title: A Preliminary Research into Clinical Semi-permeability Tolerance in the Field of Dental Rehabilitation.
abstract: To study clinical semi-permeability tolerance level in the field of dental restoration.
  
  
  
  Vita 95 enamel porcelain powder was adopted and 6.0% used as the control transmissivity. Discoid porcelain plates with different transmissivity, namely increasing transmissivity (0.25%, 0.5%, 1.0%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% and 4.5%) and decreasing transmissivity (-0.25%, -0.5%, -1.0%, -1.5%, -2%, -2.5%, -3% and -3.5%) were made. Forty observers judged these according to six grades: same, similar, slightly different, visibly different, recognizable and significantly different, and under the observation conditions of a neutral grey background and 45°/0°lighting. The judgment results were analysed statistically.
  
  
  
  When the transmissivity of the control porcelain plates was 6.032%, and the transmissivity of test porcelain plates decreased by 1% or increased by 3%, observers could find slight differences between the test samples and the control samples. When transmissivity of test samples decreased by 2.5% or increased by 4.5%, observers thought that the two porcelain plates belonged to different orders of magnitude.
  
  
  
  Under the experimental conditions, the upper and lower limits of clinical semi-permeability tolerance were 3% and 1%, respectively.
authors.affiliation: Department of Maxillofacial Surgery, West China College of Stomatology, Sichuan University, Chengdu 610041, China.
authors.forename: H
authors.initials: H
authors.lastname: Xia
authors.affiliation: Department of Prosthodontics, West China College of Stomatology, Sichuan University, Chengdu 610041, China. E-mail: xofa@163.com.
authors.forename: F
authors.initials: F
authors.lastname: Xiong