Purpose. To assess the quantity of exposed dentin detected by 3 operators for 2 different geometries of tooth preparations, window (WI) and butt-joint (BJ).

Methods. 20 intact maxillary central incisors were collected. One prosthodontist prepared the specimens for porcelain laminate veneers to a depth of 0.6 mm, with a cervical chamfer-line of 0.3 mm, using a silicone index. Subsequently, each prepared tooth was analyzed by 3 operators with different clinical experience, student (ST), medium experienced (ME), and expert (EX) to calculate the percentage of exposed dentin at sight under magnification. In addition to descriptive statistics (CI 95%), a 2-way ANOVA and the Games-Howell test were used to analyze differences among groups (α=.05).

Results. The means of the calculated percentages of dentin exposure were: WI=30.48%; BJ=30.99%; ST/WI=22.82%; ME/WI=58.05%; EX/WI=10.55%; ST/BJ=28.99%; ME/BJ=40.56%; EX/BJ=23.42%.

The 2-way ANOVA detected significant differences among operators (p<.001) but not between WI and BJ (p=.898). The Games-Howell test detected differences between ST/WI and ME/WI (p=.005) and between ME/WI and EX/WI (p<.001).

Conclusions. There is no difference in the detection of exposed dentine among operators with different expertise for BJ preparation, whereas differences were detected between ME and the other 2 operators in the WI preparation.

The mean values of exposed dentin found in WI and BJ were approximate of 30%, falling within the ideal range of enamel preservation (50%-70%) to achieve optimal adhesion. Moreover, the quantity of exposed dentin is not related to different tooth preparation geometry.