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

Abstract

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 2 mm and with a scan velocity of 5.5 mm Á s À1. The treatment parameters are: helium process gas flow 3.525 slm, plasma excitation by 2.45 GHz with an average pulsed microwave power of 2 W, single pulse power of 250 W, pulse width 5 ms. 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 CÀO-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.

Effects of a modified cold atmospheric plasma jet treatment on resin-dentin bonding

“…Extending the conventional CAP treatment time to 10 s significantly lowered the immediate bonding strength compared to the non-treatment group. This phenomenon was also reported in previous studies 8,32) that reported an absence of visible collagen fibers on the dentin surface after plasma treatment and a decreased bond strength following prolonged exposure to the CAP.…”

Nonthermal Atmospheric Plasmas in Dental Restoration

“…Similarly, weaker carbon signals were spotted on NTAP-treated zirconia and titanium surfaces, attributed to the removal of organic contaminants (Silva et al 2011;Valverde et al 2013). Due to this etching effect, NTAP treatment significantly increased surface roughness of bovine dentin, but the difference in bovine enamel was not statistically significant possibly due to low protein content (Lehmann et al 2013). Roughness change in NTAP-treated human dentin was reported to be insignificant, but it was likely a result of nonpolished dentin specimens (Koban et al 2011).…”

“…It implies that excessive NTAP treatment may damage dentin collagen and thus decrease bond strength (discussed below). Regarding the modification process, EDX/XPS studies affirmed significant increase in oxygen content on NTAP-treated dental surfaces, reflecting the important role of reactive oxygen species in introducing polar, oxygen-containing groups to the substrates (Koban et al 2011;Silva et al 2011;Lehmann et al 2013;Valverde et al 2013;Chen et al 2014). XPS narrow scans suggested that NTAP treatment induced substantial increase in C-O-, O=C-O-, and CO 3 2-signals on enamel (Lehmann et al 2013), and FTIR analysis revealed an increase in the amount of carbonyl groups (1,760 cm -1 ) on demineralized dentin collagen (Ritts et al 2010).…”

“…With argon or helium as carrier gas, with or without additional O 2 /H 2 O 2 gas feeding, NTAP has demonstrated the ability to reduce water and ethanol contact angles on a variety of dental substrates, including zirconia, titanium, bovine and human dentin/enamel, as well as cured dental composites (Koban et al 2011;Silva et al 2011;Chen et al 2013;Lehmann et al 2013;Valverde et al 2013;Han et al 2014;Hirata et al 2015). NTAP's alteration to surface hydrophilicity is believed to involve 2 mechanisms: etching/ablation and modification.…”

Plasma deposited silicon oxide films for controlled permeation of copper as antimicrobial agent

“…The plasma jet source and the microwave pulse generator are described in detail by Lehmann et al [16]. A schematic drawing of the source and the system is shown in Fig.…”