Effect of drying methods on hybrid layer thickness.

PURPOSE: To evaluate the effect of drying methods used in scanning electron microscopy on the thickness of the hybrid layers created by several different adhesive systems. METHODS: A total etch dry bonding system, (Photobond), a three-step bonding adhesive system, (Scotchbond Multi-Purpose), a wet-bonding adhesive system (All-Bond 2) and a self-etching primer system (Mac Bond II) were used in this study. To permit measurement of the thickness of the hybrid layer, the resin-dentin interfaces were polished and etched briefly to remove polishing debris followed by immersion in 10% NaOCl for 4 hours. Half of the specimens in each group were subjected to fixation and critical-point drying followed by gold sputter-coating. The remaining specimens were allowed to air dry prior to gold sputter-coating. SEM observations were carried out to determine the structure and thickness of the hybrid layers. RESULTS: The thickness of hybrid layers were affected by the drying methods with the critical-point drying methods producing the thickest hybrid layers (P < 0.05). The thickest hybrid layers were created by Photobond, with Scotchbond Multi-Purpose and All-Bond 2 producing intermediate thickness hybrid layers, among the total etch systems. The thinnest hybrid layer among all of the adhesive systems was produced by the self-etching primer, Mac Bond II.

Effect of EDTA conditioning on bond strength to bovine dentin promoted by four current adhesives.

PURPOSE: To investigate the effect of disodium dihydrogen ethylenediamine tetraacetate dihydrate (EDTA) conditioning prior to the application of adhesive systems on the bond strength of resin composite to dentin. METHODS: 80 bovine teeth were ground with 600-grit SiC paper to obtain flat dentin surfaces. Half of the specimens were conditioned with 0.5 mol EDTA aqueous solution (pH 7.4) for 60 seconds, water-rinsed and air-dried, and the other half were used without any treatment. The specimens were randomly divided in four groups of 10 each. The dentin surfaces were treated with each of two "all-in-one" adhesive systems (One-up Bond F, OB; Reactmer Bond, RB), a self-etching priming system (Clearfil SE Bond, SE), and a total-etch one-bottle bonding system (Single Bond, SB). For SB, the adhesive was applied on EDTA-conditioned dentin without H3PO4 etching. Then a layer of resin composite was placed and light-cured for 40 seconds. The tensile bond strength was measured and the resin-dentin interface was observed using a scanning electron microscope. RESULTS: The mean and standard deviation of tensile bond strength in MPa to ground dentin were 9.3+/-3.5/OB, 11.6+/-2.0/RB, 23.2+/-4.9/SE and 19.7+/-4.1/SB. Bond strengths to EDTA-conditioned dentin were 15.0+/-3.0/OB, 16.8+/-3.6/RB, 22.8+/-5.2/SE and 19.4+/-5.1/SB. Duncan's Multiple Range test revealed that the EDTA-conditioned dentin showed significantly higher tensile bond strength than the non-conditioned one for "all-in-one" adhesive systems (P < 0.05) but no significant difference was found for the self-etching priming and total-etch one-bottle bonding systems. At the resin-dentin interface, EDTA-conditioned specimens formed thicker hybrid layers than non-conditioned ones for all systems except for SB.