Surface morphology, elemental distribution, and spectroscopic changes subsequent the application of nanosecond pulsed Nd:YAG laser on dental enamel surface

Abstract

Application and development of new methods in caries prevention is of paramount importance to reduce the incidence of chronic cases of the caries disease and to preserve dental structure. In this work, we tested nanosecond pulsed Nd:YAG laser on enamel surface examining the changes laser-induced by means SEM, EDS, and FTIR. SEM revealed, the existence of melted zone and bubble inclusions when 40 J/cm2 (τ=6 ns, 5 Hz) was applied on human sound enamel surface. The morphological alteration to 10 J/cm2 (τ=6 ns, 5 Hz) and to 20 J/cm2 (τ=200 ns, 7 Hz) no presented melting aspect, but a greater number of bubble inclusions. We have indicated that the Ca/P ratio increased to irradiation conditions employed here. In our previous study, the combination of the laser parameters not produce an excessive increase in temperature. The temperature variation was less than 2.5°C in the dental pulpal, following application of the energy density of 40 J/cm2. Our results suggest that nanosecond pulsed Nd:YAG laser can be used to obtain minimal morphological alteration associated with a chemical reorganization enhancing the microhardness values and consequently inhibiting the acid dissolution by bacterial agents. In this work, the Vickers microhardness was quantified. Our results of FTIR analysis indicated that the laser effects occurring substantially in the organic compounds (such as water and proteins groups) and are reduced for mineral contend (such as phosphate and carbonate groups).

Dental Enamel Irradiated with Infrared Diode Laser and Photo-Absorbing Cream: Part 2—EDX Study

“…The reduced acid solubility of dental enamel after irradiation with high-intensity lasers has been well documented in literature, 4,[20][21][22][42][43][44][45][46][47] and this change is related to the physical and chemical alterations caused by photothermal and photochemical effects. 46 It is well known that intrinsic factors of the laser source (wavelength, emission mode, pulse energy, spot size, pulse duration, and application method on the tissue) and external parameters (energy density and time exposition) are relevant to understanding the mechanism of interaction between the laser and biological tissue.…”

“…46 It is well known that intrinsic factors of the laser source (wavelength, emission mode, pulse energy, spot size, pulse duration, and application method on the tissue) and external parameters (energy density and time exposition) are relevant to understanding the mechanism of interaction between the laser and biological tissue. 45 The absorption coefficient of tissue components determines the degree of interaction between laser and tissue.…”

“…3) was preserved or increased in all experimental groups, except for the FCL group, which showed decreases like the CTR group. Antunes et al 45 observed that after laser irradiation (Nd:YAG) on enamel surfaces, there were decreases in calcium and phosphorus content. They attributed the phosphorus reduction after irradiation to a volatilization caused by temperature, but this did not happen in our study.…”

“…5), denoting greater preservation of calcium mineral, even under cariogenic challenge. Studies with Nd:YAG 45 and ARF excimer laser 59 showed that after irradiation, the Ca=P ratios were higher when compared with nonirradiated controls; however, these samples were not submitted to cariogenic challenge. However, Muller et al, 60 using a low-power laser, did not find a statistically significant difference in the calculated Ca=P weight (as %) after lasing treatments.…”

Laser Technology for Caries Removal

“…These results suggest that USPLs do not significantly increase the temperature of HAp. On the other hand, the use of Nd:YAG operating with pulse duration of 6 ns and 200 ns on enamel promote melting and recrystallization of this tissue (Antunes et al, 2005), indicating temperature rises up to 1200 o C. Also, with the pulse duration of 6 ns, Nd:YAG promoted changes on organic content of enamel and dentin (Antunes et al, 2006). Thermal measurements were performed using a laser with pulse width of fs on enamel using thermocouples, and it was detected temperature rises about 2 o C on enamel surfaces after a 8 ms train of 70 fs pulses (Pike et al, 2007).…”