TROUBLESHOOTING IN FIXED PARTIAL DENTURE.pptx

TROUBLESHOOTING IN
FIXED PARTIAL
DENTURE
1

CONTENTS
• Introduction
• Objectives of fixed prosthodontic treatment
• Classification of Failures
• Biological Failures
• Mechanical Failures
• Porcelain Fractures
• Esthetic failures
• Maintenance failures
• Repair of fractured porcelain units
• Summary & Conclusion
• References 2

INTRODUCTION
Fixed prosthodontic treatment transforms an
unhealthy, unattractive dentition with poor function
into a comfortable, healthy occlusion capable of
giving years of further service while greatly enhancing
esthetics.
To achieve such success, however, requires
meticulous attention to every detail from initial
patient interview, through the active treatment
phase, to a planned schedule of follow-up care.
Failure to achieve the desired specifications of design
for function and esthetics would result in failure of
the prosthesis. 3

OBJECTIVES OF FIXED PROSTHODONTIC
TREATMENT
Preservation and improvement of related hard- and
soft-tissue structures
Preservation or improvement of oral function
Improvement or restoration of esthetics
Ensuring restoration retention, resistance and stability
Providing restoration with mechanical or structural
integrity
Preserving or improving patient comfort
Designing restorations for maximum longevity.
4
Manappallil JJ. Classification system for conventional crown and fixed partial
denture failures. J Prosthet Dent 2008;99:293-298

The causes of FPD failures were summarized as early as in
1920 by Tinker as:
1. Faulty, and in some cases, no attempt at diagnosis and
prognosis.
2. Failure to remove foci of infection in attention to treatment
and care of the investing tissues and mouth sanitation.
3. Disregard for tooth form
4. Absence of proper embrasures
5. Inter-proximal spaces
6. Faulty occlusion and articulation
6
Tinker ET. Fixed bridge-work. J Natl Dent Assoc 1920;7:579-95

ROBERT’S CLASSIFICATION-
1970
 Cementation failure
 Mechanical breakdown
 Flexion, tearing, or fracture of the gold
 Solder joint failure
 Pontic fracture
 Bonded porcelain failure
 Gingival irritation or recession
 Periodontal breakdown
 Caries
 Necrosis of the pulp.
7
Roberts DH. The failure of retainers in bridge prostheses. An
analysis of 2,000 retainers. Br Dent J 1970;128:117-24.

BENNARD G. N. SMITH-
1985
1. Loss of retention
2. Mechanical failure of crowns or bridge components
a. Porcelain fracture
b. Failure of solder joints
c. Distortion
d. Occlusal wear and perforation
e. Lost facings
3. Changes in the abutment tooth
a. Periodontal disease
b. Problems with the pulp
8
Smith B, Howe L. Planning and Making Crowns and Bridges. 4th ed.:CRC
Press; 2013.

a. Caries
b. Fracture of the prepared natural crown or root
c. Movement of the tooth
4. Design failures
a. Under-prescribed FPDs
b. Over-prescribed FPDs
5. Inadequate clinical or laboratory technique
a. Positive ledge
b. Negative ledge
c. Defect
d. Poor shape and color
6. Occlusal problems
9
Smith B, Howe L. Planning and Making Crowns and Bridges. 4th ed.:CRC
Press; 2013.

10
JOHN F. JOHNSTON-
1986
Dykema RW, Goodacre CJ, Phillips RW. Johnston’s Modern Practice in Fixed
Prosthodontics. 4th ed. Philadelphia, London: W B Saunders Co.; 1986.

11
CAUSES FOR FAILURE
1. Discomfort
 Malocclusion or premature contact
 An oversized or poorly positioned mastication area, with retention of
food by pontics or retainers.
 Torque produced from the seating of the bridge or from occlusion
 An excess of pressure on the tissue
 Plus or minus contact area
 Over protected or under protected gingival and ridge tissue.
 Thermal shock

12
2. Looseness of FPD
 Deformation of the metal casting on the abutment
 Torque
 Technique of cementation
 Solubility of cement
 Caries
 Mobility of one or more abutments
 Lack of full occlusal coverage
 Insufficient retention in the abutment preparation
 Poor initial fit of the casting.

