Alternative surface treatment of an indirect composite resin by MTBS

Objective: to evaluate the microtensile bond strength of an indirect composite resin (ICR) to a resin cement, after surface treatment with 10% hydrofluoridric acid (HF) and thermocycling. Methods: an acrylic block (6 x 6 x 6mm) was molded with polivinilsiloxane obtaining a mold to build 30 blocks of ICR (Vita VMLC) according to manufacturerxs instructions. The blocks were divided in 6 groups (n=5): G1 (negative control): without HF; G2: HF 60s; G3: HF 90s; G4: HF 120s; G5: HF 180s; G6 (positive control): sandblasting (Cojet Sand) (10 s,10 mm of distance, 2.8 bars of pressure); washed with distilled water and dried with air. 30 blocks of direct composed resin (DCR) (W3D) were built obtaining a block of RCD for each block of RCI. On RCI block surface was applied silane (Monobond-S), adhesive (Excites DSC) and it was cemented to RCD blocks by resin cement (Variolink II) under load of 750g. They were stored in distilled water (37șC/24hs). The blocks were cut in machine obtaining 9 samples (n=9) with cross section area of 0,64mm2, submitted to thermocycling (6000 cycles, 5șC to 55șC, 30s). Each sample was set in a caliper adapted to an universal machine with speed of 1mm/min. Results: ANOVA (a=0.05) showed that the bond strength was not affected by the surface treatment (p>0.05). It was verified that G5 (41.86±7.01b) was statistical different from G1 (35.64±4.95a); and G2 (40.20±5.63a), G3 (40.96±5.18a), G4 (40.61±3.17a) was statistical different from G6 (47.38±6.12b) (Dunnet test). Conclusion: the surface treatment with HF 180s of the indirect composite produced the highest values of microtensile bond strength to a resin cement after thermocycling.