FAILURES IN FIXED PARTIAL DENTURE

CONTENTS

A bridge is a custom-made device anchored to neighboring natural teeth, which replaces one or more missing teeth. When a lost tooth is replaced with bridgework, the teeth on either side of the missing one are prepared as crowns to hold the bridge in place. Bridges, sometimes referred to as a fixed partial denture, look natural and literally bridge the gap where one or more teeth may have been. Fixed bridges appear and function similar to natural teeth.

INTRODUCTION:
DENTAL RESTORATIONS ,NO MATTER HOW CAREFULLY PLACED, MAY REQUIRE MODIFICATION OR
REPLACEMENT. THE ORIGINAL EVALUATION AND TREATMENT SHOULD HAVE ENSURED GOOD ABUTMENT SELECTION , CROWN PREPARATION WITH ADEQUATE MARGIN PLACEMENT, PONTIC DESIGN AND CORRECT OCCLUSION.  NO GUARANTEE CAN BE GIVEN CONCERNING THE LONGEVITY OF ANY PROSTHESIS .  PATIENTS SOMETIMES CAN PRESENT WITH ONE OF A NUMBER OF MAJOR PROBLEMS AFTER CROWNS OR FIXED PARTIAL DENTURES HAVE BEEN CEMENTED.

CAUSES OF FAILURE

• Caries
• Pulp degeneration
• Periodontal breakdown
• Occlusal problems
• Tooth perforation
• Temperomandibular disorders
• Mechanical failures:
• Loss of retention
• Connector failure
• Occlusal failure
• Cementation failure
• Tooth fracture/ root fracture
• Porcelain fracture
• Maintenance failures
• Esthetic failures
• Facing failures

Caries:

• One of the most common biologic failures.
• Usually perceived by the patient as
•  Pain or sensitivity to hot ,cold or sweet foods & liquids.
• Dysgeusia
• Halitosis
• Loose restorations
• Fractured teeth
• Discolored teeth

Small lesions :

• Gold foil – filling material of choice for restoring marginal caries.
• Amalgam – best alterative to gold foil filling because ofits ability to produce long term marginal seal.
• Composite – indicated for restoration of caries in esthetic zone.
• Glass ionomer cement.
• Proximal lesions :
• Removal of prosthesis is required to obtain access to caries.
• If the lesion is small, the tooth preparation can be extended to eliminate the caries and a new prosthesis can be fabricated.
• When the lesion is large, an amalgam restoration is often required.
• An extensive lesion may require endodontic treatment when pulp has been encroached.
• A grossly destroyed teeth by caries that cannot be restored must be extracted.
• Schwartz et al (1970) & Randow et al (1986) both reported caries to be the most frequent cause of failure of existing restorations (36% & 18.3%).
• Glantz et al .in 1993 reported that of 77 bridges reviewed at 15yrs , 32.5% required removal. Further reported in 1993 that the incidence of caries was not related to the age of the patient , rather , to the time that the bridge had functioned .

Pulp degeneration:

• This is usually perceived by the patient as:
• pain – either spontaneous or related to hot or cold or sweet stimuli.
• pain which is accentuated by lying down or exercise

Causes :

• Extensive preparation
• Excess heat generation during preparation
• Indication for endodontic treatment
• Post insertion pulpal sensitivity on abutment teeth that doesn’t subside with timeà intense painà periapical pathology detected radiographically

Management:

• Access preparation – a hole is drilled in the prosthesis through which the biomechanical preparation (BMP) is completed.
• The access cavity is restored with
• Gold foil
• Amalgam
• Cast metal inlay
• If the retainer come loose during access opening or if the porcelain fractures, then remaking of the prosthesis may be necessary.
• A post and core restoration should be considered if little sound tooth structure is remaining.
• Survival of endodontically treated , post-restored teeth depends on a multitude of factors , all of which are practically impossible to include in a randomized , controlled clinical study.

