Safety and Efficacy of the Erbium Laser in Debonding Dental Accessories: A Narrative Review

Objective: This article aims to review the safety and efficacy of the Er:YAG laser in debonding dental accessories. Methods: This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Articles published between 2010 and 2022 on the removal of dental accessories using erbium laser were searched. The selected articles were then classified according to the accessories used: adhesives, brackets, restorations, or implant crowns. Enamel surface roughness, shear bond strength, adhesive remnant index, duration time (t), pulp chamber temperature (T), morphology (M), and other variables were then noted. Results: The dental accessories and adhesives used were described along with the laser parameters used, such as frequency, pulse width, irradiation time, scanning mode, water-air cooling, and other variables. Conclusions: Laser removal using Er:YAG laser of dental accessories such as brackets, crowns, and veneers is fundamentally safe, time-saving, and does not cause damage to the enamel nor the underlying dentin. However, there was no distinct advantage with laser removal seen, such as those residual adhesives of brackets on the tooth surface and temporary adhesives of restorations.

Assessment of Smear Layer Formation After Caries Removal Using Erbium Laser and Papain-Based Chemo-Mechanical Caries Removal Agent: An In Vitro Scanning Electron Microscopy Study

Introduction With the advancement in the field of adhesive dentistry, there has been a significant and groundbreaking shift toward the adoption of minimally invasive caries removal techniques where substrate modification is known to enhance adhesive bonding. The smear layer has always been controversial, as its modification helps in bonding, but if contaminated with bacteria, it compromises the formation of a satisfactory marginal seal. Thus, the recognition of the role played by the smear layer highlights the importance of the type of caries removal method employed. Hence, the aim of the present study was to assess and compare smear layer formation after caries removal using an erbium laser and chemo-mechanical caries removal agent by scanning electron microscopy. Methods The study involved the evaluation of 30 extracted human molars with occlusal caries. Based on the method of caries excavation, the samples were allocated into two separate groups: group 1 - caries removed using erbium laser (Waterlase, Biolase, Lake Forest, CA); group 2 - caries removed using papain-based chemo-mechanical caries removal agent (Carie Fix, Dengen Dental, Bahadurgarh, India). To assess the smear layer, the samples underwent examination using a scanning electron microscope at 1500x and 3000x magnification after removal of caries. Statistical analysis was done using SPSS version 22 software (IBM Corp., Armonk, NY). Mann-Whitney test was used to compare the mean smear layer (nonparametric) between both groups. Results Group 1 (Er:YAG laser) showed significantly greater removal of the smear layer than group 2 (papain-based chemo-mechanical caries removal agent) on the excavated caries surfaces (p < 0.001). In group 1, the dentinal tubules exhibited greater patency when compared to the partial patency observed in group 2. Conclusion Both techniques for caries removal were effective; however, the Er:YAG laser method was determined to be more efficient in comparison to the chemo-mechanical agent. These caries removal methods can be considered the future of minimally invasive dentistry.

Isthmus morphology influences debridement efficacy of activated irrigation: A laboratory study involving biofilm mimicking hydrogel removal and high-speed imaging

AIM

Little is known about the influence of isthmus morphology on the debridement efficacy of activated irrigation. The aim of this study was to investigate the influence of isthmus morphology on the debridement efficacy of laser-activated irrigation (LAI), EDDY and needle irrigation (NI), and to explain the methods of isthmus cleaning by LAI and EDDY.

METHODOLOGY

Four root canal models (apical diameter: 0.30 mm, taper: 0.06, curvature: 23°, length: 20 mm) were produced by CAD-CAM with different isthmus morphologies: long-wide (4 mm; 0.4 mm), long-narrow (4 mm; 0.15 mm), short-wide (2 mm; 0.4 mm) and short-narrow (2 mm; 0.15 mm). The isthmuses were filled with a hydrogel containing dentine debris. The canals were filled with irrigant and models were assigned to the following irrigation protocols (n = 240): needle irrigation (NI) with a 30G needle, Eddy, and LAI (2940 nm Er:YAG-laser, 15 Hz, 40 mJ, SWEEPS, tip at the canal entrance). Standardized images of the isthmuses were taken before and after irrigation, and the amount of removed hydrogel was determined using image analysis software and compared across groups using Kruskal-Wallis test followed by Dunn's multiple comparison. Visualization of the isthmus during activation was achieved using a high-speed camera. The pattern and speed of the flow in the isthmus as well as transient and stable cavitation were analysed using imaging software.

