Bacterial reduction effect of four different dental lasers on titanium surfaces in vitro

Advanced and Readily-Available Wireless-Powered Blue-Light-Implant for Non-Invasive Peri-Implant Disinfection

Non-invasive light-based antibacterial therapy has a good prospect in non-surgical treatment of peri-implant infections. However, its applications are severely limited by poor penetration of light into human tissues, leading to unsatisfying outcomes. Moreover, as an essential prerequisite for traditional light therapy, lasers can no longer meet the patients' needs for convenient treatment at any time. To break through the spatial and temporal limitations of traditional light therapy, a wireless-powered blue-light zirconia implant for readily available treatment of peri-implant infection is proposed. In space, complete irradiation to complex peri-implant structure is realized by the built-in wireless-powered light source, thus improving the efficacy. In time, wireless-powering allows timely and controllable anti-infection treatment. Blue micro-light emitting diodes are used as therapeutic light sources, which effectively kill peri-implant infection-related bacteria without exogenous photosensitive agents. Porphyromonas gingivalis biofilm on implant surface can be completely killed after 20 min irradiation in vitro. The bactericidal rate of peri-implant methicillin-resistant Staphylococcus aureus infection reaches 99.96 ± 0.03% under 30 min per day blue light exposure in vivo. Within the scope of this study, the treatment of peri-implant infection with blue-light implant has preliminary feasibility, giving a new approach to non-invasive treatment of deep oral infections, including peri-implant infections.

Effect of a neodymium-doped yttrium aluminium garnet laser on the physicochemical properties of contaminated titanium surfaces and macrophage polarization

AIM(S)

The objective of this study was to evaluate the changes in the physical and chemical properties of titanium surfaces contaminated by a Nd:YAG laser with different levels of energy and the regulation of macrophage polarization.

MATERIALS AND METHODS

The titanium specimens were divided into four groups. The blank control group consisted of the above-mentioned contaminated titanium specimens, and the conditioned control group consisted of sandblasted and acid-etched (SLA) titanium surfaces. The blank control and condition control groups were sealed and preserved in a sterile dark box. There were two experimental groups treated with the Nd:YAG laser-one with 0.5 W and the second with 1.0 W. Surface characteristics were evaluated using scanning electron microscopy, surface profilometry, and contact angle assays. The macrophage viability and proliferation of mouse RAW246.7 were analysed, and the macrophage surface markers, macrophage cytokines, and inflammatory and anti-inflammatory genes were expressed.

RESULTS

The Nd:YAG laser increased the hydrophilicity and roughness of the titanium surface after decontamination. Fewer RAW264.7 cells were observed on the titanium surface after Nd:YAG decontamination than on the contaminated titanium surface expressing the M1-type macrophage marker CCR7, whereas more cells were observed after decontamination than on the contaminated titanium surface expressing the M2-type macrophage marker CD206. Following Nd:YAG laser treatment, the secretion of the inflammatory cytokines IL-1β and TNF-α by RAW264.7 cells on the titanium surface was decreased, whereas the secretion of the anti-inflammatory cytokines IL-4 and IL-10 was increased. RAW264.7 cells cultured for 3 days on the titanium surface after Nd:YAG decontamination treatment expressed significantly reduced levels of the inflammation-related genes IL-1β, TNF-α, IL-6 and iNOS. The expression of the anti-inflammatory genes Arg-1, IL-4, IL-10 and TGF-β by RAW264.7 cells was significantly up-regulated after 3 days of incubation on the titanium surface after Nd:YAG decontamination treatment.

CONCLUSION(S)

The Nd:YAG laser increased the hydrophilicity and roughness of the titanium surface after decontamination, and this change inhibited M1-type macrophage polarization and promoted M2-type macrophage polarization.

In vitro investigation of the antibacterial and anti-inflammatory effects of LED irradiation

PURPOSE

This study aimed to investigate the proper wavelengths for safe levels of light-emitting diode (LED) irradiation with bactericidal and photobiomodulation effects in vitro.

METHODS

Cell viability tests of fibroblasts and osteoblasts after LED irradiation at 470, 525, 590, 630, and 850 nm were performed using the thiazolyl blue tetrazolium bromide assay. The bactericidal effect of 470-nm LED irradiation was analyzed with Streptococcus gordonii, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, and Tannerella forsythia. Levels of nitric oxide, a proinflammatory mediator, were measured to identify the anti-inflammatory effect of LED irradiation on lipopolysaccharide-stimulated inflammation in RAW 264.7 macrophages.

RESULTS

LED irradiation at wavelengths of 470, 525, 590, 630, and 850 nm showed no cytotoxic effect on fibroblasts and osteoblasts. LED irradiation at 630 and 850 nm led to fibroblast proliferation compared to no LED irradiation. LED irradiation at 470 nm resulted in bactericidal effects on S. gordonii, A. actinomycetemcomitans, F. nucleatum, P. gingivalis, and T. forsythia. Lipopolysaccharide (LPS)-induced RAW 264.7 inflammation was reduced by irradiation with 525-nm LED before LPS treatment and irradiation with 630-nm LED after LPS treatment; however, the effects were limited.

CONCLUSIONS

LED irradiation at 470 nm showed bactericidal effects, while LED irradiation at 525 and 630 nm showed preventive and treatment effects on LPS-induced RAW 264.7 inflammation. The application of LED irradiation has potential as an adjuvant in periodontal therapy, although further investigations should be performed in vivo.

Assessment of Disinfection Potential of Q-Switch Nd: YAG Laser on Contaminated Titanium Implant Surfaces

Peri-implantitis (PI) is a relatively frequent pathology that compromises the overall survival of the dental implant. Adjunctive approaches for the conventional mechanical debridement are being suggested to optimize the treatment of PI. The goal of the study was the assessment of the disinfection potential of the Q-Switch Nd: YAG laser on contaminated titanium implant surfaces. A total of 72 sterile titanium discs were used and divided into three groups: 24 contaminated titanium discs treated with the laser (study Group L), 24 contaminated titanium discs with no treatment (control 1—Group C), and 24 sterile titanium discs with no treatment (control 2—Group S). Multi-species biofilm was used: Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, Streptococcus mutans, Streptococcus sobrinus, and Prevotella intermedia. Commensal bacteria were included also: Actinomyces naeslundii, Actinomyces viscosus, Streptococcus cristatus, Streptococcus gordonii, Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis, Streptococcus parasanguinis, and Veillonella parvula. Parameters delivered per pulse on the targeted surfaces of the titanium discs were an energy density of 0.597 J/cm² each pulse, a pulse power of 270 mW, a laser beam spot of 2.4 mm in diameter, and a rate of repetition of 10 Hertz (Hz) for a pulse duration of 6 nanoseconds (ns). The mode was no contact, and a distance of 500 micrometers was used with a total time of irradiation equal to 2 s (s). The collection of microbiological samples was made for all groups; colony-forming units (CFU) were identified by two different practitioners, and the average of their examinations was considered for each sample. The average of the TBC (CFU/mL) was calculated for each group. Values were 0.000 CFU/mL, 4767 CFU/mL, and 0.000 CFU/mL for Group L, Group C, and Group S, respectively. Therefore, the suggested treatment protocol was able to provoke a total disinfection of the contaminated titanium surfaces. A statistical difference was only found between Group L vs. Group C and between Group S vs. Group C. The difference was not significant between Group S and Group L. In conclusion, the present study confirmed that the Q-Switch Nd: YAG laser under our specific conditions can provide a total disinfection of the contaminated titanium surfaces.