In vitro dentin pretreatment: Surface roughness and adhesive shear bond strength

The aim was to define the morphology and roughness of dentin from different tooth areas after various pretreatments to identify the effect of hybrid l ayer, resin tags, and mineralised dentin surface on shear bond strength. Th irty-eight extracted molars were used, each providing two sections of cervi cal (c) and lateral (1) dentin. Five pretreatments were performed: A) 0.2% EDTA; B) abrasion with Al2O3 particles, 0.2% EDTA; C) 10% H3PO4; D) 10% H3P O4 and immersion in a collagenase solution; E) control: no treatment. 2100 composite resin cylinders were bonded to the specimens with All Bond 2 bond ing resin and tested for shear bond strength. Twelve other specimens from e ach group were analysed with an optical profilometer and an atomic force mi croscope, and four were further examined by scanning electron microscopy (S EM). Mean shear strength values in MPa were: Ac: 8.36 +/- 4.23 Al: 8.77 +/- 3.68; Be: 6.05 +/- 3.62; B1: 8.39 14.60; Cc: 6.87 +/- 3.45; Cl: 9.00 +/- 5 .62; Dc: 13.30 +/- 5.45; D1: 8.44 +/- 4.47; Ec: 4.10 +/- 1.54; El: 6.09 +/- 4.34. No statistically significant difference for cervical versus lateral dentin was found within treatments except for group D. Treatments performed on lateral dentin did not differ significantly. In cervical dentin, A diff ered from E; C from E; and D from A, B, C and E. An increased surface rough ness was found in group D. Shear bond strength to dentin did not seem to de pend on a hybrid layer formation, but on the direct contact of the adhesive with the mineralised dentinal surface and partly on the orientation of the dentinal tubules.