Effect of light source direction and restoration thickness on tensile strength of a dual-curable resin cement to copy-milled ceramic.
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).
Foxton
Richard M
RM
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
Pereira
Patricia N R
PN
Nakajima
Masatoshi
M
Tagami
Junji
J
Miura
Hiroyuki
H
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
C096475:Bistite Resin Cement; D003188:Composite Resins; D019279:Resin Cements; D003776:Dental Porcelain