Nanoleakage at the dentin adhesive interface: a new application for laser ablation-sector field-ICPMS

Abstract

Laser ablation-sector field-inductively coupled plasma mass spectrometry has been used for in situ determination of silver concentration in treated human teeth. Silver nitrate has long been used to trace the presence of micro sized gaps between the walls of dental restorations and teeth, and more recently, to trace the presence of nanometer sized voids within resin-bonded restorations. This study examines the diffusion of silver nitrate into submicron voids beneath resin-bonded composite restorations. The silver treated-teeth were analyzed for ⁴³Ca, ¹⁰⁷Ag, and ¹⁰⁹Ag isotopes. Elemental data were obtained by ablation with Nd:YAG laser operating in the UV region 266 nm and 213 nm by New Wave-Merchantek and isotopic analysis with a sector field ICP MS by Finnigan MAT. A 50 ppm glass standard (NIST-612) was also analyzed for the same isotopes. Quantification was performed by assuming a uniform nominal calcium concentration value of 27 g per 100 g of dry dentin across the root and using the ⁴³Ca signal for internal calibration. The precision (RSD%) of measurements for ⁴³Ca for the NIST-612 glass standard was found to be within 1.8% to 2.5% and for the tooth samples within 2.8% to 7.1%. The precision of analysis for ¹⁰⁷Ag for the NIST-612 glass standard was between 2.6% and 4.4%. The analysis revealed a significant penetration of resin-bonded dentin by silver, ranging from ∼35000 ppm at the very bottom of the resin-infiltrated demineralized dentin to only 10 s of ppm in the areas within the underlying mineralized dentin. The analysis revealed that a significant amount of silver penetrated through resin-dentin bonds, and that the amount of silver increased with increased acid-etching time. The results from this study suggest that current adhesive resin system do not create perfect bonds and that laser ablation sector field ICPMS can be used to quantify the amount of nanoleakage of bonded restorations.