Effect of abutment design on fracture resistance of resin-matrix ceramics crown for dental implant restoration: an in vitro study

Abstract

Background: The purpose of this study is to investigate the performance and fracture resistance of different resin-matrix ceramics materials as implant-supported single crowns with respect to the abutment design (crown thickness: 1 mm, 2mm and 3 mm). Methods: Forty-eight aboutments and crowns were fabricated on implants right lower first molar simulating. Two resin-matrix ceramics materials for dental crowns were selected for study, (1)glass-ceramic in a resin interpenetrating matrix (Vita Enamic, Vita, Germany) and (2) resin-based composite with nanoparticle ceramic filler (Lava Ultimate, 3M ESPE, USA). The abutment is designed into the following three types: 1 mm thickness crown + custom titanium abutment, 2 mm thickness crown + custom titanium abutment and 3 mm crown + prefabricated titanium abutment. The experiment was divided into 6 groups (n=8) according to the crown materials and the abutment designs. After 10,000 thermocycling, fracture resistance was measured using a universal testing machine. The statistical differences in various groups were analyzed with ANOVA test followed by a post hoc Tukey’s honestly significant difference test. The surface of the fractured specimen was examined with the scanning electron microscopy (SEM). Results: 2-way ANOVA revealed that the factor of the abutment designs (F=28.44，P=1.52x10-8<0.001) and the crown materials (F=4.37，P=0.043<0.05) had a significant effect on the fracture resistance of implant crown restoration. The Lava Ultimate-2 mm group showed the highest fracture resistance of 2222.74±320.36 N, and the Vita Enamic-3 mm group showed the lowest fracture resistance of 1204.96±130.50 N. Most of the 1 mm and 2 mm groups had partial crown fracture that could be repaired directly with resin, while the 3 mm group had longitudinal fracture of the crown, and the crown was detached from the abutment. Conclusion: Based on the in vitro data of this study, the fracture resistance of the 2 mm thick resin-matrix ceramics crown design is higher than that of the 1 mm and 3 mm groups. The 2 mm thick resin-matrix ceramics crown and personalized abutment are an option to replace zirconia as an implant crown restoration.