Clinical failures/ cosmetic dentistry training


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Clinical failures/ cosmetic dentistry training

  1. 1.
  3. 3. CONTENTS • Introduction • Causes of failure • Biologic failures • Mechanical failures • Esthetic failures • Facing failures • Removal of restorations • Conclusion
  4. 4. CAUSES OF FAILURE A. Biologic failures 1) Caries 2) Pulp degeneration 3) Periodontal breakdown 4) Occlusal problems 5) Tooth perforation B. Mechanical failures 1) Loss of retention 2) Connector failure 3) Occlusal wear 4) Tooth fracture 5) Acrylic veneer wear / loss 6) Porcelain fracture C. Esthetic failures D. Facing failures
  5. 5. BIOLOGIC FAILURES Caries : • One of the most common biologic failures. • Early detection possible mainly through comprehensive probing of the margins of the prosthesis and tooth surfaces with a sharp explorer. • Radiographs are helpful to detect caries on proximal surfaces.
  6. 6. Management : Small lesions : • Gold foil – filling material of choice for restoring marginal caries. • Amalgam – best alterative to gold foil filling. • Composite – indicated for restoration of caries in esthetic zone. – Less desirable • Glass ionomer
  7. 7. Proximal lesions : • Removal of prosthesis is required to obtain access to caries. If the lesion is small, the tooth preparation can be extended to eliminate the caries and a new prosthesis can be fabricated. • When the lesion is large, an amalgam restoration is often required. • An extensive lesion may require endodontic treatment when pulp has been encroached. • A grossly destroyed teeth by caries that cannot be restored must be extracted.
  8. 8. Pulp degeneration : Causes : • Extensive preparation • Excess heat generation during preparation • Post-insertion pulpal sensitivity. May manifest as  sensitivity which does not subside with time  Intense pain  Periapical pathology Management : Endodontic intervention
  9. 9. Procedure : Access preparation – a hole is drilled in the prosthesis through which the biomechanical preparation (BMP) is completed. The access cavity is restored with • Gold foil • Amalgam • Cast metal inlay If the retainer come loose during access opening or if the porcelain fractures, then remaking of the prosthesis may be necessary. A post and core restoration should be considered if little sound tooth structure is
  10. 10. Periodontal breakdown : It can be localized around the prosthesis, as a result of inadequate instruction in prosthesis hygiene or a restoration that hinders good oral hygiene. Aspects of the prosthesis that interfere with effective plaque removal include • Poor marginal adaptation • Overcontouring of the axial surfaces of the retainers • Excessively large connectors that restrict cervical embrasure space
  11. 11. • A pontic that contacts too large an area on the edentulous ridge. • A prosthesis with rough surfaces which promote plaque accumulation. Management : • Recontour to eliminate the defects • Remake to correct the
  12. 12. OCCLUSAL PROBLEMS Interfering centric and eccentric occlusal contacts can cause • Excessive tooth mobility • Irreversible pulpal damage Management : • When detected early occlusal adjustment should be done to eliminate these interferences without permanent damage. • Occasionally, a combination of excessive mobility and reduced bone support require extraction of abutment teeth • Irreversible pulpal damage requires endodontic
  13. 13. Tooth perforation : Improperly located pinholes or pins used in conjunction with pin-retained restorations may perforate the tooth laterally. Management : depends on the location of the perforation. • Occlusal to periodontal ligament • Extend the preparation to cover the defect. • Extends into periodontal ligament • Perform periodontal surgery • Smoothening of the projecting pin • Place a restoration into perforated area • Furcation region • Surgically inaccessible • Severe periodontal problems may ultimately lead to extraction of the tooth. • Pulp chamber • Endodontic treatment
  14. 14. MECHANICAL FAILURES Loss of retention : A prosthesis can come loose from an abutment tooth and if this occurrence is not detected early, extensive caries often develops. The loss of retention can be detected by several ways 1. Patients awareness of looseness or sensitivity to temperature or sweets. He may experience bad taste or odor. 2. Periodic clinical examinations that includes attempts to unseat existing prosthesis by lifting the retainers up and down (occlusocervically) while they are held between the fingers and a curved explorer placed under the
  15. 15. Management : • Removal of the prosthesis • Evaluation of the abutment  Caries  restoration  Preparation form  modify the preparation poor • Fabricate new restoration If the span length is excessive or occlusal forces heavy then a removable partial denture may be the only satisfactory solution.
