Influence of repair-bonding and/or silane-application on shear-bond-strengths of repaired composites

Fractured or discoloured composite restorations can be repaired by surface reduction and application of a universal repair bonding agent (Ahlers et al., J Dent Res 1996). Further studies suggested that silane solutions could enhance repairbond-strenghts, too (Söderholm, Scand J Dent Res 1986). However, these findings were not confirmed by other authors (Saunders, J Dent 1990). Objectives: The aim of this study was to compare bond strengths of repairs with the bonding agent tested before to a commercially available silane solution or combinations of these, applied on composites of different anorganic filler portions. Methods: Substrates repaired were 3 composites: a microfiller (Durafill, Kulzer), a macrofiller (Superlux Universalhybrid, DMG-Hamburg) and a fineglass-composite (Ecusite, DMG-Hamburg). 10 cylindrical samples (Ø 8mm, height 6mm) per group were thoroughly polymerised (Kulzer Dentacolor XS, 180s from top and bottom). After wet storage for two weeks (37ºC) the surfaces were wet ground (80 grid) and dried. Repair bonding agent (Ecusit Composite Repair, DMG-Hamburg), silane solution (Monobond S, Vivadent) or both in two sequences were then applied in small amounts (4 protocols). Fluids were brushed into the surface for 60s and light-cured 20s each (Kulzer Translux EC, distance 2mm). As addition, Durafill was applied (ISO TR 11405) and polymerised (Kulzer Translux EC / distance 2mm / 40s). Shear bond strengths were measured according to ISO TR 11405. Results: Means of 12 groups ranged between 12.25 ± 1.21 (microfiller + repair-bonding) and 15,33 ± 1.32 MPa (fineglass composite + silane + repair-bonding). Difference between means were not statistically significant (F-Test, p=0.0119). Instead, the only factor leading to statistically significant differences were the substrates used, with Durafill resulting in comparatively smaller strenghts (Tukey-Procedure, p<0.01). Conclusions: The results indicate that additional application of the silane solution does not offer a significant advantage compared to application of the repair bonding agent alone.