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Abstract
Purpose
The purpose of this study was to compare the fracture strength of the zirconia ceramic crowns according to tooth position.
Material and methods
After 10 metal dies were made for each group, the zirconia ceramic crowns were fabricated using CAD/CAM system (LavaTM All-Ceramic System) and each crown was cemented on each metal die with resin cement (Rely XTM Unicem). The cemented zirconia ceramic crowns mounted on the testing jig were inclined with 30 degrees to the long axis of the tooth and the universal testing machine was used to measure the fracture strength.
Results
1. The fracture strength of the zirconia ceramic crown in the lower 1st molar (2963 N) had the highest and that in the lower central incisor (1035 N) had the lowest. 2. The fracture strength of zirconia ceramic crown was higher than that of the IPS Empress crowns in all tooth position. 3. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the long axis of the crowns. 4. There were no significant differences on the fracture strength of the zirconia ceramic crowns according to tooth position except in premolar group.
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Fig. 1.
Metal dies were fabricated on upper central incisor (A) and lower 1st molar (B) with 8 degree axial inclination and 2.0 mm incisal reduction and 1.5 mm occlusal reduction.
Fig. 3.
Cemented upper zirconia ceramic crowns on the metal die for fracture test (A, central incisor; B, canine; C, 1st premolar; D, 1st molar).
Fig. 4.
Cemented lower zirconia ceramic crowns on the metal die for fracture test (A, central incisor; B, canine; C, 2nd premolar; D, 1st molar).
Table I.
Fracture strength of zirconia crowns on upper teeth (unit: Newton)
| Maximum | Minimum | Mean | SD | |
|---|---|---|---|---|
| Central incisor | 1525 | 955 | 1110 | 172 |
| Canine | 1881 | 972 | 1343 | 355 |
| 1st premolar | 1505 | 903 | 1101 | 194 |
| 1st molar | 3378 | 2059 | 2820 | 489 |
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