Lasers in Medical Science

This study aimed to evaluate the effect of IPL treatment on Asian skin by reflectance confocal microscopy (RCM) analysis. Ten Asian female volunteers (39~54 years old, Fitzpatrick skin type III~IV) received five monthly IPL treatments. RCM skin images were evaluated, and several skin physiological parameters including thickness of stratum corneum, minimal thickness of epidermis, thickness of basal layer, density of dermal papillae, and mean diameter of papillae capillaries were measured both at baseline and 1 month after the last treatment. Transepidermal water loss (TEWL) was evaluated, as well. Thickness of stratum corneum was 4.80 ± 1.48 μm before IPL treatment and 5.50 ± 1.35 μm after treatment (p = 0.322). Both minimal thickness of epidermis and thickness of basal layer were significantly increased (p = 0.002 and 0.018, respectively) after IPL treatment. Dermal papillae density was significantly increased (p = 0.035), whereas mean capillary diameter was reduced significantly (p = 0.035). TEWL was slightly increased after treatment, while the difference was not significant on either T-zone or U-zone (p = 0.085 on T-zone and p = 0.114 on U-zone). RCM imaging is a feasible method to evaluate the effect of IPL effect on human skin. Moreover, IPL treatment serves to be highly safe in skin rejuvenation.

This research work mainly deals with studying qualitatively the changes in the dermal collagen of two forms of striae distensae (SD) namely striae rubrae (SR) and striae albae (SA) when compared to normal skin (NS) using confocal Raman spectroscopy. The methodology includes an in vivo human skin study for the comparison of confocal Raman spectra of dermis region of SR, SA, and NS by supervised multivariate analysis using partial least squares discriminant analysis (PLS-DA) to determine qualitatively the changes in dermal collagen. These groups are further analyzed for the extent of hydration of dermal collagen by studying the changes in the water content bound to it. PLS-DA score plot showed good separation of the confocal Raman spectra of dermis region into SR, SA, and NS data groups. Further analysis using loading plot and S-plot indicated the participation of various components of dermal collagen in the separation of these groups. Bound water content analysis showed that the extent of hydration of collagen is more in SD when compared to NS. Based on the results obtained, this study confirms the active involvement of dermal collagen in the formation of SD. It also emphasizes the need to study quantitatively the role of these various biochemical changes in the dermal collagen responsible for the variance between SR, SA, and NS.

Low-level laser therapy (LLLT) is widely used in regenerative medicine and in dental therapy by virtue of its beneficial effects in a plethora of pathological conditions. In this study, the effect of a 980 nm diode laser on pre-osteoblasts proliferation has been evaluated, along with reactive oxygen species (ROS) production. We hypothesized that ROS were a key factor in LLLT-induced pre-osteoblasts proliferation, as it is known that ROS can induce the activation of many biological pathways, leading to cell proliferation, differentiation or apoptosis. Murine pre-osteoblasts MC3T3 cells were irradiated with different energy outputs (1–50 J) in the absence or presence of the antioxidant N-Acetyl-L-cysteine (NAC). Laser treatment, in the absence of NAC, was able to induce a fluence-dependent statistically significant increase in ROS generation, while the presence of NAC strongly inhibited it. Cell proliferation, measured after laser stimulation, was significantly increased both at low and higher energy, with a peak at 10 J in the absence of the antioxidant. On the contrary, in the presence of NAC, laser irradiation was not able to induce any cell proliferation, suggesting a crucial role of ROS in this laser-induced cell effect. These results suggest that LLLT may be a useful tool for bone regeneration therapy and an effective range of fluences to be used is indicated.

