INTRODUCTION : It is important to be aware of obvious and subtle indications of prosthesis failure and to have a working knowledge of the proceduresthat are necessary to remedy the situation. It is natural that dramatic mechanical failures, such as fracture attract attention, but it must be remembered that failures can also be esthetic and biologic in nature. Some failures are the result of poor patient care, while others occur as a result of defective design or inadequate execution of the clinical or laboratory procedures. Other failures like unacceptable colour match with age are normal because changes in the oral environment that are not related to prosthesis necessitate its removal and reconstruction. Also, a restoration may simply wear out. After all, prosthesis cannot routinely be expected to last a lifetime. BIOLOGIC FAILURES : 1) CARIES : Caries is one of the most common biologic failures, it may affect a bridge in several ways, either directly at the margins of the retainer, indirectly by starting elsewhere on the tooth and spreading to the fit surface of the castings or it may follow cementation failure. A study was conducted to evaluate the causes of failure and length of service of fixed restorations. They concluded that caries was the most common cause of failure and resin veneer metal crowns provided the longest services of all crown types observed (13.9 years) and failed most frequently because of worn or lost veneers. (Joanne N.W. et al 1998) Its detection can be very difficult particularly when complete coverage is used. At each appointment, the teeth should be thoroughly dried and visually inspected. Careful use must be made of explorer when assessing early enamel lesions because “heavy-handed” examination may damage the fragile 1 demineralized enamel matrix. Radiographs are also helpful, particularly interproximally. Conventional operative dentistry procedures can generally be used to restore small carious lesions without the need to fabricate a new prosthesis. Marginal caries can be restored by using amalgam, composite resin, or gold foil. Carious lesions in certain locations, such as proximal surfaces, may require removal of the prosthesis to obtain access to the caries. Extensive lesions may encroach on the pulp, making endodontic treatment necessary, or the tooth may be so much destroyed by caries that it cannot be restored and must be extracted. Meticulous oral hygiene must be a routine procedure for patients with a high caries index and particularly for those who have a past history of developing carious lesions around restorations. Other preventive measures should include the use of fluoride containing dentrifices, home mouth rinses containing fluoride and professionally applied topical fluoride. If the caries is secondary to cementation failure, then the bridge must always be removed and the sooner the better. 2) ROOT CARIES : Caries of exposed root surfaces can be a severe problem in the age group commonly seeking fixed prosthodontic care. Root surface caries seems to be initiated by a plaque of different composition containing more anaerobic and gram negative organisms than that causing coronal caries. The presence of Actinomyces viscous is thought to be of special significance. These organisms seen to proliferate among the filiform papillae of the tongue. Tongue brushing twice daily may be an effective means of preventing the root caries. (Massler M 1980) 2 poor implementation of proper hygiene procedures. recemented or rescued by endodontics alone. as a result of inadequate instruction in prosthesis hygiene. in view of the constraints. placing the cavosurface margin subgingivally. Only a most vigorous effort on the part of the dentist and patient will lead to restoration of the problem. In some situations. the disease process may be present in both restored and non restored areas of the mouth but with no relationship to the prosthesis.2 years. The reasons for failure of 142 bridges in 130 patients were assessed. excessively large connectors that restrict the cervical embrasure space. but many bridges failed as a result of factors related to design and structure. (L. and the remainder required a removable prosthesis. yet. or a prosthesis with rough surfaces which promotes plaque accumulation. 3 .V. The main single reasons for failure were secondary caries or apical pathology. Aspects of a prosthesis that interfere with effective plaque removal include poor marginal adaptation. Foster 1990) 3) PERIODONTAL DISEASE : It is unfortunate that periodontal disease often occurs following placement of fixed prosthesis. Eighteen percent of the bridges were repaired. they are a preferred alternative to comprehensive retreatment with elaborate fixed prosthesis. 