Two hundred restorations will be performed in NCCL of volunteers of both genders, by a single operator, using the Single Bond Universal(3M ESPE) adhesive system. The restorations will be randomly allocated into 4 groups (n-50): D-SE (absence of dentinal sclerosis and self-etching protocol); D-SELETIVE (absence of dentinal sclerosis and selective enamel etching protocol); SD-SE (sclerotic dentin and self-etching protocol); SD-SELETIVE (sclerotic dentin and selective enamel etching protocol). The randomization process within subject was performed by computer-generated tables by a staff member not involved in the research protocol. Details of the allocated group were recorded on cards contained in sequentially numbered, opaque, sealed envelopes. These were prepared by a staff member who was not involved in any of the phases of the clinical trial. The allocation assignment was revealed by opening the envelope on the day of the restorative procedure.The operator was not blinded to group assignment when administering.~The evaluations of the clinical performance of the restorations will be carried out by two previously calibrated examiners, adopting the criteria of the United States Public Health Service (USPHS) for the variables retention, marginal adaptation, marginal staining and postoperative sensitivity . The intragroup statistical analysis will be performed using the McNemar test for the variables retention and postoperative sensitivity; and by Wilcoxon for adaptation and marginal staining. To compare the clinical performance inter groups in the different assessment intervals, Fisher's exact test (retention and postoperative sensitivity) and Kruskal-Wallis (adaptation and marginal staining) will be used.
The aim of this randomized, prospective, parallel, double-blind clinical trial will be to evaluate the clinical performance of restorations performed in non-carious cervical lesions (NCCL) using a soft ph universal adhesive system, varying the adhesive strategy (self-etching vs. selective etching of the enamel) and the sclerosis characteristics of the dentinal substrate over 24 months.