Marginal Adaptation, Fracture Resistance and Failure Patterns of Two CAD/CAM Overlays

Statement of problem Coronal rehabilitation of endodontically treated posterior teeth is still a controversial issue. Purpose: The purpose of this study was to investigate marginal adaptation, fracture resistance and failure patterns of two CAD / CAM overlays compared to direct fiber post reinforced composite (FPR composite). Materials and methods: Fifty maxillary premolars received endodontic treatment and cavity prepared for overlay were used and randomly distributed into 5groups and restored as following: Zirconia overlay (Katana Zirconia HT), Resin Nano Ceramic overlay (Lava Ultimate) , Glass fiber post and composite (Filtek Z250), Direct composite resin (Filtek Z250). While unrestored specimens served as a negative control. Vertical marginal gap was examined under the stereomicroscope. Fracture resistance test was carried out using a universal testing machine, and presence of micro-cracks was detected using a stereomicroscope. The fracture mode of the specimen was identified using scanning electron microscopy: (n=10, α=0.05). Results: Statistical analysis of marginal gaps revealed significant statistical differences as CAD/CAM overlays had higher vertical marginal gap, Katana zirconia (118±39.9), Lava ultimate (107.4±28.9), compared to FPR composite (73.5±21.14) and direct composite (66.6±31) (F=13.1, p =0.022).There was a statistically significant difference (F= 42.9, p<0.001) between fracture resistance of Katana zirconia overlays and all comparing groups, and Katana zirconia overlays did not showed any fracture. Conclusion: CAD/CAM overlays (zirconia and lava ultimate) showed a significantly higher marginal discrepancy than FPR composite and direct composite resin. Fracture resistance of Zirconium overlays was significantly higher than Resin Nano Ceramic and FPR composite which used for restoration of endodontic treated teeth. Clinical Implications: Zirconium overlays, Resin Nano Ceramic overlay are conservative treatment option that could be used to restore damaged endodontic treated teeth in comparison to the full crown restoration.