The effects of surface grinding and polishing on the phase transformation and flexural strength of zirconia
이지영, 장근원, 박인임, 허유리, 손미경,
소속 상세정보
이지영 ( Lee Ji-Young ) - Chosun University School of Dentistry Department of Prosthodontics
장근원 ( Jang Geun-Won ) - Chosun University School of Dentistry Department of Prosthodontics
박인임 ( Park In-Im ) - Good Face Dental Clinic
허유리 ( Heo Yu-Ri ) - Chosun University School of Dentistry Department of Prosthodontics
손미경 ( Son Mee-Kyung ) - Chosun University School of Dentistry Department of Prosthodontics
Abstract
PURPOSE: The purpose of this in vitro study was to evaluate the effect of surface grinding and polishing procedures using high speed zirconia diamond burs with different grit sizes on the phase transformation and flexural strength of zirconia.
MATERIALS AND METHODS: Forty disc shape specimens (15 × 1.25 mm) with a cylindrical projection in the center of each disc (1 × 3 mm) were fabricated with 3Y-TZP (Prettau, Zirkonzahn, Italy). The specimens were divided into 4 groups (n=10) according to the grinding and polishing procedures: Control group - grinding (coarse-grit diamond bur), Group 1 - grinding (coarse-grit diamond bur) + polishing, Group 2 - grinding (fine-grit diamond bur) + polishing, and Group 3 - grinding (fine grit diamond bur). Each specimen was analyzed by 3D-OM, XRD analysis, and biaxial flexural strength test.
RESULTS: Based on the surface morphology by 3D-OM images, polished specimens showed smoother surface and lower roughness value (Ra). In the result of XRD analysis, partial phase transformation from tetragonal to monoclinic zirconia occurred in all groups. Control group, ground with a coarse grit diamond bur, showed more t→m phase transformation and lower flexural strength than Groups 1 and 2 significantly.
CONCLUSION: The flexural strength in all specimens after grinding and polishing showed over 500 MPa, and those were clinically acceptable. However, grinding with a coarse grit diamond bur without polishing induced the phase transformation and low strength. Therefore, surface polishing is required for the occlusal adjustment using a high speed zirconia diamond bur to reduce the phase transformation and to prevent the decrease of flexural strength of zirconia.
키워드
3Y-TZP; Phase transformation; XRD; Roughness; Biaxial flexural strength
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