In vitro evaluation of the effect of two types of preparations on the fracture strength of laminates fabricated from fiber reinforced composite and ceramic

ABSTRACT

One of the popular treatment options for correction of discoloration and poorly shaped anterior teeth is veneer. Two main preparation designs for full veneers have-been developed 1. Window preparation 2, Incisal lap preparation. The aim of this study was to compare the effect of two new design preparations on the fracture strength and retention of laminate with conventional preparation. In this in vitro experimental study, 54 human extracted central and lateral maxillary and mandibular teeth were selected. Samples were divided into three main groups [n=18] with two subgroups in each [n=9]. Group 1 Incisal lap preparation of labial surface of teeth without box preparation. Group 2 Preparation of labial surface with labial box in mesial and distal surfaces. Group 3 Preparation of labial surface with proximal box in mesial and distal surfaces. In the first subgroup of all groups, indirect composite laminate and in the second subgroup, ceramic laminate was fabricated. After cementation of laminates with dual cured resin cement [Rely X ARC], we determined the fracture strength by zwick machine and type of failure by the stereomicroscope. The data were analyzed by One-Way and Two- Way ANOVA, Tukey and student-t tests. 1] There was a significant difference between fracture strength of laminates made of two different types of materials in three types of preparations [P=0.016]. 2] In composite laminates, there was a significant difference between fracture strength of group 1 and 2 and the greatest fracture strength was observed in group 1 [P=0.019]. 3] In ceramic laminates, there was no significant difference between fracture strength of the three types of preparations, although the greatest fracture strength was observed in group 2 [P=0,055], 4] There was no significant relationship between mode of failure and type of preparation in two different laminate materials. The findings of this study demonstrated that in incisal lap preparation of labial surface of tooth without box preparation, fracture strength of composite laminates was proved to be greater than ceramic laminates, while with preparation of labial surface with labial box, fracture strength of ceramic laminates was proved to be greater than composite laminates