A New Laser-Processing Strategy for Improving Enamel Erosion Resistance

Abstract

In the present study, a new automatic laser-processing strategy allowing standardized irradiation of natural tooth areas was investigated. The objective was to find a combination of laser parameters that could cause over a 600°C temperature increase at the enamel surface while not damaging enamel, avoiding temperature change above 5.5°C in the pulp and increasing enamel erosion resistance. Seventy-seven bovine enamel samples were randomly divided into 6 laser groups and 1 negative control (C/no treatment/ n = 11). A scanning strategy (7 × 3 mm) was used for the CO laser treatment (λ = 10.6 µm, 0.1-18 J/cm) with different pulse durations-namely, 20 µs (G20), 30 µs (G30), 55 µs (G55), and 490 µs (G490), as well as 2 modified pulse distances (G33d, G40d). Measurements of temperature change were performed at the surface (thermal camera/50 Hz), at the underside (thermocouples), and at the pulp chamber using a thermobath and human molars ( n = 10). In addition, histology and X-ray diffraction (XRD/ n = 10) were performed. Erosion was tested using an erosive cycling over 6 d, including immersion in citric acid (2 min/0.05 M/pH = 2.3) 6 times daily. Surface loss was measured using a profilometer and statistical analysis with a 2-way repeated-measures analysis of variance (α = 0.05). Only G20 fulfilled the temperature requirements at the surface (619 ± 21.8°C), at the underside (5.3 ± 1.4°C), and at the pulp (2.0 ± 1.0°C), and it caused no mineral phase change and significant reduction of enamel surface loss (-13.2 ± 4.0 µm) compared to C (-37.0 ± 10.1 µm, P < 0.05). A laser-scanning strategy (20 µs/2 kHz/1.25 J/cm, 3.4 mm/s) has been established that fulfilled the criteria for biological safety and significantly increased enamel erosion resistance (64%) in vitro.

Erosion of CAD/CAM restorative materials and human enamel: An in situ/in vivo study

“…In the present study, an average of 35.7 μm of enamel was lost after 280 min of in situ/in vivo erosion. Similar erosive tooth wear (37.0 μm) was achieved after 72 min of in vitro erosion using citric acid at a similar pH (Esteves-Oliveira et al, 2017). Erosive enamel loss has been reported to increase linearly with time with acidic solution exposure .…”

In situ effect of Tooth Mousse containing CPP-ACP on human enamel subjected to in vivo acid attacks

“…Currently, strategies for preventing dental erosion include fluoride application, and modification of acidic beverage, and laser irridation, etc. [8][9][10][11][12].…”

Chemical Changes of Enamel Produced by Sodium Fluoride, Hydroxyapatite, Er:YAG Laser, and Combined Treatments

“…Several studies have shown that CO 2 laser is very effective for the prevention of tooth decay and dental erosion under previously established parameters in comparison to Er:YAG laser, among other approaches [33][34][35]. However, based on the favorable chemical changes 5 Journal of Spectroscopy observed that could improve the enamel structure, it is suggested that additional studies be carried out to evaluate the acid resistance of enamel for the establishment of alternative preventive protocols and protect areas that are susceptible to caries, such as occlusal surfaces.…”