Impact of Preparation Depth and Length on Fracture Resistance of Anterior Teeth Restored by Endocrowns and Post Retained Crowns

Abstract

Objectives: To evaluate the effect of preparation depth (3mm deep endocrown, 6 mm deep endocrown and post retained crown) and different remaining coronal length (1mm & 2mm) of CAD/CAM fabricated restorations (zirconia reinforced lithium silicate) on fracture resistance of endodontically treated anterior teeth. Materials & Methods: Twenty zirconia reinforced lithium silicate restorations, VITA Suprinity ceramic (VITA Zahnfabrik, Germany) were fabricated through CAD-CAM on a central incisor root. The specimens were randomly divided to divided into four Groups (n = 5 in each) Group I: CAD/CAM zirconia reinforced lithium silicate short endocrown (3mm depth) with 1mm remaining coronal length, Group II: CAD/CAM zirconia reinforced lithium silicate short endocrown (3mm depth) with 2mm remaining coronal length, Group III: CAD/CAM zirconia reinforced lithium silicate long endocrown (6mm depth) with 1mm remaining coronal length and Group IV: zirconia reinforced lithium silicate crown retained by glass fiber post (Glassix radiopaque, H Nordin, Chailly/Montyreux, Switzerland) and composite core (nano hybrid universal A3 shade Z250XT (3M ESOE Z250XT, Seefeld,Germany)with 1mm dentin collar (conventional treatment). Then, all the specimens subjected to thermocycling (Robota BILGE,Turkey) and fracture resistance test was performed by using a universal testing machine (Lloyd LRX, Lloyd Instruments, Fareham Hants, UK) at 45o angle to the long axis of the teeth. The data was statistically explored using one-way ANOVA and post-hoc Tukey tests (P value < 0.05)Results: The highest mean fracture resistance value was obtained on group II (835.3±7.9 N). While, the lowest mean value of fracture resistance was obtained in group IV (286.8-295.4N). Furthermore, the fracture resistance mean value hadn’t statistically significant different between all tested groups. Conclusions: Anterior endocrown monoblock restorations with short depth (3mm) and 1mm ferrule height can be used as an unusual to post retained crown restorations.