Comparison of fracture resistance for chairside cad/cam lithium disilicate crowns and overlays with different designs- An original research
European Journal of Molecular & Clinical Medicine,
2022, Volume 9, Issue 7, Pages 8764-8768
AbstractAim: The purpose of the research was to evaluate the fracture resistance of conventional full coverage crowns and two different designs of overlay restorations with margins located 2 and 4 mm above the gingival level.
Methodology: CAD/CAM lithium disilicate (IPS e.max CAD for CEREC/HT A1 C14, Ivoclar Vivadent) restorations (15 specimens/group) with 1.5 mm occlusal thickness and 1.0 mm chamfer were designed and fabricated with a chairside CAD/CAM system (CEREC, Dentsply Sirona). The restorations were prepared in three different designs: (1) full coverage crowns, (2) overlays with the margin located 2 mm above the gingiva, and (3) overlays with the margin located 4 mm above the gingiva. Restorations were cemented using conventional resin luting cement (Multilink, Ivoclar Vivadent) then finally loaded with a steel indenter until failure. Scanning electron microscopy observations of fractured surfaces were also conducted. Group results were analyzed with one-way analysis of variance, and the medians were evaluated independently with Kruskal-Wallis.
Results: The fracture force of CAD/CAM lithium disilicate restorations was significantly different (p < 0.001) depending on the design of the restoration. Full coverage crowns showed significantly higher force to fracture (1018.8 N) than both
types of overlays (p = 0.002 for overlay 2.0 mm and p < 0.001 for overlay 4.0 mm above gingiva).
Conclusion: Full coverage chairside CAD/CAM lithium disilicate premolar crown showed higher fracture resistance than overlay restorations
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