Failure Of Restorations PDF

.DR. FATEMA ALDABBAR MASTER DEGREE OF OPREATIVE DENTISTRY FAILURE OF RESTORATIONS FAILURE OF RESTORATIONS Failure of restorations is a major problem in dental ,practice.especially in treatment of adults Decisions to replace restorations if reasons are associated with recurrent caries, overhang...

.DR. FATEMA ALDABBAR MASTER DEGREE OF OPREATIVE DENTISTRY FAILURE OF RESTORATIONS FAILURE OF RESTORATIONS Failure of restorations is a major problem in dental ,practice.especially in treatment of adults Decisions to replace restorations if reasons are associated with recurrent caries, overhangs, open contacts, fractures or inappropriate contours. Restorations with doubtful integrity were not.debated The most difficult decisions were related to the.tooth/restoration interface Criteria of successful :restorations The restoration replicates the missing part of.1 the tooth in size, form, color, translucency and.texture The margins of the restoration are flushed with.2 the tooth surface and remain free from any caries.recurrence or discoloration The restoration remains integral without.3 fracture, securely retained in the preparation and dimensionally.stable.The restoration is durable.4 The surrounding tissues are healthy and suffer.5 Successful and durability of restoration require the presence of restorative :materials that Have mechanical properties (identical to tooth -.substance) Biological properties (identical to tooth -.substance) Esthetic properties that is identical to tooth -.substance.Must be adhesive to the tooth - Unfortunately, this material is still not *.available When to consider a restoration ?as failed restoration :Failure occurs when A restoration reaches a level of degradation that - precludes proper performance either for esthetic or.functional reasons Or Because of inability to prevent new recurrent -.caries Types of failure.Mechanical failure.Biological failure.Esthetic failure Causes of Failure Failure has been attributed to three principal.factors I. Patient II. Material III. Dentist Causes of Failure :I. FOR THE PATIENT FACTOR The direct effect of patient in the success or failure of restoration is related to the desire of the patient to co- operate with the dentist in following the prescribed.instructions A. The tooth nature: The need to replace missing enamel and dentin in a restorative material and get exactly the same biomechanical and esthetic properties of both tissues combined, regardless of bulk limitations, is too difficult to achieve because of the great differences in properties and variations in architectural.design Causes of Failure B. Accessibility: Access to the conservative dentistry field presents a difficult problem. The conservative dentist has to introduce his hands suction mechanisms and instruments into a very limited area of the mouth, which is very constrained by the tongue, cheeks and teeth of the opposite arch. The more the mouth opening is restricted and the more the inaccessibility of the lesion, the more difficult the clinical management.and success of such case Causes of Failure C. The corrosive potentials: The saliva with its salt content acts as a good electrolyte. The warm atmosphere activates any oxidation, reduction or sulfurization of metallic restorations specially those of non-homogenous structures as.amalgam D. The aqueous nature: Saliva in the mouth creates problems for the restorative dentist who has to work hard to eliminate it from the conservative dentistry field through application of rubber dam, use of suction and cotton rolls because it adversely affects.all restorations Causes of Failure :E. Thermal changes i. Thermal Fluctuations are a common occurrence in the mouth. Thermal cycling of restored tooth results in variable degreesof differential expansion and contraction of restoration and tooth depending on their relative difference in coefficient of thermal.expansion ii. Thermal conductivity: Metallic restorations transmit thermal stimuli to the underlying dentin and pulp, which may cause discomfort or elicit pain.response particularly in deep cavity Causes of Failure F. The oral microbes In the presence of saliva, bacteria in dental plaque rapidly metabolize and cause decalcification of enamel and initiation or.recurrence of caries G. Forces in the mouth: Type of forces: Restorations are subject to mastication forces of multiple types including the compressive, the tensile and shear, static and dynamic, which occur in repetitive.cycles Magnitude of forces: These biting forces vary in magnitude from one individual to another and at.different areas of the same mouth Causes of Failure II. FACTORS RELATED TO RESTORATIVE PROCEDURE Failure of various restorations can occur in one or · :more of the following a) Failure of tooth structure b) Failure of restorative material c) Failure related to tooth restoration inter-face Causes of Failure a) Failure of tooth structure Failure of Enamel Margin )1 Wedge shaped defects along the margins of restoration Cause: incorrect cavity design. The margin may - have been placed too far up the medially facing cuspal incline and, as a result, may be subjected.to heavy occlusal load Failure of Dentin Margin )2 -.Usually occur in the gingival margin - Cause: failure to adapt or condense the - - restorative material adequately at the margin or Causes of Failure Bulk Loss of Tooth Structure )3 Loss of an entire cusp Cause: the dentist has failed to take into account - the weakened nature of remaining tooth structure in an extensively restored tooth and failed to provide some form of protective restoration. Thus becoming subject to lateral.stresses Split Root )4 This usually occurs in non-vital tooth that has been.restored with a post crown Causes of Failure b) Failure of restorative material he selection of material by dentists is often based on compromise between properties and handling.characteristics Marginal failure of restoration.1 DENTAL AMALGAM RESTORATIONS: Amalgam* restoration is a brittle material that does not bond to tooth structure. It does not emit fluorides; however, its adaptation enhances by time through deposition of.corrosion products Marginal degradation It is ditching, fracture or crevicing refers to breakage of a thin edge of a restoration.creating an irregular V-shaped crevice Causes of Failure Causes of Failure :Causes.a. Depletion of support at margins.b. Insufficient bulk at margins.c. Voids.d. Excess mercury :Treatment: Protection against marginal fracture by Following biomechanical principles of cavity.1 design Proper selection of the alloy.2 Proper manipulation of the material.3 Causes of Failure RESIN COMPOSITE RESTORATIONS.