Microtensile Bond Strength of CAD-CAM blocks Using Self-adhesive Resin Cement

Objective: To determine microtensile bond strength of ceramic and composite CAD-CAM blocks bonded to dentin and to composite material using self-adhesive and conventional resin cements. Methods: Occlusal surfaces of extracted sound human molars were sectioned horizontally below the DEJ to produce dentin sections 3mm thick. Composite discs 3mm thick were made from Z100 composite (3M/ESPE) using a special mold. Three types of Vita CEREC Blocks: Mark-II (GroupI), Trilux (GroupII) and Esthetic-line (GroupIII) (Vita Zanfabrik) and composite block (Paradigm Z-100, 3M/ESPE) (GroupIV) were sectioned into slices 3mm thick. Ceramic sections were surface-treated using a porcelain treatment kit. Each group was subdivided into 2 subgroup: 1 was cemented to dentin and the other to composite using 2 resin cements, conventional cement (Calibra/ Prime & Bond-NT, Dentsply) as control; and self-adhesive cement (Rely-X-Unicem, 3M/ESPE). Bonded specimens were stored in water for 24h at 37°C then sectioned to obtain rods 1x1x6 mm using slow-speed diamond saw. The rods were then tested in microtensile testing machine (Bisco). Means and SDs were calculated and data statistically-analyzed using ANOVA and tukey's post hoc tests. Results: Microtensile bond strengths to dentin with Calibra in MPa were: GroupI: 20.4(2.3), GroupII: 17.6(2.6), GroupIII: 19.9(2.9), GroupIV: 24.5(2.5). With Rely-X Unicem values were: GroupI: 10.1.4(2.5), GroupII: 13.2(4), GroupIII: 15.8(3.1), GroupIV: 33.3(2). For both cements Paradigm Z-100 blocks had significantly higher bond strengths to dentin compared with 3 ceramic blocks (p<.05). Microtensile bond strengths to composite with Calibra in MPa were: GroupI: 31.1(4.8), GroupII: 29.5(5.8), GroupIII: 27.5(6), GroupIV: 24.2(7). For Rely-X Unicem values were: GroupI: 37.2(6.1), GroupII: 29.7(3.2), GroupIII: 31(3.8), GroupIV: 23.4(3.6). All groups showed higher bond strength to composite material with the 2 cements except for Paradigm Z-100. Conclusions: A Composite CAD-CAM block (Paradigm Z-100) had higher microtensile bond strength to dentin compared to 3 ceramic CAD-CAM blocks. Acknowledgements: 3M/ESPE and Dentsply.