Histomorphologic characterization and bond strength evaluation of caries-affected dentin/resin interfaces: effects of long-term water exposure.
OBJECTIVE
To evaluate the longevity of sound (SD) and caries-affected dentin (CAD) bonds made with etch-and-rinse and self-etching adhesives after a 6-month water-storage period, using bond strength and morphological evaluations.


METHODS
Extracted human molars with coronal carious lesions were selected. Flat surfaces of CAD surrounded by SD were bonded with etch-and-rinse (Adper Scotchbond 1) or with self-etching (Clearfil Protect Bond and AdheSE) adhesives. Trimmed resin-dentin bonded interfaces (1mm2) were stored in distilled water for 24h or 6 months and subjected to microtensile bond strength (microTBS) evaluation. The quality of the dentin beneath fractured specimens was measured by Knoop microhardness (KHN). ANOVA and multiple comparisons tests were used (P<0.05). Fractographic analysis and interfacial nanoleakage evaluation were performed by scanning electron microscopy (SEM). Resin-dentin bonded sections (10microm thick) were stained with Masson's trichrome and examined using light microscopy. Collagen exposure and adhesive penetration were examined qualitatively.


RESULTS
microTBS to SD was significantly higher than that to CAD for all bonding agents. Bonds made with AdheSE were weaker than the other adhesives after 6-months storage regardless of the dentin substrate. CAD bonded specimens presented a significant muTBS decrease over time. Lower KHN was recorded in CAD compared to SD. An increase in the exposed collagen zone and a decrease in the quality of the adhesive infiltration were observed in CAD interfaces.


CONCLUSIONS
CAD bonded interfaces are more prone to hydrolytic degradation than SD bonds. Additionally, as compared to SD, there were remarkable differences in depth of demineralization, adhesive infiltration and interfacial bond strength with CAD.
Erhardt
Maria Carolina G
MC
Department of Restorative Dentistry, Division of Operative Dentistry, School of Dentistry at Piracicaba, University of Campinas, Piracicaba, Brazil.
Toledano
Manuel
M
Osorio
Raquel
R
Pimenta
Luiz André
LA
D000134:Acid Etching, Dental; D000180:Acrylic Resins / Q000737:chemistry; D001391:Azo Compounds; D003094:Collagen / Q000648:ultrastructure; D004396:Coloring Agents; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003731:Dental Caries / Q000473:pathology* / Q000503:physiopathology; D003763:Dental Leakage / Q000145:classification; D003804:Dentin / Q000503:physiopathology / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D004801:Eosine Yellowish-(YS); D006244:Hardness; D006801:Humans; D008422:Materials Testing; D008739:Methyl Green; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D000180:Acrylic Resins; C489662:AdheSE cement; D001391:Azo Compounds; C503075:Clearfil Protect Bond; D004396:Coloring Agents; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; C017768:trichrome stain; D014867:Water; D008739:Methyl Green; D003094:Collagen; C041330:Scotchbond; D004801:Eosine Yellowish-(YS)