RESULTS

Laser-activated irrigation, EDDY and NI removed more hydrogel in short-wide isthmuses than in narrow isthmuses (p < .001). LAI and EDDY removed more hydrogel than NI in every isthmus configuration (p < .001). EDDY showed eddies and stable cavitation, and LAI showed transient cavitation at each pulse, and pulsed horizontal flow with the highest particle speed in closed short isthmuses.

CONCLUSIONS

Isthmus morphology influences debridement in all irrigation groups. Short-wide isthmuses were the easiest to clean while narrow isthmuses were the most challenging to clean. Width seems to be a more critical anatomical parameter than length. LAI and EDDY resulted in the greatest biofilm removal and performed better than NI. EDDY produced eddies and stable cavitation in the isthmus, and LAI showed transient cavitation and pulsed horizontal flow.

The In Vitro Effect of Laser Irradiation (Er:YAG and CO(2)) and Chemical Reagents (Hydrogen Peroxide, Sodium Hypochlorite, Chlorhexidine, or Sodium Fluoride) Alone or in Combination on Reducing Root Caries Bacteria

(1) Lasers have been used for the treatment of dentinal hypersensitivity and bacterial reductions in periodontology. The purpose of this in vitro study was to evaluate the effect of Carbon Dioxide (CO₂) and Erbium-doped Yttrium Aluminum Garnet (Er:YAG) lasers with chlorhexidine (CHX), hydrogen peroxide (H₂O₂), sodium hypochlorite (NaOCl), or sodium fluoride (NaF) on the viability of oral bacteria associated with root caries. (2) Streptococcus mutans, Streptococcus sanguinis, and Enterococcus faecalis were grown in Brain Heart Infusion (BHI) broth, diluted to an OD660 of 0.5, and treated with antiseptics with or without simultaneous irradiation with the Er:YAG and CO₂ lasers for 30 s repeated three times. The treatment groups consisted of 1: no treatment, 2: 0.5% H₂O₂ alone, 3: 0.5% NaOCl alone, 4: 0.12% CHX alone, 5: 2% NaF alone, 6: laser alone, 7: laser with 0.5% H₂O₂, 8: laser with 0.5% NaOCl, 9: laser with 0.12% CHX, and 10: laser with 2% NaF for both lasers. The microbial viability was determined through plating and viable colonies were counted, converted into CFU/mL, and transformed into log form. The statistical analysis was performed using a two-tailed paired t-test. (3) The use of CO₂ and Er:YAG lasers alone failed to show statistically significant antibacterial activity against any of the bacteria. The only effective monotreatment was CHX for S. mutans. The combined treatment of 0.5% NaOCl with Er:YAG produced the greatest reduction in overall viability. (4) The combination of the Er:YAG laser with 0.5% NaOCl resulted in the largest reduction in bacterial survival when compared to monotherapies with antimicrobial solutions or lasers.

Effect of Er:YAG, Co2 lasers, papain, and bromelain enzymes dentin treatment on shear bond strength of composite resin

OBJECTIVE

Effective bond strength of composite resin restoration leads to its durability, so evaluation of dentin surface treatment with enzymes and laser for higher bond strength is an important factor.

MATERIALS AND METHODS

Sixty human molar teeth were cut at a depth of 2 mm of occlusal part and divided into six groups (n = 10). G1: etched with 37% phosphoric, G2 and G3: 10% papain or bromelain enzymes were used on the dentinal surface, G4: 10% papain and bromelain enzyme mixture were used for. Then, the specimens were washed with distilled water. In G5 and G6: Er:YAG or Co2 lasers were used on the dentin surface. An adhesive system was applied and then nanohybrid composite was placed in teflon mold and light cured. Samples were subjected to a shear bond strength (SBS) test by universal testing machines. Statistical analysis was performed, using one-way analysis of variance and Tukey HSD tests (p < .05).

