Clinical performance of monolithic polymer-infiltrated ceramic and lithium disilicate posterior crowns: A controlled, randomized, and double-blind clinical trial.

STATEMENT OF PROBLEM: The success rate of monolithic polymer-infiltrated ceramic posterior crowns after 1 year is unclear. PURPOSE: The purpose of this controlled, randomized, and double-blind clinical trial was to evaluate the performance of posterior complete crowns in polymer-infiltrated and lithium disilicate ceramics and to assess the impact of oral rehabilitation on esthetic satisfaction, quality of life, and periodontal health. MATERIAL AND METHODS: A total of 33 crowns were provided in 18 participants allocated to 2 groups: Control (Lithium disilicate-IPS e.max CAD; Ivoclar AG) and Experimental (Polymer-infiltrated ceramic-Vita Enamic; Vita Zahnfabrik). The crowns were evaluated before treatment (T0) and after 1 (T1), 6 (T2), and 12 (T3) months by using modified United States Public Health Service (USPHS) criteria, visual analog scales (VASs), oral impacts on daily performances (OIDP), and periodontal parameters. Survival analysis was performed by using Kaplan-Meier followed by the log-rank test (α=.05). The OIDP and USPHS data were analyzed descriptively while VASs for esthetic satisfaction and periodontal parameters were statistically evaluated by using the Mann-Whitney Friedman, and Wilcoxon post hoc tests. RESULTS: For 18 participants with a mean age of 47.2 years, 19 crowns were manufactured in lithium disilicate and 14 in polymer-infiltrated ceramic. The Kaplan-Meier test revealed similar survival rates of 92.5% for polymer-infiltrated ceramic and 94.7% for lithium disilicate (P>.05). The analysis of periodontal parameters revealed a significant increase in the bleeding on probing (BOP) for polymer-infiltrated ceramics (P=.032) but for lithium disilicate, it was not significant (P=.387). CONCLUSIONS: Survival rates between the evaluated materials were not significantly different, with acceptable clinical performance after 1 year of follow-up.

Influence of restoration thickness on the stress distribution of ultrathin ceramic onlay rehabilitating canine guidance: a 3D-finite element analysis.

BACKGROUND: The rehabilitation of canine guidance can be performed with adhesive indirect materials, but can the restoration thickness be reduced without mechanical disadvantages? Thus the goal of this study was to analyze the stress of upper canines which received different thicknesses of ceramic fragments for the rehabilitation of the canine guidance using finite element analysis. METHODS: A superior canine was modeled using a computer aided design software. The dental tissues were individually shaped containing enamel, dentin and periodontal ligament. The following three different ceramic fragment thicknesses were then implemented: 0.3, 0.7 and 1.5 mm. Lithium disilicate was chosen as the ceramic material. The solid geometries were exported to the analysis software. The materials were considered isotropic, homogeneous and linear. The set was submitted to efforts in the incisal third in the palatine face to analyze maximal principal stress, mimicking mandibular lateral movement. The applied load was 100N, and the fixation region was on the medullary bone. RESULTS: For restoration, the thinner the ceramic, the higher the stress concentration was; while for the adhesive surface of teeth, the thicker the ceramic, the higher the stress concentration. CONCLUSIONS: The smaller the ceramic thickness was, the lower stress concentration showed at the adhesive interface, while the stress concentration was higher on the restoration intaglio surface.