13
3. Recurrence of caries
 Over extension of margins
 Short castings
 Open margins
 Wear
 A retainer becoming loose
 Pontic form that fills the embrasure
 Poor oral hygiene
 Use of wrong type of retainer, which will promote caries susceptibility
 Permanent displacement of the gingiva due to temporary protection

14
4. Recession of supporting structure
 Length of the span
 Size of the occlusal table
 Embrasure form
 Few extensions of the cervical margins
 Impression technique can also stimulate recession of the gingiva.
5. Degeneration of Pulp
6. Fractures of bridge components
 A faulty solder joint
 Incorrect casting technique
 Overwork of the metal due to length of the span or parts that are too
small.

15
7. Loss of veneers
 Little retention
 Badly designed metal protection
 Deformation of the protecting metal
 Malocclusion
 Improper fusing or technique
8. Loss of function
 They don’t function in occlusion
 They have no contact with opposing teeth
 They have permanent contact
 Over carved or under carved occlusal surface may impair efficiency
 Loss of opposing or approximating teeth

16
9. Loss of teeth tone or form
 Pontic design
 Position and size of the joints
 Embrasure form
 Over contouring or under contouring of retainers
 Oral hygiene practiced by the patient
10. Failure to seat
 The abutment preparations may not be near parallel
 Soldering assembly may have been incorrect, or relationship of the
retainers may have been altered during soldering.

17
LOMBARDI CLASSIFICATION OF
ESTHETIC ERRORS
Lombardi RE. A method for the classification of errors in dental
esthetics. J Prosthet Dent 1974;32:501-13.

18
Lombardi RE. A method for the classification of errors in dental
esthetics. J Prosthet Dent 1974;32:501-13.

19
BARRETO CLASSIFICATION
– 1984
Barreto MT. Failures in ceramometal fixed restorations. J Prosthet
Dent 1984;51:186-9.

20
THAYER CLASSIFICATION –
1984
Thayer KE. Textbook of Fixed Prosthodontics. 2nd ed. Chicago, Year Book
Medical Publishers, Inc. 1984

21
SELBY CLASSIFICATION –
1984
Selby A. Fixed prosthodontic failure. A review and discussion of
important aspects. Aust Dent J 1994;39:150-6.

22
1.General pathosis
2. Periodontal problems
3. Caries
4. Pulpal changes
5. Erosion
6. Cracked teeth
7. Subpontic inflammation
8. Temporomandibular joint disorders
9. Occlusal problems.
WISE CLASSIFICATION –
1999
Wise MD. Failure in the restored dentition; management and
Treatment. Quintessence: London. 1995;397-412.

HOW TO HANDLE FAILURES -
MANAPPALLIL
Class I Cause Of Failure Is Correctable Without Replacing
Restoration
• High spots
• First time dislodgement
• Small perforations
• Small facing repairs
denture failures. J Prosthet Dent 2008;99:293-298.

Class II Cause Of Failure Is Correctable Without Replacing
Restoration; However, Supporting Tooth Structure Or
Foundation Requires Repair Or Reconstruction
• Marginal caries
• Minor periodontal treatment
• Need for endodontic treatment

Class III: Failure Requiring Restoration Replacement Only.
Supporting Tooth Structure And/Or Foundation Acceptable
• Esthetically poor
• Fractured, perforated
• Improper fit
• Poor margins and contacts

Class IV: Failure Requiring Restoration Replacement In Addition To
Repair Or Reconstruction Of Supporting Tooth Structure And/Or
Foundation.
• Faulty restoration
• Repeated dislodgement
• Large caries lesion
• Need for endodontic treatment
• Need for periodontal treatment

27
Class V : Severe Failure With Loss Of Supporting Tooth Or Inability To
Reconstruct Using Original Tooth Support. Fixed Prosthodontic Replacement
Remains Possible Through Use Of Other Or Additional Support For Redesigned
Restoration
• Repeated dislodgement
• Loss of supporting tooth

Class VI: Severe Failure With Loss Of Supporting Tooth Or Inability
To Reconstruct Using Original Tooth Support. Conventional Fixed
Prosthodontic Replacement Is Not Possible.
• Loss of critical abutment tooth/teeth making it long span, distal
extension

PHILIPS AND DYKEMA
A) Biological Failures
Diagnosis and treatment planning.
Abutment selection.
Caries.
Pulpal degeneration.
Periodontal breakdown.
Occlusal problems.
Changes in vertical dimension.
Tooth perforation.
Subpontic inflammation.
Temporomandibular disorders.
29
Dykema RW, Goodacre CJ, Phillips RW, Johnston JF. Johnston's
modern practice in fixed prosthodontics. Saunders; 1986.

