BACKGROUND: Enamel demineralisation is an initial step of the serious dental problem including dental caries, white spot lesions and dental erosion. AIM: Compare the effect of Er, Cr: YSGG (λ = 2780 nm) and nanosecond Nd: YAG (λ = 1064 nm) laser on enamel acid resistance. MATERIAL AND METHODS: Thirty non-carious human premolars, extracted for orthodontic reasons, were used. The experimental groups (n = 10 each group) were: Group I, untreated (control); Group II, Er,Cr:YSGG laser irradiation (0.75 W, 20 Hz, 140 μs, 10 s); Group III, nanosecond pulsed Nd:YAG laser irradiation (0.8 W, 10 Hz, 7 ns, 10 s). Scanning electron microscope and Energy Dispersive X-ray Spectroscopy (EDX) were used to assess acquired enamel resistance to PH cycling. RESULTS: After subjecting the three experimental groups to PH cycling, scanning electron microscopic examination revealed irregular porous dissoluted enamel surface in group I. However, groups II and III demonstrated partially dissoluted enamel surface. EDX analysis demonstrated the lowest mean percentage decrease in calcium and phosphorus content in group II followed by group III, then the highest mean percentage decrease was observed in untreated group I. One-way ANOVA revealed significant differences (p < 0.0001) between the tested groups. CONCLUSIONS: Both Er, Cr: YSSG and nanosecond Nd: YAG laser irradiation were able to improve the acid resistance of enamel. However, enamel surface treated with Er, Cr: YSSG laser showed the lowest mean percentage decrease of calcium and phosphorus (highest acid resistance).

AIM: Recent studies have demonstrated that low-level laser therapy (LLLT) can accelerate orthodontic tooth movement. However, there is still controversy about the optimum parameters that can cause acceleration. The present study was designed to examine two different doses of LLLT in the acceleration of orthodontic tooth movement and their effect on relapse. METHODS: An orthodontic appliance was designed to induce tooth movement on lower incisors of rabbits. The in-al-as diode laser was used to radiate different groups of rabbits according to a specific protocol. The amount of tooth movement was measured for 21 days, and then the orthodontic appliance was removed, and the relapse was measured till day 28. RESULTS: The amount of tooth movement was significantly greater in the group with irradiation of low dose in comparison with the high dose group and the control group. The relapse was greatest in the group of low dose irradiation and least in the control group. CONCLUSION: The findings suggest that LLLT with a low dose accelerate the orthodontic tooth movement while LLLT with a high dose was not able to have the same effect. LLLT had a reverse effect on relapse tendency; an increase in the relapse tendency was seen with low dose irradiation.

Background:Titanium alloys are widely used in dental applications as they have good mechanical and biological properties. Implant failure is more likely to occur in inflammatory diseases related to acidic pH. The aim of the present study was to assess the effect of erbium chromium-doped yttrium-scandium-gallium-garnet 2780 nm laser surface treatment on the electrochemical behavior of titanium alloy (Ti-6Al-4V) at acidic pH.Materials and Methods:In this in vitro study, a total of 20 discs of titanium alloy (Ti-6Al-4V) were used. First group, ten discs were irradiated with Er, Cr: YSGG laser which was operating in a normal room atmosphere and temperature at power 2W for 20 s at a constant distance of 0.5–1 mm with the laser system. The second group, ten discs untreated. The electrochemical behavior for both groups was investigated in simulated body fluid at pH 5.20 for up to 864 h at 192, 360, 696, and 864 h intervals using potentiodynamic polarization test and electrochemical impedance spectroscopy to evaluate the corrosion resistance.Results:Laser-treated Ti-6Al-4V showed higher corrosion resistance at pH 5.20 compared to the untreated alloy. Immersion time affected the electrochemical behavior.Conclusion:Er, Cr: YSGG laser could improve the corrosion resistance of Ti–6Al–4V at acidic pH.

Background The field of laser-based photochemical reactions receives a great promising for additional applications especially for targeting cells, pathogens, or molecules. Limited studies have investigated the impact of light-emitting diode on stem cell behavior. Thus, the aim of the present study was to assess the effect of diode laser irradiations on the proliferation of stem cells isolated from the human dental pulp. Isolation procedures were according to previously developed protocols for dental pulp stem cells (DPSCs). Low-level laser therapy irradiation (LLLT) was applied in two doses (0.5 J/cm2 and 1 J/cm2 for 20 s) into 96-well plates by the diode laser device (970 nm) through the fiber optic (SiroLaser fibers 320) at a distance from the opening of the wells to be accurate for equal distribution of the laser irradiation. To assess the proliferation capacity of the isolated stem cells, MTT assay was performed 24 h, 48 h, and 72 h. Results There was no significant difference among the different groups (gp 1 control, gp II dose 0.5 J/cm2, gp III dose 1 J/cm2) on day 1. While on day 2, the optical density of DPSCs subjected to dose 1 was found to be significantly higher than that of those subjected to dose 2. This was also demonstrated on day 3. It was also demonstrated that the proliferation of DPSCs subjected to dose 1 increased compared to that of DPSCs subjected to dose 2 from day 1 to day 2. There was a significant decrease in the cell number in both groups by 72 h. Conclusion In conclusion, the use of LLLT as a stimulatory factor for enhancing and proliferation of the stem cells is very promising.

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