61% were replaced by a new bridge. The results showed that the mean age of the bridges at failure was 6. or a restoration that hinders good oral hygiene. It also can be localized around the prosthesis. overcontouring of the axial surfaces of the retainers. xerostomia as a consequence of aging or caused by medication or irradiation has been implicated as contributing to the etiology of rampant caries. Often this requires the placement of large cervical amalgam or glass ionomer restorations that wrap around the periphery of previously placed cast restorations. Such restorations are difficult to place.Similarly. a pontic that contacts too large an area on the edentulous ridge. the interferences can be eliminated by occlusal adjustment without permanent damage. A prosthesis that hinders effective plaque removal must be reconstructed or remade to correct such defects. and calculus formation as early signs of periodontal disease. but treatment often involves surgery. remake will be necessary. 4 . The prosthesis may have to be removed and the teeth bilaterally braced with a removable partial denture. 4) OCCLUSAL PROBLEMS : Interfering centric or eccentric occlusal contacts can cause excessive tooth mobility. which may produce an unacceptable relationship between the prosthesis and the soft tissue. The canines. This may be result of faulty design. If mobility of bridge abutments is noticed. furcation involvement. which cannot be reduced or eliminated through adjustment of the interfering areas. in particularly should be inspected because wear here will soon lead to excursive interfering contacts on the posterior teeth. If this is detected early. The patient is examined for signs of occlusal dysfunction at each appointment. traumatic occlusion on teeth previously weakened by periodontal disease or the long term presence of occlusal interferences on teeth with normal bone support can lead to mobility.Periodontal disease can produce extensive bone loss that in time results in the loss of abutment teeth and attached prosthesis. Articulated diagnostic casts should be periodically remade and compared with previous records. it may be due to periodontal overloading. for instance incorporating too few abutment teeth in the prosthesis or due to incorrect occlusion. but if latter. At recall appointments particular attention is given to sulcular hemorrhage. occlusal equilibration should be done. However. Less severe breakdown can be treated without fear of loss of the teeth. so any occlusal changes can be monitored and corrective treatment initiated. If former is the case. An examination of the occlusal surfaces may reveal abnormal wear facts. discoloured root of a non-vital tooth. generalized periodontal therapy may be indicated. over contouring of buccal and lingual surfaces. since occlusal adjustments that are required to allow the mandible to be properly positioned may cause perforation of the prosthesis or make the restoration esthetically unacceptable. and inadequate interproximal embrasures. because of lack of care or because of the design of the bridge makes this difficult. However. If the latter and there are no aesthetic considerations. 6) GINGIVAL RECESSION : This may be local or general. Acrylic is a particularly bad offender in this respect and the gingival irritation it causes may be further aggravated by the deposition of calculus on it. The presence of interfering occlusal contacts can also cause irreversible pulpal damage requiring endodontic treatment. the situation may be acceptable as it stands. Irritation of the mucosa by the pontic may also be due to the wrong choice of material for its fit surface. In some cases local gingivectomy has to be done for satisfactory maintenance of gingiva in region of bridge especially in case of sanitary pontic where gingival proliferation is likely to occur. incorrect occlusal anatomy. the reason should be assessed and if possible eliminated. Neuromuscular discomfort related to improper occlusion can result in prosthesis failure. Other factors may be faulty margins of the retainers. 5) GINGIVAL IRRITATION : The commonest cause of gingival irritation around a prosthesis is plaque retention because of patient’s poor oral hygiene.Occasionally the combination of excessive mobility and reduced bone support require extraction of abutment teeth. If the former. such as the exposed. 