Participants were scheduled as they were accepted in the study, and operators were scheduled to place the restorations according to the Department of Operative Dentistry master schedule. For each participant, the adhesive used (OptiBond XTR or OptiBond FL) in the first restoration placed was chosen on the flip of a coin, and the subsequent restorations (if more than one tooth was to be restored on that participant) were done using the other adhesive and so on. Consequently, if the participant had two or more lesions to be restored, he/she received both adhesives. Every effort was made to distribute the restorations evenly in the mouth, i.e., restorations placed with both adhesives were equally distributed in anterior/posterior teeth, and in maxillary/mandibular teeth.