Under-prescribed: too few abutments – eg. Long span cantilever
Over-prescribed: more abutment than necessary – eg. Upper canines and 1st premolars on both sides to replace four inciosrs
Positive Ledge: Excess of crown material protruding beyond the margin of the preparation. Overhang.
Negative Ledge: Deficiency of crown material that leaves the margin of the preparation exposed bt with no major gaps between the crown and the tooth.
Defect: Gap between the crown and preparation margin
A – spray not direct on the bur B – spray not directed at the tip C – unrestored abutment
Low speed - <6000rpm Medium Speed - 6000 – 1,00,000 rpm High speed - > 1,00,000 rpm
A – Access through retainer B – Rct completed
Inadequate endodontic treatment in premolar accompanying periapical lesion
Poor marginal adaptation Poor oral hygiene
The location of the perforation can be verified by passing a gutta-percha point through the sinus tract and making a radiograph.
Sub-pontic inflammation due to pontic contacting a large area. Improper prosthesis design with a lateral incisor used as a cantilever abutment to replace a central incisor, resulting in intermittent pressure under pontic surface resulting in hyperplastic tissue. Super-floss in use to clean beneath the pontics.
Ideal , optimum and acceptable taper???????
6 degree – angle of convergence – 3 degree on each side with bur
For the restoration to succeed, the length must be great enough to interfere with the arc of the casting pivoting about a point on the margin on the opposite side of the restoration.
The fit of casting can be defined best in terms of the “misfit” measured at various points between the casting surface and the tooth.
Supraeruption of upper first molar. Causing connector failure.
Inadequate occlusal preparation.
In facings, when angle between veneering surface and nonveneered aspect of casting is less than 90°.
(A) Fractured ceramic portion on second molar retainer. (B) Examination reveals metal perforation.
Fracture of ceramic due to placement of metal ceramic junction at the contact of mandibular incisal edge. Ceramic should end at a stress-free rounded butt joint prepared on the metal.
Incorrect acute angle formed between veneering surface and nonveneered aspect of casting, will lead to porcelain fracture. Correct incisolingual angle.
Ultrasonic cleaning to remove cement. Cracks in porcelain following such cleaning.
Resin repair of porcelain fracture – porcelain surface etched with hydrofluoric acid and exposed metal is roughened. Silane coupling agent applied, followed by bonding agent and application of opaque composite paste. Composite resin of appropriate shade contoured and finished.
Facing repair. A thin metal with porcelain superstructure is fabricated indirectly and cemented over the labial metal surface.
Metamerism: pairs of objects that have different spectral curves but appear to match when viewed in a given hue;
Metamerism should not be confused with the terms ﬂair or color constancy, which applies to apparent color change exhibited by a single color when the spectral distribution of the light source is changed or when the angle of illumination or viewing is changed.
Back action crown remover. Spring loaded crown remover.
Failures in Fixed Partial Denture
Dr. Jehan Dordi
2nd Yr. MDS
Failures in Fixed Partial Denture
Methods of Removing a Failed FPD
Review of Literature
Fixed prosthodontic treatment can offer exceptional satisfaction for both patient
It can transform 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.
It is important to analyze failure so that the reasons can be evaluated and
prevention is imparted.
A fixed partial denture (FPD) can fail as a result of:
Poor patient care
Inadequate execution of clinical procedures
Inadequate execution of lab procedures
The causes of FPD failures were summarized as early as in 1920 when Tinker wrote -
“ Chief among the causes for such disappointing results have been:
First : Faulty, and in some cases, no attempt at diagnosis and prognosis.
Second: Failure to remove foci of infection in attention to treatment and care of the
investing tissues and mouth sanitation.
