Promotion of adhesive penetration and resin bond strength to dentin using non‐thermal atmospheric pressure plasma

Abstract

Non-thermal atmospheric pressure plasmas (NT-APPs) have been shown to improve the bond strength of resin composites to demineralized dentin surfaces. Based on a wet-bonding philosophy, it is believed that a rewetting procedure is necessary after treatment with NT-APP because of its air-drying effect. This study investigated the effect of 'plasma-drying' on the bond strength of an etch-and-rinse adhesive to dentin by comparison with the wet-bonding technique. Dentin surfaces of human third molars were acid-etched and divided into four groups according to the adhesion procedure: wet bonding, plasma-drying, plasma-drying/rewetting, and dry bonding. In plasma treatment groups, the demineralized dentin surfaces were treated with a plasma plume generated using a pencil-type low-power plasma torch. After the adhesion procedures, resin composite/dentin-bonded specimens were subjected to a microtensile bond-strength test. The hybrid layer formation was characterized by micro-Raman spectroscopy and scanning electron microscopy. The plasma-drying group presented significantly higher bond strength than the wet-bonding and dry-bonding groups. Micro-Raman spectral analysis indicated that plasma-drying improved the penetration and polymerization efficacy of the adhesive. Plasma-drying could be a promising method to control the moisture of demineralized dentin surfaces and improve the penetration of adhesive and the mechanical property of the adhesive/dentin interface.

Effect of non‐thermal atmospheric plasma on the dentin‐surface topography and composition and on the bond strength of a universal adhesive

“…However, the cohesive failure modes also increased after aging, corroborating the findings of the present study for the direct water exposure storage protocol. Previous studies have reported that NTAP treatment of dentin before application of etch‐and‐rinse adhesive increased the μ TBS , supporting the findings of the present investigation for the simulated pulpal pressure‐aging protocol.…”

“…F). Previous reports are in agreement with these findings and the fourth null hypothesis might be rejected as NTAP treatment produced differences in interfacial regions, as analyzed by scanning electron microscopy. If a larger area of dentin matrix, exposed by the use of etch‐and‐rinse adhesives, induces higher enzymatic activity, it would be expected that the groups presenting larger numbers of dentin tubules filled with thicker resin tags would also present higher collagenolytic/gelatinolytic activity because the acidic monomers would be in more intimate contact with a larger area of the collagen fibril meshwork.…”

“…However, evidence of polymer degradation by hydrolysis was not reported under the limitations of the present study in which only 1 yr of water storage was investigated. Unlike other studies , the dentin was not rewetted after NTAP application. Kim et al .…”

“…Kim et al . suggested that NTAP‐drying could be a promising method for using to control the moisture, improve the penetration of the adhesive, and also enhance the mechanical properties of the adhesive–dentin interface.…”

“…These highly reactive particles can cross‐link rapidly to form various chemical functional groups on the surface of substrates . Overall, NTAP was demonstrated to affect different properties of relevance to dental bonding, such as increased dentin‐surface wettability , improved resin polymerization , and deeper resin penetration . Another possible reason for the bond‐promotion effect is that NTAP activates the dentin surface by depositing free radicals or peroxides, thereby intensifying the interaction between adhesive monomers and dentinal collagen .…”