B) Mechanical Failures
Loss of retention
Connector failure
Occlusal failure
Tooth fracture
Root fracture
C) Porcelain Fractures
Metal ceramic porcelain failures
Occlusion
Metal handling procedures
Metal with porcelain incompatibility
30

Preparation, impression and insertion.
Porcelain jacket crown failures
Vertical fracture.
Facial cervical fracture.
Lingual fracture.
D) Esthetics
E) Maintenance Failure
31

32
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.

33
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.

34
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, a restoration is often required.
The abutment preparation is extended to cover the filling, and a new
restoration is fabricated.
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.

35
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 through the prosthesis

36
The access cavity is restored with
Gold foil
Amalgam
Cast metal inlay
 If the retainer becomes 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.

37
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
Over contouring of the axial surfaces of the retainers
Excessively large connectors that restrict cervical embrasure space

38
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 defects

39
OCCLUSAL PROBLEMS
Interfering centric and eccentric occlusal contacts can cause
• Excessive tooth mobility
• Irreversible pulpal damage

40
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.

41
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

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Furcation region
•Surgically inaccessible
•Severe periodontal problems may ultimately lead to extraction
of the tooth.

43
MECHANICAL FAILURES
Loss of retention :
A prosthesis can become 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 (occluso cervically) while they
are held between the fingers and a curved explorer placed under the
connector.

44
If a casting is loose, the occlusal motion causes fluids to be drawn under the
casting and when it is reseated with a cervical force the fluid is expressed,
producing bubbles as the air and liquid are simultaneously displaced.

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

46
CONNECTOR FAILURE
A connector failure between an abutment retainer and a pontic or between
two pontics can occur.
• Under occlusal forces
• Internal porosity is 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.

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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

48
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.

49
• 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 fabricated
• When porcelain occlusal surfaces opposes a natural tooth, dramatic wear of
enamel may occur with eventual perforation into the dentin.
This problem is exacerbated by heavy chewing forces, clenching or
bruxing and often requires the restoration of the abraded teeth.

• Same problem occurs when porcelain opposes metallic
restorations. So, in mouths in which occlusal wear is
anticipated, it is better to place metal over occluding
surfaces when natural teeth or metallic restorations are
present in the opposing arch.
50

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TOOTH FRACTURE
Causes :
Coronal fractures :
1) Excessive tooth preparation – leaving insufficient tooth structure to resist
occlusal forces.
2) Use of restorative material which was not retained in sound dentin with
pins.
3) Presence of interfering centric of eccentric occlusal contacts
4) Heavy occlusal forces on a properly adjusted restoration.
5) Attempting to forcefully seat on improperly fitting prosthesis.
6) Incorrect unseating of a cemented bridge.
7) Around inlays and partial veneer crowns, as a result of increasing
brittleness, of tooth structure with age.

52
Radicular fractures :
• Trauma
• Forceful seating of a post and core.
• Attempting to seat an improperly fitting post and core.
• Fractures occurring during endodontic treatment.
If 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.

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• If there is question regarding the integrity of the remaining tooth structure or
restoration, a new prosthesis should be fabricated so that it encompasses the
fractured 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.

54
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 resin.
• Composites
- More resistant to wear
-Maintain function and appearance longer
than acrylic resin repairs.

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PORCELAIN FRACTURE
Porcelain fractures occur with both metal-ceramic and all-ceramic 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.

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

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• An overly thin metal casting does not adequately support porcelain, so that
flexure and porcelain fracture may result
0.2 mm over large areas of the veneering surface, the potential for failure is
greater.
• Also, when the angle between the veneering surface and the non-veneered
aspect of the casting is less than 90 degrees, it allows occlusal forces to
cause localized burnishing of the metal and distortion, which leads to
premature porcelain 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.

58
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.
• Separation of the porcelain from the metal has been observed in cases of
severe contamination.
• Excessive oxide formation on the alloy surface can also cause separation of
porcelain from the metal.

59
Preparation, impression and Insertion :
• A tooth preparation with a slight undercut can cause binding of the prosthesis as
it is seated, which initiates a crack in the porcelain.
An impression that is slightly distorted can also lead to the same problem.
• Teeth prepared with feather edge finish lines or impressions that donot record
all of the finish line can lead to an extension of metal beyond the actual
termination of tooth reduction, because the technician cannot determine from
the die or impression where to terminate the wax pattern.
o The thin metal may bind against the tooth and initiate a crack in the
overlying porcelain.
• Definite finish lines and impressions record detail are prerequisites to
acceptable ceramics.

