Failure of restorations


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Restorative Dentistry
Fifth Year

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Failure of restorations

  1. 1. 14/06/33 FAILURE OF RESTORATIONS 5 T H YEA R 2 012 Topic outline  Criteria of successful restoration  Factors affect the success and failure of restorations  The success and failure of restoration attribution  Failure of amalgam restoration  Failure of cast restoration  Failure of glass ionomer restoration  Failure of composite restoration  Failure versus repair 1
  2. 2. 14/06/33  The restorative dentistry is provided with a wide range of materials to restore any derangement of lesion in hard tooth substances. These lesion includes caries, erosion, attrition, traumatic fracture, discoloration as well as minor abnormalities in form, size alignment or occlusion of teeth . Criteria of successful restorations Objectives of operative dentistry: 1- stop of the original insult and prevention of its recurrence. 2-restoration of function 3-restoration of esthetics 4-while maintaining the physiological integrity of the teeth in good relationship with the adjacent hard and soft tissues. 2
  3. 3. 14/06/33 Criteria of successful restoration:  Regard to the objectives of the operative dentistry. The successful restoration should fulfill the objective beside to be durable, less costly and easy to do. Success and failure of restorations depend on many factors: 1- the degree of involvement 2-The skill of the operator 3- the properties and the limitations of the existing restorative material and techniques. 3
  4. 4. 14/06/33 The success and failure of the restoration is attributed to:  I- misjudgment in selection of the restorative material: A. this selection should be based on logical and through analysis of all variables including properties of available restoratives, the demands and the limitations of the oral environment and the past experience of the operator. Ex. Both amalgam and gold serve satisfactorily as individual restorations but if used in the same mouth , excessive tarnish, corrosion due to galvanic activities and patient discomfort and pain maybe inevitable.  II-Cavity preparation: More than 60% of failure may be due to improper cavity preparation. The design of the preparation affect the mechanical integrity of both the tooth and the restoration, the biological influences of the restoration on the dentino-pulpal organ and also has an important effect on the esthetic of the restoration. 4
  5. 5. 14/06/33 III-Material manipulation: Incorrect material manipulation is responsible for about40% of failure of the restorations. IV-The nature of the oral environment: 1-Accessibility 2-The patient demands 3-The corrosive potentials 4-The aqueous nature 5-The thermal changes 6-The oral microbes 7-Forces in the mouth Failure of amalgam restorations I- Marginal degradation (ditching ): Def: marginal degradation ,ditching, fracture or crevicing refers to breakage of a thin edge of a restoration creating an irregular V shaped crevice. Causes : 1-Depletion of support at margins 2- Voids entrapment 3- Excess mercury 5
  6. 6. 14/06/33 1-depletion of support at margins: Amalgam is a brittle material with low tensile and shear strength so; it must be supported by tooth structure.  Depletion of support may be due to Lack of support or insufficient bulk of material at margins  Lack of support may be due to: excessive expansion caused by ----under trituration ----excess mercury ----moisture contamination ----age dependant changes in the microstructure as creep. 6
  7. 7. 14/06/33  Creep: Time dependant changes in the form of amalgam under constant loads and temperature.  Insufficient bulk at margins: Strength of amalgam is essentially thickness dependent .why? Insufficient bulk may be due to: ---Beveling preparation ---Over carving ---Leaving thin marginal flashes. 7
  8. 8. 14/06/33  2- Voids: The presence of voids in amalgam decrease the density and strength of the amalgam Voids may be due to: ---corrosion ---to dry mix ---inadequate condensation ----moisture contamination of amalgam  3-Excess mercury: Excess mercury tends to decrease the strength of amalgam. Excess mercury may be due to: ---wrong proportioning of alloy/mercury ratio. ---under trituration . ---inadequate condensation force 8
