Review articles

By Dr. Hari Haran Ramakrishnan
Corresponding Author

Submitting Author Dr. Hari Haran Ramakrishnan
Other Authors Dr. Hari Haran Ramakrishnan
Ragas dental college and hospital,Department of prosthodontics and implantology, - India 600058


Types of failures, symptoms of failures, incidence of failures.

Haran Ramakrishnan H. Understanding Problems and Failures in TSFDP. WebmedCentral DENTISTRY 2015;6(7):WMC004931

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Submitted on: 06 Jul 2015 03:27:02 PM GMT
Published on: 08 Jul 2015 10:46:30 AM GMT

Cover Letter

The Editor in chief

Sub: Submission of Manuscript for publication

Dear Sir,

I intend to publish an article entitled “ Understanding Problems and Failures in Teeth supported fixed dental prosthesis ’’ in your journal as an review article. I am the contributor and will act and guarantor and will correspond with the journal from this point onward.

Thanking you,
Yours’ sincerely,
Dr. Hariharan. Ramakrishnan


Fixed  prosthodontic  treatment in the  form of  teeth supported fixed  dental prosthesis  (TSFDP) is  hugely a popular treatment in many countries.  The treatment  usually helps in restoration of missing natural tooth or teeth  by way of  crown preparation of potential  existing natural teeth called abutments  which shall be covered by retainers and the pontic shall replace the  missing dentition.  Numerous biological,mechanical, technical,  and esthetic factors  should always be considered before concluding on the  treatment plan. Proper treatment planning shall consist of  selection of abutment teeth, their periodontal status, number of abutments,  angulation, relative parallelism, mode of preparation of abutments,  selection of pontic, design, nature of residual ridge, choice of  restorative material,  shade selection, choice of luting agent. Unless  due attention is given to the factors mentioned above , the  failure in a fixed prosthesis is always a possibility. This article describes the  various failure modes of FDP ( fixed dental prosthesis) in an orderly manner  and possible reasons for the same.


Important  signs and symptoms which  points out  development of problems or failures in a fixed dental prosthesis which had been given recently to the patient or which had been given  several months or years had been pointed out below

Looseness of the FDP
Rocking on chewing & during function
Continued Ingress of food and saliva
Caries under the FDP
Increased Gingival inflammation under the pontic/retainer
Progressive Gingival recession
Periapical inflammation of abutment
Food impaction
Tooth mobility
Fracture or loss of facing
Perforation of metal frame
Pain on percussion or Sensitivity of abutment
Outright fracture of FDP
Supra eruption/mesial drifting of adjacent teeth  

Charles etal1 Described the Incidence of Failures  in His Article
Single Crown Complications Duration-1 to 23 years. (studies) Incidence of complications 11%
FDP complications Duration-1 to 20 years. (studies) Incidence of complications 27 %
All Ceramic Complications Duration-1 month to 14 years. (studies) Incidence of complications 8 %
Resin Bonded prosthesis Complications Duration-1 month to 15 years. (studies)
Incidence of complications 26 %
CLASSIFICATION  - Bennard G. N. Smith
Loss of retention
Mechanical failure of crowns or bridge components
Porcelain fracture
Failure of solder joints
Occlusal wear and perforation
Lost facings
Changes in the abutment tooth
Periodontal disease
Problems with the pulp
Fracture of the prepared natural crown or root
Movement of the tooth
Design failures
Under-prescribed FPDs
Over-prescribed FPDs

Inadequate clinical or laboratory technique
a. Positive ledge
b. Negative ledge
c. Defect
d. Poor shape and color

Occlusal problems
Oginni2  described the failures of FPD fabricated in a Nigerian dental school. John J Manapallil3 described  a classification system for conventional crown and fixed partial dentures failures. He described  it  based  on the   increasing severity  from class 1 to class 6. Grading of failures based on severity

Class I    - Cause of failure is correctable without replacing restoration
Class II   - Cause of failure is correctable without replacing restoration; however, supporting tooth structure or foundation requires repair or reconstruction
Class III  - Failure requiring restoration replacement only. Supporting tooth structure and/or foundation acceptable.
Class IV   - Failure requiring restoration replacement in addition to repair or reconstruction of supporting tooth structure and/or foundation
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.
Class VI  - Severe failure with loss of supporting tooth or inability to reconstruct using original tooth support. Conventional fixed prosthodontic replacement is not  ossible.

Selby4  reviewed the important aspects of fixed prosthodontic failure.
For ease of understanding  problems and failures of FDP , in this article the following description had been given.