5 . Access to pulp requires preparation of a hole in the prosthesis through which the necessary treatment is completed. When little healthy tooth structure remains. intense pain. One advantage of partial coverage restoration is that pulp health can be monitored with an electric pulp tester. If the perforation is located occlusal to the periodontal ligament. an assessment should be made of the quantity and quality of tooth structure remaining for support and retention of the restoration. amalgam. During endodontic treatment. 8) TOOTH PERFORATION : Pinholes or pins used in conjunction with pin-retained restorations can be improperly located and may perforate the tooth laterally. the perforation can be restored with gold foil. The retainer casting may come loose during preparation of the access opening or the porcelain may fracture. or periapical abnormalities that are detected radiographically often indicate the need for endodontic intervention. or a cast metal inlay without compromising the prosthesis. although the vitality of any tooth with a complete crown can still be assessed by thermal means. It is recommended that endodontically treated teeth be reviewed radiographically every few years. Appropriate corrective measures can then be taken. Post insertion pulpal sensitivity on abutment teeth that does not subside with time. This could indicate the loss of vitality of an abutment tooth and should be investigated. necessitating remaking of the prosthesis. it is often possible to extend the tooth preparation to cover the defect. When the perforation extends in to periodontal ligament. the patient may reveal having experienced one or more episodes of pain during the previous months. it may be possible to perform 6 . Frequently. it may be necessary to place a post and core and to fabricate a new restoration.7) PULP AND PERIAPICAL HEALTH : At the recall appointment. Other times a direct pull with hemostat forceps succeeds. Certain locations (such as furcations) may not be surgically accessible and perforation can lead to extraction of the tooth. Removing the prosthesis intact for recementation is often difficult or impossible. it is much more difficult. which must be differentiated from similar symptoms caused by poor oral hygiene or periodontal problems. Sometimes judicious malleting or the use of a crown remover is successful. extensive caries often develops. Periodic clinical examinations should include attempts to unseat existing prostheses by lifting the retainers up and down (occlusocervically) while they are held between the fingers and a curved explorer placed under the connector. and if this occurrence is not detected early. Occasionally these perforations are accessible and can be restored with amalgam. (metal7 . becoming apparent only after insertion of prosthesis. The patient may be aware of looseness or sensitivity to temperature or sweets. to detect a single loose retainers. but more often the tooth is lost. and when the casting is reseated with a cervical force. MECHANICAL FAILURES : 1) LOSS OF RETENTION : A prosthesis can come loose from an abutment tooth. Endodontic treatment is required when pinholes or pins perforate in to pulp chamber. the fluid is expressed. generally producing bubbles as the air and liquid are simultaneously displaced. there may be a recurring bad taste or odour. When more than two abutment teeth are involved in a prosthesis. This loss of retention can be detected in several ways. the occlusal motion causes fluids to be drawn under the casting. Also. If the casting is loose. Lateral perforations may not be detected initially.periodontal surgery and to smoothen off the projecting pin or place a restoration in to the perforated area. and sometimes impossible. Some fixed partial dentures come loose even when maximally retentive preparations have been developed. 8 . 2) CONNECTOR FAILURE : An improperly fabricated connector may fracture under functional loading. The effect of prolonged ultrasonic instrumentation on the retention of cemented cast restoration was examined. For this reason. A loose retainer is usually a sign of inadequate tooth preparation. Depending on the design and location of the FPD. Olin 1990). In this case the tooth requires repreparation and a new prosthesis. an abutment tooth may fracture.ceramic crowns should first be coated with autopolymerizing acrylic resin so they do not chip or crack). When trying to remove a permanently cemented prosthesis. the prosthesis should be removed and remade as soon as possible. and this can allow excessive forces to be developed on abutment tooth. or caries. pontics are placed in a cantilevered relationship with the retainer