  9. 9. 14/06/33  Clinical picture: All cavity margins are prone to ditching especially buccal end of proximal marginal ridge appear like irregular V shape crevice: this wall should be prepared in the form of reverse curve to provide CSA 90 How to prevent 1- follow the principle of cavity preparation 2-proper selection of the alloy 3-proper manipulation of the material Treatment: The actual treatment depend on the extent of ditching: Very small finishing of the margin Moderate size repair with cermet or bonded amalgam Gross ditching total replacement of the restoration 9
  10. 10. 14/06/33  II.Isthmus fracture:  Def: Isthmus: it is the narrowest junction between the occlusal and the auxiliary portion of the cavity(buccal, lingual or proximal)  Factors that attributed to isthmus fracture: A .factors increase flexural stresses ---inadequate resistance form ---inadequate retention ---sharp angles or irregular surface  B .factors decrease flexural strength: ---insufficient bulk of amalgam ---excess mercury ---structural discontinuities(corrosion, dry mix, moisture contamination, improper condensation) 10
  11. 11. 14/06/33  Clinical picture: It start as crack line may be propagate and widened with masticatory force Hypersensitivity with eating and drinking Food impaction Recurrent caries Periodontal irritation  Treatment: 1- proper examination to understand the cause of isthmus fracture 2-improve the resistance and the retention form 3-removal of any surface discontinuity. 4-selective grinding of opposing plunger cusp. 5-increase bulk of amalgam at this isthmus area by rounding the axio-pulpal line angle . 6- proper handling and manipulation of the amalgam 11
  12. 12. 14/06/33  III- Tooth fracture: Def: fractured cusp or ridge under functional forces Causes : Amalgam lacks sufficient tensile strength to support remaining tooth substance and much less able to reinforce weak cusps and ridges  Treatment : 1- eliminate all undermined enamel. 2-conserve the integrity of the remaining tooth structure 3-restore the very weakened tooth structural with inlay, onlay, or even full coverage  IV-Recurrent caries: Def: Caries developed in previously restored tooth Causes: 1- incomplete elimination of the lesion 2-improper outline form 3-improper restoration of the anatomy 4-rough surface retention of bacterial plaque 12
  13. 13. 14/06/33  Clinical picture: Carious lesion at the margin of the restoration or extend deeper underneath the restoration.  Treatment : Prevention adequate cavity preparation conservative treatment of non carious pit and fissures by enameloplasty, application of fissure sealant. Management replacement of the restoration repair of the marginal defects with glass ionomer (cermet) or bonded amalgam  V-Excessive discoloration:  Clinical picture: Tarnish loss of surface luster Corrosion rough pitted amalgam surface Amalgam blues dark bluish discoloration Tarnish :surface discoloration of amalgam with loss of its luster Formation of a surface film of discoloring oxides and sulfides  Causes: excess Hg under trituration improper condensation improper finishing moisture contamination 13
  14. 14. 14/06/33 Corrosion :actual disintegration of the bulk of amalgam. Chemical corrosion: due to lack of polishing and food stagnation Electric corrosion: setting of electromotive force between two different electrodes (two dissimilar metallic restoration) likes -old and new similar metallic restoration -polished and unpolished areas of the same restoration. -the same restoration but heterogonous in structure -accumulation of certain types of food on a site of restoration making it different in its electric potential from other sites of amalgam.  Amalgam blues: the amalgam hues appear through the enamel surface due to: thin or undermind enamel. penetration of metallic ions and corrosive products of amalgam through the dentinal tubules.  Treatment: 1- Tarnish requires repolishing 2- Corrosion may require replacement of old restoration 14
  15. 15. 14/06/33  VI-Post restoration hypersensitivity:  Hypersensitivity in a recently amalgam restored tooth may be due to stimulation of freshly exposed dentine by: Galvanic , thermal , chemical or premature contact.  Clinical picture: Pain occur in recent restoration  Treatment : Elimination of the cause Application of desensitizing agent Elimination of premature contact  VII- Gingival and periodontal affections:  Causes : 1- gingival overhangs 2-thick sub gingival margin 3-ragged cavity margins 4-rough margin restoration 5-open contact lead to food impaction 15