Cementation failure
Mechanical failure
Gingival and periodontal breakdown
Pulp degeneration
Biomechanical failure
Esthetic failure

CEMENTATION FAILURE  Can be broadly divided into:
Cement failure
Retention failure
Occlusal problems
Distortion of FDP 

Cement failure
Causes of cement failure

Cement selection
Old cement
Prolonged mixing time
Thin mix
Cement setting prior to seating
Inadequate isolation
Incomplete removal of temporary cement
Thick cement space
Inclusion of cotton fibers
Insufficient  finger pressure causing incomplete seatings

Complications due to incomplete seating

Creation of premature contacts
Alteration of contact areas with adjacent teeth
Reduction in crown retention by 19-32%
Discrepancies in the marginal fit of the crown
Cement wash out at the margins ill fitting margins- expose large amounts of cements to oral fluids- increasing rate of deposition of plaque.

Methods to improve marginal fit:

Internal relief  (clinically acceptable – 20- 40µm)
Selection of luting agent
The primary function of the luting agent is to provide a seal preventing marginal leakage and pulp irritation. The luting agent should not be used to provide significant retentive and resistive forces.
An ideal luting agent should have the following properties:

Adequate working time
Adhere well to both tooth structure  and metal surface
Provides a good seal
Non toxic to the pulp
Have adequate strength properties
Be compressible into thin layers
Have low viscosity and solubility
Exhibit good working time  and setting properties

B.     Retention failure
For a restoration to accomplish its purpose, it must stay in place on the tooth. The geometric configuration of the tooth preparation must place the cement in compression to provide the necessary retention and resistance.

Causes for Retention Failure

Excessive taper
Short clinical crowns
Excessive taper:
The axial walls of the preparation must  taper slightly to permit the restoration to  get seated . Recommendations for optimal axial wall taper of tooth preparations for cast restorations ranged from 10 to 12 degrees.

Short clinical crown :
Cement creates a weak bond largely by mechanical interlocks between the inner surface of the restoration and the axial wall of the preparation. Therefore, the greater the surface area of the preparation the greater is its retention.

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 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
Additional pins
2. In case of short crowns:

Crown lengthening procedure
Modification of supra-gingival margin  to sub-gingival margin
Additional retentive grooves  and proximal box
Incorporation of pins
Addition of extra abutments

The measurement of misfit at different locations and geometrically related to each other and defined as :

Internal gap
Marginal gap
Vertical marginal discrepancy
Horizontal marginal discrepancy
Over-extended margin
Under-extended margin

A. Causes for misfit

Defective casting
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 with abutment teeth
Incorrect manipulation of luting agents
Insufficient pressure during cementation procedure

B. Misalignment

It is more difficult to differentiate whether a FDP 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 FDP will have some ‘spring’action 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.
Casting defects
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 FDP and open margin (can be detected by observing the blanching of the tissue or patient may complain of pressure on the pontic region).

C.  Occlusal problems
Following the placement of a dental restoration, a patient might report discomfort ranging from a feeling of ‘lameness’ to ‘severe and constant pain’. Sensitivity, in most cases, is due to pulp irritation from traumatic contact or greater leverages. When the occlusion has been adjusted, each type of discomfort may be relieved almost instantly and should disappear shortly

Causes in occlusal problems
Immediate problems
Occlusal interference
Marginal ridges at different levels
Supra eruption of the opposing tooth
Parafunctional habits

2 . Delayed problems

Wearing of occlusal surface
Loss of occlusal contacts
Perforation of occlusal surface due to Porcelain Vs  resin  or Porcelain Vs gold
Food lodgement due to plunger cusp
Fracture of facing due to defective occlusal contact
Periodontal or gingival breakdown due to improper  occlusal contacts
Tenderness due to food lodgement

D. Distortion of FDP

The completed restoration should go into place without binding of its internal aspect against the occlusal surface or the axial walls of the tooth preparation. In other words, the best adaptation should be at the margins. If the indirect procedure is handled properly, there should be no noticeable difference between the fit of a restoration on the die and that in the mouth.

Causes of distortion
Casting defects-
Distorted margin,
Rough castings,
Bending of the FPD due to improper care  taken during wax pattern making,
Investing and casting procedures.
Bending of long span FPDs due to Thin crown, Soft metal, Heat treatment not being done, Porosity in the metal
Distortion of the metal substructure during the porcelain firing.


