Co-influence of restoration bonding and inlay cavity design on fracture load of restored tooth

Abstract

The aim of this study was to investigate the co-influence of indirect mesio-occlusal-distal (MOD) cavity geometry and inlay restoration bonding on quasi-static fracture load of the restored tooth.

Forty-eight intact human molar teeth were selected and prepared for standardized edge-shaped or round-shaped MOD cavities. The inlays were milled from CAD/CAM resin composite blocks (Cerasmart, GC) and bonded with the state-of-the-art inlay bonding protocol or with intentionally deteriorated bonding using n-hexane-wax solution for preconditioning. Restored teeth were quasi-statically loaded along the long axis of the tooth using a steel ball. Ultimate fracture load was recorded, and the type of fracture was visually determined and classified. Statistical analysis of load values was performed by Kruskal-Wallis test.

Round-shaped cavity design with bonded restoration presented the highest fracture load (1658N). Bonding had significant influence on the fracture load of the round-shape cavity design tooth (p=0.0003), whereas cavity design had no influence when the bonding was deteriorated (p=0.8075). Fracture type analysis showed that in the case of deteriorated bonding, either the inlay or tooth fractured separately whereas in the bonded inlays fractures were commonly found both in the tooth and inlay.

According to this study, bonded inlay restoration increased fracture resistance of the restored tooth, which highlight the importance of bonding of the inlay restoration. The findings of this study suggest that bonding has more influence on the strength of restored tooth compared to cavity bottom geometry, which had no statistical influence.