Third: Disregard for tooth form
Fourth: Absence of proper embrasures
Fifth: Inter-proximal spaces
Sixth: Faulty occlusion and articulation
Bennard G. N. Smith
1. Loss of retention
2. Mechanical failure of crowns or bridge components
Failure of solder joints
Occlusal wear and perforation
3. Changes in the abutment tooth
Problems with the pulp
Fracture of the prepared natural crown or root
Movement of the tooth
4. Design failures
5. Inadequate clinical or laboratory technique
Poor shape and color
6. Occlusal problems
John F. Johnston
Malocclusion or premature contact
An oversized or poorly positioned mastication area, with retention of food by pontics or
Torque produced from the seating of the bridge or from occlusion
An excess of pressure on the tissue
Improperly protected gingival and ridge tissue
2. Looseness of FPD
Deformation of the metal casting on the abutment
Technique of cementation
Solubility of cement
Mobility of one or more abutments
Lack of full occlusal coverage
Insufficient retention in the abutment preparation
Poor initial fit of the casting
3. Recurrence of caries
Improper extension of margins
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
4. Recession of supporting structure
Length of the span
Size of the occlusal table
Improper extensions of the cervical margins
Improper 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
7. Loss of veneers
Badly designed metal protection
Deformation of the protecting metal
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
9. Loss of teeth tone or form
Position and size of the joints
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
Failures in FPDs can be simply classified as:
Biologic Mechanical Esthetic Psychogenic
Caries Loss of Retention Immediate Lack of Counselling
Pulpal Degeneration Connecter Failure Delayed
Endodontic Occlusal Wear
Periodontal Tooth Fracture
Tooth Perforation Porcelain Fracture
Caries is the most common cause of biologic
failure. This can be of the following types.
1. Secondary Caries:
This can happen under the margins of the retainers.
Marginal leakage due to poor margins (open
margins) or poor maintenance by patient.
Perceived by the patient as pain or sensitivity to hot, cold and sweet
Visually (if present on labial surface)
By probing (Tactile)
Radiographs (if present interproximally)
If the caries is minor and restricted to the facial surface restore without
removing the prosthesis
Material used for such restoration in order of preference is silver amalgam,
composite resins and glass ionomers, depending on location on anterior or
Extensive lesions may require
Removal of prosthesis and restoration
Extraction followed by fabrication of a new prosthesis
Ensuring adequate marginal adaptation during try-in of restoration
Educating the patient in maintaining oral hygiene
Reviewing the same during recall appointments
2. Caries of Tooth Adjacent to Retainer:
The main cause for this is lack of proximal contact at the time of cementation.
3. Root Caries:
This is a problem associated in the elderly patients with FPDs.
It can occur even in the absence of gingival recession and pockets.
As the elderly patients may also have reduced salivary flow due to medications
and sometimes radiation, the problem is accentuated.
The cause has been identified as Actinomyces viscosus commonly present in the
filiform papillae of the tongue.
Advising meticulous oral hygiene measure along with cleaning of tongue for
such patients may reduce the risk of developing this problem.
Pulpal Degeneration of Abutment
Tooth preparation without sufficient cooling or an improperly directed water
An abutment with an old restoration with secondary caries or unrestored carious
Cements like zinc phosphate, glass ionomers and resin cements can cause
pulpal irritation, especially if the preparation is close to the pulp leading to
Presence of interfering occlusal contacts.
Perceived by patient as pain which could be spontaneous or related to
hot/cold/sweet food or accentuated by lying down/exercising.
Usually based on symptoms as vitality testing is difficult because of the
presence of retainer.
Radiograph may be useful only if periapical lesions are present.
Access is made through the retainer and endodontic treatment is performed.
The access opening can then be restored with a post and/or a core.
If occlusion is the problem, it should be corrected.
The water spray of the high speed handpiece should be cleaned regularly and
checked before tooth preparation.
All carious lesions on abutment teeth should be restored prior to preparation.
Even old restorations may be removed and new restorations made.
Occlusion should be corrected before cementing the prosthesis and the same
should be verified in recall appointments.
Endodontic Failure of Abutment
The endodontic treatment of the abutment was
improper or inadequate.
A root perforation or crack of the tooth during the
old endodontic treatment may manifest much later.
Perceived by patient as pain on biting or swelling.
With the help of symptoms and radiographs.
