title: Effect of light source direction and restoration thickness on tensile strength of a dual-curable resin cement to copy-milled ceramic.
abstract: OBJECTIVE
  To evaluate the effects of exposure duration and source direction on bond strength of a dual-curable resin cement to copy-milled ceramic
  
  
  METHODS
  Ceramic blocks (Vita Celay Blanks) were cut into 1 mm, 2 mm and 3 mm thick slices. Following silanization (Tokuso Ceramic Primer), the slices were bonded using dual-cure resin cement (Bistite II) and subjected to one of four photo-curing strategies: no light-cure (control), 20 seconds light-cure from one direction, 120 seconds from one direction, and 20 seconds from each of six directions. After 24-hour water storage at 37 degrees C, the microtensile bond strengths and resin cement Knoop Hardness of the bonded specimens were determined. The data were analyzed using two-way ANOVA and Fisher's PLSD test at a confidence level of 95%. Specimen failure modes were determined using a laser-scanning confocal microscope.
  
  
  RESULTS
  The KHN of the control group was significantly lower than those of the light-cured groups (P < 0.05). There were no significant differences in bond strength and microhardness when the 1 and 2 mm thick ceramic slices were light-cured for either 120 seconds from one direction, or for 20 seconds from six directions (P > 0.05). However, when ceramic thickness increased from 2 to 3 mm, significant reduction in bond strength occurred when light-cure was applied for 120 seconds from one direction, but not when applied for 20 seconds each from six directions (P < 0.05).
authors.affiliation: Fixed Prosthodontics, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. r.foxton.fpro@tmd.ac.jp
authors.forename: Richard M
authors.initials: RM
authors.lastname: Foxton
authors.forename: Patricia N R
authors.initials: PN
authors.lastname: Pereira
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakajima
authors.forename: Junji
authors.initials: J
authors.lastname: Tagami
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Miura
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000528:radiation effects; D001840:Dental Bonding / Q000379:methods*; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D006244:Hardness; D008027:Light; D008422:Materials Testing; D018613:Microscopy, Confocal; D019279:Resin Cements / Q000528:radiation effects*; D013674:Technology, Dental / Q000379:methods*; D013718:Tensile Strength
chemical_list: C096475:Bistite Resin Cement; D003188:Composite Resins; D019279:Resin Cements; D003776:Dental Porcelain