casting. In some cases if a solder joint fails. Even by the use of prolonged ultrasonic vibration. poor cementation technique. When fracture occurs. the patient may complain of varying degree of pain. Wedges can sometimes be positioned to separate the individual FPD components enough to permit the correct diagnosis. He concluded that the use of vibration is considered an advantageous adjunct to other cast restoration removal devices (Paul S. Unless force is applied in the path of withdrawl. and a removable partial denture may be the only satisfactory solution. crown retention can be decreased. This problem is generally caused by excessive span length or heavy occlusal forces. the dentist must use great caution. Failures of both cast and soldered connectors have been observed and are generally caused by internal porosity that has weakened the metal. 3) OCCLUSAL WEAR : Heavy chewing forces. in mouths where occlusal wear is anticipated. If the perforation is detected early.H. a casting perforation may develop after several years which allow leakage and caries to occur. It is sometimes desirable to repair a broken joint in fixed prostheses or to replace one loose crown in a multiple unit splint by using a parallel pin repair rather than to attempt to remove the prosthesis and risk the possibility of destroying the entire restoration or damaging abutment teeth (T. which ultimately leads to prosthesis failure. gold foil. When the occluding surfaces are restored with metal. Thayer 1971). dramatic wear of enamel of opposing natural teeth or the opposing metallic restoration can occur. However. it is better to place metal over occluding surfaces when natural teeth or metallic restorations are present in the opposing arch. amalgam or resin can be used to restore the area. if the metal surrounding the perforation is extremely thin. or bruxism. Small coronal tooth fractures occurs primarily around inlays and partial coverage crowns as a result of wear and apparent increasing brittleness of tooth structure with age. Miller and K. clenching. 4) TOOTH FRACTURE : Coronal tooth fracture can be minor or considerable loss of tooth structure. This problem is exacerbated by heavy chewing forces.porcelain facings can be detached by boiling in acid and components are cleaned and relocated in the mouth before they are resoldered. a new prosthesis should be fabricated. When occlusal surfaces are covered with porcelain. . Large 9 . a gold or amalgam restoration can be placed that seals the area. So.E. or bruxism can produce accelerated occlusal wear of a prosthesis. If the restoration and tooth structure surrounding defect can be adequately prepared and still possess sufficient strength. c) Attempting to forcibly seat an improperly fitting prosthesis. They can also occur during endodontic treatment. the tooth may require a separate pin-retained restoration to serve as a core and provide support and retention for a new prosthesis.coronal fractures generally requires a full coverage restoration to be made. In such cases. or simply heavy occlusal forces on a properly adjusted restoration. This condition necessitates removal of the prosthesis. Root fractures are most often caused by trauma. Abutment tooth fractures under full coverage retainers usually occur horizontally at the level of the finish line. and expose the fracture site so it can be encompassed by a new prosthesis. forceful seating of a post and core. Several conditions known to promote extensive coronal fractures of abutment teeth are : a) Excessive tooth preparation leaving insufficient tooth structure to resist occlusal forces. so that little or no coronal tooth structure is left. it may be possible to perform periodontal surgery. endodontic therapy. Root fractures are often located well below the alveolar bone crests so that the tooth must be extracted and a new prosthesis fabricated. If the fracture causes a pulp exposure. b) Presence of interfering centric or eccentric occlusal contacts. However. ocasionally the fracture terminates at or just below the alveolar bone. 5) PONTIC FRACTURE : Mechanical failures of pontic may occur because of inadequate strength. a post and core. Similarly the gold framework must always be of 10 . Thus an all-porcelain occlusal pontic should never be used unless the occlusion is favourable. endodontic treatment followed by placement of a post and core is necessary prior to fabrication of a new prosthesis. and a new prosthesis. However. or the attempt to fully seat an improperly fitting post and core. d) Attempting to unseat a cemented bridge incorrectly. remove bone. 7) CEMENTATION FAILURE : It may be either partial or complete. failure can also occur because of a poor cementation technique. failure to observe manufacturer’s mixing instructions. full crowns showed be employed. an inadequate powder / liquid ratio. Even slight flexion will cause cementation failure or the fracture of the porcelain facing. Where full crowns are being employed. 