RESULTS

The mean SBS in G1 was significantly higher in comparison with the other groups (p < .0001). On the other hand, a comparison of mean SBS between groups 2, 3, 4, and 5 shows no significant differences (p = .221). The mean SBS in group 6 (Co2 laser) was significantly lower in comparison with the other groups (p < .0001).

CONCLUSION

Results showed that SBS of composite resin to dentin was not significantly affected, using either bromelain or papain 10% enzymes or erbium laser. Co2 laser had a negative effect on dentin and decreased the SBS. Phosphoric acid has the best result.

Treatment of scars with autologous fat grafting and 1540 nm non-ablative erbium laser

Scars may be devastating for patients. Fat grafting and non-ablative lasers are available options for improvement. The former reshapes and improves scar quality by adding volume and regenerative adipose-derived stem cells, whereas the latter facilitates synthesis and deposition of new dermal collagen. The combination may be synergic, leading to better cosmetic outcome.This was a prospective study of 16 consecutive patients treated with autologous fat grafting and non-ablative 1540-nm erbium laser for facial scars between January 2015 and December 2015. Treatment protocol included fat injection followed by five treatments with 1540-nm erbium laser (ICON^TM Cynosure; Westford, MA, USA) a month later. We evaluated patients before, after treatments, and 6 months after the final treatment.Sixteen patients participated in our study. Mean patient age was 42 years (range 16-59 years). Scars were either traumatic (73%) or acne induced (27%). Traumatic scars were mainly new scars, with the majority of patients were treated within 30 days of injury. There were no reported complications. Scars improved in both texture and appearance and patient satisfaction was high in all cases.Treatment of scars with autologous fat grafting and fractional non-ablative 1540-nm erbium laser is safe and efficient and results in improved scar appearance and texture.

Short-term effects of an erbium/neodymium laser combination in superficial dyspareunia: a pilot study

OBJECTIVE

This prospective pilot study aimed to evaluate the effects of associating a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser with a vaginal erbium laser (VEL), as a non-ablative photothermal therapy for superficial dyspareunia in postmenopausal women (PMW) suffering from genitourinary syndrome of menopause (GSM).

METHODS

Two groups of sexually active PMW reporting superficial dyspareunia were selected: one (15 patients, VEL) was treated using an erbium:yttrium-aluminum-garnet laser crystal (XS Fotona SMOOTH; Fotona, Ljubljana, Slovenia) with a wavelength of 2940 nm; in the other group (15 patients, VEL + Nd:YAG) this treatment was followed by Nd:YAG laser (Fotona SP Dynamis, PIANO mode) treatment. Treatment consisted of three laser applications at 30-day intervals. Symptoms were assessed before, after each laser application and after 1 and 3 months from the end of the treatment, using the subjective visual analog scale (VAS) for superficial dyspareunia.

RESULTS

Both groups showed a rapid and significant improvement of superficial dyspareunia over time (p < 0.001) independently from age and years since menopause. The VEL + Nd:YAG group showed a greater improvement of superficial dyspareunia (p < 0.001); this difference was evident since the first treatment and remained stable over time.

CONCLUSIONS

The addition of Nd:YAG to VEL may induce greater improvement in superficial dyspareunia in PMW with GSM.

Fibroblasts Adhesion to Laser-Modified Titanium Surfaces-A Systematic Review

OBJECTIVE

Laser treatment has been recently introduced in many fields of implant dentistry. The systematic review tried to address the question: "How does laser modification of titanium surface influence fibroblast adhesion?".

METHODS

An electronic search of the PubMed and Scopus databases was performed. The following keywords were used: (laser) AND (fibroblast) AND (titanium) AND (implant OR disc) AND (proliferation OR adhesion). Initially, 136 studies were found. Ten studies met the inclusion criteria and were included in the review. All studies chosen to be included in the review were considered to have a low risk of bias.