1.      Retainer failure
2.      Pontic failure
3.      Connector failure

Marginal discrepancy
Facing failure
           Wen Kou etal5 conducted a study to examine the fracture mechanism and process of  ceramic fixed partial denture (FPD) framework under simulated mechanical loading using a recently developed  numerical modeling code, the R-T2D code, and also to evaluate the suitability of R-T2D code as a tool for this purpose. Based on the findings in the study, the R-T2D code seems suitable for use as a complement to other tests and clinical observations in studying stress distribution, fracture mechanism and fracture processes in ceramic FPD frameworks.

A. Perforation


Insufficient occlusal reduction
Insufficient occlusal material
High points in opposing dentition (plunger cusp)
Premature contacts
Contaminated metal
Porosity in metal work (subsurface, back pressure, suck back)
Due to improper melting temperature
Improper pattern position
Improper sprue (too thin)
Improper location
Parafunctional habits                                                                                                                                                                      
Burak etal6 conducted a study  to evaluate the clinical performance of crowns and fixed partial dentures (FPDs) made with the Empress 2 system over a 2-year period.  U.S. Public Health Service criteria showed 100% Alpha scores concerning recurrent  caries for both crowns and FPDs. No crown fractures were observed during the 2-year followup, however, 10 (50%) catastrophic failures of FPDs occurred. Five (25%) failures occurred within the 1-year clinical period and the others (25%) within the second year.

B. Marginal discrepancy

Selection of  finish margin
Improper preparation and failure to establish the margin properly
Failure to do gingival retraction prevents definite margin location and subsequently in impression
Selection of the impression material
                        i. Shrinkage in material (condensation silicone)
                        ii. Distortion of material (alginate)

Improper impression procedures
Voids in the impression
Variation in pressure application in wash technique
Delayed pouring of die material
 Distortion of wax patterns at margins

I)       Selection of tray – correct size
Under extended – insufficient coverage
Over extended – distortion
II)    Moisture control – successful impression making
III) Adequate tissue retraction
IV) Do not remove the impression before it sets
V)    Voids, incomplete details are the usual errors made with hasty handling of the impression material
VI) An acceptable impression must include sufficient unprepared tooth immediately adjacent to the margins for the dentist and lab technician to identify the contour of the tooth and all the prepared tooth surfaces
VII)    Particular attention to the lingual contour of the anteriors as they  influence the anterior guidance
VIII) Impression defects- visible flaws
IX)       Finish line not visible
Gingival inflammation and bleeding
Subgingival finish line
Localized Gingival overgrowth
Retraction cord displaced
X)          Air bubbles in critical places
XI)       Voids and drags
XII)    Unset impression material – latex contamination
XIII)  Impression defects- Invisible flaws,  restoration fit on the die , but not on the mouth
XIV) Tray and impression recoil  Detachment of impression from the tray
XV)    Permanent deformatiom
K)  Insufficient flow of metal
L)  Shrinkage of metal
M)  Nodules in margins and inner side of coping
            i. Due to inadequate vacuum during investing
            ii. Improper brushing technique
            iii. No surfactant

N)  Excessive sand blasting
O)  Distortion due to degassing procedure
P)  Open margins due to porcelain shrinkage (opaque porcelain)
Q)  Thick mixing of luting agent
R)  Cement setting prior to seating
S)  Insufficient pressure application during cementation

C . Facing failure
     Types of veneer failures

a) Fracture
            Panida etal7  conducted a study to  test the hypothesis that fracture toughness of the veneers in clinically failed zirconia-based fixed partial dentures (FPDs) is not significantly different from that of the in vitro group and to determine the potential reasons for their  failures. The  study showed that Fractal analysis is shown to be an alternative analytic tool for clinically failed ceramic restorations, especially for those with fracture origins chipped off during mastication and hence could not be analyzed using other techniques, such as fractography.

b) Wearing of facing (resin veneers)
c) Discoloration

Pontic is  the articial tooth which replaces the natural missing tooth or teeth

Factors  affecting selection and failure of pontics
1) Pontic space
2) Residual ridge contour
3) Biological consideration
            a. Ridge relation
            b. Dental plaque
            c. Gingival surface of pontic
                        (Contact with mucosa)
                        i. Mucosal contact
                        ii. Non mucosal contact
4)  Pontic ridge relationship
5)  Pontic material
6)  Biocompatibility
7)  Occlusal forces
8)  Metal substructure support

What factors should be considered when choosing a pontic?
Tissue contact
Post insertion hygiene
Pontic design
Ridge lap pontic
Modified ridge lap pontic
Sanitary pontics


The connector is that part of the FPD or splint that joins the individual components (retainers and pontics) together.

