Twenty-four hour microtensile bond strength of four adhesives to dentin

Objectives: To measure and compare the 24-hour microtensile bond strength of four self etching adhesives (Table) to dentin.� Methods: Freshly extracted human molars were wet-ground with a series of silica carbide paper ending with 320 grit to obtain flat intermediate level dentin surfaces and a uniform smear layer using a rotational polishing device (Buehler/Evanston/IL). The teeth were randomly assigned to one of four groups and the adhesives for each group was applied following manufacturers' instructions. Resin composite (Z100/3M ESPE) was placed in 2mm increments over the cured adhesive and light-cured (Elipar S10/3M ESPE/1100mW/cm�) until a 10mm thickness was obtained. Specimens were stored (distilled water/37�C/24h) then sectioned into approximately 1x1mm thick beams comprised of dentin, adhesive and composite build-up using a slow-speed cutting device (Isomet) and a 0.004� thick blade with water-cooling. Before testing, the dimensions of each beam was measured with a digital micrometer to calculate the bonded surface area at the adhesive-dentin interface. The beams were attached horizontally to the microtensile testing machine fixture, attached to Instron (5565) and loaded in tension until failure using a 1mm/min cross head speed. Tested samples were examined with a digital microscope (Keyence/VHX-600) at 100X to determine failure mode. Failure mode was classified as adhesive to the dentin or composite, cohesive to the dentin or composite or mixed (a combination of adhesive and cohesive).� Data was analyzed with ANOVA and Tukey/Kramer tests (p=0.05).

�Results: (Mean�SD).

	Bond Strength (MPa)
MTB 200/Kuraray	40.2�17
iBond/Heraeus Kulzer	29.9�15
OptiBond All-In-One/Kerr	40.7�14
Xeno IV/L.D. Caulk	34.5�12

Conclusions: OptiBond All-In-One and MTB 200 had higher microtensile bond strengths to dentin compared to iBond (p=0.0004). No other differences were found between the tested materials. Supported in part by a grant from Kuraray.