RESULTS

Studies included in the review varied with laser parameters or ways of observing fibroblast behavior. Studies showed that fibroblasts tend to take different shapes and create extensions on modified surfaces and that their metabolic activity is more intense. One study concentrated on laser application and showed that three-directional laser application is the most successful in terms of fibroblast adhesion. Studies which concentrated more on laser parameters showed that too low energy density (lower or equal to 0.75 J/cm2) does not influence fibroblast adhesion. Increasing the energy density over 0.75 J/cm2 causes better cell adhesion of fibroblasts to the laser-modified sample. One included study focused on increasing titanium surface wettability, which also positively influenced cell adhesion.

CONCLUSION

The studies included in the review proved a positive effect of laser-modified titanium surfaces on fibroblast adhesion. However, the application of an appropriate laser energy dose is crucial.

Safety of vaginal erbium laser: A review of 113,000 patients treated in the past 8 years

Background: Energy-based devices are becoming a popular option for minimally invasive vaginal procedures. The aim of this study was to obtain information on the frequency of occurrence of adverse effects (AEs) related to vaginal erbium laser (VEL™) treatment.Materials and methods: The global survey was conducted among practitioners using the non-ablative VEL™ (Fotona, Ljubljana, Slovenia). Users were invited to provide the number of patients treated with VEL™ and the number of observed laser-related AEs.Results: The survey was conducted from August 2018 to April 2019. Responses from 535 practitioners were collected, with a total of 113,174 patients treated in the period from 2012 to 2019. Out of 535 respondents, 160 (30%) shared detailed information about the indications they treated in a population of 62,727 patients, whereas 188 (35%) respondents provided information on the frequency of AEs observed in their treated population of 43,095 patients. All observed AEs were mild to moderate, transient and appeared with low frequencies.Conclusions: Minimally invasive thermal-only laser treatment using the non-ablative VEL™ procedures appears to be safe and the incidence of AEs is low.

Histological findings after non-ablative Er:YAG laser therapy in women with severe vaginal atrophy

Objective: The aim of this study was to evaluate the effect of non-ablative erbium vaginal laser treatment on vaginal mucosa tissue affected by severe atrophy.Methods: Ten patients with severe genitourinary syndrome of menopause were treated with two sessions of the non-ablative erbium-doped yttrium aluminium garnet laser (Er:YAG laser) separated by 4 weeks. Vaginal biopsies were performed before and 3 months after the second treatment. The improvement in vaginal atrophy was assessed using multiple measuring tools before and 6 months after the treatment. The degree of patients' satisfaction was also assessed.Results: Microscopic examination showed significant changes in the main structural components of the vaginal wall mucosa after two non-ablative Er:YAG laser sessions. The epithelial thickness increased from 45 µm (10-106 µm) to 153 µm (97-244 µm) measured 3 months after the final laser treatment. Vaginal atrophy improved in all patients by all measured outcomes. The degree of patient satisfaction was very high (3.6 on the Likert four-point scale). No adverse events or complications were observed in any of the sessions. Conclusion: The non-ablative Er:YAG laser seems to be a safe and effective method to increase epithelial thickness of the vaginal mucosa in patients with severe vaginal atrophy.

The Effect of Er:YAG Lasers on the Reduction of Aerosol Formation for Dental Workers

Infection prevention in dental practice plays a major role, especially during the COVID-19 pandemic. This study aimed to measure the quantity of aerosol released during various dental procedures (caries and prosthetic treatment, debonding of orthodontic brackets, root canal irrigation) while employing the Er:YAG lasers combined with a high-volume evacuator, HVE or salivary ejector, SE. The mandibular second premolar was extracted due to standard orthodontic therapy and placed in a dental manikin, to simulate typical treatment conditions. The particle counter was used to measure the aerosol particles (0.3–10.0 μm) at three different sites: dental manikin and operator’s and assistant’s mouth area. The study results showed that caries’ treatment and dental crown removal with a high-speed handpiece and the use of the SE generated the highest aerosol quantity at each measured site. All three tested Er:YAG lasers significantly reduced the number of aerosol particles during caries’ treatment and ceramic crown debonding compared the conventional handpieces, p < 0.05. Furthermore, the Er:YAG lasers generated less aerosol during orthodontic bracket debonding and root canal irrigation in contrast to the initial aerosol quantity measured in the dental office. The use of the Er:YAG lasers during dental treatments significantly generates less aerosol in the dental office setting, which reduces the risk of transmission of viruses or bacteria.