Extraction must be postponed if possible.
Endodontic retreatment and apicoectomy may be attempted through the retainer
or after removing the prosthesis.
Karlsson (1986) demonstrated that 10% of 641 bridge abutments exhibited
periapical lesions after 10 years, 19.8% of 303 root filled abutments exhibited
non-healed periapical lesions.
This conveys that just the presence of lesions on radiographs may not
necessitate any treatment.
Patient symptoms need to be assessed.
Endodontically treated teeth must be used as abutments only after thorough
If endodontic treatment is found inadequate, retreatment may be performed.
When in doubt, the design of the prosthesis should be altered to exclude the
tooth as abutment.
1. Faulty prosthesis which hinders maintenance of oral
hygiene is due to:
Poor marginal adaptation
Overcontouring of retainer axial surfaces
Pontic contact a large tissue area
Prostheses with rough surfaces
2. Poor maintenance by patient
3. Patient with existing periodontal disease
4. Lack of abutment support due to improper treatment
Severe bone loss loss of abutment teeth and attached prosthesis.
In less severe breakdown periodontal surgery but may produce an
unacceptable relationship between the prosthesis and soft tissue.
If the problem is localized and related to a prosthesis that hinders effective oral
hygiene, prosthesis may be recontoured or remade to correct the defect.
Any existing periodontal disease must be eliminated and tissues should return to
optimal health before commencing fixed prosthodontics treatment.
The prosthesis should be supported adequately by sufficient number of abutments
to function on a long term basis.
Patient should be instructed on proper oral hygiene measures and implementation
must be verified through recall appointments.
Tooth perforation can occur during:
Placement of pinholes/pins
Preparation for post and core
Endodontic treatment is performed when pinholes or pins perforate into pulp
If perforation is located occlusal to alveolar crest, preparation can be extended to
If located below crest and is accessible, perforation can be sealed through
If perforation is inaccessible then the abutment requires extraction.
Excessive pressure by pontic due to improper pontic design and pontic
contacting too large an area
Improper prosthesis design
Poor maintenance by the patient
Perceived by the patient as pain, swelling, bad breath, bad taste, bleeding gums
and poor aesthetics.
If improper design is the problem, the prosthesis should be refabricated with
proper design after allowing the inflammation to subside.
Patient should be educated to maintain the pontic space using aids like
Problems in occlusion is perceived by the patient as discomfort on biting, sore
teeth, loose teeth or bridges, sensitive teeth and tired or sore muscles.
Causes and Treatments:
Interfering centric or eccentric contacts tooth mobility and irreversible pulpal
Tooth mobility is reversible if problem is detected early and adjusted but
correction may cause prostheses failure due to perforation and loss of aesthetics.
Pulpal damage should receive endodontic treatment following occlusal
Mobility due to long term occlusal interferences on normal teeth and due to
traumatic occlusion on teeth weakened by periodontal disease, are treated by
removing FPD and splinting teeth with removable prosthesis.
If mobility is severe, extraction is necessary.
An altered vertical dimension also leads to occlusal problems.
This is the result of poor treatment planning and needs to be identified and
It may also lead to temporomandibular disorders.
Failure to diagnose a pathological change, having a vital bearing on the patient’s
life expectancy is a failure.
For example a patient with a squamous cell carcinoma being treated for missing
teeth with a FPD instead of the more important condition is a failure.
Many times patients come back to the dentist after many years for restorative
treatment. Patient’s current medical condition should be evaluated.
A change in a patient’s medical condition like cerebral hemorrhage alters
patient’s motivation, physical ability to maintain teeth, diet and general
resistance, leading to a deterioration of restorations and abutments.
Maintenance of the prosthesis is very important for the biologic survival of the
Failure may be due to:
Failure of the dentist to prescribe a maintenance program
Failure to implement or prescribe a recall system
Inadequate motivation of patient
Inadequate motivation by dentist
Loss of Retention
For a restoration to accomplish its purpose, it must stay in place on the tooth.
