FAILUREin Fixed Prostheses

FAILURE :A general term used to imply that

a part in service ;

• Has become completely inoperable.

OR

• Is still operable but, unable to adequately

performing its intended function.

OR

• Has deteriorated seriously, to the point that it

has become unreliable or unsafe for

continued use.

Failure may be:

I. Immediate, short term:

Ex inadequate fit, bad esthetics ex improper shade

selection, pulp trauma.

II. Progressive, long term:

In which multiple factors play an active role. Ex

Steps that are overlooked during patient selection,

treatment plan, faulty preparation, temporization,

soft tissue handling, Impression taking, restoration

design, faulty margins and occlusion.

Why We Fail ?

A failure may result when a fault has

occurred . Fault is an incorrect step or

process.

Improper case selection .

Improper diagnosis and treatment planning .

Inaccurate clinical procedures .

Inaccurate laboratory procedures .

Insufficient post insertion care and

maintenance .

Types Of Failure

Factor causing failure of crowns and

bridges could be classified according to

the stage in which it occurs as follows:

1-Before preparation

2-During preparation of the teeth

3-During construction

4-During cementation

5-After cementation

Biological failures

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y:or SensitivitPain, Discomfort, -A

Patient may complain of sensitivity

during cementation due to irritant nature

of some cement ex zinc phosphate.

Varnish or bonding agent minimizes

irritation of zinc phosphate cement..

Patient may complain of pain due to:1- Excessive pressure on ridge or soft tissue:

a. Foreign body on ridge.

b. Overextended cervical margin.

c. Faulty proximal margin resulting in food

impaction.

d. Improper labial and lingual contour

2- Food retention on the occlusal surface of the

prosthesis.

3- Traumatic occlusion resulting in premature

contact and pain

Discomfort , pain and sensitivityDiscomfort , pain and sensitivity

• Excessive pressure on the soft tissue.

• Retention of food on the occlusal surface .

• Traumatic occlusion .

• Cervical hyper sensitivity.

• Torque

• Excessive pressure on the soft tissue.

• Retention of food on the occlusal surface .

• Traumatic occlusion .

Due to presence of premature contact.

• Cervical hyper sensitivity

Pulp injuryPulp injury

The patient complains from:• Intense spontaneous pain .

• Pain is related to hot ,cold or sweet.

• Increase at night and by lying down

position .

Pulp Injury may be due to ;

• Over heating and dehydration of dentine .

• Over reduction .

• Inadequate treatment of caries .

• Minute unnoticed pulp exposure .

• Inadequate protection of the prepared tooth

.

• Using of irritating luting agent .

• Low grade pulp infection activated by

traumatic occlusion .

• In a study investigating causes of pulp

necrosis for a period of 8 years , Found

that;

• 15% of teeth were used as abutments.

• 3% were non-abutment teeth.

• Another study showed that 4% of vital teeth

developed pulpal necrosis after

placement of single crowns.

• In a third study 57% of all failed

bridges had one or both of their

abutments so affected .

• The survival probability of the pulp in

vital teeth restored with single unit

crown was higher than in those teeth serving

as an abutment of fixed- fixed bridge .

• 84% single crown.

• 71% bridge retainer .

• Greater number of maxillary anterior

teeth serving as bridge abutments

developed pulpal necrosis more than

any other tooth type .

:Caries-CPoor oral hygiene is a prime factor in initiating

carious lesion.

Patient complains from sensitivity to cold : Diagnosis

or sweet foods and liquid, bad taste, bad breath and

retainer looseness.

• Caries is One of the most biologic failures in fixed

prosthodontics

• It represent 36% of frequent causes of

failure.

• Another study found that the incidence

of caries was not related to the age of

patient but, rather to the time that the

bridge had functioned.

The patient complains from:

• Pain or sensitivity to cold and sweet

• Bad taste and breath.

• Loose restoration.

• Unsatisfied esthetic.

:Marginal caries) 1Generally begins at the surface and progresses inward. It

may be the result of incomplete caries removal, or a loose

retainer that allows leakage. Space between the restoration &

preparation allows cement solubility resulting in gingival

inflammation, caries and pulpal lesions resulting in gingival

inflammation. It is detected by probing with a sharp explorer

Treatment: In case of marginal caries: gold foil was

considered to be the best choice, amalgam maybe used as

restorative in posterior areas due to its long term marginal

seal. While composite or glass ionomer may be used where

esthetics is of value..

Caries at the margin Caries at the margin

• Mainly as the result of inaccurately fit

margins;

• Open.