  16. 16. CONNECTOR FAILURE A connector between an abutment retainer and a pontic or between two pontics can occur. • Under occlusal forces • Internal porosity in the cast or soldered connectors When fracture occurs, pontics are placed in a cantilevered relationship with the retainer casting and this can allow excessive forces to be developed on the abutment tooth. Management : • Prosthesis should be removed and remade as soon as possible. • An inlay like dovetailed preparation can be developed in the metal to span the fracture site and a casting can be cemented to stabilize the prosthesis. • Pontics can be removed by cutting through the intact connectors and a temporary removable partial denture can then be inserted to maintain the existing space and satisfy esthetic
  17. 17. OCCLUSAL WEAR An accelerated occlusal wear of a prosthesis can be produced due to • Heavy chewing forces • Clenching or bruxing After several years, a casting perforation may develop, thus allowing leakage and caries to occur, which ultimately lead to prosthesis failure. • If the perforation is detected early, a gold or amalgam restoration can be placed to seal the area and provides additional years of service. • If the metal surrounding the perforation is extremely thin, a new prosthesis should be
  18. 18. TOOTH FRACTURE Causes : Coronal fractures : 1. Excessive tooth preparation – leaving insufficient tooth structure to resist occlusal forces. 2. Presence of interfering centric of eccentric occlusal contacts 3. Heavy occlusal forces. 4. Incorrect unseating of a cemented bridge. 5. Around inlays and partial veneer crowns, as a result of increasing brittleness, of tooth structure with age.
  19. 19. Radicular fractures : • Trauma • Forceful seating of a post and core. • Attempting to seat an improperly fitting post and core. • Fractures occurring during endodontic treatment. • sIf the surrounding tooth structure can be adequately prepared and still possess sufficient strength, then gold foil, amalgam, or resin can be used to restore the area.
  20. 20. • When fracture occurs under a full coverage retainers, it is usually horizontal, at the level of the finish line. • This necessitates removal of prosthesis, endodontic therapy, a post and core, and a new prosthesis. • Certain single restorations can be salvaged if the finish line and a little coronal tooth structure remain intact after the fracture. A post and core fabricated can be made to fit both the restoration and the prepared tooth.
  21. 21. ACRYLIC VENEER WEAR OR LOSS • Abrasion can result in loss of severe amounts of acrylic on acrylic veneer crowns and pontics. Cause • Functional loading or abrasive foods and habits. • Tooth brush abrasion Repair • Replacing lost contours with autopolymerizing resin. • Composites - Mechanical retention is required - More resistant to wear and -Maintain function and appearance longer than acrylic resin repairs.
  22. 22. PORCELAIN FRACTURE • Porcelain fractures occur with both metal – ceramic and all – ceramic crown restorations. Metal – ceramic porcelain failures : Frame work design : • Sharp angles or extremely rough and irregular areas over the veneering area serve as points of stress concentration that cause crack propagation and ceramic fracture.
  23. 23. • Perforations in the metal can also cause failure for the same reason. Sharp angles Rough surfaces Perforations Stress concentrations Crack propagation Ceramic fracture
  24. 24. • With facially veered restorations, porcelain fracture results from a framework design that allows centric occlusal contact on, or immediately next to, the metal ceramic junction.
  25. 25. Occlusion : • The presence of heavy occlusal forces or habits such as clenching and bruxism can cause failure. • Centric or centric occlusal interferences and uncorrected occlusal sides which create deflective contact of the opposing teeth can cause fracture of porcelain. Metal handling procedures : • Metal contamination due to improper handling during casting, finishing or application of the porcelain can lead to formation of bubbles at the metal ceramic junction when porcelain is applied, creating stress and possibly cracks. • . • Excessive oxide formation on the alloy surface can also cause separation of porcelain from the
  26. 26. Dealing with failures of all ceramic crowns : • There are no satisfactory methods of repairing fractures of all ceramic restorations. A new restoration must be fabricated. • In early failures, in the absence of clinical or laboratory defects, occlusal forces are likely to be present that exceed the strength of the restoration. • In such case, a metal – ceramic restoration should be seriously considered for the new restoration. • If many years of good service occurred prior to failure and optimal esthetics is still required, a new all ceramic restoration should be considered
  27. 27. ESTHETIC FAILURES • Ceramic restorations more often fail esthetically than mechanically or biologically. Poor color match is the frequent reason for most of the remakes of the restorations. Causes : For unacceptable color match. 1) Inability to match the patients natural teeth with available porcelain colors. 2) Inadequate shade selection. 3) Metamerism. 4) Insufficient tooth reduction. 5) Failure to properly apply and fire the porcelain – creating a restoration that does not match the shade guide itself or the surrounding teeth.