6) FLEXION. The sides of the preparation should be as near parallel to each other as possible. It is also necessary to remember that the longer the span. Most of these disasters may be avoided by providing gold of adequate thickness. and is normally the result of retainers which are inadequate for the bridge in question. They may also result in cementation failures of the retainers or loss of facing. Even slight flexion will cause cementation failure and this can only be prevented by using a hard gold and making certain that it has been correctly heat-treated and is of sufficient thickness. Likewise if the teeth are not dried off carefully before cementation. TEARING OR FRACTURE OF THE GOLD : These may of themselves result in failures of the bridge. using a proper casting technique to ensure freedom from porosity. the bond will be weakened. Another important factor is the rigidity of the casting. the use of old or contaminated stock. This may be due to the wrong choice of material. With fixed-fixed designs if there is any doubt regarding the adequacy of retention and particularly if clinical crowns are short. the stronger and thus the thicker the gold will have to be. venting is usually indicated. and making certain that the occlusion is correct. This latter may result in a weak cement and a casting which is incompletely seated. Besides an inadequate retainer. or the insertion of prosthesis when the cement has started to set. carrying out heat treatment.adequate rigidity. 11 . Failures occurred more frequently in men than in women. Marinello et al 1990). This can be done without removing remaining resin. Results revealed that rebonding often leads to repeated failures where as renewals showed a failure rate similar to the whole of the investigated failures (C. Eighty-five patients with a total of 103 resin bonded bridges placed between 1982 and 1989 were evaluated.Study of 703 resin-bonded fixed partial dentures. The results showed that failures occurred more when endodontically treated abutments were used and overall success rate of cantilever fixed prostheses was 70% over a period of 18 years (Veerle Decock et al 1996).P. The results showed that debonding occurred most frequently in the mandibular arch. 8) ACRYLIC VENEER WEAR OR LOSS : Abrasion can result in loss of severe amounts of acrylic on acrylic veneer crowns and pontics. Evaluation of 137 cantilevered fixed partial dentures made between 1974 and 1990 clinically and radiographically. Repairs may be effected by replacing lost contours with autopolymerising resin. the success rates of two study groups were analysed where rebonding or renewals were necessary. They are more resistant to wear and maintain function and appearance longer than acrylic resin repairs. It may or may not be necessary to add mechanical retention in the form of undercuts or threaded posts. but probably tooth brush abrasion is the most common cause. Abrasion can be caused by functional loading or abrasive foods and habits. and prosthesis with more than two retainers had twice the probability for problems (Paul S. 12 . The composites are now becoming more popular for these repairs. Olin et al 1991). 9) PORCELAIN FRACTURE : A) METAL –CERAMIC PORCELAIN FAILURES : 1) FRAMEWORK DESIGN : Sharp angles or extremely rough and irregular areas over the veneering area serve as points of stress concentration that can cause crack propagation and ceramic fracture. the potential for failure is much greater regardless of the type of casting alloy. 2) OCCLUSION : The presence of heavy occlusal forces or habits such as clenching and bruxism and centric or eccentric occlusal interferences can cause failure. These designs allow occlusal forces to cause localized burnishing of the metal and distortion. This is most frequently caused by improper conditioning of the alloys. An impression that is slightly distorted can also lead to some problem. When the framework thickness is less than 0. Excessive oxide formation on the alloy surface can also cause separation of the porcelain from the metal. or application of porcelain can lead to metal contamination which can create stress and possibly cracks. the metal-ceramic junction or the angle between the veneering and nonveneered aspect is less than 90 degrees. which initiates a crack in the porcelain. finishing. IMPRESSION AND INSERTION : A tooth preparation with a slight undercut can cause binding of the prosthesis as it is seated. Perforations in the metal can also cause failure for the same reason. Teeth prepared with a feather edge finish lines or impressions that do not record all of the finish line can lead to an extension of metal beyond the 13 . which leads to premature porcelain fracture. 