Clinical failures/ cosmetic dentistry training

CLINICAL FAILURES IN
FPD
- CAUSES AND MANAGEMENT
www.indiandentalacademy.com

CONTENTS
• Introduction
• Causes of failure
• Biologic failures
• Mechanical failures
• Esthetic failures
• Facing failures
• Removal of restorations
• Conclusion www.indiandentalacademy.com

CAUSES OF FAILURE
A. Biologic failures
1) Caries
2) Pulp degeneration
3) Periodontal breakdown
4) Occlusal problems
5) Tooth perforation
B. Mechanical failures
1) Loss of retention
2) Connector failure
3) Occlusal wear
4) Tooth fracture
5) Acrylic veneer wear / loss
6) Porcelain fracture
C. Esthetic failures
D. Facing failures

BIOLOGIC FAILURES
Caries :
• One of the most common biologic failures.
• Early detection possible mainly through comprehensive probing
of the margins of the prosthesis and tooth surfaces with a sharp
explorer.
• Radiographs are helpful to detect caries on proximal surfaces.

Management :
Small lesions :
• Gold foil – filling material of choice for restoring marginal caries.
• Amalgam – best alterative to gold foil filling.
• Composite – indicated for restoration of caries in esthetic zone.
– Less desirable
• Glass ionomer cement.www.indiandentalacademy.com

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.

Pulp degeneration :
Causes :
• Extensive preparation
• Excess heat generation during preparation
• Post-insertion pulpal sensitivity. May
manifest as  sensitivity which does not
subside with time
 Intense pain
 Periapical pathology
Management :
Endodontic intervention

Procedure :
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.www.indiandentalacademy.com

Periodontal breakdown :
It can be localized around the prosthesis, as a result of
inadequate instruction in prosthesis hygiene or a restoration that
hinders good oral hygiene.
Aspects of the prosthesis that interfere with effective plaque
removal 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 :
• Recontour to eliminate the defects
• Remake to correct the defectswww.indiandentalacademy.com

OCCLUSAL PROBLEMS
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.www.indiandentalacademy.com

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

MECHANICAL FAILURES
Loss of retention :
A prosthesis can come loose from an abutment tooth and if this
occurrence is not detected early, extensive caries often develops.
The loss of retention can be detected by several ways
1. Patients awareness of looseness or sensitivity to temperature or
sweets.
He may experience bad taste or odor.
2. Periodic clinical examinations that includes attempts to unseat
existing prosthesis by lifting the retainers up and down
(occlusocervically) while they are held between the fingers and a
curved explorer placed under the connector.www.indiandentalacademy.com

Management :
• Removal of the prosthesis
• Evaluation of the abutment
 Caries  restoration
 Preparation form  modify the preparation poor
• Fabricate new restoration
If the span length is excessive or occlusal forces heavy then a
removable partial denture may be the only satisfactory solution.

CONNECTOR FAILURE
A connector between an abutment retainer and a pontic or between
two pontics can occur.
• Under occlusal forces
• Internal porosity in the cast or soldered connectors
When fracture occurs, pontics are placed in a cantilevered
relationship with the retainer casting and this can allow excessive
forces to be developed on the abutment tooth.
Management :
• Prosthesis should be removed and remade as soon as possible.
• An inlay like dovetailed preparation can be developed in the
metal to span the fracture site and a casting can be cemented to
stabilize the prosthesis.
• Pontics can be removed by cutting through the intact connectors
and a temporary removable partial denture can then be inserted
to maintain the existing space and satisfy esthetic requirements.www.indiandentalacademy.com

OCCLUSAL WEAR
An accelerated occlusal wear of a prosthesis can be produced
due to
• Heavy chewing forces
• Clenching or bruxing
After several years, a casting perforation may develop, thus
allowing leakage and caries to occur, which ultimately lead to
prosthesis failure.
• If the perforation is detected early, a gold or amalgam
restoration can be placed to seal the area and provides
additional years of service.
• If the metal surrounding the perforation is extremely thin, a
new prosthesis should be fabricatedwww.indiandentalacademy.com

TOOTH FRACTURE
Causes :
Coronal fractures :
1. Excessive tooth preparation – leaving insufficient tooth
structure to resist occlusal forces.
2. Presence of interfering centric of eccentric occlusal contacts
3. Heavy occlusal forces.
4. Incorrect unseating of a cemented bridge.
5. Around inlays and partial veneer crowns, as a result of
increasing brittleness, of tooth structure with age.

