Fracture Forces of Various CAD/CAM Manufactured Ceramic Anterior Three-Unit Bridges

Objectives: This study evaluated the fracture forces of anterior three-unit bridges made from various ceramic CAD/CAM materials. Materials and Methods: The investigated materials were Ivoclar Vivadent® IPS e.max® CAD (EM), 3M™ Lava™ Esthetic Fluorescent Full-Contour Zirconia Disc (LE) and 3M Lava Plus High Translucency Zirconia Disc shaded with Lava Plus Dyeing Liquid (LP). Wall thickness of the crowns were 1.2mm (EM), 0.8mm (LE), or 0.5mm (LP) with connector cross-sectional areas of 16mm2 (EM), 12mm2 (LE), or 7mm2 (LP). EM (n=14) bridges were ground using Sirona CEREC® inLab® MC XL. LE and LP bridges were milled on Sirona inLab®MC X5. Force was applied to the bridge pontic using an Instron 5566® universal testing machine to determine fracture force. 2-sample-t-tests (p<0.05) were performed for all groups. Results: Mean fracture force was significantly higher for LE (1789N) and LP (1745N) as compared to EM (1458N). There was no statistically significant difference of mean fracture forces between LE and LP. Zirconia bridges made from LE and LP with thinner wall thicknesses and lower cross-sectional connector areas compared to EM showed higher fracture forces. Conclusion: Within the confines of this study, zirconia bridges offer higher mechanical properties and therefore allow more tissue preserving tooth preparation. Clinical Relevance: The clinical relevance of using novel zirconia ceramic materials is tissue preserving tooth preparation and the materials' performance with its minimum design requirements in regard to fracture forces of bridges.