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 5000×), blocks were subjected to one of 9 repair procedures: no treatment (control), diamond bur, sandblasting alumina particles, CoJet™, phosphoric acid, 3% hydrofluoric acid 20s or 120s, 9.6% hydrofluoric acid 20s or 120s. 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.