Milling properties of low temperature sintered zirconia blocks for dental use.
To investigate the milling properties of different yttria-tetragonal zirconia polycrystalline (Y-TZP) block materials by applying a dental computer numerical control (CNC) milling center. Low temperature sintering zirconia block denoted by KMUZ (experimental) with two commercial zirconia blocks for T block made in Taiwan and a G block made in Germany were compared for the milling properties. Seventy-two specimens were milled using the same CNC milling center, and properties were evaluated by measuring the weight loss (g), milling time (s), margin integrity (%) and broken diameter (μm). The crystalline phases contents were identified by X-ray diffraction and the microstructures of the sintering specimens were observed by scanning electron microscopy and transmission electron microscopy. The mean milling time of G and KMUZ were significantly shorter than T (P<0.05). The KMUZ samples exhibited the least weight loss among the three kinds of blocks (P<0.05). The percentages of marginal integrity after milling were high in G and KMUZ but low in T (P<0.05). The mean broken diameters were from 90μm to 120μm. The phase transformation of t-ZrO2(KMUZ: 7.4%, G: 5.9%, T: 3.2%) to m-ZrO2when facing the milling pressure in ZrO2blocks was observed by XRD. The result of TEM microstructure of KMUZ revealed that Y and Si were soluble in grain boundaries. The results show that the milling properties of KMUZ were better than one commercial T and near the G. The hindered grain growth, as a result of the Y3+content in the grain boundaries, also plays a role in promoting the abnormal grain growth of 3Y-TZP.
Department of Prosthodontics, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan; School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80728, Taiwan.
Ting-Hsun
TH
Lan
Department of Prosthodontics, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan; School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80728, Taiwan.
Chau-Hsiang
CH
Wang
Department of Conservation, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan; School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80728, Taiwan.
Ker-Kong
KK
Chen
Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80728, Taiwan; Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, 80756, Taiwan. Electronic address: mcwang@kmu.edu.tw.
Moo-Chin
MC
Wang
Department of Prosthodontics, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan; School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80728, Taiwan. Electronic address: huerle@kmu.edu.tw.
Huey-Er
HE
Lee
D003080:Cold Temperature; D003460:Crystallization; D003813:Dentistry; D008422:Materials Testing / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D014961:X-Ray Diffraction; D015040:Zirconium / Q000737:chemistry*
D015040:Zirconium; C028541:zirconium oxide
CAD/CAM; CNC; Milling properties; Y-TZP