Is there one optimal repair technique for all composites?

Objectives. The aim of this study was to investigate the effectiveness of a variety of techniques to bond new composite to artificially aged composite of different compositions. Methods. Composite resin blocks were made of five different commercially available composites (n = 30) (Clearfil AP-X, Clearfil PhotoPosterior, Photo Clearfil Bright, Filtek Supreme XT and HelioMolar). After aging the composite blocks (thermo-cycling 5000x), blocks were subjected to one of 9 repair procedures: no treatment (control), diamond bur, sandblasting alumina particles, CoJet (TM), phosphoric acid, 3% hydrofluoric acid 20 s or 120 s, 9.6% hydrofluoric acid 20 s or 120 s. In addition, the cohesive strength of the tested composites was measured. Two-phase sandwiches ('repaired composite') were prepared using each of the 9 repair protocols, successively followed by silane and adhesive (OptiBond FL) treatment, prior to the application of the same composite. Specimens were subjected to micro-tensile bond strength testing. Data were analyzed using ANOVA and Tukey's HSD (p < 0.05). Results. For all composites the lowest bond strength was obtained when no specific repair protocol (control) was applied; the highest for the cohesive strength. Compared to the control for the microhybrid composite (Clearfil AP-X) five repair techniques resulted in a significantly higher repair strength (p < 0.05), whereas for the nano-hybrid composite (Filtek Supreme XT) and hybrid composite containing quartz (Clearfil PhotoPosterior) only one repair technique significantly increased the bond strength (p < 0.01). Significance. None of the surface treatments can be recommended as a universally applicable repair technique for the different sorts of composites. To optimally repair composites, knowledge of the composition is helpful. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.