1.1

Repair of resin-based composites

Resin-based composite (RBC) restorations have, as all restorative materials, a limited longevity, with a mean annular failure rate of 2.2% . Fractures and secondary caries are the most frequent reasons for replacement . Failed restorations are commonly treated by total replacement, which leads to a significant amount of tooth structure loss . Repair, refurbishing and sealing are alternative treatments, but there is still a lack of evidence for the longevity of these options .

First hints for the clinical practicability of repair were already presented in 1976 and 1978 . Katsuyama et al. described in 1979 the prognosis of resin-based composite restorations, including the possibility of repair . In 1993 Mjor pointed out, that detailed criteria are necessary to distinguish between failed restorations which can be repaired or have to be replaced. Numerous factors play a role in the decision making, including the clinical condition, the used restorative material or the cost-effectiveness-relation. Tyas et al. reported in 2000, that repair is not well accepted by practitioners, being considered as “patchwork dentistry”. Most of them choose repair as a treatment in a case-by-case basis. Therefore, 50–71% of a dental practitioner’s activity is replacement of restorations .

1.2

Repair of amalgam restorations

Despite the continuously increasing number in resin based composite restorations, the use of amalgam is still considered an important restorative treatment option in many dental practices due to relatively low cost and long-term cost effectiveness . The primary reasons for replacement of amalgam restorations are secondary caries and restoration fracture . Total replacement is the most common treatment for defective amalgam restorations, leading however to a significant loss in tooth structure . Alternative options for treating defective restorations are repair, sealing or refurbishing . Repaired and replaced amalgam restorations have a similar survival after 5 years. However, after 10 years, repaired amalgam restoration performed worse .

1.3

Repair of glass-ionomer cements (GIC)

Hickel and Voss published data of repair of restorations with GIC (Cermet) up to 3.5 years. All types of failures and restorations were included. The success rate after 2.5–3.5 years was only 73.9%, with most of the failed repair fillings showing wear, fractures, defects or even a complete loss in occlusal areas. One reason for these results was the use of GIC not only to repair marginal defects but also fractured tooth cusps or fractured restorations ( Fig. 1 ).

Repair of imperfect restorations with GIC (silver reinforced). (a) Bridge with undermining caries at the distal crown, margin had to be shortened for access and removal of caries. (b) Fractured cusp at gold onlay after caries adjacent to restoration. (c) Wear of GIC repair filling of marginal gap after 6 months. (d) Fractured cusp of tooth with amalgam filling repaired with GIC. Repair filling 3.5 years old.

1.4

Repair of ceramic and porcelain fused to metal systems

Due to patient’s increasing esthetic demands, the use of all-ceramic restorations, including inlays, onlays, veneers, all-ceramic crowns and all ceramic-bridges, continue to expand. However, ceramic restorations may fail in clinical service . The major causes for replacement of all-ceramic and metal-ceramic restorations are secondary caries, porcelain fracture and chipping . Possible reasons for porcelain fractures are errors or contamination in fabrication and an incorrect treatment planning. This includes inappropriate use of materials, especially in relation to the occlusion, as well as an inadequate creation of sufficient space for the restoration .

A possible classification and treatment recommendation for a chipped ceramic restoration was published by Heintze and Rousson . A chipping grading scale comprising three grades was established according to the treatment that followed the chipping as: small veneer chippings receive grade 1, moderate veneer chipping receive grade 2 and severe chipping receive grade 3. Grade 1 chippings can be treated with polishing, grade 2 chippings can be repaired with resin composites and grade 3 chippings led to replacement of the entire restoration . Following criteria for replacement (grade 3) are proposed :

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  The fracture surface extends into a functional area and repair is not feasible.

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  Recontouring will result in a significant unacceptable alteration of the anatomic form from the original anatomy.

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  Recontouring will significantly increase the risk of pulp trauma by the generation of heat.

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  Repair with a resin composite will result in esthetic changes that are unacceptable to the patient.

Blum et al. proposed a classification of fractures occurring in metal-ceramic restorations in simple and complex fractures. Simple fractures are those involving only the porcelain, originating from intra ceramic defects, trauma and parafunctional habits . Complex fractures are associated with exposure of the metal substructure, resulting from failures at the metal-ceramic interface, an improper design, an inadequate framework support for the porcelain, fatigue of the metal substructure or internal stresses induced by incompatibilities between the coefficients of thermal expansion of porcelain and metal .

All-ceramic systems, in particular when used for bridges, have mostly a two-layer structure consisting of a high strength ceramic substructure core and a weaker veneering ceramic layer . The fractures occur predominantly in form of internal surface crack formation, owing to high stress concentration areas. The fractures were shown to initiate from the inner fitting surface and to propagate the veneering ceramic material, leading to a fracture and exposure of the substructure core . Bulk fracture of ceramic is the main reason for failure in all-ceramic restorations .

1.5

Repair of gold restorations

Though being clinically a need, the efficiency of methods used for repairing gold restorations are insufficient analyzed. Beside some case reports, only two older publications attested in SEM analysis that resins and glass-ionomer cements are suitable materials for repairing gold restorations .

The aim of the paper was to systematically review the clinical and the in vitro aspects of repair by considering different restorative materials – resin-based composites, amalgam, glass-ionomer cements, ceramics or metals. Furthermore, the occurrences of teaching repair in different universities and how defect restorations should be treated are indicated.