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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
11
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
22
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 ?