Bonding to root canal: structural characteristics of the substrate.
OBJECTIVE
To evaluate in vitro the dentin morphology in root canals in terms of tubule orientation, density and increase in surface area after etching.


METHODS
Thirty anterior teeth were divided in 3 groups at random: the samples of Group 1 were used to study tubular morphology in SEM. Groups 2 and 3 samples were etched with 32% phosphoric acid. The teeth in Group 2 were examined by SEM without further treatment. The samples in Group 3 were treated with a bonding system and fiber posts were luted into the canal. These teeth were then processed for evaluation of hybrid layer formation and resin tags in dentin tubules. The observations were made according to location in the root dentin, tubule density was estimated, and the increase in area available for bonding after etching was calculated.


RESULTS
The observations revealed variability in tubule density and orientation within different areas of any one sample. Statistically significant differences in the density of tubules were found depending on location. The dentin surface area available for bonding increased by 202% after etching in the cervical third, 156% in the middle third, and 113% in the apical third of the root dentin. Group 3 samples showed that the thickness of the hybrid layer depended on the density of tubules. In the sectors with a low density of tubules, the hybrid layer was significantly thinner than in areas with a higher density of tubules. The increase in dentin surface area might be responsible for the enhanced bond strength after acid etching, but not all areas exhibited equal responses to etching.
Ferrari
M
M
University of Siena, Italy. md3972@mclink.it
Mannocci
F
F
Vichi
A
A
Cagidiaco
M C
MC
Mjör
I A
IA
D000134:Acid Etching, Dental; D000704:Analysis of Variance; D001896:Boron Compounds / Q000737:chemistry; D001840:Dental Bonding; D003786:Dental Pulp Cavity / Q000187:drug effects / Q000648:ultrastructure*; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006171:Gutta-Percha / Q000737:chemistry; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D008768:Methylmethacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000008:administration & dosage; D011176:Post and Core Technique / Q000295:instrumentation; D019279:Resin Cements / Q000737:chemistry; D012387:Root Canal Filling Materials / Q000737:chemistry; D012388:Root Canal Irrigants / Q000737:chemistry; D018915:Root Canal Preparation; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000737:chemistry; D013223:Statistics as Topic; D013499:Surface Properties; D019227:Tooth Apex / Q000648:ultrastructure; D019237:Tooth Cervix / Q000648:ultrastructure; D014092:Tooth Root / Q000648:ultrastructure
D001896:Boron Compounds; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D008768:Methylmethacrylates; D010756:Phosphoric Acids; D019279:Resin Cements; D012387:Root Canal Filling Materials; D012388:Root Canal Irrigants; C100742:All-Bond 2; D006171:Gutta-Percha; C049495:Super-bond; D012973:Sodium Hypochlorite