Dentin etch chemistry investigated by Raman and infrared spectroscopy

Abstract

Micro-Raman and infrared spectroscopy were used to investigate the influence of surface treatment on the diffusion of a dental adhesive into dentin. The commercial dentin adhesive Scotchbond MultiPurpose Plus (3M) was placed on coronal dentin substrates that were cut from extracted, unerupted third molars. Prior to placement of the adhesive, one surface was treated with a phosphoric acid etch and the other with a citric acid-iron(III) chloride etch. Thin sections, ~3 μm in thickness, were prepared and mounted on silver chloride disks for infrared spectroscopic studies with the remaining bulk sample being used for the Raman studies. The infrared studies were performed at the Aladdin Synchrotron radiation source at the Synchrotron Radiation Center, Stoughton, WI, USA. The Raman studies employed a krypton ion laser in conjunction with a microscope equipped with a 100x objective and confocal aperture. In both studies the sample was translated in 1 μm steps at the focus of the respective radiation, providing a line scan across the interface. The infrared results clearly show the interface but owing to the diffraction limit of ~15 μm, accurate dimensional information could not be obtained. The Raman results clearly indicate a broad interface associated with the sample etched with phosphoric acid and the presence of a much more abrupt interface with the citric acid etch. Additionally, a thin layer of exposed collagen exists at the dentin-adhesive interface. Copyright (C) 2000 John Wiley and Sons, Ltd.