Effect of operator skill in relation to microleakage of total-etch and self-etch bonding systems

Objectives To evaluate the influence of operator skill on microleakage in class V restorations using two-step bonding systems. Methods Two standardized box cavities were made on the buccal and lingual surfaces of 54 human bicuspid teeth, with the cervical margin in dentin. The teeth were randomly assigned to two groups according to the operatorʹs skill. Students group: undergraduate students. Expert group: a dentist with 20 years of clinical experience in dental adhesion. The buccal cavities of each tooth were treated with Prime&Bond NT (two-step total-etch system); the lingual cavities were treated with AdheSE (two-step self-etch system). All cavities were restored by a single calibrated operator with one bulk increment of resin composite (InTens; Ivoclar Vivadent). Specimens were thermocycled, immersed in 2% methylene blue and sectioned in a bucco-lingual plane in the middle of the restorations. They were then examined under a stereomicroscope and scored according to microleakage by two operators who were blind to the specimen preparation. The data was subjected to a multilevel statistical model. Results The microleakage resulting from the self-etch adhesive was similar in the student and in the expert groups. On the other hand, the total-etch adhesive microleakage within the expert group resulted lower than that within the student group. However, the interaction term skill × adhesive resulted statistically significant at the dentin margin (p = 0.0474) but not at the enamel margin (p = 0.1267). Conclusion While the total-etch adhesive used in this study showed to be skill-sensitive, the self-etch one proved to be less skill-sensitive in obtaining a reliable seal with dentin.