Dentin etch chemistry investigated by Raman and infrared spectroscopy

Micro-Raman and infrared spectroscopy were used to investigate the influenc e of surface treatment on the diffusion of a dental adhesive into dentin, T he 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 et ch. Thin sections, similar to 3 mu m in thickness, were prepared and mounte d on silver chloride disks for infrared spectroscopic studies with the rema ining bulk sample being used for the Raman studies. The infrared studies we re 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 mu m steps at the focus of the respective radiation, providing a line scan acros s the interface, The infrared results clearly show the interface but owing to the diffraction limit of similar to 15 mu m, accurate dimensional inform ation could not be obtained. The Raman results clearly indicate a broad int erface associated with the sample etched with phosphoric acid and the prese nce 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 & Sons, Ltd.