Influence of different surface treatments on microshear bond strength of repair resin composite to two CAD/CAM esthetic restorative materials

Objective: The aim of this in vitro study was to evaluate which surface treatment and adhesive type might provide the most predictable microshear bond strength results of repair resin composite to lithium disilicate ceramic and a newly introduced resin nanoceramic (RNC). Methods: A total of thirty six slices were prepared out of resin nanoceramic (Lava Ultimate) and lithium disilicate (IPS e.max CAD ceramic blocks) with dimensions of 14 x 12 x 3 mm (n = 18 for each material). The slices were divided into three main groups according to surface treatment: Control group (CN) received no treatment, group (DB) roughened with diamond bur and group (CJ) silica coated with Cojet system. Each group was subdivided into two subgroups according to the type of adhesive system used for repair: Subgroup (MH): Treated with Monobond plus and Heliobond adhesive system and subgroup (SBU): treated with Single bond universal adhesive system. The adhesives were applied according to the manufacturers instructions. Five transparent microtubules were adjusted on each substrate slice and then repair resin composite (Tetric Evoceram, shade A3) was applied and light cured (n = 15 for each subgroup). After 24 h storage in distilled water, microshear bond strength (μSBS) was measured for each specimen of tested groups. Results: Lava Ultimate RNC showed statistically significant higher mSBS compared to IPS e.max lithium disilicate ceramic. The use of diamond bur in conjunction with Monobond plus and Heliobond adhesive system showed higher μSBS compared to all tested groups. Conclusions: The effect of different surface treatments on the μSBS to the repair resin composite is material dependent. Combination of the abrasive action of diamond bur and adhesive with separate silane treatment modalities had a synergistic influence on μSBS of the repair resin composite under the current circumstances.