The aim of this study was to evaluate in vitro the influence of high-power lasers (Nd:YAG and diode 980 nm) associated with mineral coal as fotopotencializer on bond strength of an epoxy resin-based root canal sealer to root dentin, using the pushout test, and on the dentin/filling material interface, using confocal laser microscopy. For this purposes, 50 canines were instrumented with Mtwo rotary system up to #50.04 instrument and randomly assigned to five groups (n = 10): group I—control EDTAC; group II—EDTAC and Nd:YAG laser; group III—EDTAC and diode laser 980 nm; group IV—EDTAC, Nd:YAG laser and mineral coal 5 g/100 mL; and group V—EDTAC, diode laser 980 nm and mineral coal 5 g/100 mL. All data were analyzed by ANOVA (at 5% significance level) following the Kruskal-Wallis, Dunn and Tukey tests. The group I increased more bond strength of the sealer to root dentin that treated with only EDTAC 17% (17.21 ± 21.75 MPa), similar to the group II (12.21 ± 18.20 MPa) and group IV (14.92 ± 28.06 MPa), both treated with Nd:YAG laser, with the exception of group IV, which was added to mineral coal. The group V (8.75 ± 13.42 MPa) had similar results to the groups II and IV, but the same similarity were found when compared with group III (7.11 + 11.28 MPa), with lower results. Regarding the root thirds, the apical third (23.27 ± 29.21 MPa) presented a statistically higher value on bond strength than the cervical third (5.92 ± 5.33 MPa) and middle third (6.93 ± 7, 11 MPa) (p > 0.05). Group II (86.27 μm) showed the highest tags penetration values, with a statistically difference to the group III (51.57 μm), IV (36.77 μm) and V (32.37 μm) (p < 0.05). Group I (71.63 μm) was statistically similar to groups II and III (p > 0.05). Group IV had the lowest values and was statistically similarity to groups III and V (p > 0.05). It was concluded that the treatment with Nd:YAG laser provides better results than the diode 980 nm laser, except when was added mineral coal. The control and diode 980 nm laser groups presented less adhesive failures and more mists failures than the other groups. Both lasers did not interfere negatively compared to the control group.

This study evaluated the resistance to demineralization and fluoride incorporation of enamel irradiated with Er:YAG. A total of 110 bovine teeth were selected and divided into eight groups: unlased, 37% phosphoric acid, and samples irradiated with the Er:YAG laser at several fluences (31.84 J/cm2, 25.47 J/cm2, 19.10 J/cm2, 2.08 J/cm2, 1.8 J/cm2, and 0.9 J/cm2). The application of acidulated phosphate fluoride was performed after treatments. All samples were immersed in 2 ml of 2.0 M acetic–acetate acid solution at pH 4.5 for 8 h, and fluoride, calcium, and phosphorus ions dissolved were analyzed by atomic absorption spectrometry and spectrophotometry. The phosphoric acid and 31.84 J/cm2 groups presented the lowest dissolution of calcium and phosphorus ions. Higher fluoride incorporation was observed on 1.8 J/cm2 and 0.9 J/cm2 groups. Based on these results, Er:YAG laser was able to decrease acid dissolution and increase fluoride uptake and can be a promissory alternative for preventive dentistry.

Beneficial medical laser ablation removes material efficiently with minimal collateral damage. A Mark-III free electron laser (FEL), at a wavelength of 6.45 μm has demonstrated minimal damage and high ablation yield in ocular and neural tissues. While this wavelength has shown promise for surgical applications, further advances are limited by the high overhead for FEL use. Alternative mid-infrared sources are needed for further development. We compared the FEL with a 5-μs pulse duration with a Q-switched ZGP-OPO with a 100-ns pulse duration at mid-infrared wavelengths. There were no differences in the ablation threshold of water and mouse dermis with these two sources in spite of the difference in their pulse structures. There was a significant difference in crater depth between the ZGP:OPO and the FEL. At 6.1 μm, the OPO craters are eight times the depth of the FEL craters. The OPO craters at 6.45 and 6.73 μm were six and five times the depth of the FEL craters, respectively. Bright-field (pump-probe) images showed the classic ablation mechanism from formation of a plume through collapse and recoil. The crater formation, ejection, and collapse phases occurred on a faster time-scale with the OPO than with the FEL. This research showed that a ZGP-OPO laser could be a viable alternative to FEL for clinical applications.