4) PREPARATION. Porcelain fracture may also occur if the framework design allows centric occlusal contact on. 3) METAL HANDLING PROCEDURES : Improper handling of the alloy during casting.2mm over large areas of the veneering surface. or immediately next to. The preparation from must be ideal to optimize success. Attempts to achieve complete seating of a ceramic restoration by using a mallet and wooden stick during trial insertion or cementation can also produce porcelain fracture. b) Sharp line angles or incisal edge which acts as area of stress concentration. an alloy and porcelain are found to be truly incompatibly and successful bonding without loss of the veneer or cracking is impossible. 14 . Definite finish lines and impressions that record proper detail are prerequisites to acceptable ceramics. 1) VERTICAL FRACTURE : The reasons for this are : a) If tapered finish line is used (such as chamfer).actual termination of tooth reduction and this thin metal may bind against tooth and initiate a crack in the overlying porcelain. greater leverage is developed because of the distance from the point of force application to the underlying prepared tooth which can cause rotation of prosthesis and leading to expansive forces and vertical fracture. clenching or bruxism. so that the forces attempt to expand the prosthesis and leading to vertical fracture. PORCELAIN JACKET CROWN FAILURES : All ceramic restorations are more likely to fail in the presence of heavy occlusal forces. 5) METAL AND PORCELAIN INCOMPATIBILITY : In rare instances. When occlusal forces are applied to the marginal ridge. c) When a large portion of the proximal preparation form is missing and is not restored prior to the impression procedure. the restoration may contact on a sloping surface. This occlusal relationship can also lead to facial cervical porcelain failures. These repairs appear to have reasonable strength. When opposing tooth contact is located incisally to the prepared tooth. REPAIR OF FRACTURED PORCELAIN VENEER : If the porcelain has fractured on an otherwise satisfactory multi-unit prosthesis. where forces on the porcelain are more shear in nature and not as well resisted. an attempt at repair rather than a remake may be justified. Such repair is considered to have only temporary benefit. to save the patient from additional discomfort. forces applied at the incisal edge attempt to tip the prosthesis facially and cause cervical porcelain fracture. it can sometimes be bonded in place with a porcelain repair system using silane coupling agents or 4-META to promote bonding with acrylic or composite resin. Unfortunately.2) FACIAL CERVICAL FRACTURE : It often assumes a semilunar from and generally occurs with a short tooth preparation. time and expense. 3) LINGUAL FRACTURE : Semilunar lingual fractures are observed when the occlusion is located cervically to the cingulum of the preparation. with the restoration having a fulcrum on the cervically located incisal edge. Other lingual fractures. When the preparation is short. When the fractured porcelain is not missing and there is little or no functional loading on fractured site. are the result of inadequate lingual tooth reduction in which less than 1mm of porcelain is present. not necessarily semilunar in form. 15 . The inciso-cervical length of the preparation should be two-thirds to three-quarters that of the final restoration. Exceptionally heavy occlusal forces can also cause lingual fractures even when adequate porcelain thickness is present. however-the strength of joints diminish with changes in temperature and with prolonged water storage. tipping forces are more frequently developed. Highton et al 1979). The effectiveness of two new porcelain repair systems which use coupling agents were compared. The mean bond strengths were : 24 hours 17. Nowlin et al 1981). Cooley et al 1991). the factures area may be repaired with composite resin retained by means of mechanical undercut and use of silane coupling agent. 