Some of the bonding systems used in this study have achieved unchanged dentin bond strengths after thermal cycling. Therefore, by choosing appropriate adhesive systems, the simplified clinical procedures offered by single-step self-etch systems can be exploited even after thermal cycle stress. SUMMARYThis study investigated the influence of thermal cycling on the dentin bond strengths of singlestep self-etch adhesive systems. The Absolute, Clearfil Tri-S Bond, G-Bond and One-Up Bond F Plus systems were used. Bovine mandibular incisors were mounted in self-curing resin, and the facial surfaces were wet ground with #600 SiC paper. Adhesives were applied to the prepared dentin surfaces, and they were light irradiated according to each manufacturer's instructions. Resin composites were condensed into a mold (4 mm in diameter and 2 mm in height) and light irradiated for 30 seconds. Bonded specimens were divided into three groups and subjected to different storage conditions as follows: 37°C water for 24 hours; 37°C water for 24 hours followed by 10,000 thermal cycles between 5°C and 60°C or 37°C water for 24 hours followed by 20,000 thermal cycles between 5°C and 60°C. Ten samples per group were tested in a shear mode at a crosshead speed of 1.0 mm/minute. Analysis of variance and Tukey's HSD test at the 0.05 significance level were used to compare the three storage conditions for each adhesive system. After 24 hours storage in water, the mean dentin bond strengths ranged from 11.4 MPa to 17.1 MPa. The Clearfil Tri-S Bond system showed the highest bond strength. After 10,000 thermal cycles, the mean bond strengths remained unchanged Youhei Asaka, DDS, graduate student,

Operative Dentistry, 2006, 31-1, 18-24 Y Asaka • M Miyazaki T Takamizawa • K Tsubota • BK Moore Clinical RelevanceThe delay in placement of composite over single-application self-etching adhesive systems was a crucial factor influencing dentin bond strength compared to a composite placed immediately after the polymerization of adhesives. UMMARYThis study examined the relationship between delay in composite placement over cured adhesives and the dentin bond strength of several singleapplication self-etch adhesive systems. The adhesive system/resin composite combinations used were: Adper Prompt L-Pop/Filtek Z250 (AP), AQ Bond Plus/Metafil C (AQ), Fluoro Bond Shake One/Beautifil (FB), G-Bond/Solare (GB), One-Up Bond F Plus/Palfique Estelite (OF), Xeno IICF Bond/Xeno CF (XE). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600 SiC to expose labial dentin. The adhesives were applied according to each manufacturer's instructions, and resin pastes were condensed into a mold (ø4x2 mm) immediately, and 1, 2, 5 and 10 minutes after light irradiation of the adhesives. Ten samples per test group were stored in 37°C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVA followed by Tukey's HSD test (α=0.05) was done. SEM observations of the dentin surface after the tests were also conducted. Dentin bond strength ranged from 9.5 ± 2.2 to 14.0 ± 2.4 MPa for AP, 7.3 ± 2.2 to 12.2 ± 3.1 MPa for AQ, 10.0 ± 3.5 to 16.3 ± 2.4 MPa for FB, 11.4 ± 1.5 to 16.3 ± 1.2 MPa for GB, 14.2 ± 3.4 to 15.1 ± 3.0 MPa for OF and 11.5 ± 2.4 to 15.9 ± 2.2 MPa for XE. Except for OF, no significant differences were found among the 2 to

The purpose of this study was to clarify the effect of thermal cycling on dentin bond strengths of single-step self-etch adhesives. Five commercially available single-step self-etch systems were used. The adhesives were applied to the dentin surfaces of bovine incisors, and then light-irradiated. Resin composites were condensed into a mold and light-irradiated. Bonded specimens were divided into two groups and stored in water at 37 degrees C for 24 h without thermal cycling, or in water at 37 degrees C for 24 h followed by 10,000 thermal cycles between 5 degrees C and 60 degrees C. Ten samples per group were tested for shear strength at a crosshead speed of 1.0 mm/min. The data were analyzed by Student's t test and Tukey HSD test at a probability level of 0.05. After 24 h of storage in water, the mean dentin bond strengths ranged from 9.3 MPa to 14.0 MPa. After 10,000 thermal cycles, the mean bond strengths remained unchanged. Failure after the test was commonly due to adhesive breakdown associated with partial cohesive failure of the resin. The present results suggest that the benefit of using single-step self-etch systems, in terms of simplifying the clinical procedure, might be acceptable even after thermal stresses.