Causes for connector failure

Improper selection of connector
Thin metal at the connector
Incorrect selection of solder
Solder gap – narrow or wide
Insufficient metal around
Defective occlusal contacts over thin connectors

Garry etal 8  conducted a  study to assess the effect of core to dentine thickness ratio on the bi-axial flexure strength and fracture mode and failure origin  using bilayered ceramic specimens as an in vitro assessment for all-ceramic crowns and the connector area of fixed partial dentures(FPDs). The fracture mode and failure origin in bilayered ceramics tested to represent the failure mode of all-ceramic crowns and FPDs was dependent upon the core to dentine thickness ratio employed. However, the conventional wisdom regarding bilayered ceramic specimens with core thicknesses greater than 1mm are not followed when the core thickness was reduced to 1mm since the fracture resistance was not dependent on the core to dentine thickness ratio.



Margins are one of the most important and weakest links in the success of FPD restorations. One of the prime goals of restorative therapy is to establish a physiologic periodontal health.
A successful prosthesis depends on a healthy periodontal environment and periodontal health depends on the continued integrity of the prosthodontic restoration.
The margin is one of the components of the cast restoration most susceptible to failure, both biologically and mechanically. Most of the investigative proof shows that supragingival margins are kinder to the gingiva than are subgingival margins. However, practicality dictates that  supragingival margins are not always usable
Failure to  reproduce the margin of the preparation in the impression leads to failure in the marginal integrity of the restoration.
Using of gingival retraction technique in case of sub gingival preparation is mandatory.
However, all displacement techniques have the potential to damage gingiva, attachment apparatus and bone, especially if anatomic forms are weak or if disease is present.
In healthy patients, properly used cord displacement or copper band methods have proved to be atraumatic.

Overcontoured restoration - plaque accumulation and gingival inflammation
Buccally and lingually crown should follow the outline of the tooth
Interproximally - slightly concave to permit optimal plaque control without compromising aesthetics

Must allow access for plaque control
Axial reduction must allow for thickness of restorative material and oral hygiene
May have to compromise in anterior region due to black triangles leading to poor aesthetics

Contact points are required to prevent food packing.
Position varies depending which tooth contact is made; 

upper central incisors - incisal third
upper central and lateral incisors - middle third
upper laterals and canines - gingival third

When the margin of the restoration intrudes into the biologic width, the inflammation and osteoclastic activity are stimulated Bone resorption will continue until the alveolar crest is at least 2mm from the restoration margin.

Iatrogenic (dentists’ role)

Failure to identify caries in abutments
Incomplete removal of caries in abutments
Marginal discrepancy with subsequent plaque accumulation and microleakage
Subgingival marginal placement in inaccessible areas or regions
Burning of root dentin or cementum in electro surgical technique (leads to damage or rough surface and causes plaque retention)
Over contouring of the cervical thirds of crowns or bridges prevents the physiologic tooth cleaning by tongue or muscles
Thick cement space in margins leads to cement dissolution.
Narrow embrasures (inaccessibility to maintain hygiene)
Wide connector

Patient role

Systemic factors
Due to radiation therapy
Drug induced
Endocrine disorders
Epilepsy (difficult to maintain the oral hygiene)
Rheumatoid arthritis
Local factors
Improper brushing and flossing
Dietary habits
Failure to understand importance of oral hygiene.


Pulp  reactions to various procedures should always be considered

Each step in full crown preparation is hazardous, to the pulp. In general, heat desiccation or chemical injury or over preparation with less than 1mm of reaming dentin.

The result may be pulpitis or even necrosis.

Preservation of tooth structure
Devan – “preservation of what remains is most important than the restoration what is lost” Use of partial coverage rather than the complete coverage Preparation of teeth with minimum convergence angle (taper) between the axial  walls of Preparation. Anatomic reduction of the occlusal surface, so reduction follows the anatomic planes to give uniform thickness in the restoration .


