KMID : 1023820180100020079
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The Journal of Advanced Prosthodontics 2018 Volume.10 No. 2 p.79 ~ p.84
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In-vitro performance and fracture strength of thin monolithic zirconia crowns
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Weigl Paul
Sander Anna Wu Yanyun Felber Roland Lauer Hans-Christoph Rosentritt Martin
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Abstract
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PURPOSE: All-ceramic restorations required extensive tooth preparation. The purpose of this in vitro study was to investigate a minimally invasive preparation and thickness of monolithic zirconia crowns, which would provide sufficient mechanical endurance and strength.
MATERIALS AND METHODS: Crowns with thickness of 0.2 mm (group 0.2, n=32) or of 0.5 mm (group 0.5, n=32) were milled from zirconia and fixed with resin-based adhesives (groups 0.2A, 0.5A) or zinc phosphate cements (groups 0.2C, 0.5C). Half of the samples in each subgroup (n=8) underwent thermal cycling and mechanical loading (TCML)(TC: 5¡É and 55¡É, 2¡¿3,000 cycles, 2 min/cycle; ML: 50 N, 1.2¡¿106 cycles), while the other samples were stored in water (37¡É/24 h). Survival rates were compared (Kaplan-Maier). The specimens surviving TCML were loaded to fracture and the maximal fracture force was determined (ANOVA; Bonferroni; ¥á=.05). The fracture mode was analyzed.
RESULTS: In both 0.5 groups, all crowns survived TCML, and the comparison of fracture strength among crowns with and without TCML showed no significant difference (P=.628). Four crowns in group 0.2A and all of the crowns in group 0.2C failed during TCML. The fracture strength after 24 hours of the cemented 0.2 mm-thick crowns was significantly lower than that of adhesive bonded crowns. All cemented crowns provided fracture in the crown, while about 80% of the adhesively bonded crowns fractured through crown and die.
CONCLUSION: 0.5 mm thick monolithic crowns possessed sufficient strength to endure physiologic performance, regardless of the type of cementation. Fracture strength of the 0.2 mm cemented crowns was too low for clinical application.
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KEYWORD
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Zirconia, Minimal invasive, Monolithic crown, Cementation, Ceramic
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