poor marginal adaptation of retainers.Over contouring of retainersExcessively large contours that restrict the cervical embrasure space.Pontic, that contacts too large area on the edentulous ridge.Rough prostheses.

Bridge with defective Margins and extensiveGingival inflammation

Apically repositionedFlap, the retainer marginsAdjusted by grinding and polishing

Treatment

If mobility of one of the abutment teeth is noticed, the whole prosthesis must be reconstructed or remade to correct such defects.

Occlusal problems

Faults in the occlusion involve damage to the retainers and pontic by wear and fracture.

The occlusion can change as a result of the extraction of other teeth, or their restoration, or through wear on the occlusal surface.

MECHANICAL FAILURES

These includeLoss of retentionConnector failurePontic failureOcclusal wearTooth fractureCasting failure

LOSS OF RETENTION

causes:

Improper preparation form of tooth.

Improper cementation procedure such as contamination with moisture.

Because of long span of bridge.

Heavy Occlusal forces.

Diagnosis

Loss of retention can be detected in several ways.The patient may be aware of looseness or sensitivity to temperature and sweets. Patient experiences bad taste or odour from debris accumulated.Loose retainer can be detected, by pressing the bridge up and down and looking for small bubbles in the saliva at the margins of the retainers.

If one retainer becomes loose, it is necessary to remove at least that retainer, and usually the whole bridge.

If there is no extensive damage to the preparation, it may be possible to recement the crown or bridge.

Treatment

If a fixed-fixed minimal preparation bridge becomes loose at one end but seems firmly attached at the other, one option is to cut off the loose retainer, leaving the bridge as a cantilever.

CONNECTOR FAILURE

The connector between an abutment retainer and a pontic or between two pontics can fracture under Occlusal forces. Failures of both cast & soldered connectors have been observed and it is generally caused by internal porosity.

Failure of solder joint is mainly due to:

A flaw or inclusion in the solder itself.

Failure to bond to the surface of the metal.

The solder joint not being sufficiently large for the conditions in which it is placed.

OCCLUSAL WEAR

Heavy chewing forces, clenching or bruxism can produce Occlusal wear of a prosthesis.When the occlusing surfaces are restored with metal, the casting perforation may develop after several years .

Treatment

If the perforation is detected early, a gold or amalgam restoration can be placed that seals the area.

However, if the metal surrounding the perforation is extremely thin, a new prosthesis should be fabricated.

TOOTH FRACTURE

Tooth fracture could be Coronal fracture

Radicular fracture

CORONAL FRACTURES

causes :Excessive tooth reduction .The presence of interfering centric or eccentric Occlusal contacts.Heavy forces on a properly adjusted restoration.Attempting to forcibly seat an improperly fitting prosthesis . Unseat a cemented bridge incorrectly.

RADICULAR FRACTURES

Root fractures are most often caused by

Trauma

can also occur during endodontic treatment

Forceful seating of a post & core

Large coronal fractures necessitates removal of the prosthesis endodontic therapy, a post & core and a new prosthesis.

Treatment

Treatment

In cases of root fracture, when the fracture terminates at or just below the alveolar bone periodontal surgery may be performed to remove bone, and expose the fractures site so that it can be accompanied by a new prosthesis.

Otherwise tooth have to be extracted.

PONTIC FAILURES

Causes:

1. Faulty occlusion, particularly in lateral excursions, which was not corrected when the bridge was placed.

2. Inadequate strength.

PORCELAIN FRACTURES

Porcelain fractures occurs with both metal ceramic and all-ceramic restorations.

Causes:1. Improper Metal frame work design.2. Improper occlusion.3. Improper metal handling procedures.4. Failure due to improper preparation,

impression and insertion.5. Porcelain – metal incompatibility.

REPAIR OF FRACTURED METAL-CERAMIC RESTORATIONS

The best method is the fabrication of a new prosthesis.

Small gaps can be repaired with GIC, composite materials (with a separate silane coupling agent that allows optimum bonding).

Small gap at the mesial margin of the upper canine retainer.

Defect repaired With GIC

Permanent repair when adequate metal thickness is available:

1. Removal of the remaining porcelain on the fractured unit to expose the underlying metal.

2. Drilling of several pinholes (4 or 5) into the framework to a depth of at least 2mm and making an impression.

3. Creation of a pin-retained metal casting 0.2 to 0.3mm thick .

4. Fusion of porcelain to the pin-retained casting and reestablishment of normal form.

5. Cementation of the casting in position.

PORCELAIN JACKET CROWN FAILURES

All ceramic restorations are more likely to fail in the presence of heavy occlusal forces, clenching or bruxism.

VERTICAL FRACTURE

Causes:If a tapered finish line (such as a chamfer) is used, the restoration may contact the tooth on a sloping surface.

Sharp areas on the prepared tooth, such as the line angle or the incisal edge.

A round preparation form.

FACIAL CERVICAL FRACTURE

Fracture of the facial cervical porcelain, often assumes a “half moon” shape.

Causes:1. Short tooth preparation. 2. When the opposing tooth contact is

located incisally to the prepared tooth.

A shoulder of uniform width (approx 1mm)is used as gingival finish line to provide a flat seat to resist forces directed from the incisal.The incisal edge should be flat and placed at a slight inclination towards the linguogingival to meet forces on the incisal edge and prevent shearing.All sharp angles should be slightly rounded.

Prevention

LINGUAL FRACTURE

Causes:

when the occlusion is located cervically to the cingulum of the preparation.

Inadequate lingual tooth reduction in which less than 1mm of porcelain is present.

Heavy Occlusal forces.

CONCLUSION

The longevity of a restoration is dependent on many factors The type and design of prosthesis.The degree of functional & Para functional loading.The structural integrity and biologic status of the supporting teeth & tissues.Appropriate maintenance and home care Precision with, which the technical and clinical work has been carried out.