No cements that are compatible with living tooth structure and the biologic
environment of the oral cavity possess adequate adhesive properties to hold a
restoration in place solely through adhesion.
The geometric configuration of the tooth preparation must place the cement in
compression to provide the necessary retention and resistance.
Short clinical crowns
Improper cementation procedure
Poor fit of casting
Excessive span length
Heavy occlusal forces like cantilevers if designed improperly
If not detected early, a loose retainer can lead to extensive caries of the
As a cast metal or ceramic restoration is placed on or in the preparation after the
restoration has been fabricated in its final form the axial walls of the
preparation must taper slightly to permit the restoration to seat.
Theoretically, the more nearly parallel the opposing walls of the preparation are,
the greater should be the retention.
Recommendations for optimal axial wall taper of tooth preparations for cast
restorations ranges from 10 to 12 degrees.
Tooth preparation taper should be kept minimal because of its adverse effect on
retention, but Mock estimates that a minimum taper of 12 degrees is necessary
just to insure the absence of undercuts.
Short clinical crown:
Cements create mechanical interlocks between the inner surface of the
restoration and the axial wall of the preparation.
Greater the surface area of the preparation greater is its retention.
Preparations on large teeth >> retentive >> preparations on small teeth.
A short, over-tapered or short clinical crown would be without retention
many paths of removal.
A shorter wall cannot afford enough resistance. The walls of short preparations
should have as little taper as possible.
Clinical conditions with excessive taper and short clinical crowns should be
treated with :-
1. In case of excessive taper:
Incorporation of proximal grooves
Additional retentive grooves (should be along with the path of insertion)
2. In case of short crowns:
Crown lengthening procedure
Modification of supra-gingival margin sub-gingival margin
Additional retentive grooves and proximal box
Incorporation of pins
Addition of extra abutments
The misfit can occur at different locations :
1. Internal gap
2. Marginal gap
3. Vertical marginal discrepancy
4. Horizontal marginal discrepancy
5. Over-extended margin
6. Under-extended margin
Causes for misfit:
Distortion of the metal substructure
Distortion of the margins (towards the
Improper water/powder ratio
Improper mixing time
Improper burnout temperature
Metal bubbles in occlusal or marginal
Inadequate vacuum during investing
Porcelain flowed inside the retainer
Excessive oxide layer formation in
inner side of the retainer (due to
contaminated metal or repeated
firing of porcelain)
Tight contact points
Thick cement space
Insufficient pressure during
In case of the cemented FPD, it is more difficult to differentiate whether an FPD
is not seating because of a faulty fit, or the alignment of the retainers relative to
each other is incorrect.
The only difference which may sometimes be apparent is that, in the case of
misalignment, the FPD will have some ‘spring’ in it and tend to seat further on
pressure due to the abutment teeth moving slightly, whereas in the case of a
defective fit, the resistance felt will be solid.
Causes for misalignment:
Abutment displacement due to improper temporization
Distortion of wax pattern while sprueing and investing
Distortion of metal frameworks in porcelain firing
Porcelain flow inside the retainers
Misalignment of soldering points
Insufficient pressure in cementation
Thick cement film
Excessive metal or porcelain in tissue surface (ridge lap) of pontic prevents the
proper seating of FPD and open margin (can be detected by observing the
blanching of the tissue or patient may complain of pressure on the pontic
Patient may perceive a loose retainer as sensitivity to
temperature or sweets and bad taste or odour.
A curved explorer is placed under the connector and an
occlusal force is applied.
The retainer is then pressed cervically with a finger.
If retainer is loose, the occlusal force causes fluids to be
drawn under, the casting is reseated with a cervical force,
the fluid is expressed in the form of bubbles as air and
liquid are simultaneously displaced.
Prosthesis must be removed. It can be recemented if the reason was a
cementation problem and it is intact.
If loss of retention is due to preparation design, the teeth should be modified to
improve retention and resistance form and new prosthesis fabricated.
