Effect of different adhesive strategies on microtensile bond strength of computer aided design/computer aided manufacturing blocks bonded to dentin

Abstract

Background: The aim of this study was to determine the microtensile bond strength (μTBS) of

ceramic and composite computer aided design‑computer aided manufacturing (CAD‑CAM) blocks

bonded to dentin using different adhesive strategies.

Materials and Methods: In this in vitro study, 30 crowns of sound freshly extracted

human molars were sectioned horizontally 3 mm above the cementoenamel junction to

produce flat dentin surfaces. Ceramic and composite CAD/CAM blocks, size 14, were

sectioned into slices of 3 mm thick. Before bonding, CAD/CAM block surfaces were

treated according to the manufacturer’s instructions. Groups were created based on

the adhesive strategy used: Group 1 (GI) – conventional resin cement + total‑etch adhesive

system, Group 2 (GII) – conventional resin cement + self‑etch adhesive system, and

Group 3 (GIII) – self‑adhesive resin cement with no adhesive. Bonded specimens were stored

in 100% humidity for 24h at 37°C, and then sectioned with a slow‑speed diamond saw to

obtain 1 mm × 1 mm × 6 mm microsticks. Microtensile testing was then conducted using a

microtensile tester. μTBS values were expressed in MPa and analyzed by one‑way ANOVA

with post hoc (Tukey) test at the 5% significance le vel.

Results: Mean values and standard deviations of μTBS (MPa) were 17.68 (±2.71) for GI/ceramic;

17.62 (±3.99) for GI/composite; 13.61 (±6.92) for GII/composite; 12.22 (±4.24) for GII/ceramic;

7.47 (±2.29) for GIII/composite; and 6.48 (±3.10) for GIII/ceramic; ANOVA indicated significant

differences among the adhesive modality and block interaction (P < 0.05), and no significant

differences among blocks only, except between GI and GII/ceramic. Bond strength of GIII was

consistently lower (P < 0.05) than GI and GII groups, regardless the block used.

Conclusion: Cementation of CAD/CAM restorations, either composite or ceramic, can be

significantly affected by different adhesive strategies used.

Key Words: Adhesion, ceramic, composite resin, computer aided design/computer aided manufacturing