Postoperative pain after ultrasonically and laser-activated irrigation during root canal treatment: a randomized clinical trial

AIM

To compare the intensity of postoperative pain after primary root canal treatment of asymptomatic teeth when using ultrasonically (UAI) or laser-activated irrigation (LAI).

METHODOLOGY

In this superiority randomized clinical trial (ClinicalTrials.gov ID: NCT03981237) with parallel design, fifty-six patients with an asymptomatic tooth in need of primary root canal treatment were enrolled. After chemo-mechanical canal preparation using rotary instruments and NaOCl irrigation, teeth were randomly assigned to two groups and patients were blinded to the final irrigation protocol. In the UAI group (n = 28), 60s activation with an Irrisafe tip was done per canal. In the LAI group (n = 28), NaOCl was activated with a pulsed Er:YAG (2940 nm) laser, equipped with a conical tip, with settings of 50 µs, 20 mJ at 15 Hz for 60 s. Patients recorded their pain intensity 6, 24, 48 and 72 h after treatment on a 100 mm visual analogue scale (VAS), as well as their analgesic consumption. Pain levels and incidence were compared across groups using the Mann-Whitney U-test and chi-square test.

RESULTS

Overall, mean postoperative pain intensity was low, with the majority of patients having no or minimal pain 24 h postoperatively. At 6 h postoperatively, pain intensity and incidence were significantly higher in the UAI group compared to the LAI group (P < 0.05). For the other time intervals, no significant differences in postoperative pain incidence or intensity were found. The frequency of analgesic intake did not differ significantly between the two groups. Neither of the activation methods resulted in any adverse effects.

CONCLUSIONS

Ultrasonically and laser-activated irrigation resulted in low and comparable levels of postoperative pain in asymptomatic patients receiving primary root canal treatment.

Evaluation of Er:YAG and Er,Cr:YSGG laser irradiation for the debonding of prefabricated zirconia crowns

BACKGROUND

Reduced tooth structure in the pediatric and adolescent population is frequently restored with prefabricated zirconia crowns. On permanent teeth, these restorations may need to be removed and replaced with permanent restorations.

OBJECTIVES

To explore and compare the use of 2 high-powered erbium lasers for removing prefabricated zirconia crowns from molar teeth as a non-invasive alternative to rotary instruments.

MATERIAL AND METHODS

Twenty-five permanent molars were prepared to dentin and prefabricated all-ceramic zirconia crowns were fitted and cemented with resin modified glass ionomer (RMGI) cement. The teeth were randomly assigned into one of the 2 retrieval treatment groups: the erbium-doped yttrium, aluminum and garnet (Er:YAG) laser group (G1; n = 12) or the erbium, chromium-doped yttrium, scandium, gallium and garnet laser (Er,Cr:YSGG) laser group (G2; n = 13). The laser operating parameters for the Er:YAG laser were 300 mJ, 15 Hz, 4.5 W, and 50-microsecond pulse duration (SSP mode); for the Er,Cr:YSGG laser, they were 4.5 W, 15 Hz, 20 water/20 air, and 5 W, 15 Hz, 50 water/50 air, and 60-microsecond pulse duration (H mode). The experiment was repeated twice. The surface area and the volume of teeth and crowns were measured and the cement space was calculated. The retrieval time and temperature changes were tested and recorded. The data were analyzed with the t-test. The surfaces of the dentin and the crown from each group were further examined using scanning electron microscopy (SEM).

RESULTS

The average time for crown removal using the Er:YAG laser was 1 min 32.7 s; for the Er,Cr:YSGG laser it was 3 min 13.9 s (p < 0.0001). The mean temperature changes were 1.41 ±1.36°C for the Er:YAG laser and 2.2 ±0.99°C for the Er,Cr:YSGG laser (p = 0.0321). The SEM examination showed no damage or major structural changes caused by treatment with either erbium-family laser.

