title: In vitro comparison of the radiopacity of cavity lining materials with human dental structures.
abstract: OBJECTIVE
  To compare the optical densities (OD) of calcium hydroxide (CH) and glass ionomer cement with the same thicknesses of the dental structures.
  
  
  METHODS
  Eighteen specimens of each material, with thicknesses of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm were made in a Teflon matrix. To compare the radiopacity of the materials with the dental structures, dental cuts of the first molars, increasing in thickness from 0.5 to 3.0 mm, were obtained. To standardize the radiographs, a transparent acrylic matrix (Standardizing Device) was developed and used. Thirty radiographs were taken, five for each tested material.
  
  
  RESULTS
  Statistical analysis (Two-way ANOVA - Bonferroni, P < 0.05) demonstrated that when the materials were compared, there was statistically significant difference between the ODs, only for the thickness of 1.0 mm (P < 0.05).
  
  
  CONCLUSIONS
  The thickness of the material contributed to its radiopacity, and these materials had to be used in a thickness between 1.5 and 2.0 mm.
authors.affiliation: Department of Dental Materials and Prosthodontics, Ribeirao Preto School of Dentistry, University of São Paulo, Ribeirao Preto, SP, Brazil.
authors.forename: Fernanda Cp
authors.initials: FC
authors.lastname: Pires de Souza
authors.forename: Luiz C
authors.initials: LC
authors.lastname: Pardini
authors.forename: Diogo R
authors.initials: DR
authors.lastname: Cruvinel
authors.forename: Hisham M
authors.initials: HM
authors.lastname: Hamida
authors.forename: Lucas Fr
authors.initials: LF
authors.lastname: Garcia