Modification of Enamel and Dentin Surfaces by Non-Thermal Atmospheric Plasma

Tooth material surface chemical and micromechanical properties are important for success and sustainability in restorative dentistry. Modification by cold atmospheric plasma jet treatment may help to improve presently existing shortcomings as a part of future restorative therapies. The present study has been focused on changes of surface properties of tooth substances by this approach. Polished and etched enamel and dentin slices from the vestibular face of bovine incisors are used. A plasma jet modifies these surfaces at a distance of 2mm and with a scan velocity of 5.5mm center dot s1. The treatment parameters are: helium process gas flow 3.525slm, plasma excitation by 2.45GHz with an average pulsed microwave power of 2W, single pulse power of 250W, pulse width 5 mu s. The surface modifications are subjected to laser scanning microscope roughness-measurement, contact angle measurements, X-ray photoelectron spectroscopy (XPS) analysis and morphological visualization by scanning electron microscopy (SEM). Plasma treatment causes changes of surface roughness and morphological alterations on dentin, while no such changes are measureable on etched dentin and polished and etched enamel surfaces. Plasma causes contact angle reductions for both, water and ethylene glycol. XPS analyses show significant carbon reduction on enamel surfaces after plasma treatment. Admixture of 30% of hydrogen peroxide or deionized water, respectively, as precursors in the plasma jet processing gas flow generates measureable amounts of CO-bindings at the surfaces assigned to hydrophilic groups. Surface modifications by plasma treatment might enable interesting new options for dental procedures in all areas of interaction between tooth substance and restorative materials. [GRAPHICS] .