If excessive span length is the problem, a removable partial denture may be the
Inadequate connector width if posterior - occlusocervical, if anterior -
This is usually due to supraeruption of opposing tooth leaving no space for
pontic in height
Internal porosity, incomplete casting or soldering which has weakened the metal
can also cause connector failure.
If the cause is supraeruption offending tooth may be contoured to provide
If severe, intentional endodontics may be required, following which a new
prosthesis is made.
If casting defect was the problem most often a new prosthesis is made.
Insufficient thickness of restoration due to inadequate preparation of occlusal
surface or lack of functional cusp bevel.
Heavy chewing forces/bruxism
Rough porcelain occlusal surfaces cause wear of opposing natural teeth
If wear is due to inadequate preparation a new prosthesis is made after
providing adequate clearance
Any rough porcelain surface should be polished or glazed.
For bruxers, a night guard may be a solution.
When occlusal wear is anticipated it is better to plan metal occlusal surfaces
opposing natural teeth or metallic restorations.
1. Crown fracture:
Excessive tooth preparation leaving insufficient tooth structure to resist occlusal
Endodontically treated abutment with excessive tooth structure loss.
Abutment with large restorations.
Interfering centric/eccentric contacts.
Attempting to forcibly seat an improperly fitting prosthesis.
Unseating a cemented bridge incorrectly.
Small coronal fractures common around inlays and partial veneer crowns. These can
Large fractures around partial veneer crowns require a build-up and full veneer crown.
Fracture around partial veneer crowns with pulp exposure will require endodontic
treatment with/without post and core followed by full veneer crown.
Fracture around full crowns if occurs horizontally at level of finish line, is treated by
endodontics, followed by post and core and a new prosthesis.
If finish line is intact then ‘retrofit technique’ can be attempted to salvage the retainer
In this technique, a post and core is fabricated to fit an existing fractured
abutment tooth with an intact crown or retainer. Hence, it is termed ‘retrofit’.
The procedure for fabricating a retrofit cast post and core is as follows:
A post space is prepared in the abutment tooth.
A resin pattern of the post and core is fabricated to fit the crown.
The pattern is cast and cemented along with the crown.
2. Root Fracture:
Improperly designed or a poorly fitting post
Root fracture occurring during endodontic or post treatment, but manifests later
Reduced neural feedback leading to increased loading in endodontically treated
Extraction followed by a new prosthesis
1. Metal-ceramic fracture
Improper framework design:
Sharp angles or irregular areas over coping surface stress concentrations
Perforations in metal or overly thin metal casting inadequate support for
With facings, occlusal contact on or adjacent to metal-to-ceramic junction
causes porcelain fracture
Any unsupported porcelain can fracture.
Heavy occlusal forces like clenching, bruxism.
Centric or eccentric occlusal interferences.
Metal handling procedures:
Improper handling of alloy during casting, finishing or porcelain application can
cause contamination which leads to ceramic fracture.
Excessive oxide formation in metal can also cause porcelain fracture.
This is caused by improper conditioning of base metal alloys.
During clinical procedures:
Teeth prepared with slight undercut can cause bending of prostheses during
insertion, which initiates crack propagation.
Distorted impressions can also cause prosthesis failure.
When teeth are prepared with feather-edge finish lines or if finish lines are not
recorded properly in impression, the technician may extend the metal beyond
finish line as finish line is vague.
The thin metal may bind against tooth and initiate crack of overlying porcelain.
Cleaning fitting surface of prosthesis using ultrasonic scalers can initiate cracks
in the porcelain.
This typically happens when the prosthesis has been fixed provisionally or when
a dislodged prosthesis is recemented.
Metal and porcelain incompatibility:
This happens rarely. This can be easily prevented if manufacturer’s instructions
are followed when choosing the porcelains for a particular metal.
The best method is to fabricate a new prosthesis.
Repairs can be attempted until a new prosthesis is fabricated.
A. Resin Repair:
Composite resins of appropriate shade are used and repair is made directly in
The exposed ceramic surface is etched with hydrofluoric acid for 30sec.
The exposed metal surface can either be sandblasted or roughened for
A silane coupling agent is applied and allowed to remain on the surface for 1
min. It is not light cured.
