Bonding mechanism and ultrastructural interfacial analysis of a single-step adhesive to dentin.
OBJECTIVE
to characterize the interaction of 4-acryloxyethyltrimellitic acid (4-AET), a key ingredient in a commercial all-in-one adhesive (Reactmer Bond) with dentin apatite, to measure the solubility of 4-AET calcium (4-AETCa), and to examine the ultrastructure of the resin-dentin interface bonded by this adhesive.


METHODS
solubility of synthesized 4-AETCa in several solutions was measured. Flattened bovine dentin blocks were treated with 0.1wt% NaOCl for 10 min, or 5.0wt% NaOCl for 10 min, or 30 min. Fourier transform infrared analysis using attenuated total reflection (FT-IR/ATR) was performed on these four substrates before and after treatment with a 4-AET mixture (4-AET/HEMA: 40/60wt%). Undemineralized, unstained sections of human sound dentin that were bonded with the same comonomers were examined by transmission electron microscopy (TEM).


RESULTS
the respective solubilities of the 4-AETCa in water, 2-hydroxyethyl methacrylate (HEMA; 100wt%) and HEMA/water (70/30wt%) were 0.023, 0.003 and 0.014 mol/l after 2 min. The IR analysis indicated that Ca-carboxylate (new bands: nuCz.dbnd6;O:1580 and 1413 cm(-1)) was formed on all dentin specimens following application of 4-AET, with or without NaOCl pretreatment. TEM showed a 1 micro m thick hybrid layer with some remnant apatite crystallites that were encapsulated by a layer of less electron-dense material.


CONCLUSIONS
the results suggest that ionized carboxyl groups in 4-AET may interact with Ca(2+) from apatite crystallites within the partially demineralized hybrid layer to form an insoluble calcium salt (4-AETCa) that may aid in bonding this resin system to dentin.
D000818:Animals; D001031:Apatites / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry; D002417:Cattle; D003461:Crystallography; D001840:Dental Bonding; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D008854:Microscopy, Electron; D016877:Oxidants / Q000494:pharmacology; D012973:Sodium Hypochlorite / Q000494:pharmacology; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D001031:Apatites; D017220:Dentin-Bonding Agents; D005609:Free Radicals; D005899:Glass Ionomer Cements; D008689:Methacrylates; D016877:Oxidants; C447779:reactmer bond; D014867:Water; D002245:Carbon Dioxide; C041069:carboxyl radical; C005044:hydroxyethyl methacrylate; D012973:Sodium Hypochlorite; D002118:Calcium