Survival and Quality of Amalgam Repair Restorations after Ten Years

With the concept of minimal invasive therapy the repair of restorations became a treatment option. Studies concerning the repair of defective amalgam restorations - condensing a new restoration in an existing one - mainly focus on material properties and only few data are available from longitudinal clinical studies. Objectives: Therefore the objectives of this study were (1) to quantify the survival rate of repair restorations over a ten year period and (2) to characterize and compare their surface quality and marginal integrity. Methods: 37 amalgam restorations used as repair for cohesively fractured amalgam restorations („knot hole fractures“) were followed up over a ten year period and evaluated using the USPHS-compatible CPM-Index (Clinical-Photographical-Micromorphological coding). Results: After ten years 16 repair restorations were found still in situ. There was a drop out of 7 restorations, 9 were lost because of a later total re-restoration with amalgam and 5 had been replaced by cast restorations. At the end of the study the repairs/restorations were clinically rated according to the C-criteria of the CPM-Index. Additionally, replicas were made and rated according to the M-criteria of the CPM-Index. The clinical criteria have shown predominant homogeneous surface structures and an intact interface. The excellent clinical parameters (C codes) were supported by the micromorphologic findings (M codes). Conclusion: It is concluded that (1) there is an indication for repair of cohesively fractured amalgam restorations and (2) the results support the need for further investigations concerning the indication of repair restorations.