Following conclusions were derived:

• Fracture of the tooth was the most common type of failure among the failed post-retained restorations followed by loosening of the post & fracture .
• Tapered posts more often displayed fracture of the tooth and less often fracture of the post.
• Fracture of the post was more common among male patients than among female patients.
• Periodontal breakdown:
• This is usually perceived by the patient as:
• Looseness of teeth or bridgework
• Drifting teeth
• Bleeding tissues
• Changes in color of the gums
• Bad breath
• Bad taste
• Pain
• Abscess formation
• Poor aesthetics
• Periodontal disease can produce extensive bone loss , which in course of time results in the loss of abutment teeth and attached prosthesis.
• Aspects of the prosthesis that interfere with effective plaqueremoval include:
• Poor marginal adaptation
• Overcontouring of the axial surfaces of the retainers
• Excessively large connectors that restrict cervical embrasure space
• A pontic that contacts too large an area on the edentulous ridge.
• A prosthesis with rough surfaces which promote plaque accumulation.

Management :

• Plaque accumulation àProphylaxis, removal of local factor
• Tissue hyperplasia àGingivoplasty
• Devitalized & severe bone lossà Endodontic procedure/ bicuspidization hemisection of teeth.
• Less severe breakdown can be treated without fear of loss of teeth, with small surgery which may produce an unacceptablerelationship between prothesis & the soft tissue.

Occlusal problems:

• Patients may be uncomfortable with their new occlusions.
• Some patients tolerate gross occlusal discrepancies without complaining , whereas others are intolerant to discrepancies
• in the range of 10-15 microns.
• Occlusal discomfort is perceived by the patient as:
• General discomfort with the “bite”
• Sore teeth
• Loose teeth or bridges
• Sensitive teeth
• “Tired” or “sore” muscles
• Interfering centric and eccentric occlusal contacts can cause:
• Excessive tooth mobility
• Irreversible pulpal damage

Management :

• When detected early occlusal adjustment should be done to eliminate these interferences without permanent damage.
• Occasionally, a combination of excessive mobility and reduced bone support require extraction of abutment teeth.
• Irreversible pulpal damage requires endodontic treatment.
• Change in vertical dimension:
• VD may be decreased as a result of severe attrition or increased as a result of poor restorative planning.
• Porcelain occlusal surfaces in short clinical crowns-vd increases
• Following symptoms may be perceived by the patient:
• Altered facial appearance
• Dribbling of saliva àloss of VD can precipitate “angular chelitis”
• Extreme changes in VD can convert an asymptomatic
• internal derrangement into a symptomatic one.àalteration in muscle activity can cause “myalgia”.
• Extreme increase in VD reduces ability of tongue to create a seal during swallowing
• Compensating movement of the larynx during swallowing
• Muscle strain & symptoms such as “sore throat” or “tired tongue”
• Teeth can become sensitive either due to loss of occlusal tissue or due to trauma to the teeth from the increased VD.
• Clenching of teeth because of premature contact.
• Loss of posterior vertical dimension à lower anterior teeth occluding more heavily with the palatal surface of the upper anterior teeth causing drifting or failure of anterior restorations.
• Decrease in the VD can result in occluding of the lower incisors with the palatal soft tissues giving rise to soreness & possible periodontal complications.
• Decrease or increase in VD
• Difficulty in mastication
• Gross increase in the VD
• Speech problems particularly with sibilants.

Tooth perforation:

• Improperly located pinholes or pins used in conjunction with pin-retained restorations may perforate the tooth laterally.
• Management : depends on the location of the perforation.
• Occlusal to periodontal ligament
• Extend the preparation to cover the defect.
• Extends into periodontal ligament
• Perform periodontal surgery
• Smoothening of the projecting pin
• Place a restoration into perforated area
• Furcation region
• Surgically inaccessible
• Severe periodontal problems may ultimately
• lead to extraction of the tooth.
• Pulp chamber
• Endodontic treatment
• Subpontic inflamation:
• Perceived by the patient as :
• Pain
• Swelling
• Bad breath
• Bad taste
• Bleeding gums
• Poor esthetics