The durability of adhesion to phosphoric acid etched, wet dentin substrates.
OBJECTIVE
The purpose of this study was to investigate the influence of remaining non-resin-impregnated, phosphoric acid demineralized dentin upon the long-term durability of specimens that were wet-bonded to bovine dentin substrates.


METHODS
Prepared bovine dentin samples were etched with 65% phosphoric acid then rinsed with water and kept wet during application of 5 wt% 4-methacryloyloxyethyl trimellitate anhydride (4-META) in acetone primer. This was followed by application of a photocured dentin-bonding agent consisting of 4-methacryloyloxyethyl trimellitate anhydride/triethyleneglycol dimethacrylate-camphorquinone/N-phenylglycine (4-META/TEGDMA-CQ/NPG). The tensile bond strength (TBS) of bonded specimens was determined after immersion in 37 degrees C water for various time intervals. Generated data were analyzed for statistical significance by one-way ANOVA and Duncan's New Multiple Range Test (p < 0.05). The dentin side of the tensile-load-fractured specimens was examined under optical and scanning electron microscopes (SEM).


RESULTS
TBS decreased from 6.6 +/- 1.0 MPa after 1-day water immersion to 3.4 +/- 1.7 MPa after 1 month of water immersion. After 6 months of water immersion, TBS was found to be 3.9 +/- 0.9 MPa and this decreased to 2.0 +/- 1.0 MPa for specimens immersed in water for 1 year, a statistically significant difference (p < 0.05). Optical microscopic and SEM observations disclosed failure patterns within demineralized, non-resin-impregnated dentin that increased with the period of water immersion.


CONCLUSIONS
The bond durability to wet dentin was poor when demineralized dentin was not resin-impregnated, resulting in exposure of collagen fibrils which hydrolyzed during long periods of water immersion.
Kato
G
G
Division of Organic Materials, Tokyo Medical and Dental University, Japan.
Nakabayashi
N
N
D000134:Acid Etching, Dental; D000180:Acrylic Resins; D000268:Adhesiveness; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003094:Collagen / Q000737:chemistry; D001840:Dental Bonding; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D017220:Dentin-Bonding Agents; D005998:Glycine / Q000031:analogs & derivatives; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000494:pharmacology; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D018709:Statistics, Nonparametric; D013718:Tensile Strength; D013729:Terpenes; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D017220:Dentin-Bonding Agents; D010756:Phosphoric Acids; D011109:Polymethacrylic Acids; D013729:Terpenes; D014867:Water; C020946:triethylene glycol dimethacrylate; C021316:N-phenylglycine; D011092:Polyethylene Glycols; C048339:camphoroquinone; C031172:4-META resin; D003094:Collagen; C030242:phosphoric acid; D005998:Glycine