title: [Comparison of machinability of two types of dental machinable ceramic].
abstract: OBJECTIVE
  In terms of the problems of now available dental machinable ceramics, a new type of calcium-mica glass-ceramic, PMC-I ceramic, was developed, and its machinability was compared with that of Vita MKII quantitatively. Moreover, the relationship between the strength and the machinability of PMC-I ceramic was studied.
  
  
  METHODS
  Samples of PMC-I ceramic were divided into four groups according to their nucleation procedures. 600-seconds drilling tests were conducted with high-speed steel tools (Phi = 2.3 mm) to measure the drilling depths of Vita MKII ceramic and PMC-I ceramic, while constant drilling speed of 600 rpm and constant axial load of 39.2 N were used. And the 3-point bending strength of the four groups of PMC-I ceramic were recorded.
  
  
  RESULTS
  Drilling depth of Vita MKII was 0.71 mm, while the depths of the four groups of PMC-I ceramic were 0.88 mm, 1.40 mm, 0.40 mm and 0.90 mm, respectively. Group B of PMC-I ceramic showed the largest depth of 1.40 mm and was statistically different from other groups and Vita MKII. And the strength of the four groups of PMC-I ceramic were 137.7, 210.2, 118.0 and 106.0 MPa, respectively.
  
  
  CONCLUSIONS
  The machinability of the new developed dental machinable ceramic of PMC-I could meet the need of the clinic.
authors.affiliation: Department of Prosthodontics, Guanghua College of Stomatology, Sun Yat-sen University, Guangzhou 510060, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Fu
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.forename: Xinping
authors.initials: X
authors.lastname: Fan
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Lin
mesh_terms: D003776:Dental Porcelain / Q000592:standards*; D003799:Dental Stress Analysis; D006245:Hardness Tests; D013718:Tensile Strength
chemical_list: D003776:Dental Porcelain