Purpose: To examine the fracture resistance and fracture modes of Prettau Highly Translucent Zirconia and Resin Nano Ceramic Lava Ultimate CAD/CAM endocrowns versus post and core supported CAD/CAM crowns in endodontically treated extremely damaged maxillary molars.
Methods: Twenty maxillary first molars of similar size and shape were selected. The teeth were all decoronated and endodontically treated, then they were randomly divided equally into four groups (5 each) as follows; Group I: Five teeth restored by post and core supported Prettau Highly Translucent Zirconia (PZ) crowns. Group II: Five teeth restored by PZ endocrowns. Group III: Five teeth restored by post and core supported Resin Nano Ceramic Lava Ultimate (LU) crowns. Group IV: Five teeth restored by LU endocrowns. All specimens were scanned, designed and milled using ZirkonZahn CAD/CAM 5 Tec machine. After cementation, all specimens were thermocycled, then they were subjected to fracture resistance test and fracture mode analysis. The data were collected, tabulated and statistically analyzed.
Results: Group I exhibited the highest fracture resistance followed by group IV then group III while group II exhibited the lowest fracture resistance. Groups I and II resulted in unfavorable unrestorable failures while Groups III and IV resulted in favorable restorable failures.
Conclusions: Endocrowns can be used as a conservative clinical alternative for restoring severely damaged endodontically treated posterior teeth. Resin composites seem to be the material of choice to build-up endocrown restorations.
Clinical Significance: Restoration of extremely damaged and endodontically treated teeth present a critical and time consuming clinical situation.
Key words: Translucent Zirconia, Resin Nano Ceramic, Endocrowns, CAD/CAM Technology.
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