The impact of laser application on periodontal and peri-implant wound healing

Evaluation of the effect of adjunctive diode laser application on peri-implant crevicular fluid biomarker levels: a randomized controlled trial

OBJECTIVES

To assess both the clinical and immunological effectiveness of diode laser therapy when used as an adjunct to non-surgical mechanical therapy in managing peri-implantitis.

MATERIALS AND METHODS

A cohort of 27 participants, comprising 21 females and 6 males, agreed to take part in this investigation. 37 dental implants with peri-implantitis diagnosis were randomly allocated to either the laser group (n = 19) or the control group (n = 18). Evaluation of peri-implant clinical parameters and collection peri-implant crevicular fluid (PICF) samples occurred at baseline, as well as at 3 and 6-month follow-up intervals. The level of various biomarkers (TWEAK, IL-1β, sclerostin, IL-17, RANKL, OPG and IL-10) within the PICF were quantified using enzyme-linked immunosorbent assay.

RESULTS

Significant time-dependent decreases in clinical and biochemical parameters were detected in both groups compared to the baseline. There were marked differences between the groups in terms of periodontal parameters, except probing depth, and IL-1β, IL-17, sclerostin levels in PICF at 3rd month follow-up. However, no statistically significant difference was detected at 6th month.

CONCLUSIONS

Diode laser seems to be a reliable tool as an adjunct for supporting the nonsurgical mechanical treatment during the early stages of peri-implantitis. Furthermore, the findings suggest that IL-17, sclerostin and IL-1β may serve as promising biomarkers for assessing efficacy of peri-implantitis treatment.

CLINICAL RELEVANCE

Based on these outcomes, clinicians may consider the application of adjunctive use of diode laser to non-surgical peri-implantitis treatment to achieve better clinical and immunological improvements than nonsurgical peri-implantitis therapy alone in just early healing period. However, it should be noted that there was no difference between the two methods in the long term.

Diode laser as an adjunctive treatment for periodontitis: Arandomized controlled trial

OBJECTIVE

The aim of this randomized controlled trial was to assess clinical and patient reported outcomes of subgingival instrumentation (SI) with adjunctive use of diode laser (DL) versus SI alone in the treatment of periodontitis.

METHODS

Participants requiring non-surgical periodontal treatment were randomly allocated into two treatment groups: SI with DL or SI alone. Clinical parameters [full mouth bleeding and plaque scores (FMBS and FMPS), probing pocket depth and clinical attachment level] were recorded at baseline, three and 6 months post-treatment. Visual analogue scale was used to evaluate postoperative participants' perception of pain, swelling, bleeding, bruising and root sensitivity. The impact of periodontal treatment on quality of life was assessed using the General Oral Health Assessment Index (GOHAI) at 6 months.

RESULTS

A total of 22 participants with stage III/IV periodontitis completed the 6-month follow-up. SI with or without DL resulted in statistically significant reduction in FMBS, FMPS, PPDs, and percentage of PPDs of ≥5 mm at 3- and 6-month follow-up visits (p = 0.001 to <0.001). The participants in SI/DL group had a greater reduction in the percentage of deep PPDs (≥5 mm) compared to those receiving SI alone, but statistically significant differences between the two groups were not observed (16.40 ± 9.57 vs. 32.50 ± 38.76 at 3 months and 7.20 ± 6.86 vs. 19.50 ± 35.06 at 6 months). The difference in the mean total GOHAI scores was not statistically significant at 6 months with total GOHAI scores of 7.25 ± 2.45 and 5.40 ± 3.06 for SI and SI/DL groups, respectively.

CONCLUSION

Within the limitations of this study, the use of DL as an adjunct to SI in the treatment of stage III/IV periodontitis did not produce significant additional improvement in clinical parameters or patient reported outcomes in the 6-month observation period.

Efficacy of laser in re-osseointegration of dental implants-a systematic review

Despite their high success rates, peri-implantitis can affect the stability and function of dental implants. Various treatment modalities have been investigated for the treatment of peri-implantitis to achieve re-osseointegration. An electronic literature search was performed supplemented by a manual search to identify studies published until January 2022. Articles that evaluated re-osseointegration in peri-implantitis sites in animal models following laser therapy or antimicrobial photodynamic therapy (aPDT) were included. Case reports, case series, systematic reviews, and letters to the editor were excluded. Risk of bias and GRADE assessment were followed to evaluate the quality of the evidence. Six studies out of 26 articles identified on electronic search were included in this review. The studies included animal studies conducted on canine models. Four out of six studies reported a higher degree of re-osseointegration following treatment of implants with laser therapy. The findings suggest that laser decontamination shows potential in enhancing re-osseointegration, particularly with the Er: YAG laser, which effectively decontaminated implant surfaces. However, conflicting outcomes and limitations in the evidence quality warrant caution in drawing definitive conclusions. Based on the limited available evidence, laser therapy may show a higher degree of re-osseointegration of implants than mechanical debridement.

