Microleakage after thermocycling of 4 etch and rinse and 3 self-etch adhesives with and without a flowable composite lining.

This study evaluated the microleakage of composite fillings prepared with 4 etch and rinse and 3 self-etch adhesive systems after thermocycling. Also evaluated was the potential improvement of cavity sealing when utilizing a low charged resin lining for cavity preparations. Seventy recently extracted teeth were randomly allocated to 7 experimental adhesive systems: two 3-step etch and rinse adhesive systems, Scotchbond Multipurpose (SBMP) and Optibond Solo Plus (OS); two 2-step etch and rinse adhesive systems, referred to as "one-bottle," Scotchbond 1 (SB1) and Gluma Comfort Bond + Desensitizer (G); and 3 self-etch "all-in-one" adhesives, Adper Prompt-L-Pop (PLP), Xeno III (X-III) and iBond (iB). On each tooth, 2 rectangular cavities were prepared at the cemento-enamel junction: 1 cavity was prepared with adhesive and the hybrid composite and the second was filled with the same adhesive and a thin layer of flowable composite (Filtek Flow) under the resin composite (Z100). All teeth were thermocycled for 800 cycles (5 degrees C-55 degrees C, 30 seconds dwell time). Leakage was evaluated on a 6-point (0-5) severity scale for enamel and dentin on 4 interfaces for each restoration. The results are expressed as means +/- standard deviation (SD). Microleakage scores were analyzed by means of generalized linear mixed models (GLMM), assuming an ordinal logistic link function. Covariates in the model were: (1) adhesives, (2) fluid composite and (3) interface. The model also accounts for repeated measurements on the various teeth. The authors found that the mean score of microleakage per tooth was significantly higher at the enamel rather than at the dentin interfaces (1.21 +/- 0.51 and 0.87 +/- 0.48; p<0.0001). In this study, there was no significant difference among the 4 etch and rinse adhesive systems. On the other hand, these adhesives yielded smaller mean scores of microleakage than the 3 self-etch systems (respectively, 0.85 +/- 0.2 and 1.3 +/- 0.5; p<0.0001). Among the self-etch adhesives, microleakage was significantly greater for PLP (1.74 +/- 0.46) than for the other self-etch products (p<0.0001), while X-III, an intermediary strong self-etch, was found to be as good as the etch and rinse systems, with a mean score of 0.97 +/- 0.27. In addition, results have also shown that an under layer of flowable composite significantly improved the water tightness of the PLP adhesive restorations (p=0.042). This in vitro study concluded that the self-etch adhesives remain less effective than etch and rinse. Nevertheless, X-III, a self-etch adhesive, showed acceptable performance in accordance with this study's 6-point severity scale of microleakage, but this needs to be confirmed in further clinical studies. On the other hand, this study failed to reveal that the addition of a thin layer of fluid composite improved the water tightness of the restoration, except for PLP.