A composite bonding agent is applied and light cured for 10sec.
An opaque composite paste is applied on the exposed metal surface to mask the
colour of metal and light cured for 20sec.
Composite resin of appropriate shade is selected and contoured on the surface,
light cured for 20sec, finished and polished.
B. Facing Repair:
This is a repair made with porcelain indirectly in the laboratory.
It is a more definitive repair but requires adequate framework thickness. It
works well with facings.
The fractured porcelain is completely removed from the metal by grinding.
Four to five pinholes are made on the metal surface.
Impression is made and a thin metal with porcelain superstructure is fabricated.
This is cemented over the labial metal surface.
2. All ceramic fracture
Inadequate finish lines like feather edge.
Sharp areas on prepared tooth.
Large portion of proximal preparation form is missing and not restored prior to
Round preparation form without resistance to rotational forces.
If tooth is over-prepared and it is less than two-third or three-fourth of final
restoration in height, this fracture occurs due to poor resistance.
Opposing tooth contact located incisally to prepared tooth.
Inadequate lingual tooth preparation.
Immediate Aesthetic Failure
Aesthetic problems at the time of cementation can be due to:
Poor shade match – reasons for this may be:
Inadequate selection and communication
Insufficient tooth preparation
Failure to properly apply and fire porcelain
Poor tooth contour, gingival contour, pontic ridge contour and embrasure
Poor margin placement
Framework design that displays metal
Unrealistic expectations of patient due to poor communication
DELAYED AESTHETIC FAILURE
These occur over a period of time following cementation due to:
Gingival recession due to:
Excessive trauma during tooth preparation and impression making.
Subpontic tissue shrinkage following extraction – if insufficient time for healing
After periodontal surgery – margins will be exposed due to gingival recession if
insufficient healing time.
Unglazed porcelain can cause unsightly wear of opposing natural teeth.
Poorly glazed porcelain restorations also develop black specks over time.
When all the parameters for a successful FPD have been met with,
rarely a patient may still feel uncomfortable with the restoration.
This has been attributed to the stress and behavioural changes in the
The patient may require counselling to get over this problem.
A failure to recognize this problem during the diagnostic phase itself,
can lead to a failure of the prosthesis.
If a FPD fails; usually it needs to be removed for any
Most often it cannot be removed intact and must be cut off
from the abutment.
It is necessary at least to attempt intact removal.
The following methods can be employed with abundant
caution not to damage the abutment:
1. Using a straight chisel:
By applying a sharp force in an occlusal direction using a
mallet, with a sharp chisel placed under the retainer margin.
The tapping should be done parallel to the path of
withdrawal of prosthesis.
2. Using a crown remover:
These are commercially available and may be of
the following common types:
i. Back action:
Uses a weight to deliver a force directed
backward with the tip placed such that it
transfers the force occlusally.
ii. Spring loaded:
Uses a spring mechanism to deliver a sudden
Uses compressed air to deliver a controlled force to remove crowns and bridges.
They are all manufactured with different tips to engage retainers and pontics.
Other commercial examples include – Richwill, Metalift and Coronaflex, each
with its own unique method of usage.
CORONAFLEX crown remover
Air driven device that connects to standard handpiece hoses via Kavo’s
The crown remover controlled low amplitude impact at its tip.
Kit includes loop to thread under FPD’S connectors that is attached to a holder
and an adhesive clamp to obtain a purchase on single crowns.
It delivers the impact in the long axis of the tooth.
The loop is threaded under the connector.
The tip of the crown remover is placed on the bar and the impact is activated by
releasing the index finger from the air valve.
The adhesive clamp is attached with autopolymerising resin used to remove a
METALIFT crown and bridge removal system
Access to the metal on each abutment is provided by preparing through the
porcelain around bur to create a pilot channel in each abutment
The pilot hole is followed by the special drill.
Cement should be visible through the hole
The metalift instrument is threaded into the holes and the FPD removed.
It can be recemented for further service.
