Interfacial chemistry of moisture-aged class II composite restorations

Under in vivo conditions, the adhesive/dentin bond at the gingival margin of class 11 composite restorations can be the first defense against substances that may penetrate and ultimately undermine the composite restoration. Deterioration of this bond during aqueous aging is an area of intense investigation, but to date, the majority of our techniques have provided only an indirect assessment of the degrading components. The purpose of this study was to analyze the in. situ molecular structure of adhesive/dentin interfaces in class 11 composite restorations, following aging in aqueous solutions. Class 11 preparations were cut from 12 unerupted human third molars, with a water-cooled, high-speed, dental handpiece. The prepared teeth were randomly selected for restoration with single bond (SB) and Z100 (W). Teeth were restored, as per the manufacturer's directions, tinder environmental conditions that simulated humidity and temperature characteristics of the oral cavity. Restored teeth were kept in sterile Delbecco's phosphate saline for 48 h or 90 days. The samples were sectioned occlusogingivally and micro-Raman spectra were acquired at similar to 1.5 mu m spatial resolution across the composite/adhesive/dentin interfaces at the gingival margins. Samples were wet throughout spectral acquisition. The relative intensity of bands associated with the adhesive in the interfacial region decreased dramatically after aqueous storage. This decrease in concert with the similar depth of dentin demineralization provides direct spectroscopic evidence of leaching of adhesive monomer from the interface during the 90 days of storage. SIR adhesive infiltrated 4-5 mu m of 12-mu m demineralized dentin at the gingival margin. After 90 days of aqueous storage, SB adhesive infiltration was reduced to similar to 2 mu m, leaving similar to 10 mu m of demineralized dentin collagen exposed at the gingival margin. The unprotected collagen at the gingival margin of the aged class 11 composite restorations was disorganized, suggesting hydrolysis of the collagen, with 90 days of aqueous storage. (c) 2005 Wiley Periodicals, Inc.