This study evaluated the combined effect of Nd:YAG laser irradiation and fluoridated gels containing photo absorbers against enamel erosion. Enamel specimens from bovine teeth were polished, eroded (10 min, with 1% citric acid, pH = 2.6), and randomly allocated into the experimental groups (n = 8), according to the different surface treatments: fluoridated gels (F: 9047 ppm F and F + Sn: 9047 ppm F and 3000 ppm Sn), with or without photo absorbers (E: erythrosine and MB: methylene blue), and associated or not with Nd:YAG laser irradiation (in contact; 0.5 W; 50 mJ; ~41.66 J/cm2; 10 Hz; 40 s; pulse duration of 120 μs). A placebo gel (PLA) associated or not with laser was used as control. All gels had pH = 4.5 and were applied for 2 min. Laser irradiation was performed during gel application. The specimens were then submitted to a 5-day erosion-remineralization cycling model using 0.3% citric acid (pH = 2.6), 4×/day. Enamel surface loss (SL) was analyzed by optical profilometry in the end of the cycling (in μm). Data were analyzed by ANOVA and Tukey tests (α = 0.05). Means (SD) of SL for the groups were the following (different superscript letters imply significant difference among groups): PLA (21.02 ± 1.28)a, PLA + laser (19.20 ± 0.96)ab, laser (17.47 ± 1.50)b, F + Sn + E + laser (13.69 ± 0.62)c, F + E + laser (13.52 ± 1.16)c, F (13.10 ± 1.08)c, F + laser (11.94 ± 1.44)cd, F + Sn + MB + laser (11.90 ± 4.02)cd, F + MB + laser (11.42 ± 1.42)cd, F + Sn (11.12 ± 1.20)cd, and F + Sn + laser (10.35 ± 0.89)d. In conclusion, all fluoridated gels and the Nd:YAG laser irradiation reduced erosion development, but the combination of treatments did not promote further protection. The addition of photo absorbers to the fluoridated gels did not influence the anti-erosive effect of the combination of laser plus fluoridated gels.

The aim of this study was to evaluate and compare the reparative and inhibitory effects of single wavelength photobiomodulation (SW-PBM) and of cumulative increased wavelength photobiomodulation (CW-PBM) on orthodontically induced inflammatory root resorption (OIIRR). Thirty-three Wistar albino rats were divided into five groups: untreated group (negative control), only relapse group (positive control-1), only retention group (positive control-2), SW-PBM group (650 nm, 100 mW/cm2), and CW-PBM group (532–650–940 nm, 100 mW/cm2). Orthodontic tooth movement was induced experimentally in rats for 10 days with an applied force of 50 cN; retention and therapeutic approaches were performed concurrently. At the end of the experiment, maxillary quadrants were prepared for micro-CT analysis and real-time polymerase chain reaction (RT-PCR) analysis. After the Shapiro-Wilk normality test, Kruskal-Wallis test followed post hoc Bonferroni test and paired samples t test was used for statistical evaluation of the data. Resorption lacunae volume (p < 0.001), number of resorption lacunae (p < 0.05), and percentage of the resorption (PR) lacunae (p < 0.001) decreased with PBM applications when compared with the positive control groups, and the mean PR was similar in the negative control group when compared with SW-PBM group. Receptor activator of nuclear factor kappa B ligand (RANKL) levels of the PBM groups were lower (p < 0.05) than those of the positive control groups. Cyclooxygenase-2 (COX-2) expression levels significantly decreased with PBM administration (p < 0.05). No significant change was found in osteoprotegerin (OPG) expression levels and OPG/RANKL ratios (p > 0.05). PBM applications showed marked inhibitory and reparative effects on OIIRR by modulating the RANKL and COX-2 expression levels. However, the effects of the different wavelengths were similar to each other. Graphical abstract