서로 다른 연마 기구가 치과용 지르코니아 물성에 미치는 영향

Abstract

Purpose: Grinding and trimming with less stress on zirconia through proper selection of methods and instruments can lead to a long-term success of prosthesis. The purpose of this study is to compare and evaluate the prismal phase change and physical properties after zirconia surface grinding with 3 different grinding instruments.

Methods: Fourty specimens of Yttrium oxide-stabilized zirconium oxide(Prettau, Zirkonzahn, Italy) of a disc shape were fabricated. They had 14mm in diameter and 1.4mm in thickness. Each of these specimens was divided into 4 groups(n=10). Supremax ceramic stone(NTI, Kahla, Germany) was used in group A, Dura-dia Green stone(Shofu Inc, Kyoto, Japan) in group B, Dura green stone(Shofu Inc, Kyoto, Japan) in group C. The remaning 10 specimens were not grinded and used as a control group. XRD analysis, surface roughness test, FE-SEM imaging, and biaxial flexural strength test were performed.

Results: In the result of XRD analysis, an phase change occurred in all experimental groups compared to that in the control group. Group A and B showed statistically significant increasing pattern of phase changes, followed by group C and the control group. In surface roughness test and FE-SEM images, group A and B had more increase in roughness compared to group C and the control group. In the biaxial flexural strength test, all experimental groups showed lower average strength than control group. Especially, group C showed statistically significant decrease in strength compared to other groups.

Conclusions: After grinding of TZP, the amount of phase change from tetragonal to monoclinic and roughness increased in Group A and B compared to those in Group C and the control group. Results of the flexural strength test in all specimens were over 500MPa, and those were clinically acceptable. However, flexural strength of group C was lower than those of other groups. The adjustment amount needs to be minimized by exact occlusal bite taking and prosthodontics fabrication because surface grinding such as occlusal adjustment may decrease the strength and reliability of prosthodontics.

Keyworlds: 3Y-TZP, Phase transformation, XRD, Roughness, Biaxial flexural strength