Resin adhesion to carious dentin.
OBJECTIVE
To investigate the microtensile bond strength (microTBS) of a self-etching priming adhesive system to normal, caries-affected and caries-infected dentin, and to observe the ultrastructure of the resin-dentin interface by transmission electron microscopy (TEM).


METHODS
Twelve extracted human molar teeth with deep occlusal caries were stained with caries detector solution and ground flat occlusally. The red-stained soft dentin was classified as caries-infected. The surrounding discolored dentin was classified as caries-affected dentin. The surrounding normal dentin served as a control. The entire flat surface was bonded with Clearfil Liner Bond 2V (CV) and covered with resin composite to form a composite crown 5 mm high. One day later the specimens were serially sectioned vertically into multiple slabs 0.8 mm thick. Under microscopic observation, the specimens were divided into normal or caries-infected or caries-affected dentin. These regions were isolated by cutting away the remaining dentin to form hour-glass shapes with the smallest surface area at the test site. After measuring the areas, the specimens were fixed to a microtensile tester and pulled under tension to failure. Additional slabs that were not used for bond strength tests were processed for TEM. Bond strength data were analyzed by Kruskal-Wallis one-way ANOVA and Student-Newman-Keuls multiple comparisons.


RESULTS
The microTBS of CV to normal, caries-affected and caries-infected dentin were 45 +/- 10 MPa, 30 +/- 10 MPa, 10 +/- 5 MPa, respectively. TEM images showed that CV formed thin hybrid layers that were less than 1 microm thick in normal dentin, but that were between 6-8 microm thick in caries-affected dentin. Bacteria were only sparsely observed in the dentin tubules of bonded caries-affected dentin. However, in caries-infected dentin, an unusual interface was seen in which carious bacteria within disorganized non-banded collagen fibrils could be seen embedded by the adhesive. The hybrid layer in caries-infected dentin was found to be 30-60 microm thick.
Department of Operative Dentistry, Okayama University School of Dentistry, Japan.
Masahiro
M
Yoshiyama
Franklin R
FR
Tay
Yasuhiro
Y
Torii
Yoshihiro
Y
Nishitani
Junichi
J
Doi
Kousuke
K
Itou
Bernard
B
Ciucchi
David H
DH
Pashley
D000134:Acid Etching, Dental / Q000379:methods; D001840:Dental Bonding; D003731:Dental Caries / Q000473:pathology / Q000517:prevention & control*; D003737:Dental Cavity Preparation / Q000379:methods*; D018772:Dental Marginal Adaptation; D003799:Dental Stress Analysis; D003804:Dentin / Q000473:pathology / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000627:therapeutic use*; D006801:Humans; D066298:In Vitro Techniques; D008689:Methacrylates / Q000627:therapeutic use*; D008854:Microscopy, Electron
C112274:Clearfil Liner Bond 2; D017220:Dentin-Bonding Agents; D008689:Methacrylates