Failure in selection of right abutment
Lack of retention and resistance form
Incorrect design of FPD
Wrong material selection
Such failures can be avoided in the following ways
Retention and Resistance Form given in  abutment helps in

Degree of Taper - parallelism
Minimise shear forces - grooves, boxes
Large surface area of cement
Preparation length and width
Path of insertion

Structural Durability achieved by
Adequate Anatomic Occlusal Reduction
Functional Cusp Bevel  - Given  on the functional cusps
Lingual  inclines of the maxillary lingual cusp
Buccal inclines of the mandibular buccal cusp


Failure to identify patient expectations regarding esthetics
Improper shade selection
Excessive metal thickness at incisal and cervical regions
Thick opaque layer application
Surface blistering (chalky appearance)
Over glazing or too smooth a surface
Metal exposure in connector, cervical and incisal regions (anteriors) 

Kugel etal9 also described  restoration of edentuluous anterior maxilla using alumina and zirconia based cad cam restorations.

Failure to produce incisal and proximal translucency
Improper contouring
Failure to harmonize contra lateral tooth morphology
Dark space in cervical third due to improper pontic selection
Discoloration of facing

Esthetical  Considerations in Tooth Preparation

Facially inclined tooth  – overcutting of the mesiofacioocclusal corner – display of metal
Lingually inclined tooth – facial surface intersects lingual-shorter preparation, may encroach on pulp 
Under preparation results in poor aesthetics or an over built crown (dotted line) with periodontal and occlusal consequences.
Conversely over preparation can be compensated by making a thicker and perhaps very aesthetic crown, but the strength and pulpal vitality of the underlying tooth may be compromised.
In reality, preparations should be planned according to each individual case and in each case the  existing situation will be different.

Goodacre etal10 conducted a MEDLINE search, 50-year literature review of survival and   failure modalities of FPD. Fixed partial dentures failures: caries (18% of abutments and 8% of      prostheses), endodontic treatment(11% of abutments and 8% of prostheses), loss of retention    (7% of prostheses), esthetics ( 6% of prostheses),periodontaldisease (4% of prostheses), tooth     fracture (3% of prostheses), and prosthesis/porcelain fracture (2% of prostheses). Lindquist etal11  also conducted a study on success and failure retes of FPD after 20 years in service.


It is imperative to understand that  a successful fixed prosthodontic practice requires Knowledge of sound biological and mechanical principles involved in abutment selection and subsequent preparation techniques. Growth of desirable and acceptable manipulative skills to implement the treatment plan identified for the particular patient. Development of a critical eye and judgment for assessing details of the treatment and subsequent prognosis.


1. Charles J Goodacre, Guillermo Bernal, Kitichai Rungcharassaeng, Joseph Y.K Kan: Clinical complications in fixed prosthodontics , J Prosthet Dent 2003:90 (1); 31-41
2. Oginni AO: Failures related to crowns and fixed partial dentures fabricated in a Nigerian dental school. J Contemp Dent Pract; 2005 Nov 15;6(4):136-43.
3. John Joy Manappallil, MDS : Classification system for conventional crown and fixed partial  denture failures .  J Prosthet Dent 2008;99:293-298.
4. Selby A. :  Fixed prosthodontic failure. A review and discussion of important aspects. Aust Dent J, 1994;39:150-6.
5. Wen Kou , Shaoquan Kou , Hongyuan Liu , Goran Sjogren :  Numerical modeling     of  the fracture process in a three-unit all-ceramic fixed partial denture materials 23(20071042–1049 .
6. Burak Taskonak, Atilla Sertgoz :  Two-year clinical evaluation of lithia-disilicate  based all-ceramic crowns and fixed partial Dentures .  dental materials  2006;22: 1008–1013 .
7. Panida Bulpakdi  , Burak Taskonak , Jiahau Yan , John J. Mecholsky Jr. : Failure  analysis of clinically failed all-ceramic fixed Partial dentures using fractal geometry .dental materials 25(2009)634–640.
8. Garry J.P. Fleming, Michelle Dickens, Laura J. Thomas, Jonathan J. Harris :  in vitro failure of all ceramic crowns and the connector area of fixed partial dentures using bilayered ceramic specimens : The  influence of core to dentin  thickness ratio  . Dental  Materials  2 2 ( 2 0 0 6 ) 771–777
9. Kugel A, Perry RD, Aboushala A  :  Restoring anterior maxillary dentition using  zirconia-basedCAD-CAM restorations.  Compend Contin Educ Dent 2003;24:569-72.
10. Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JY. : Clinical complications in fixed Prosthodontics . J Prosthet Dent 2003;90:31-41.
11. Lindquist E, Karlsson S: Success rate and failures for fixed partial dentures after 20 years of service: Part I. Int J Prosthodont; 1998 Mar-Apr;11(2):133-8.

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