• Short.

• Over extended.

That leads to dissolution of luting cement

and allow leakage of saliva and micro-

organisms.

• A higher caries incidence was found

around crowns with poor margins

compared to those with good margins.

Caries beneath the restorationCaries beneath the restoration

• This can be due to;

• Incomplete removal of caries

• Loose retainer.

• A study studying caries beneath

restoration found that ;

• 0.4% under single crowns.

• 18% under fixed partial denture.

• 0.8% under all ceramic crown.

• 2% under post and core.

2) Proximal caries:

Detected radio graphically.

Treatment: It requires prosthesis removal

for proper access and complete elimination.

:Root caries) 3Higher incidence in old age due to

decreased salivary flow or medication.

diuretics. Such as beta blockers &

Treatment:

New prosthesis should be done with

margins extending below the lesion on

sound tooth structure

Root surface cariesRoot surface caries• Commonly associated with gingival

recession and periodontal pockets .

• Reduced salivary flow .

• A study on 196 cases ;

• 52% root caries were found in men .

• 35% root caries were found in women .

• There was no correlation between the

root caries incidence and the number

of daily medication taken.

Caused byTorque on abutment teeth: -D

a. Alteration in the axial relation of abutments due to

absence of temporary restorations allowing abutment

movement.

b. Improper bridge assembly

C. Connector fracture resulting in excessive load on

the remaining abutments.

• Torque

o Improper parallel relationship between axial

walls.

o Absence of temporary protection.

o Improper assembly during soldering.

:Periodontal BreakdownE.

a. Localized periodontal involvement maybe induced

by poorly designed or maintained restorations. i. Prosthesis which hinder plaque removal and oral hygiene

measures.

ii. over contoured retainers caused by insufficient axial

reduction

iii. Large connectors that hinder interproximal hygiene.

iv. Rough surface which allow plaque accumulation.

In case of early detection the cause is corrected and no

further treatment is required.

Generalized bone loss caused by B .

periodontal disease may result in mobility

.and eventual loss of abutment

If periodontal breakdown is advanced then the

progress is arrested by periodontal treatment

which may include surgery. Prosthetic design

maybe altered to suit the oral conditions

established, some abutments maybe lost and

new ones selected in a new designed

prosthesis depending on their eva

Periodontal breakdownPeriodontal breakdown

The patient complains from:• Looseness of teeth and restoration.

• Bad taste and breath.

• Pain.

• Movement of teeth.

• Bad esthetic.

• Redness, swelling and bleeding gingiva.

• Periodontal pocket and abscess.

CausesCauses

• Bad oral hygiene .

• Periodontaly affected abutment .

• Improper bridge design .

• Insufficient reduction .

• Subgingival finish line .

• Trumatic gingival retraction .

• Improper cervical margin .

• Improper pontic design .

• A study reported only 0.6 % difference in

periodontal complication between the

restored teeth ( single crowns) and unrestored

teeth. Which increased around bridge

abutment 4 %.

• Some studies have shown a high incidence of

periodontal disease associated with fixed

prostheses , while other studies have shown a

low incidence of this complication .

Tooth Perforation:-FMay occur during pinhole, post insertion or during root

canal treatments. It may be occlusal to the periodontal

ligament, in the bifurcation, or even in the pulp. Treatment

depends on accessibility

if perforation is located occlusal to the periodontal

ligament, preparation maybe extended to cover the defect.

Root canal therapy is indicated in case of perforations into

the pulp.

In other cases periodontal surgery may be performed and

a restoration is placed into the perforated area.

Inaccessible areas such as bifurcations may necessitate

extraction.

Tooth perforationTooth perforation

• Improper located pinholes or pins .

• Improper endodontic treatment .

• Improper post preparation .

Mineral Trioxide Aggregate (MTA)

• It is a compound mixture of hydrophilic

tricalcium silicate , tricalcium oxide and

tricalcium aluminate .

• The material sets in moist environment and

has low solubility .

:Occlusal ProblemsG. Premature contact in centric or eccentric may

result in wear facets and induce teeth mobility.

This may be controlled by occlusal

adjustment. Bruxism maybe minimized by

night guards. However, occlusal adjustment

in periodontal involved teeth will not reduce

mobility.

Occlusal problemsOcclusal problems

• General discomfort with bite .

• Pain in muscles and T.M.J .

• Loose teeth or bridge .