Radicular fractures :
• Trauma
• Forceful seating of a post and
core.
• Attempting to seat an improperly
fitting post and core.
• Fractures occurring during endodontic treatment.
• sIf the surrounding tooth structure can be adequately prepared
and still possess sufficient strength, then gold foil, amalgam, or
resin can be used to restore the area.

• When fracture occurs under a full coverage retainers, it is usually
horizontal, at the level of the finish line.
• This necessitates removal of prosthesis, endodontic therapy, a post
and core, and a new prosthesis.
• Certain single restorations can be salvaged if the finish line and a
little coronal tooth structure remain intact after the fracture. A post
and core fabricated can be made to fit both the restoration and the
prepared tooth.

ACRYLIC VENEER WEAR OR LOSS
• Abrasion can result in loss of severe amounts of acrylic on acrylic
veneer crowns and pontics.
Cause
• Functional loading or
abrasive foods and habits.
• Tooth brush abrasion
Repair
• Replacing lost contours with
autopolymerizing resin.
• Composites
- Mechanical retention is required
- More resistant to wear and
-Maintain function and appearance longer than acrylic resin repairs.

PORCELAIN FRACTURE
• Porcelain fractures occur with both metal – ceramic and all –
ceramic crown restorations.
Metal – ceramic porcelain failures :
Frame work design :
• Sharp angles or extremely
rough and irregular areas over
the veneering area serve as
points of stress concentration
that cause crack propagation
and ceramic fracture.

• Perforations in the metal can also cause failure for the same
reason.
Sharp angles
Rough surfaces
Perforations
Stress
concentrations
Crack
propagation
Ceramic
fracture

• With facially veered
restorations, porcelain fracture
results from a framework
design that allows centric
occlusal contact on, or
immediately next to, the metal
ceramic junction.

Occlusion :
• The presence of heavy occlusal forces or habits such as clenching
and bruxism can cause failure.
• Centric or centric occlusal interferences and uncorrected occlusal
sides which create deflective contact of the opposing teeth can
cause fracture of porcelain.
Metal handling procedures :
• Metal contamination due to improper handling during casting,
finishing or application of the porcelain can lead to formation of
bubbles at the metal ceramic junction when porcelain is applied,
creating stress and possibly cracks.
• .
• Excessive oxide formation on the alloy surface can also cause
separation of porcelain from the metal.www.indiandentalacademy.com

Dealing with failures of all ceramic crowns :
• There are no satisfactory methods of repairing fractures of all
ceramic restorations. A new restoration must be fabricated.
• In early failures, in the absence of clinical or laboratory defects,
occlusal forces are likely to be present that exceed the strength of
the restoration.
• In such case, a metal – ceramic restoration should be seriously
considered for the new restoration.
• If many years of good service occurred prior to failure and
optimal esthetics is still required, a new all ceramic restoration
should be considered www.indiandentalacademy.com

ESTHETIC FAILURES
• Ceramic restorations more often fail esthetically than
mechanically or biologically. Poor color match is the frequent
reason for most of the remakes of the restorations.
Causes : For unacceptable color match.
1) Inability to match the patients natural teeth with available
porcelain colors.
2) Inadequate shade selection.
3) Metamerism.
4) Insufficient tooth reduction.
5) Failure to properly apply and fire the porcelain – creating a
restoration that does not match the shade guide itself or the
surrounding teeth. www.indiandentalacademy.com

6. Incorrect form or a framework design that displays metal.
7. Age changes in the natural tooth over the years.
8. Partial veneer restorations can be esthetically unacceptable
because of over extension of the finish line facially. This
displays excessive amount of metal.
9. The marginal fit or cervical form of a prosthesis can promote
plaque accumulation, causing gingival inflammation, which
produces an unnatural soft tissue color or form that is
esthetically unacceptable.

