A minimally destructive technique for removing the smear layer from dentine surfaces

ObjectivesTo develop a minimally destructive technique for removing the smear layer produced by cutting and polishing specimens of dentine prepared for use in experimental studies, e.g. on occlusion of dentinal tubules by oral health products. The aim was to avoid the damage caused by conventional techniques utilising short exposures to solutions with very low pH.MethodsTwo acetate buffers, pH 5.5, containing different concentrations of calcium and phosphate, with −log(ion activity product with respect to hydroxyapatite) (pIHA) of 55 or 56, were tested on slices of dentine using scanning electron microscopy (SEM).ResultsA solution which, from previous work, was slightly undersaturated with respect to dentine mineral, with a pIHA of 56, was found to remove smear layers produced by cutting and/or polishing after 15 min. However, to reliably remove debris occluding the tubules an exposure time of 2 h, followed by brief ultrasonication, was necessary. After 2 h treatment with this buffer, only a small amount of demineralization of the surface was detectable by SEM, while calcium and phosphorus were detectable by X-ray dispersive spectroscopy.ConclusionIt is possible to remove smear layers, and to open dentinal tubules, by a reasonably short exposure to an acidic buffer which is undersaturated with respect to dentine mineral.