Hybridization effectiveness of a two-step versus a three-step smear layer removing adhesive system examined correlatively by TEM and AFM.
OBJECTIVE
The objectives of this study were (1) to compare the hybridization effectiveness of two adhesive systems that are applied in respectively three and two steps, and (2) to determine the best resin-dentin interface preparation technique for atomic force microscopy (AFM).


METHODS
The resin-dentin interface produced by the three-step OptiBond Dual-Cure (Kerr) and its simplified two-step successor OptiBond Solo (Kerr) was ultramorphologically examined using transmission electron microscopy (TEM) and AFM. Four different methods were used to prepare interface specimens for AFM: (1) polishing to a 0.1-micron finish with a silicon oxide suspension, (2) polishing to a 0.05-micron finish with an aluminum oxide suspension, (3) argon-ion etching, and (4) sectioning with a diamond knife.


RESULTS
Both TEM and AFM demonstrated that some collapse of the exposed collagen fibril network, due to gentle postconditioning air-drying of the dentin surface, may not have been totally recovered through hybridization by the two-step adhesive formulation as opposed to the three-step precursor. From the four interface preparation methods, only diamond-knife sectioning revealed sufficient ultramorphologic detail and high resolution that can capitalize on the high resolution offered by AFM.


CONCLUSIONS
First, the findings suggest that simplifying the application procedure of adhesives by combining the primer and adhesive resin into a single application step may reduce hybridization effectiveness. Future research should confirm this effect for other two- versus three-step adhesive systems. Second, diamond-knife sectioning should be used for future topographic imaging and physicomechanical testing of resin-dentin interfaces by AFM.
Van Meerbeek
B
B
BIOMAT-Department of Operative Dentistry and Dental Materials, School of Dentistry, Oral Pathology and Maxillo-Facial Surgery, Catholic University of Leuven, Kapucijnenvoer 7, B-3000, Leuven, Belgium. Bart.vanmeerbeek@MED.KULEUVEN.AC.BE
Yoshida
Y
Y
Snauwaert
J
J
Hellemans
L
L
Lambrechts
P
P
Vanherle
G
G
Wakasa
K
K
Pashley
D H
DH
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003094:Collagen / Q000648:ultrastructure; D001840:Dental Bonding / Q000379:methods*; D003775:Dental Polishing / Q000379:methods; D003804:Dentin / Q000648:ultrastructure; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D008867:Microtomy / Q000295:instrumentation; D019279:Resin Cements / Q000737:chemistry*; D016369:Smear Layer; D013499:Surface Properties; D019246:Tooth Preparation / Q000379:methods
D017220:Dentin-Bonding Agents; D008689:Methacrylates; C428805:OptiBond SOLO; C088316:Optibond Dual Cure; D019279:Resin Cements; D017438:Bisphenol A-Glycidyl Methacrylate; D003094:Collagen