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Metal and Porcelain Incompatibility :
• In rare instances, an alloy and porcelain are found to be truly incompatible,
and successful bonding without loss of the veneer or cracking is impossible.
However, failure resulting from improper handling of the material is often
attributed to porcelain, metal incompatibility.
Repair of Fractured Metal – Ceramic Restorations :
• The best method of repairing a fractured metal ceramic fixed partial denture
is the fabrication of a new prosthesis.
• some of the procedures available for repair can at least serve as the interim
until a new prosthesis is fabricated.
Material for repair :
1) Composite resins :
• Adequately good color matches can routinely be achieved.

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• Lack of longevity is the main drawback because true chemical bonding does
not occur between the current resins and either metal or porcelain
• Pinholes or groves must be made for mechanical interlocking.
2) A more permanent repair is possible when adequate metal
framework thickness is available.
• This techniques works best with facially veneered restorations and involves the
following steps.
Procedure :
1) Removal of the remaining porcelain on the fractured to expose the underlying
metal.
2) Drilling of several pinholes (4 or 5) into the framework to a depth of at least 2
mm.
3) Making of an impression.

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4) Creation of a pin – retained metal casing 0.2 to 0.3 mm thick out of a metal
– ceramic alloy to fit over the exposed metal framework.
5) Fusion of porcelain to the pin – retained.
6) Cementation of the casting in position.
• With full porcelain coverage prosthesis failures, the fractured area can be
prepared with an incisal or occlusal path of insertion, and a staple like
casting can be fabricated and veneered.
• The preparation should include grooves and pinholes, or both, in the
underlying framework to provide retention and stability. A metal ceramic
restoration is then fabricated and cemented in position.

64
Porcelain jacket crown failures :
• Fractures are more frequently observed when these restorations are placed on
posterior teeth and on canines because of the occlusal forces on these teeth.
• All ceramic restorations are more likely to fail in the presence of heavy
occlusal forces, clenching, or bruxism.
Vertical fracture :
• The marginal area of jacket crowns is often more closely adapted to the
prepared tooth than are other areas of restoration.
• If a tapered finish line (such as a chamfer) is used, the restoration may
contact the tooth on a sloping surface, so that forces are produced that
attempt to expand the restoration and that are not well resisted by porcelain.
A vertical fracture may occur.

65
• Vertical fractures have been observed when a large portion of the proximal
preparation form is missing and is not restored prior to the impression
procedure.
• When occlusal forces to the marginal ridge in which the missing tooth form is
located, greater leverage is developed because of the distance from the point of
force application to the underlying prepared tooth.
• Sharp areas on the preparation such
as the line angles or the incisal edge,
produce areas of high stress in the
restoration – causing fracture.

66
The occlusal forces attempt to rotate the restoration, causing expansive forces.
• A round preparation form that does not provide adequate resistance to rotational
forces can also cause vertical fracture.
Facial cervical fracture :
• Fracture of the facial cervical porcelain, which often assumes a semilunar form,
generally occurs, with a short preparation.
• The incisocervical length of the preparation should be two – thirds to three
quarters that of the final restoration.
• When the preparation is short, forces
applied at the incisal edge attempt to tip
the restoration facially and cause
cervical porcelain fracture.

67
Lingual fracture :
• Semilunar lingual fractures are observed when the occlusion is located
cervically to the cingulum of the preparation, where forces on the porcelain
are more shear in nature and not well resisted.
• Other lingual fractures, not necessarily semilunar in form are the result of
inadequate lingual tooth reduction in which less than 1 mm of porcelain is
present.
• Exceptionally heavy occlusal forces also can cause lingual fractures even
when adequate porcelain thickness is present.

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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

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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.

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6. Incorrect form or a framework design that displays metal.
7. Age changes in the natural tooth over the years.
8. When thin incisors are prepared, the metallic color of the partial
coverage casting may be visible through the remaining tooth
structure (grayness).

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FACING FAILURES
• a facing repair may be indicated if the prosthesis is otherwise satisfactory.
• It can be rebuild the desired form with a resin.
• Pins can be cemented or threaded into the casting if additional retention is
required.
• Another technique is to prepare the remaining metal casting so that a new pin –
retained casting can be fabricated and cemented in place.

74
Removal of a prosthesis :
• Many well retained restorations cannot be removed intact and to prevent
abutment tooth damage, must be cut off the prepared tooth and thereby
destroyed.
• Attempts should be made for intact removal of restorations without damaging
the abutments.
• The forces applied for removal should be sharp and in an occlusal direction.
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.

