The effect of core design on the fracture resistance of zirconia-lithium disilicate (LS2) bilayeredcrowns for anterior teeth is evaluated by comparing with that of metal-ceramic crowns. MATERIALS ANDMETHODS. Forty customized titanium abutments for maxillary central incisor were prepared. Each group of 10units was constructed using the same veneer form of designs A and B, which covered labial surface toapproximately one third of the incisal and cervical palatal surface, respectively. LS2 pressed-on-zirconia (POZ)and porcelain-fused-to-metal (PFM) crowns were divided into “POZ_A,” “POZ_B,” “PFM_A,” and “PFM_B”groups, and 6000 thermal cycles (5/55 °C) were performed after 24 h storage in distilled water at 37 °C. Allspecimens were prepared using a single type of self-adhesive resin cement. The fracture resistance was measuredusing a universal testing machine. Failure mode and elemental analyses of the bonding interface were performed.The data were analyzed using Welch’s t-test and the Games-Howell exact test. RESULTS. The PFM_B (1376. 8 ±93.3 N) group demonstrated significantly higher fracture strength than the PFM_A (915.8 ± 206.3 N) and POZ_B(963.8 ± 316.2 N) groups (P.05). There was no statistically significant difference in fracture resistance betweenthe POZ_A (1184.4 ± 319.6 N) and POZ_B groups (P.05). Regardless of the design differences of the zirconiacores, fractures involving cores occurred in all specimens of the POZ groups. CONCLUSION. The bilayeredanterior POZ crowns showed different fracture resistance and fracture pattern according to the core designcompared to PFM.
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