RICHWIL crown and bridge remover
Small cubes of adhesive water pliable resin softened in warm water (55 degrees)
for 1-2 minutes and patient is instructed to occlude on it.
The resin is cooled with water
A sharp opening action will remove the crown. It is useful for
Removing partially uncemented crowns
Retainers which have been sectioned but still resists removal
HIGA bridge remover
Removal of provisional bridges/cementation failures
A cavity is cut into the occlusal surfaces of crowns to expose the tooth.
The pins on the remover are adjusted to align with the cavities
0.5 mm of wire is passed beneath the proximal joints and extends out of the
The wire is attached to the spindle and tightened by turning the screwdriver
Further tightening applies axial load on the tooth via the pins and an occlusal
load on the bridge via the wire, and cement fracture occurs.
3. By cutting retainer:
This is the best method to prevent any damage to the abutment. But it will
destroy the prosthesis.
A thin groove is placed in the middle of the restoration with a high speed airotor
handpiece using diamonds (ceramic) and carbides (metal).
This should cut through the restoration and expose the abutment.
The groove can be placed in the facial aspect but placing it lingually especially
for anteriors, may allow the restoration to be used provisionally after removal.
A facial slot works best for maxillary and mandibular molars because lingual
access is difficult.
Removal is attempted with a crown remover following cutting through one
surface, if not, both facial and lingual surfaces are cut dividing the retainer into
It is now easy to remove with a crown remover or a sharp instrument is used to
wedge the two halves.
Koenig V, Vanheusden A, LeGoff S and Mainjot A conducted a clinical risk
factors related to failures with zirconia-based restorations: an up to 9-year
147 ZBR were evaluated after a mean observation period of 60 months.
Accessorily, zirconia implant abutments (n = 46) were also observed.
The technical and the biological outcomes of the ZBR were evaluated.
Occlusal risk factors were examined: occlusal relationships, parafunctional
habits and the presence of occlusal nightguard.
Journal of Dentistry 41 (2018) 1164 – 1174
The results showed the survival rate of crowns and FPDs was 93.2%, the
success rate was 81.63%.
The chipping rate was 15% and the framework fracture rate was 2.7%.
Most fractographic analyses revealed that veneer fractures originated from
occlusal surface roughness.
Several parameters were shown to signiﬁcantly inﬂuence veneer fracture: the
absence of occlusal nightguard, the presence of a ceramic restoration as an
antagonist, the presence of parafunctional activity and the presence of implants
The results of the study conﬁrm that chipping is the ﬁrst cause of ZBR
E. G. Kontakiotis, C. G. Filippatos, S. Stefopoulos & G. N. Tzanetakis conducted
a prospective study of the incidence of asymptomatic pulp necrosis following
A total of 120 teeth with healthy pulps scheduled to receive ﬁxed crowns.
Teeth divided into two groups:- Intact teeth and Teeth with preoperative caries,
restorations or crowns and into further four groups:- maxillary anterior and
posterior teeth, mandibular anterior and posterior teeth
Experimental and control teeth electric pulp testing on three different
occasions before treatment commencement (stage 0), at the impression making
session (stage 1) and just before the ﬁnal cementation of the crown (stage 2).
International Endodontic Journal 2017
Teeth that were considered to contain necrotic pulps were submitted to root
Upon access, absence of bleeding was considered as a conﬁrmation of pulp
The overall incidence of pulp necrosis was 9%.
Intact teeth had a signiﬁcantly lower incidence of pulp necrosis (5%) compared
with preoperatively structurally compromised teeth (13%).
No signiﬁcant differences were found amongst the four groups with regard to
They concluded that the incidence of asymptomatic pulp necrosis of teeth
following crown preparation is noteworthy.
Al-Sinaidi A and Preethanath R conducted a study on the eﬀect of ﬁxed partial
dentures on periodontal status of abutment teeth.
