Methods: In this experimental study, 40 caries-free maxillary central incisors were divided into four groups (n=10). While the control group remained unprepared, in the second, third, and fourth groups the preparation included 1 mm, 1.5 mm and 2 mm of incisal edge respectively. 30 feldespatic ceramic veneers were bonded by light cure luting cement (Choice 2). After that, specimens were loaded by universal testing machine under increasing force (1 mm/min cross head speed – 135 force angle degree) 0.5 mm lower than incisal edge until fracture was accrued. Finally, fracture loads were recorded on newton unit.
Results: The mean fracture forces for control, 1 mm, 1.5 mm and 2 mm groups were 1089.4±276.49, 921.56±399.78, 894.46 ± 538.35, and 877.28±371.5 respectively. Besides, cohesive fracture in second, third, and fourth groups were 6, 6, and 4 respectively. Also, adhesive fractures (between cement and porcelain) were 1, 1, and 2 and adhesive fractures (between cement and tooth) were 3, 2, and 3 respectively. However, in third and fourth groups one crack in porcelain without fracture was seen.
Conclusions: Under limitations of this study from fracture resistance point of view there was no significant difference between control group and the three other groups (P>0.05).