Fracture Strength and Mode of Anterior Single-retained All-ceramic Resin-bonded Bridges Using a CAD/CAM System

Purpose: To examine the performance of CAD/CAM allceramic resin-bonded bridges (RBBs) fabricated from a glass ceramic material, and determine the influence of two different preparation designs on the fracture strength of these prostheses. Materials and Methods: Twenty human central incisors were used, placed into two groups. A clinical situation where a lateral incisor was missing was simulated. A minimal preparation design (palatal veneer preparation) and one that extended into the proximal area were applied in each group. The Cerec InEos and the Cerec 3D software were used to scan, design, and mill the restorations. A lithium disilicate glass ceramic material was used for the fabrication of the bridges (IPS e.max CAD). Twenty bridges were milled which were adhesively bonded on their abutments (Variolink II). A universal testing machine was used to evaluate the fracture strength and the mode of failure of the bridges. Results: The mean fracture strength for the minimal design group was 774 N (± 341) and for the extended preparation group 814 N (± 474). No statistically significant difference was found between the two designs (p > 0.05). The mode of failure was fracture at the connector area between the pontic and the retainer wing. Conclusion: The fracture strength of the RBBs fabricated with IPS e.max CAD was in a clinically acceptable range. The two preparation designs did not have a significant influence on the fracture strength of the RBBs. Parole chiave: resin bonded bridge, Cerec, lithium disilicate, fracture strength, kompositverklebte Brücke, Cerec, Lithiumdisilikat, Bruchfestigkeit