4 MPa (± 4. H. The results showed that the repair system using a bonding agent with acrylic resin is significantly stronger than repair system using a specific composite resin (R.The flexural strength of porcelain bonded to composite resin specimens using four organosilane materials were compared.8).M. They concluded than mean strength of repaired samples was only 18% of the original strength which indicates that their use is a temporary clinical procedure (Thomas P. The bond strength of 4-META (etch free primer with C and B metabond) to porcelain was evaluated. The bond strengths of porcelain / composite resin repair samples was evaluated. These bond strengths were comparable with or exceed those of other porcelain repair systems tested (Robert L. The results showed that unhydrated specimens had significantly higher bond strength than the hydrated specimens with all products (J. Gregory et al 1988). They concluded that the mean bond strengths were significantly less after storage in water for 28 days and fractures of all specimens were caused by adhesive failures occurring at the interface (William A. 16 . thermocycled 19. The bond strength of three commercial composite resins advocated for repairing dental porcelain was evaluated.1 MPa (± 7). In either circumstances. Bailey 1989). There are no satisfactory methods for repairing fractures of allceramic restorations. c) Metamerism may contribute to poor colour matching d) Insufficient tooth reduction e) Failure to apply and fire porcelain f) Incorrect form of framework design that displays metal. The porcelain is beveled and etched and treated with silane. a metal – ceramic restoration should be considered. so an unacceptable colour match is caused over the years. Bottaro 1982). Remakes occur more frequently because of poor colour match than for any other reason. and if it is due to excessive occlusal forces which exceed the strength of the restoration.T. Barreto. g) Natural teeth undergo colour changes that do not occur in porcelain. A more permanent repair can sometimes be effected by making a metal ceramic restoration to fit over the fractured original and it is appropriate where pontic has fractured. Then the surface is rebuilt with a microfilled resin and finished by conventional methods (M. 17 . The most commonest difficulty in this is weakening of connectors during preparation with associated risk of subsequent fracture of the prosthesis. Mechanical retention on the coping must be created.A technique for repairing fractured porcelain fused-to metal restoration has been presented. a new restoration must be fabricated. It may be due to : a) Inability to match the patients natural teeth with available porcelain colours. ESTHETIC FAILURES : Ceramic restorations more often fail esthetically than mechanically or biologically. B. The metal is masked with a mix of unfilled resin and the corresponding shade of porcelain opaque powder.F. b) Inadequate shade selection. 2) USE OF A STRAIGHT CHIESEL : This is generally used as a means of applying force to a retainer on which one cannot use a crown remover. FACING FAILURES : Recementation of a loose facing is indicated if the prosthesis is otherwise satisfactory. Initially after placement of the hook at the cervical margin. a few light blows are given to provide a surface on to which the hook can engage. REMOVAL OF THE PROSTHESIS : It can be done by four different methods. which produces unnatural soft tissue colour or form that is esthetically unacceptable. Another repair process is to rebuild the desired form with a resin. It is essential that forces be applied in the correct direction. i) Visibility of metallic colour of partial coverage casting if thin incisors are prepared. if the fracture of the abutment teeth is to be avoided. A new facing can be ground to fit the prosthesis which is done on a trial and error basis and often does not yield ideal fit. Pins can be cemented or threaded into the casting if necessary to facilitate retention of resin. thus applying a sudden blow to the retainer and simultaneously second retainer should be held firmly in place by a assistant. Sometimes. 