This study was aimed to assess the periodontal status of Saudi adult females
who had received regular oral prophylaxis following the insertion of ﬁxed
The effects of sub- and supra-gingivally placed crown margins were also
Sample size - 78 females who had ﬁxed partial dentures
From each study participant, two paired eligible sites, one for the abutment and
one for the matched non-abutment teeth, were selected.
The plaque index, gingival index, probing pocket depth, tooth mobility and
locations of the crown margins were assessed and recorded by one calibrated
examiner. The Saudi Journal for Dental Research 2018.
The abutment teeth scored signiﬁcantly higher plaque and gingival indices and
greater probing pocket depth than non-abutment teeth.
In addition, the abutment teeth scored greatest mean values of the clinical
parameters in subjects who were 46 year-old or older and those who had their
functioning ﬁxed partial dentures for more than 5 years.
The teeth with supra-gingivally placed crown margins had signiﬁcantly higher
mean values of plaque index, gingival index and probing pocket depth than
teeth with sub-gingival crown margins.
The results of this study indicated that in subjects with ﬁxed partial dentures,
the abutment teeth are more prone to periodontal inﬂammation than the non-
Additionally, the individual’s age, duration of insertion of ﬁxed partial dentures
and location of the crown margins affect the periodontal health of the
Fixed prosthodontic treatment does not end with the fitting of restorations.
Subsequent maintenance is an integral part of treatment. If this is not adequately
prescribed, failure can occur.
The first consideration when confronted with any failure is to ascertain the
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 the second best to the original in one or more
Most failures are unique and present varying challenges to the dentist. Therefore
treatment plan for each situation must be individualized.
Planning and making crowns and bridges. Smith B, Howe L. 4th edition. Abingdon, Informa
Contemporary fixed prosthodontics. Rosenstiel S, Land M, Fujimoto J. 4th edition. St Louis,
Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of fixed
prosthodontics. Quintessence Publishing Company.
Koenig V, Vanheusden A, LeGoff S and Mainjot A. A clinical risk factors related to
failures with zirconia-based restorations: an up to 9-year retrospective study. Journal of
Dentistry 2018;41:1164 – 1174.
E. G. Kontakiotis, C. G. Filippatos, S. Stefopoulos & G. N. Tzanetakis. A prospective study
of the incidence of asymptomatic pulp necrosis following crown preparation. International
Endodontic Journal 2017.
Seong LG, May LW. Key Indicators of success or survival for clinical performance of fixed
partial denture. Annals of Dentistry University of Malaya. 2019 Dec 3;26:53-8.
Kapoor C, Vaidya S. Evaluation of Complications Associated with Fixed Partial Denture-An
observational study. Journal of Advanced Medical and Dental Sciences Research. 2019 Aug
Al-Sinaidi A and Preethanath R. A study on the eﬀect of ﬁxed partial dentures on periodontal
status of abutment teeth. The Saudi Journal for Dental Research 2018.
Triwatana P, Nagaviroj N, Tulapornchai C. Clinical performance and failures of zirconia-
based fixed partial dentures: a review literature. The journal of advanced prosthodontics.
2012 May 1;4(2):76-83.
Muddugangadhar BC, Amarnath GS, Sonika R, Chheda PS, Garg A. Meta-analysis of failure
and survival rate of implant-supported single crowns, fixed partial denture, and implant
tooth-supported prostheses. Journal of international oral health: JIOH. 2015 Sep;7(9):11.
Swain PK. Failure Rate in Fixed Partial Denture Patients-A Clinical Study. Journal of
Advanced Medical and Dental Sciences Research. 2018 Oct;6(10).
Jain JK, Sethuraman R, Chauhan S, Javiya P, Srivastava S, Patel R, Bhalani B. Retention
failures in cement-and screw-retained fixed restorations on dental implants in partially
edentulous arches: A systematic review with meta-analysis. The Journal of the Indian
Prosthodontic Society. 2018 Jul;18(3):201.
Alraheam IA, Ngoc CN, Wiesen CA, Donovan TE. Five‐year success rate of resin‐bonded
fixed partial dentures: A systematic review. Journal of Esthetic and Restorative Dentistry.