PubMed · 12762470
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Edward J Swift. 2003. Dentin bonding.. https://doi.org/10.1111/j.1708-8240.2003.tb00319.x
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The term "nanoleakage" has been introduced to explain a penetration pathway within hybrid layers of the dentin-composite junction in the absence of gap formation. This phenomenon is argued in the literature to be a risk factor for the quality of the dentin bonding. NaOCl is a well-known agent used to remove collagen layers that are exposed after acid etching. The purpose of this study was to determine the influence of an NaOCl treatment of dentin to the formation of nanoleakage. Class V cavities were prepared in 40 human molars with the cervical margins located in dentin. After etching with phosphoric acid, 20 samples were treated with 10% NaOCl for 60 s, and 20 samples were used as control. Composite restorations were placed using two different bonding systems. The specimen were exposed in silver nitrate solution and then in developer. After embedding, the teeth were sectioned, dried, coated with gold, and analyzed by SEM. For all the specimen in the control group, backscatter images indicated a silver penetration within the hybrid layer. There was no penetration of silver detectable in the teeth that were treated with NaOCl. We conclude that the removal of the collagen layer by using NaOCl avoids the formation of nanoleakages with the materials tested.
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The ultimate success of a dentin adhesive bond is dependent in large part on specific conditions at the interface between the tooth and the adhesive. Most current dentin adhesive systems use some sort of pre-treatment to demineralize the first few microns of the dentin surface, leaving a meshwork of collagen into which the adhesive resin can penetrate, infiltrate, and polymerize. The general hypothesis tested in this experiment was that the penetration and distribution of adhesive resin into the demineralized zone are a function of the conditioner used as a pre-treatment for the adhesive application. Four commercially available adhesive systems were modified to incorporate hydroxyethylthiomethacrylate (HETMA), a sulfur-substituted, traceable analogue of 2-hydroxyethylmethacrylate (HEMA), thereby allowing for a qualitative measurement of the amount and distribution of monomer in the treated dentin substrate by energy-dispersive x-ray spectroscopy (EDS) and a quantitative measurement by Auger electron spectroscopy (AES). The dentin pre-treatments investigated were: (1) 10% citric acid/3% ferric chloride, (2) 10% maleic acid, (3) 2.5% nitric acid, and (4) an alcoholic solution of HEMA with a phosphorus acid ester. These pre-treatments were applied to freshly extracted teeth that had been sectioned to expose the dentin and ground to simulate the smeared layer. After the appropriate pre-treatment was applied, a 10% (v/v) solution of HETMA in acetone was applied to the surface, followed by the corresponding adhesive resin, which was then polymerized. The samples were then processed for observation by scanning transmission electron microscopy (STEM), AES, and STEM/EDS analysis. The results indicated significant differences in the ability of HETMA to penetrate the dentin surface conditioned by the four pretreatments investigated here. This study also demonstrated that AES and STEM/EDS could be used in a correlative fashion to determine the distribution of HETMA within or adjacent to the treated dentin surface.