Thesis & Dissertations

Aim: The objective of this study was to evaluate the fracture resistance of CLVs bonded to class IV composite restorations using two different sizes of class IV compositerestorations and to two different incisal preparation designs. Methods.* Forty-two extracted human maxillary central incisors were selected for the study. Teeth were randomly divided into three main groups; GI (control): intact teethwith no class IV composite restoration, G2: with 25% size class IV composite restoration, and G3: with 40% size class IV composite restoration. Each group was further divided according to the incisal preparation design of the laminate veneers (n=7); A: incisal butt joint design and B: incisal overlap design. Class IV cavities were restored by nanohybrid resin composite and the two incisal preparation designs were made. CLVs (IPS e.max) were cemented by dual cure resin cement and aged in distilled water for six months then subjected to fracture resistance testing using a universal testing machine. Fracture resistance values and mode of failure were recorded and statistically analyzed using two way ANOVA test. Results: Class IV cavity dimension and the interaction between the two variables had no statistically significant effect on mean fracture resistance. The veneer incisal preparation design had a statistically significant effect on mean values of fracture resistance. The incisal overlap design showed statistically significantly higher mean fracture resistance values than the incisal butt joint design in G2 and 03 groups. Regardless of the incisal preparation design, there was no statistically significant difference between mean fracture resistance of intact teeth (control) as well as with Class IV composite fillings. There was no statistically significant difference between the failures modes with incisal overlap or incisal butt joint designs for all groups of the study. With incisal overlap design, G2 showed 85.7% root fracture, While G3 showed 85.7% crown and/or laminate fracture. Whereas with incisal butt joint design, there was no statistically significant difference between failure modes for all groups.