Aggressiveness of contemporary self-etching systems. I: Depth of penetration beyond dentin smear layers.
OBJECTIVE
This study examined, with the use of transmission electron microscopy (TEM), the aggressiveness of three self-etching adhesive systems in penetrating dentin smear layers of different thickness.


METHODS
Dentin disks were produced from extracted human third molars. For the control group, the middle dentin surface was cryofractured to create a bonding surface that was devoid of a smear layer. The experimental teeth were polished with wet 600 or 60-grit SiC paper to produce bonding surfaces with thin and thick smear layers. They were bonded using one of the three self-etching systems: Clearfil Mega Bond (Kuraray), Non-Rinse Conditioner and Prime&Bond NT (Dentsply DeTrey) and Prompt L-Pop (ESPE). Bonded specimens were then demineralized and embedded in epoxy resin for TEM examination.


RESULTS
For Mega Bond, thin authentic hybrid layers between 0.4-0.5 microm were found. Smear layer and smear plugs were retained as part of the hybridized complex. For Non-Rinse Conditioner/Prime&Bond NT, the authentic hybrid layers were between 1.2-2.2 microm thick. Smear layer and smear plugs were completely dissolved in dentin with thin smear layers, but were partially retained as part of the hybridized complex in those with thick smear layers. For Prompt L-Pop, authentic hybrid layers were 2.5-5 microm thick and smear layer and smear plugs were completely dissolved even in dentin with thick smear layers.


CONCLUSIONS
Contemporary self-etching systems may be classified as mild, moderate and aggressive based on their ability to penetrate dentin smear layers and their depth of demineralization into the subsurface dentin. The more aggressive system completely solubilized the smear layer and smear plugs and formed hybrid layers with a thickness approaching those of phosphoric acid conditioned dentin.
Tay
F R
FR
Conservative Dentistry, Faculty of Dentistry, The University of Hong Kong, 34 Hospital Road, Hong Kong SAR, China.
Pashley
D H
DH
D000134:Acid Etching, Dental; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure*; D003808:Dentin Solubility; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D005614:Freeze Fracturing; D006801:Humans; D008854:Microscopy, Electron; D011109:Polymethacrylic Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D016369:Smear Layer; D013499:Surface Properties
C029849:Clearfil Bonding Agent; D017220:Dentin-Bonding Agents; D011109:Polymethacrylic Acids; C103500:Prime & Bond; C408584:Prompt L-Pop; D019279:Resin Cements; D017438:Bisphenol A-Glycidyl Methacrylate