Title: 0708 - In-vitro-performance and Fracture Resistance of CAD/CAM-crowns After Long-term-storage and TCML
Martin Rosentritt (Presenter)
University of Regensburg
Verena Preis, University of Regensburg
Sibylle Schneider-Feyrer, University of Regensburg
Michael Behr, University of Regensburg
Objectives: CAD/CAM crowns may show different in-vitro performance and fracture stability during long-term water storage and thermal cycling and mechanical loading.
Methods: Extracted human molars were prepared with a worst-case design with limited retention (height ~4mm, angle ~15°, reduced fit 250µm). Teeth were positioned in resin blocks (Palapress Vario, Kulzer, D) and resilience of the human periodontium was simulated by coating the roots of the teeth with polyether (Impregum, 3M, D). Prepared teeth were digitalized (Cerec Omnicam, Sirona, D) and full-contour molar crowns were milled (Cerec, MCXL, Sirona, D). 8 molar crowns per group were milled of three different resin-based composites (Lava Ultimate, 3M, USA; Cerasmart, GC, J; experimental, Kulzer, D), one ceramic (Vita Mark II, Vita, D) and one resin-infiltrated ceramic (Enamic, Vita, D). Inner sides of the crowns were treated as recommended by the manufacturers. Adhesive bonding was performed with RelyX Ultimate, Scotchbond Universal, selective etching; polymerisation: Elipar Trilight, 5x40s (all 3M, USA). After 90 days (water, 37°C) storage thermo-cycling and mechanical loading (TC: 2x6000 cycles 5°C/55°C, dist. water, ML: 50N for 2.4x106 cycles; 1.6Hz) was performed. Crowns which failed during storage or TCML were investigated (scanning electron microscopy SEM Quanta, Phillips). Surviving restorations were loaded to fracture (1446, Zwick, v= 1mm/min). Statistics: ANOVA; Bonferroni post-hoc test; α=0.05.
Results: After TCML all crowns showed typical occlusal wear traces. After debonding, cement remained on the inner sides of the crowns.
Conclusions: CAD/CAM materials provided different in-vitro performance and fracture stability. Only one composite showed good performance during 90d and TCML. Deficient preparation and fitting may be a risk for debonding of composite crowns.
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The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: This study was supported by Kulzer.