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

76
Richwil technique :
• If the restoration cannot be removed with a crown remover the addition of
the use of an Amurol sugarless fruit drop or a Richwil crown remover can be
used.
• It is based on the principles of adhesion and depends on equal and opposing
force being applied to opposing teeth.
Liebenberg WH. Methods for removing crowns and bridges: Preserving
the restoration. Quintessence international. 1995 Jan 1;26(1).

77
• The material [Amurol sugarfree fruit drop) is tempered in water at 1450 F
for 1-2 min. Then the material is placed on the opposite to the restoration
being removed.
• The patient should close into the material compressing it to 2/3rd its original
height, holding steady for about 10 seconds.
• The patient should then open the mouth with a quick movement. This
exerts a constant negative load on the restoration in a completely vertical
direction instead of the torquing action from the crown remover.

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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

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1) Golden west crown remover :
• This uses a sized hole cut in the occlusal surface 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.

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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.

 purpose of this article was to identify the incidence of
complications and the most common complications
associated with single crowns, fixed partial dentures,
all-ceramic crowns, resin-bonded prostheses and
posts and cores.
 Conventional fixed partial dentures had the greatest
complications (27%), resin bonded prostheses (26%),
single crowns (11%) posts and cores (10%), all-
ceramic crowns had the lowest incidence (8%) of
complications. 82
Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JY. Clinical complications in
fixed prosthodontics. The Journal of prosthetic dentistry. 2003 Jul 1;90(1):31-41.

The most common complications associated with
conventional fixed partial dentures were caries in
18% of abutments
With resin bonded prostheses, the most common
complications were debonding (21% of prostheses.
The most common complications associated with
conventional single crowns were need for endodontic
treatment (3%), porcelain fracture (3%).
The most common post and core complications were
post loosening (5%)
With all-ceramic crowns, the most common
complications were crown fracture (7%) 83
Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JY. Clinical complications in
fixed prosthodontics. The Journal of prosthetic dentistry. 2003 Jul 1;90(1):31-41.

84
Compared the flexural strengths of porcelain bonded to composite resin
specimens using four organosilane materials.
1. 3M porcelain repair kit (Scotch bond) (Dental products division / 3M)
2. Fusion repair material (George Taub products, Jersey city NJ)
3. Ultrafine (Sybron / Kerr) porcelain repair bonding system.
4. Den Mat ultrabond restorative kit product.
CONCLUSION: There was no significant difference in the bond strength of
these materials. It is noted that the organosilane coupling agent did not bond
to a metal surface as it did with the porcelain. Therefore it is advisable to
create mechanical retention by using a coarse diamond when a repair
involves a large surface of metal
Bailey JH. Porcelain-to-composite bond strengths using four organosilane
materials. The Journal of prosthetic dentistry. 1989 Feb 1;61(2):174-7.

• To evaluate 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.
• CONCLUSION: 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.
85
Olin PS. Effect of prolonged ultrasonic instrumentation on the retention of
cemented cast crowns. The Journal of prosthetic dentistry. 1990 Nov
1;64(5):563-5.

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.
86
Naffah N, Chidiac JJ. Removing crowns with minimal damage. The Journal
of prosthetic dentistry. 2003;5(89):522-3.

87
Naffah N, Chidiac JJ. Removing crowns with minimal damage. The Journal
of prosthetic dentistry. 2003;5(89):522-3.

88
CONCLUSION
• The first consideration when confronted with any failure or repair situation
is to ascertain the cause.
• 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.
• 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.

References
• Tylman. Theory and practice of fixed prosthodonitcs
• Rosensteil. Contemporary fixed prosthodontics
• Shillinberg. Fundamentals of fixed prosthodontics
• Dykema R.W., Goodacre C.J. and Phillips R.W. “Johnston’s
Modern Practice in Fixed Prosthodontics”. Fourth Edn,
W.B. Saunders Co. Philadelphia, London.
• Thayer. Fixed Prosthodontics. Second edition 89

 Removing crowns with minimal damage, JPD 2003; 89:522-27
 Effect of prolonged ultrasonic instrumentation on the retention of
cemented cast crowns. JPD 1990; 64; 563-65
 A survey of crown and fixed partial denture failure. JPD. 1986; 56:
415-21
 Longevity of fixed partial dentures J Prosthet Dent 1997; 78: 127
 A rationale for comparison of plaque retaining properties of crown
systems. JPD 1989; 62: 264-67
 The role of coronal contour in gingival health. J Prosthet Dent 1977;
37: 280
 Clinical evaluation of fixed bridges ten years after insertion. Journal
oral rehabilitation 1986; 13: 423
90

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