Intrapulpal Temperature Increases Caused by 445-nm Diode Laser-Assisted Debonding of Self-Ligating Ceramic Brackets During Simulated Pulpal Fluid Circulation

Use of Blue and Blue-Violet Lasers in Dentistry: A Narrative Review

Introduction: Blue and blue-violet diode lasers (450 and 405 nm) seem to represent an interesting approach for several clinical treatments today. The aim of this narrative review is to describe and comment on the literature regarding the utilization of blue and blue-violet lasers in dentistry. Methods: A search for "blue laser AND dentistry" was conducted using the PubMed database, and all the papers referring to this topic, ranging from 1990 to April 2020, were analyzed in the review. All the original in vivo and in vitro studies using 450 nm or 405 nm lasers were included in this study. All the articles on the LED light, laser wavelengths other than 405 and 450 nm and using lasers in specialties other than dentistry, as well as case reports, guideline papers and reviews were excluded. Results: From a total of 519 results, 47 articles met the inclusion criteria and were divided into 8 groups based on their fields of application: disinfection (10), photobiomodulation (PBM) (4), bleaching (1), resin curing (20), surgery (7), periodontics (1), endodontics (1) and orthodontics (3). Conclusion: Blue and blue-violet diode lasers may represent new and effective devices to be used in a large number of applications in dentistry, even if further studies will be necessary to fully clarify the potentialities of these laser wavelengths.

Cavity Disinfection With a 445 nm Diode Laser Within the Scope of Restorative Therapy - A Pilot Study

Introduction: Cavity disinfection is necessary to prevent a progressive infection of the crown dentin and pulp. Increasing intolerance and resistance to antiseptics and antibiotics as well as the controversy over the effects of those on the dental hard tissue and composite have prompted the investigation of alternative treatment options. The objective of this pilot study is to evaluate the antibacterial potential of a diode laser with a wavelength of 445 nm in the cavity preparation using the bacterium Streptococcus salivarius associated with caries in conjunction with the characteristics and influences of dentin on light transmission. Methods: The bactericidal effect of the laser irradiation was determined in culture experiments by using caries-free human dentin samples on bacteria-inoculated agar. For this, dentin discs (horizontally cut coronal dentin) of 500 µm and 1000 µm thicknesses were produced and irradiated with the laser with irradiation parameters of 0.7-1 W in a cw-mode and exposure times of between 5-30 s. Based on the different sample thicknesses, the penetration depth effect of the irradiation was ascertained after the subsequent incubation of the bacteria-inoculated agar. Additional influential parameters on the irradiation transmission were investigated, including surface moisture, tooth color as well as the presence of a smear layer on the dentin surface. Results: The optical transmission values of the laser radiation for dentin were significantly dependent on the sample thickness (P = 0.006) as well as its moisture content (P = 0.013) and were independent of the presence of a smear layer. There was a 40% reduction in bacteria after the radiography of the 500-µm-thick dentin samples, which was shown as the lowest laser dose (443 J/cm²). Conclusion: These findings indicate that the diode laser with light emission at a wavelength of 445 nm is interesting for the supportive cavity disinfection within the scope of caries therapy and show potential for clinical applications.

Effects of 445-nm Diode Laser-Assisted Debonding of Metallic Brackets on Shear Bond Strength and Enamel Surface Morphology

Objective: To evaluate the effect of a 445-nm diode laser on the shear bond strength (SBS) of metallic brackets before debonding. Background: Due to the new blue laser technology, very few studies are available in this context. Methods: Seventy metallic brackets (Discovery; Dentaurum, Ispringen, Germany) were bonded to the frontal enamel surfaces of 70 caries-free bovine incisors in a standardized way. Each sample was randomly assigned to the control or laser group, with 35 samples per group. The brackets in the laser group were irradiated with the diode laser (SIROLaser Blue^®; Sirona, Bensheim, Germany) on three sides of the bracket bases for 5 s each (lateral-coronal-lateral, a total of 15 s) immediately before debonding. SBS values were evaluated for the control group and laser group. Micrographs of the enamel surface were taken with 10 × magnification to assess the adhesive remnant index (ARI) and the degree of enamel fractures after debonding. Results: There were no statistically significant differences in SBS in the laser group in comparison with the control group (p > 0.05). The distribution of ARI scores was also not statistically significantly different in the laser group in comparison with the control group (p > 0.05). Three enamel fractures occurred in the control group and one in the laser group after debonding. Conclusions: Irradiation of metallic brackets with the 445-nm diode laser before debonding does not significantly reduce the SBS values and does not influence the remaining amount of adhesive on the enamel surface. The risk of enamel fractures during debonding is therefore not clinically affected.

Using 445 nm and 970 nm Lasers on Dental Implants-An In Vitro Study on Change in Temperature and Surface Alterations

The aim of this study was to evaluate the safety of using a 445 nm laser on dental implants by comparing it with a laser with 970 nm wavelength. Two models, a pig mandible and glass ionomer cement, were used to evaluate the temperature increase in dental implants during laser irradiation with both wavelengths. Temperature was measured every second at four different places on the dental implants. Different power settings, effects of water cooling, distance of the laser fibre to the dental implant and continuous comparison to a pulsed laser beam were tested. Surface alterations on titanium discs after laser irradiation for 4 min at 2.0 W, were analysed in a scanning electron microscope (SEM). The maximum temperature and time to reach each of the thresholds were comparable between the 445 nm and 970 nm lasers. Neither the 445 nm nor the 970 nm wavelength showed any signs of surface alterations on the titanium discs. Using a 445 nm laser on dental implants is as safe as using a 970 nm laser, in terms of temperature increase and surface alterations. Applying a generous amount of cooling water and irradiating in short intervals is important when using lasers on dental implants.