The patient complains from:

• Traumatic occlusion : an injury to the

periodontal tissue and pulp of a tooth as the result

of occlusal forces by an opposing tooth or teeth .

• Premature contact in centric or eccentric

occlusal contact leads to :

oExcessive tooth mobility.

oPulp damage .

oT.M.J disorder .

Abutment fractureAbutment fracture

• Coronal tooth fracture :

• Over reduction .

• Recurrent caries .

• Occlusal trauma .

• Excessive trauma during seating or

removal of prosthesis .

Allergic problemsAllergic problems• Due to biological response of tissue .

Mechanical failuresMechanical failures

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er)loose retainLoss of Retention: (-ALoose retainers if not detected early may result in extensive caries.

Loose retainer may be diagnosed by

1. Presence of an acidic smell or foul odor in the

mouth.

2. The loose retainer may induce sensitivity to thermal changes and /or sweets.

3. An attempt to move the restoration occlusocervically will cause fluids to be

drawn under the casting which are expressed on seating producing

bubbles.

:Cause of loose retainers1. Improper cementation ex: moisture contamination.

2. Inadequate retention

3. Excessive span length or heavy occlusal forces.

Treatment: If restoration is removed intact it maybe recemented.

However if the cause is lack of adequate retention due to inadequate retention the

preparation needs to be modified and a new prosthesis made

Connector Failure:-B

Connectors may fracture due to metal weakening caused

metal weakening caused by casting porosity.

Connector fracture will cause excessive forces on the

surviving abutment as the prosthesis will act as a

cantilever bridge. Therefore immediate treatment should

be done.

Occlusal wear-CHeavy forces, clenching and bruxism lead to accelerated

prosthesis wear. 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 restorati In case of ceramic restorations

opposing natural teeth, enamel wear occurs that may even

reach dentine Ceramic restorations opposing metal Ceramic

restorations also cause their wear. In case of heavy bite it is

better to make castings with metal occlusal surfaces to

preserve the integrity of the opposing surfaces.

Porcelain Fracture-D.IMetal ceramic failure: maybe caused by: 1.

Incorrect framework design.

Thin metal copings (less than 0.2 mm) 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 ex too close to occlusal or proximal cutback.

Sharp angles or irregular rough areas over the veneering areas cause stress

concentration.

.II2. Occlusal interferences caused by heavy forces, eccentric contacts or Para functional

habits.

.III3. Trauma.

4. Debonding: a.

Separation of the metal and ceramic caused by improper metal handling such as

contamination and excessive oxide formation which may interfere with bonding. b.

Metal and 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. This solution is considered a temporary one

Loose retainerLoose retainer

• Bad taste or smell at the site of prosthesis .

• Sensitivity to temperature or sweet.

The patient complains from:

How to detect

looseness ?

Causes of loosenessCauses of looseness

Improper case selection Improper case selection • Mobility of abutment .

• Torque .

Improper tooth preparation Improper tooth preparation • Over reduction .

• Over convergency .

• Short preparation .

• Insufficient retentive grooves or pins in

partial coverage restoration .

Improper bridge design Improper bridge design • Selection of partial coverage when

complete coverage is indicated .

• Insufficient number of abutment in relation to

span length .

Improper construction Improper construction • Ill fitting casting .

• Poorly adapted margins .

• Improper alloy selection .

Improper cementation Improper cementation • Improper isolation or dryness .

• Improper manipulation .

• Unsteady positioning and loading during

setting .

• A study showed that using a chamfer finish

line produced significantly smaller marginal

gap than shoulder finish line .

• Another study , found smaller marginal gap

with shoulder finish line .

• A study found that, there is no difference in

marginal discrepancy between all ceramic

crowns and porcelain fused to metal crowns.

• A study showed that marginal discrepancy

increased after cementation .

• The crowns luted with resin cements were

found to have 2-5 times smaller marginal

discrepancy than crowns which luted with

zinc phosphate cement .

Prosthetic fractureProsthetic fracture

Joint fractureJoint fracture

Due to;

• Internal porosity.

• Improper solder alloy.

• Improper soldering technique.

• Strain hardening.

Veneering fracture

Due to;

• Inadequate bond between facing and

metal.

• Metal and porcelain incompatibility.

• Excessive occlusal function..

• Improper laboratory procedures.

All ceramic crown fracture

Due to;

• Improper case selection.

• Improper preparation.

• Improper construction.

• Improper cementation.

Esthetic failureEsthetic failure

33

Maintenance

failure

44

Does failed prosthetic appliance

may cause psychological

disturbance ?