PMID- 30411090 OWN - Quintessenz Verlags-GmbH CI - Copyright Quintessenz Verlags-GmbH OCI - Copyright Quintessenz Verlags-GmbH TA - Quintessence Int JT - Quintessence International IS - 1936-7163 (Electronic) IP - 1 VI - 50 PST - ppublish DP - 2019 PG - 30-39 LA - en TI - Effect of framework design and firing cycle on the success rate of bilayered zirconia crowns LID - 10.3290/j.qi.a41333 [doi] FAU - Geminiani, Alessandro AU - Geminiani A FAU - Chochlidakis, Konstantinos AU - Chochlidakis K FAU - Hosney, Sherif AU - Hosney S FAU - Corsentino, Giacomo AU - Corsentino G FAU - Ercoli, Carlo AU - Ercoli C CN - OT - all-ceramic OT - cyclic loading OT - dental technology OT - failure analysis OT - firing cycle OT - metal-ceramic OT - porcelain OT - prosthodontics OT - zirconia AB - Objective: This study investigated the effect of framework design and modification of porcelain firing cycle on the occurrence of fractures of metal-ceramic and bilayered zirconia crowns after cyclic loading. Method and materials: Twenty-four zirconia crowns with two different apicocoronal incisal veneering porcelain lengths (ZS = 2.0 mm and ZL = 4.0 mm) were fabricated. Twenty-four metal-ceramic crowns with the same apicocoronal incisal veneering porcelain lengths (MS = 2.0 mm and ML = 4.0 mm) served as the control. All the specimens (n = 48) were thermally and mechanically cycle-loaded (49 N) for 1,200,000 cycles, and then evaluated for cracks and/or bulk fractures with an optical stereomicroscope (×10). In the second part of the study, the influence of firing cycle modification on the success rate of twenty-four bilayered zirconia crowns was also evaluated. Finally, two specimens from each group (n = 12) were sectioned and analyzed using a scanning electron microscope. Load-to-failure of the specimen that did not present bulk fracture was further assessed using a universal testing machine. Statistical analysis was performed with Fisher exact test and Kruskal-Wallis test. Results: A statistically significant lower occurrence of fractures (P < .05) was found after cyclic loading for bilayered zirconia versus metal-ceramic crowns. Modification of the firing cycle did not significantly influence the outcome after cyclic loading for zirconia bilayered crowns (P > .05). Conclusion: Within the limitations of this study, porcelain-firing cycle with an extended cooling time did not appear to influence the occurrence of cracks and fractures of bilayered zirconia crowns. AID - 841175