J Korean Acad Prosthodont.  2013 Jul;51(3):160-166. 10.4047/jkap.2013.51.3.160.

Comparative study of fracture strength depending on the occlusal thickness of full zirconia crown

Affiliations
  • 1Major in Dentistry, Department of Medical Science, Hanyang University Graduate School, Seoul, Korea. leeys@hanyang.ac.kr

Abstract

PURPOSE
The purpose of this study was to compare the fracture strength of traditional metal-ceramic crowns and full zirconia crowns according to the occlusal thickness.
MATERIALS AND METHODS
A mandibular first molar resin tooth was prepared with 1.5 mm occlusal reduction, 1.0 mm rounded shoulder margin and 6degrees taperness in the axial wall. Duplicating the resin tooth, 64 metal dies were fabricated. 48 full zirconia crowns were fabricated using Prettau zirconia blanks by ZIRKONZAHN CAD/CAM and classified into six groups according to the occlusal thickness (0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm). 16 metal-ceramic crowns were fabricated and classified into two groups according to the occlusal porcelain thickness (1.0 mm, 1.5 mm). All crowns were cemented on each metal die and mounted in a universal testing machine. The load was directed at the functional cusp of each specimen until catastrophic failure occurred. One-way ANOVA, Tukey multiple comparison test (alpha=.05) and t-test (alpha=.05) were used.
RESULTS
The results were as follows. 1. The test 1 group (646.48 N) showed the lowest fracture strength (P<.05), and the value of the test 2.3.4.5 groups (866.40 N, 978.82 N, 1196.82 N, 1222.41 N) increased as thickness increased, but no significant difference were found with the groups (P>.05). The value of test 6 group (1781.24 N) was significantly higher than those of the other groups (P<.05). 2. There were no significant differences of the fracture strength of metal ceramic crowns according to occlusal porcelain thickness 1.0 mm (2515.71 N) and 1.5 mm (3473.31 N) (P<.05).
CONCLUSION
Full zirconia crown needs to be 1.0 mm or over in occlusal thickness for the posterior area to have higher fracture strength than maximum bite force.

Keyword

Full zirconia crown; Fracture strength

MeSH Terms

Bite Force
Ceramics
Collodion
Crowns
Dental Porcelain
Molar
Shoulder
Tooth
Zirconium
Ceramics
Collodion
Dental Porcelain
Zirconium
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