1) CROWN REMOVER : It is the best method because it is relatively easy to see that the force is being exerted in correct direction. j) Marginal fit or cervical form of a prosthesis can promote plaque accumulation. Initially. the chisel is placed either 18 .h) Partial veneer crowns can be esthetically unacceptable because of overextension of the finish line facially. causing gingival inflammation. it may also be used below the pontic. Then jerks are given on the end of handle. Should all the above methods fail. 3) USE OF A BRASS LIGATURE WIRE : A 4 feet length of wire is threaded between the pontic and retainer sothat a loop is created. CONCLUSION: The first consideration when confronted with any failure or repair situation is to ascertain the cause or suspected cause. Then it is positioned paralled to the line of withdrawl of retainer and sudden fairly hard blow. It will then be possible to apply an instrument which will spread the crown slightly and break the cement seal. 19 . its base will then press on the tooth tissue. of which the patient should have warning. a small hole may be drilled in this and then tapped. Great satisfaction can be achieved in meeting a situation and solving it in an effective and economical manner. it should be taken care of first. one end of it held firmly. Repairs are usually the second best to the original in one or more ways. Care should be taken not to become involved in repairs that should have been remakes. If there is a cause that is correctable. at an angle of 450 and tapped sufficiently to create a facet. A metal bar is put through this loop. is then applied. A threaded bolt is now inserted into the hole until it reaches the bottom. and a sudden blow applied to the other end. Imagination and innovation are key factors in successful repairs. the retainer must be weakened. will elevate the casting from the tooth. Great care must be taken so that the wire does not cut the patient lips. and with a little good fortune. If the bolt continues to be turned. in the case of full crown by cutting up its side and in case of three-quarter crown by cutting across the occlusal surface. 4) USE OF A SCREW THREAD : When the retainer has a gold occlusal surface.mesially or distally. 292-294. 11) R. 147. 563-5. “Intra oral repair of fixed partial dentures.H. “Evaluation of 4-META porcelain repair system”. G. 2nd edition. Br Dent J 1990. S. 199-201. 44. Agar. Johnsion. 174-7. Thayer. J Esthet dent. 46(5). D.A. 11-13. FOSTER: “Failed conventional bridge work from general dental practice : clinical aspects and treatment needs of 142 cases”. Evans. Thayer 4) Fixed bridge prostheses. Matyas. JPD 1990. Keith E. 168. 61.H. Length of service and reasons for replacement”. Merling. 4th edition. 416-21. JPD 1989. 5) Walton J. Miller. Tseng. Keith E. Rosenstiel 3rd edition 2) Modern practice in fixed prosthdontics. “Effectivness of porcelain repair systems”. 516-518. JPD 1979.V. Roberts. 64. J. 20 . James. JPD 1981. 56(4).N. Barry K. Caputo. John R. Cooley. 3 (1).M. 13) Thomas P. “Evaluation of the bonding of three porcelain repair systems”. A. Stephen F. 25(4). Nasser Barghi. 6) Massler M : Geratric dentistry : “Root caries in the elderly”. 12) Robert L. “A survey of crown and fixed partial denture failures”. F Michael Gardner. 382-388. 7) L. JPD 1980. 3) Fixed prosthodontics. 8) Paul . Highton. JPD 1971. Olin : “Effect of prolonged ultrasonic instrumentation on the retention of cemented cast crowns”.BIBLIOGRAPHY : 1) Contemporary fixed prosthodontics. Bailey. JPD 1986. Nowlin. 10) J. 42 (3). 9) Thaxter H. Engene Y. “ Porcelain-to-composite bond strengths using four organosilane materials”. 21 . “A practical approach to porcelain repair”. A. JPD 1990. QI 1991. “18 year longitudinal study of cantilevered fixed restorations”.E. M Powers. Gregory. John. Olin. Hill. 22. Repell.14) William A. 13. Donahue. “Success rate experience after rebonding and renewal of resin – bonded fixed partial dentures”. “ Clinical evaluation of resin bonded bridges: a retrospective study”. JPD 1982. 873-877. Hagen. Kerschlaum. 349-51.T. P. 9. Katrien De Mayer. De Boever. Jan . 15) M. Bottaro. oper detn 1988.F. P. A. 18) Paul S. 331-340. 17) Veerle Decock. 16) C. “Composite resin repair of porcelain using different bonding materials”. Marinello. Elaine M.D. Th. B. IJP 1996. 63. 48(3). 114-118.P. James L.8-11. Charles. Barreto. Pfeifer. tearing or fractures of the gold g) Cementation failure h) Acrylic veneer wear or loss i) Porcelain fracture .Metal-ceramic porcelain failures .Porcelain jacket crown failures 4) ESTHETIC FAILURES 5) REMOVAL OF THE PROSTHESIS 6) CONCLUSION 7) BIBLIOGRAPHY 22 .1) INTRODUCTION 2) BIOLOGIC FAILURES a) Caries b) Root caries c) Periodontal disease d) Occlusal problems e) Gingival irritation f) Gingival recession g) Pulp and periapical health h) Tooth perforation 3) MECHANICAL FAILURES a) Loss of retention b) Connector failure c) Occlusal wear d) Tooth fracture e) Pontic fracture f) Flexion. DEPARTMENT OF PROSTHODONTICS INCLUDING CROWN AND BRIDGE COLLEGE OF DENTAL SCIENCES DAVANGERE SEMINAR ON COMPLAINTS AND FAILURES OF FIXED PARTIAL DENTURES Presented By DR. NITIN GAUTAM (2001-2002) 23 . 24 .