The influence of cervical collar height on the compressive strength of CAD/CAM zirconia-ceramic restora-tion / 实用口腔医学杂志

ABSTRACT

Objective:To evaluate the influence of cervical collar height on the compressive strength of CAD/CAMzirconia-ceramic restoration.Methods:Zirconia cores were manufactured and divided into 5 groups (n =1 0)based on the cervical collar height(mm)0.0(A),1 .0(B),1 .5(C),2.0(D)and 2.5(E).After veneered with porcelain,all the samples were cemented on the metal tooth analog and then mounted in an universal test machine.The force was applied at a crosshead speed of 1 mm/min until catastrophic fail-ure occurred.Fracture loads and failure modes were recorded.Results:Mean of the fracture strength values(kN)in group A,B,C, D and E were 0.95 ±0.39,1 .29 ±0.50,1 .54 ±0.28,2.04 ±0.1 9 and 2.27 ±0.53 respectively(among groups,P <0.05).Two types of fracture modes were observedchipping of the veneering porcelain and fracture of the veneering porcelain together with the framework.Conclusion:Zirconia coping design with 1 .5 mm cervical collar height may increase the compressive strength of CAD/CAMzirconia-ceramic restoration.