CONCLUSIONS

Both lasers are effective, non-invasive tools to remove prefabricated zirconia crowns cemented with resin cement and should be considered as viable alternatives to rotary instrumentation.

[Comprehensive treatment of indolent trophic ulcers of venous aetiology]

AIM

The study was undertaken to evaluate efficacy of comprehensive treatment with the use of erbium laser radiation in patients suffering from venous trophic ulcers of lower limbs.

PATIENTS AND METHODS

The study included a total of seventy-six 45-to-80-year-old patients. Of these, there were 43 (56.6%) women and 33 (43.4%) men. The duration of the disease averagely amounted to 10.8±4.8 years. In 38 patients, the bottom of the ulcerative defect was with pronounced periulcerative inflammation and various degree of purulent discharge. All patients were admitted to the surgical department and underwent meticulous examination. Erbium laser irradiation was carried out with consideration for the ulcer size. Laser irradiation was performed at a wavelength of 2940 nm, pulse duration - 0.3 ms, laser beam diameter - 7 mm with radiation power of 2.19 J/cm2.

RESULTS

Efficacy of treatment was assessed in dynamics by the degree of pain syndrome, ulcer size upon completion of treatment, as well as the rate of trophic ulcer epithelialisation. In 15 (19.7%) patients with varicose disease the vertical and horizontal reflux was eliminated with performing phlebectomy and echosclerotherapy. The obtained findings demonstrated that 42 (91.3%) patients of the study group had decreased terms of the beginning of purification of the fundus of the ulcer. After 6 months of rehabilitation and follow up, complete ulcer healing was achieved in 18 (64.3%) patients of the control group and in 39 (86.7%) patients of the study group.

CONCLUSION

The obtained findings showed that laser radiation proved to be an effective method of treatment in patients presenting with indolent trophic ulcers. Comprehensive treatment made it possible to effectively influence the microflora and the state of regional lymph drainage, to stimulate the processes of reparative regeneration.

Evaluation of Enamel Topography after Debonding Orthodontic Ceramic Brackets by Different Er,Cr:YSGG and Er:YAG Lasers Settings

In the last decade, the success of lasers in simplifying many dental procedures has heightened the need for research in the orthodontic field, in order to evaluate the benefits of laser-assisted ceramic brackets debonding. Conventional ceramic brackets removal delivers a high shear bond strength (SBS), which might lead to enamel damage. Nowadays, debonding ceramic brackets by Er:YAG laser seems a viable alternative technique; however, there is no data on the use of Er,Cr:YSGG in the literature. We aimed to evaluate the difference in enamel topography derived from different erbium laser settings used during debonding. One hundred and eighty bovine incisors teeth were randomly divided into fifteen experimental groups, according to different erbium laser settings using scanning methods. SBS testing was performed after debonding; stereomicroscopic and SEM analyses were done after cleaning the remaining adhesive so as to assess the incidence of enamel microcracks formation and enamel loss. There were no statistically significant differences between the proportions of teeth with normal enamel topography within the control group when compared with any of the Er:YAG groups. However, the proportion of teeth with a normal enamel topography in Er,Cr:YSGG was 4 W/20 Hz (83.3%) and in Er:YAG was 5 W/20 Hz (91.7%), which was statistically significantly higher than the control group (41.7%). The selection of erbium lasers' optimal parameters during debonding influences the enamel topography. When considering the evaluation of both microscopic and statistical analyses, irradiation by Er:YAG (120 mJ/40 Hz) displayed a significant reduction in microcracks compared with conventional debonding, even though some microstructural changes in the enamel could be noted. Er,Cr:YSGG (4 W/20 Hz) respected the enamel topography the most out of the studied groups.