  16. 16. 14/06/33  Clinical picture: Gingival and periodontal inflammation with increased tendency to bleeding Discomfort Tooth mobility  Treatment: Defining and removal of the cause  VIII-Dislodgment of the restoration:  Causes: 1- inadequate retention form 2- fracture of the restoration 3-fracture of the tooth 4- recurrent caries Treatment : Evaluation of the retention followed by replacing the restoration 16
  17. 17. 14/06/33 Failure of cast restoration: I-Recurrent caries:  Causes : 1- fitting discrepancies a. distortion of impression, dies, or wax pattern. b. incorrect compensation of casting shrinkage leading to under or over sized restoration c. roughness of the fitting surface d. modification by grinding 2- Improper cementation: a. high solubility b. low strength c. thick consistency d. moisture contamination 17
  18. 18. 14/06/33 3- Under extension of cavity outline: a. not include all defective pits and fissures b. improper placement of the cavity margins in self cleansable area. 4- Stagnation of bacterial plaque: a. due to lack of polish b. presence of marginal overhangs c. poor oral hygiene Treatment : evaluation of the cause followed by remake of the restoration. 18
  19. 19. 14/06/33 II- Dislodgment of restoration: Causes : 1-Inadequate mechanical retention due to over divergence of the cavity walls 2- Recurrent caries 3- Improper cementation 4- Excessive torque by occlusal interference 5- Premature loading of the restoration Treatment: Evaluation of the cause and remake of the restoration if needed. 19
  20. 20. 14/06/33 Failure of glass ionomer restoration: I- Increased opacity: Causes : 1- dehydration and biodegradation by oral fluids 2- inadequate powder /liquids ratio 3- injudicious finishing 4- incorporation of air voids II- Loss or dislodgment of the restoration: Causes : 1- moisture contamination 2-premature setting 20
  21. 21. 14/06/33 Failure of composite restoration: I- post operative hypersensitivity: Dentin hypersensitivity is more frequently to occur with Class II,V composite restoration as a result of: 1- leakage 2- cusp deflection by polymerization shrinkage stresses. Treatment : Replacement or repair of the restoration II- Recurrent caries: Causes : 1-marginal leakage due to polymerization shrinkage 2-rough restoration surface due to low wear resistance of the composite restoration 21
  22. 22. 14/06/33 Clinical picture: If catching discrepancies are identified in a composite restoration, recurrent caries must be expected Treatment : Repair or replacement of the restoration. III- Cyto-toxic pulp reaction: Pulp reaction occur more frequently under composite restoration that may be due to steps of application (acid etching, bonding agent) Or the chemical composition of the composite material itself and its toxic effect on the pulp. Bacterial invasion associated with the leakage is the first cause of pulp inflammation 22
  23. 23. 14/06/33 This is accompanied with the sign and symptoms of reversible or irreversible inflammation These reactions did not occur immediately after placement Treatment : The restoration must be replaced IV- Discoloration: 1- incorrect color determination 2- marginal discoloration 3- surface discoloration 4-bulk discoloration Treatment : It essential depend on the extent of the discoloration and generally ranges between resurfacing, veneering or total replacement. 23
  24. 24. 14/06/33 V- Dislodgment of restorations: Causes : 1- Improper application of the adhesive system 2- Excessive force Treatment : Total replacement of the restoration Proper application of the adhesive system VI-gross fracture: Causes: Composite is a brittle material with low flexure strength Similar to amalgam restoration , fracture may result of unbalance between flexure strength of composite and flexure stresses developed in the restoration Treatment: Repair or total replacement 24
  25. 25. 14/06/33 VII- Biodegradation: Causes : It is gradual break down of the material in the oral environment with biological activity It includes disintegration and dissolution in saliva, as well as other types of chemical/physical degradation such as wear Bio-degradation rate accelerated with acidic media (bad oral hygiene). Treatment :replacement of restoration  Thank you 25