  28. 28. 6. Incorrect form or a framework design that displays metal. 7. Age changes in the natural tooth over the years. 8. Partial veneer restorations can be esthetically unacceptable because of over extension of the finish line facially. This displays excessive amount of metal. 9. The marginal fit or cervical form of a prosthesis can promote plaque accumulation, causing gingival inflammation, which produces an unnatural soft tissue color or form that is esthetically unacceptable.
  29. 29. FACING FAILURES • Recementation of a loose facing is a simple process, but when fracture has occurred, a facing repair may be indicated if the prosthesis is otherwise satisfactory. .
  30. 30. Removal of a prosthesis : 1) Straight chisel and mallet technique : • The chisel is kept as nearly parallel as possible to the path of withdrawal and mallet is used to tap with sharp blows, not so intense to cause tooth fracture or extreme pain.
  31. 31. 2) Reverse mallet technique 3) Crown removers : • These can be placed around retainers or under pontics and connectors so that occlusally directed forces can be applied
  32. 32. Advantage : • Effective and highly successful in highly retentive restorations. • Eliminates any marginal damage that could occur with metal instrument. Modification techniques : 1) Typing of ligature wire around contacts. 2) Application of a grappling hook to improve the direction of unseating forces. 3) Ultrasonic instrumentation
  33. 33. Effect of prolonged ultrasonic instrumentation on the retention of cemented cast crowns. Paul S. Olin. JPD 1990 Vol 64(5) p. 563-565. He studied the effect of ultrasonic instrumentation on the retention for both zinc phosphate and glass ionomer cemented cast crowns. A 12 minutes vibrations showed a significant decrease in retention for both the cements. He concluded that when it is desirable to try removal and recementation of a cast restoration instead of refabrication, vibration used for the specified length of time can be a valuable aid, used in conjunction with other removal devices.
  34. 34. 4) Copper band and stainless steel wire soldering technique Removing crowns with minimal damage : Nicholas Naffah, JPD, 2003; 89:522. A copper band is prepared by adapting it to the crown to be removed and soldering a 0.9mm metallic SS wire on the buccal and lingual sides to form a handle. Several holes are made in the band body and abraded with air borne particles on the inner surface. Band is placed on the crown and autopolymerising acrylic resins is added on the entire crown and allowed to set. Once set the crown is removed and the copper band is separated using a disk. • If the restoration is not removed intact a variety of crown removal kits are
  35. 35. 1) Golden west crown remover : • This uses a sized hole cut in the occlusal of posterior units. A hollow core tap, threaded both inside and outside is tapped into the sized opening and against tooth structure. A pin is inserted into the core of the tap, which engages tooth structure. A small bolt is threaded into the inside of the tap to engage the pin at which point a strong and effective unseating force may be exerted. • This is much less traumatic than the blow imparted by the crown remover but care must be taken not to drive the pin through foundation or tooth structure into the pulp.
  36. 36. 2) Sectioning and prying method : • The safest but most destructive method of removing cemented units is by cutting a channel through the restoration to prepared tooth structure on the facial or lingual and occlusal or incisal aspects and gently expanding the casting with a large spoon excavator to break the cement joint. • When this removal technique is used it is advantageous to use a round bur for cutting the metal. The curved cutting leaves of the round bur remain intact and sharper for a much longer time than the angular leaves of a fissure or an inverted cone bur. This results in more efficient cutting and a major saving of
  37. 37. CONCLUSION • The first consideration when confronted with any failure or repair situation is to ascertain the cause or suspected cause. Sometimes this is easy and obvious. If there is a cause that is correctable it should be taken care of first. Care should be taken not to become involved in repairs that should have been remakes. Repairs are usually second best to the original in one or more ways. • Imagination and innovation are key factors in successful repairs. Most failures are unique and present varying challenges to the dentist. Great satisfaction can be achieved in meeting a situation and solving it in an effective and economical
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