Influence of multi‐wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 μm on surface morphology, permeability, and acid resistance

Abstract

Objective Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments. Methods Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 μm (CO2 laser), and surfaces were exposed an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements. Results Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups. Conclusion Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces.

Chemical and morphological changes of femtosecond laser‐irradiated enamel using subablative parameters

“…Enamel ablation by femtosecond lasers has been demonstrated by several authors (Chen et al, 2015; Chen et al, 2016; Le, Bertrand, & Vilar, 2016; Loganathan, Santhanakrishnan, Bathe, & Arunachalam, 2021; Yuan, Zheng, Sun, Wang, & Lyu, 2017). Nevertheless, there is no detailed characterization of femtosecond laser‐irradiated surfaces using subablative parameters, since previous studies have demonstrated the ability of high‐power lasers with subablative parameters to make dental enamel more acid‐resistant (Behroozibakhsh et al, 2018; Chang et al, 2017). The role of laser irradiation in caries prevention has been widely studied with a focus on the increase of caries resistance caused by a decrease in the enamel demineralization rate (Geraldo‐Martins et al, 2013; Tavares et al, 2012).…”

“…Due to the difficulty of controlling the enamel demineralization processes, new technologies have been studied, such as the use of irradiation with high‐intensity lasers, which have been used in dental enamel with subablative parameters for the prevention and control of caries lesions (Fornaini, Brulat, Milia, Rockl, & Rocca, 2014). When used for preventive purposes, the irradiation of dental enamel with CO 2 , Er,Cr:YSGG, Er:YAG and Nd:YAG lasers modifies the enamel morphology and physical properties, including melting, recrystallization, and melting of hydroxyapatite crystals (Fornaini et al, 2014; Chang et al, 2017; Geraldo‐Martins, Lepri, & Palma‐Dibb, 2013; Tavares, de Eduardo, Burnett Jr, Boff, & de Freitas, 2012). The objective of modifying the chemical and crystalline structure of dental enamel is to favor the stabilization of calcium and phosphate ions by significantly reducing the content of intercrystalline organic material, water, and carbonate, increasing tissue resistance to demineralization (Corrêa‐Afonso, Bachmann, Almeida, Corona, & Borsatto, 2012).…”

Effects of Treatment Combining 9300 nm Carbon Dioxide Lasers and Fluoride on Prevention of Enamel Caries: A Systematic Review and Meta-Analysis

“…Studies have indicated that laser treatment can work synergistically with the application of topical fluoride to further enhance its inhibitory effect [11,21]. Many studies have shown the effect of treatment combining irradiation by carbon dioxide laser at different wavelengths and topical fluoride application on inhibiting tooth demineralization [17,[22][23][24][25][26][27]. A study demonstrated that the combined use of a CO 2 laser and sodium fluoride can significantly increase the uptake of fluoride ions [28].…”

The Impact of CO2 Laser Treatment and Acidulated Phosphate Fluoride on Enamel Demineralization and Biofilm Formation

“…10 This process decreases the permeability and hampers the acid diffusion, thereby reducing enamel demineralization. [11][12][13] Some CO2 parameters, such as output power 14,15 and a wavelength of 10.6 um 3,12, [16][17][18] have been widely studied to prevent demineralization or increase enamel microhardness. However, different pulse emission modes of the CO 2 laser have not yet been investigated.…”