Effect of Er:YAG laser irradiation on deciduous enamel roughness and bacterial adhesion: An in vitro study

Laser irradiation has been proposed as a preventive method against dental caries since it is capable to inhibit enamel demineralization by reducing carbonate and modifying organic matter, yet it can produce significant morphological changes. The purpose of this study was to evaluate the influence of Er:YAG laser irradiation on superficial roughness of deciduous dental enamel and bacterial adhesion. Fifty-four samples of deciduous enamel were divided into three groups (n = 18 each). G1_control (nonirradiated); G2_100 (7.5 J/cm² ) and G3_100 (12.7 J/cm² ) were irradiated with Er:YAG laser at 7.5 and 12.7 J/cm² , respectively, under water irrigation. Surface roughness was measured before and after irradiation using a profilometer. Afterwards, six samples per group were used to measure bacterial growth by XTT cell viability assay. Adhered bacteria were observed using confocal laser scanning microscopy (CLSM) and a scanning electron microscopy (SEM). Paired t-, one-way analysis of variance (ANOVA), Kruskal-Wallis and pairwise Mann-Whitney U tests were performed to analyze statistical differences (p < .05). Before treatment, samples showed homogenous surface roughness, and after Er:YAG laser irradiation, the surfaces showed a significant increase in roughness values (p < .05). G3_100 (12.7 J/cm² ) showed the highest amount of Streptococcus mutans adhered (p < .05). The increase in the roughness of the tooth enamel surfaces was proportional to the energy density used; the increase in surface roughness caused by laser irradiation did not augment the adhesion of Streptococcus sanguinis; only the use of the energy density of 12.7 J/cm² favored significantly the adhesion of S. mutans.

Use of Er:YAG laser in the treatment of vulvar lichen sclerosus

Objective

The aim of this research was to evaluate the efficacy and safety of Er:YAG lasers to improve signs and symptoms of vulvar lichen sclerosus.

Methods

The study population consisted of 28 women with symptomatic vulvar lichen sclerosus. Three nonablative, thermal-only Er:YAG laser treatment sessions (7 J/cm², 2 Hz, 7 mm spot) were performed at 4-week intervals. Each patient was asked about the presence of symptoms, such as itching, pain, and coital pain. Clinical diagnosis was established on the basis of the presence of lesions such as hypopigmentation, ecchymosis, hyperkeratosis, excoriations, or fissures. The affected areas were divided by zones (clitoris, introitus, labia minora, labia majora, perineum, labial fusion, and effacement) and were visually evaluated. Based on the presence of symptoms, lesions, and affected zones, a scale with a maximum of 14 scores was established for use before and after treatment. The impact of lichen sclerosus on patients' lives before and after treatment was evaluated with an 11-point visual analogue scale, and treatment discomfort was assessed at each session.

Results

After analysis of each scoring component, individual statistically significant reductions were observed in itching, pain, ecchymosis, excoriations, and hypopigmentation.

Conclusion

The Er:YAG laser is a safe, well tolerated, and effective method for the adjuvant treatment of vulvar lichen sclerosus. Three sessions with monthly intervals using the indicated parameters can quantifiably reduce the impact of lichen sclerosus on patients' lives.

Fe3O4 nanoparticles as a saturable absorber for giant chirped pulse generation

Fe₃O₄ nanoparticles (FONPs) are magnetic materials with a small band gap and have well-demonstrated applications in ultrafast photonics, medical science, magnetic detection, and electronics. Very recently, FONPs were proposed as an ideal candidate for pulse generation in fiber-based oscillators. However, the pulses obtained to date are on the order of microseconds, which is too long for real application in communication. Here, we report the use of FONPs synthesized by a sol-hydrothermal method and used as a saturable absorber (SA) to achieve nanosecond pulses in an erbium-doped fiber laser (EDFL) for the first time. The proposed fiber laser is demonstrated to have a narrow spectral width of around 0.8 nm and a fixed fundamental repetition rate (RPR) of 4.63 MHz, whose spectra and pulse dynamics are different from the mode-locked lasers reported previously. It is demonstrated that the proposed fiber laser based on a FONP SA operates in the giant-chirp mode-locked regime. The most important result is the demonstration of a pulse duration of 55 ns at an output power of 16.2 mW, which is the shortest pulse based on FONPs for EDFLs reported to date. Our results demonstrate that the FONP dispersion allows for an excellent photonic material for application in ultrafast photonics devices, photoconductive detectors, and optical modulators.