Title: Fracture Forces of Various CAD/CAM Ceramic Anterior Three-unit Bridges
Sangita Murali (Presenter)
Tufts University School of Dental Medicine
Sunny Gaudet, Tufts University School of Dental Medicine
Gerard Kugel, Tufts University School of Dental Medicine
Objectives: To test the fracture forces of anterior three-unit bridges made from various ceramic CAD/CAM materials.
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) (Figure 1). EM (n=14) bridges were ground using Sirona CEREC® inLab® MC XL. LE (n=15) and LP (n=12) bridges were milled on Sirona inLab®MC X5. All restorations were heat-treated based on the manufacturers’ instructions using an Ivoclar Vivadent Programat® EP5000G2 furnace for crystallization (EM) or 3M Lava Furnace 200 for final sintering (LE, LP). All restorations were cemented on tooth shaped abutments made from a composite material to simulate dentin. 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) have been 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 (Figure 2).
Conclusions: Zirconia bridges made from LE and LP with thinner wall thicknesses and lower cross sectional connector areas compared to EM showed higher fracture forces. Within the confines of this study, zirconia bridges offer higher mechanical properties and therefore allow more tissue preserving tooth preparation.
Wall thickness of the crowns were 1.2mm (EM), 0.8mm (LE), or 0.5mm (LP) with connector cross-