* Marginal failure of composite is different from that of amalgam, as it has no resistance at all for recurrent caries. If the margins are left open on the occlusal surface, plaque will be forced into the gaps under the high hydraulic pressure generated by mastication,.and recurrent caries will develop rapidly Marginal chipping Treatment: · Treatment involves repair of existing restoration employing the acid-etch and bond technique. The bond between old and new composite is mechanical (macro mechanical through.roughening) Causes of Failure Causes of Failure GLASS IONOMER MATERIALS As they are not placed at areas of heavy occlusal load, they are not usually subjected to marginal.failure LOSS OF LUTING CEMENT All indirectly fabricated restorations carry the risk of dissolution of the luting agent over time. The use of low solubility cement, combined with high quality laboratory techniques to ensure an accurate fit, is the best methods of control. Improper manipulation of the cement will increase its.dissolution tendency Causes of Failure Fracture collapse of restorative materials.2 Fracture through the main bulk of a restoration is potentiality dangerous, particularly if a segment is.retained within the cavity after becoming mobile i. DENTAL AMALGAM RESTORATIONS Isthmus fracture (Mechanical failure) Definition: It is the narrowest junction between the principle portion (occlusal) and the auxiliary portion.(buccal, lingual or proximal) Isthmus fracture: A fracture of compound amalgam restoration at the junction between the principle portion and the auxiliary portion of the.cavity Causes of Failure Causes of Failure :Causes It is necessary to have a state of balance between § the flexural stresses at the isthmus area and the.flexural strength of the amalgam at the same area The increase in stress or decrease in amalgam § strength could be due to defects in cavity preparation or restoration by the.dentist or due to patient factors Causes of Failure :Fracture due to faults in cavity preparation.Incorrect resistance and inadequate retention.1.Inclined or absent gingival seat- - Walls are not parallel or perpendicular to forces - - Inadequate retentive feature as divergent buccal and lingual -.wall Amalgam is a brittle material with low tensile and shear - strength, which needs bulk of at least 1.5-2 mm to have sufficient.flexural strength Sudden constriction at the isthmus portion with no gradual flare-.from occlusal to proximal portion Recurrent caries at gingival seat that destroy the gingival- - and/or buccal and lingual walls of the proximal box leading to lack of support to amalgam proximally with development of.tensile stresses at the isthmus and isthmus fracture Causes of Failure :Fracture due to faults in restoration -.Presence of premature contact.1 -.Surface and structural discontinuities.2 -.Excess mercury.3 - :Fracture due to patient factors - Sudden biting on a hard object - - Presence of protruded or over erupted opposing - - plunger cusp Biting on amalgam before sufficient setting - - Causes of Failure N.B. Remake of amalgam is preferable than repair :due to Repair will not allow correcting the cavity -.preparation.Lack of bond between the old and new amalgam -.Corrosion between old and new amalgam - Causes of Failure ii. RESIN COMPOSITE RESTORATIONS It may fail in the same manner as amalgam, although it is rather flexible and failure will.normally occur at the margins rather than bulk Gross fracture (Mechanical failure) Composite is a brittle restorative with low flexure.strength Similar to amalgam, isthmus fracture may occur as a result of unfavorable tipping in the balance between flexure strength of composite and the.flexure stresses developed at the isthmus area Causes of Failure Total loss of a restoration.3 Rigid restorations: This is usually the result of loss of cementation of rigid cemented restoration Dislodgment of restoration (Mechanical failure) :Causes Inadequate mechanical retention due to over.1 divergence of the cavity walls Recurrent caries.2.2 Poor cementation.3.3 Excessive torque by occlusal interference.4.4 Treatment: Evaluation of the cause and.5.remake of the restoration if needed Causes of Failure :Discoloration.4 i. DENTAL AMALGAM RESTORATIONS Excessive discoloration ) Esthetic failure( :Definitions Tarnish: Surface discoloration of amalgam with loss of its luster Corrosion: Actual disintegration of the bulk of amalgam Amalgam blues: The amalgam shown through enamel Causes of Failure ii. RESIN COMPOSITE RESTORATIONS Failure of resin composite restorations due to discoloration.is not uncommon It is manifested either initially due to improper color selection or subsequently in the form of marginal, surface or bulk.discoloration :Discoloration (Esthetic failure) :There are three types of discoloration a) Marginal discoloration due to Gross marginal leakage of environmental fluids and.1 smoke stains Poor application of bonding systems.2.2 Moisture contamination.3.3 Causes of Failure III. FACTORS RELATED TO OPERATOR/ DENTIST The knowledge of the operator: Including his knowledge.1 of: - The nature of oral environment as well as, - The properties and limitations of existing restorative materials and techniques, - Factors which will affect or get affected by his choice of material (or combination of materials), plan of treatment and execution of the restorative ,procedures Selection of the most appropriate restorative for each.2 ,individual case Establishment of a cavity suitable for the selected.3 ,restorative The ability of the operator to manipulate different.4.restorative materials correctly Causes of Failure So failure of a restoration due to factors related to :dentist could be due to a. Misjudgment in selection of the restorative.material.b. Cavity preparation c. Material manipulation