FACING FAILURES
• Recementation of a loose facing is a simple process, but when
fracture has occurred, a facing repair may be indicated if the
prosthesis is otherwise satisfactory.
.

Removal of a prosthesis :
1) Straight chisel and mallet technique :
• The chisel is kept as nearly
parallel as possible to the path
of withdrawal and mallet is
used to tap with sharp blows,
not so intense to cause tooth
fracture or extreme pain.

2) Reverse mallet technique
3) Crown removers :
• These can be placed around retainers or under pontics and
connectors so that occlusally directed forces can be applied

Advantage :
• Effective and highly successful in highly retentive restorations.
• Eliminates any marginal damage that could occur with metal
instrument.
Modification techniques :
1) Typing of ligature wire around contacts.
2) Application of a grappling hook to improve the direction of
unseating forces.
3) Ultrasonic instrumentation

Effect of prolonged ultrasonic instrumentation on the retention
of cemented cast crowns.
Paul S. Olin. JPD 1990 Vol 64(5) p. 563-565.
He studied the effect of ultrasonic instrumentation on the
retention for both zinc phosphate and glass ionomer cemented cast
crowns. A 12 minutes vibrations showed a significant decrease in
retention for both the cements.
He concluded that when it is desirable to try removal and
recementation of a cast restoration instead of refabrication,
vibration used for the specified length of time can be a valuable aid,
used in conjunction with other removal devices.

4) Copper band and stainless steel wire soldering technique
Removing crowns with minimal damage : Nicholas Naffah,
JPD, 2003; 89:522.
A copper band is prepared by adapting it to the crown to be
removed and soldering a 0.9mm metallic SS wire on the
buccal and lingual sides to form a handle.
Several holes are made in the band body and abraded with air
borne particles on the inner surface.
Band is placed on the crown and autopolymerising acrylic
resins is added on the entire crown and allowed to set.
Once set the crown is removed and the copper band is
separated using a disk.
• If the restoration is not removed intact a variety of crown
removal kits are available.www.indiandentalacademy.com

1) Golden west crown remover :
• This uses a sized hole cut in the occlusal of posterior units. A
hollow core tap, threaded both inside and outside is tapped into
the sized opening and against tooth structure. A pin is inserted
into the core of the tap, which engages tooth structure. A small
bolt is threaded into the inside of the tap to engage the pin at
which point a strong and effective unseating force may be
exerted.
• This is much less
traumatic than the
blow imparted by the
crown remover but
care must be taken not
to drive the pin
through foundation or
tooth structure into the
pulp. www.indiandentalacademy.com

2) Sectioning and prying method :
• The safest but most destructive method of removing cemented
units is by cutting a channel through the restoration to prepared
tooth structure on the facial or lingual and occlusal or incisal
aspects and gently expanding the casting with a large spoon
excavator to break the cement joint.
• When this removal technique is
used it is advantageous to use a
round bur for cutting the metal.
The curved cutting leaves of the
round bur remain intact and
sharper for a much longer time
than the angular leaves of a fissure
or an inverted cone bur.
This results in more efficient cutting and a major saving of time.www.indiandentalacademy.com

CONCLUSION
• The first consideration when confronted with any failure or
repair situation is to ascertain the cause or suspected cause.
Sometimes this is easy and obvious. If there is a cause that is
correctable it should be taken care of first. Care should be taken
not to become involved in repairs that should have been
remakes. Repairs are usually second best to the original in one
or more ways.
• Imagination and innovation are key factors in successful
repairs. Most failures are unique and present varying challenges
to the dentist. Great satisfaction can be achieved in meeting a
situation and solving it in an effective and economical manner.www.indiandentalacademy.com

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Clinical failures/ cosmetic dentistry training

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