2020 Volume 54 Issue 2 Pages 245-249
We compared the fracture strength of telescopic Ce-TZP/A secondary crowns of different taper and thickness. Both primary and secondary crowns were made of Ce-TZP/A. The half taper angles of the primary crowns were 2° and 4°. The thicknesses of the secondary crowns were 0.5 and 1.0 mm. After the secondary crowns were placed on the primary crowns, a load was applied with a stainless steel ball of 10 mm diameter on the occlusal surface of the secondary crowns to measure the force required to break the secondary crowns. We performed a two-way analysis of variance with the taper angle and secondary crown thickness as the factors. We found that only the secondary crown thickness was a significant factor in resisting the load (p<0.01). The mean fracture strength was 524 N for the secondary crowns with a thickness of 0.5 and 1,814 N for those with a thickness of 1.0 mm. This finding implies that while secondary crowns with a thickness of 1.0 mm can provide adequate resistance clinically, those with a thickness of less than 0.5 mm have a risk of breaking because of insufficient strength. We found that a minimum thickness of 0.6 mm was required for Ce-TZP/A secondary crowns to resist the maximum occlusal force. (J Osaka Dent Univ 2020; 54: 245-249)