Surgical Treatment of Peri-Implantitis Using a Combined Nd: YAG and Er: YAG Laser Approach: Investigation of Clinical and Bone Loss Biomarkers

The current study aimed to investigate the effect of the combined Nd-Er: YAG laser on the surgical treatment of peri-implantitis by evaluating clinical markers and biomarkers of bone loss (RANKL/OPG). Twenty (20) patients having at least 1 implant diagnosed with peri-implantitis were randomly assigned to two groups for surgical treatment. In the test group (n = 10), Er: YAG laser was used for granulation tissue removal and implant surface decontamination, while Nd: YAG laser was employed for deep tissue decontamination and biomodulation. In the control group (n = 10), an access flap was applied, and mechanical instrumentation of the implant surface was performed by using titanium curettes. The following clinical parameters were evaluated at baseline and six months after treatment: Full-mouth Plaque Score (FMPS), Probing Pocket Depth (PPD), Probing Attachment Levels (PAL), recession (REC), and Bleeding on probing (BoP). Peri-implant crevicular fluid (PICF) was collected at baseline and six months for the evaluation of soluble RANKL and OPG utilizing enzyme-linked immunosorbent assay (ELISA). Baseline clinical values were similar for both groups, with no statistical differences between them. The study results indicated statistically significant improvements in the clinical parameters during the 6-month observation period in both groups. More specifically, PPD, PAL, and REC were improved in the test and control groups with no differences in the between-groups comparisons. However, a greater reduction in the BoP-positive sites was noted for the laser group (Mean change 22.05 ± 33.92 vs. 55.00 ± 30.48, p = 0.037). The baseline and six-month comparisons of sRANKL and OPG revealed no statistically significant differences between the two groups. The combined Nd: YAG—Er: YAG laser surgical therapy of peri-implantitis seemed to lead to more favorable improvements in regard to bleeding on probing six months after treatment compared to the conventional mechanical decontamination of the implant surface. None of the methods was found superior in the modification of bone loss biomarkers (RANKL, OPG) six months after treatment.

Influence of Clinical Decontamination Techniques on the Surface Characteristics of SLA Titanium Implant

The study aims: 1. To perform diode laser, titanium (Ti) brush, and Ti curette treatment on sandblasted and acid-etched (SLA) Ti surfaces, with/without H2O2 and CHX, 2. To investigate the influence of decontamination techniques on implant surface topography and hydrophilicity. Diode laser, Ti brush, and Ti curette treatments were performed on the Grade 4 Ti discs, with/without treatment with 3% H2O2 solution or 0.2% CHX. Surface characteristics were investigated via SEM, optical profilometry, and water contact angle meter. SEM findings revealed flat and scratched areas when treated with Ti curette and Ti brush. For diode laser, SEM showed melting in specific areas. Ra and Rt values were lower in all test groups than in the control group (p < 0.05). The adjunctive chemical treatment showed negligible effects in SEM images and surface roughness measurements compared to laser and mechanical treatment-only groups. H2O2 treatment resulted in enhanced hydrophilicity in either treatment modalities with a significant difference compared to the negative control group (p < 0.05). In all test groups, the hydrophilicity was enhanced compared to the negative control group (p < 0.05). Diode laser treatment had the least disruptive effect on the Ti surface characteristics. The use of other mechanical methods caused significant alterations in the surface roughness.

Fracture strength of Er,Yag laser treated PMMA denture-based polymer (DBP) colonized with C. albicans, S. aureus, S.mutans, and E.coli

AIM

To assess and equate the efficacy of different disinfection protocols autoclave, chlorhexidine (CHX), PDT utilizing Rose Bengal (RB), chitosan, and Er, Yag laser and their effect on fracture strength of PMMA denture-based polymer (DBP) colonized with C. Albicans, S. aureus, S.mutans, and E.coli.

MATERIAL AND METHODS

A total of 50 (n = 10) PMMA DBP were manufactured and adulterated with the American Type Culture Collection (ATCC) of diverse microbial colonies inhabited by C. Albicans, S. aureus, S.mutans, and E.coli. The specimens were subjected to different denture disinfection approaches by randomly distributing in into five groups i.e., Er, Yag laser, RB, autoclave, CHX, and Chitosan, respectively for appraising antimicrobial effectiveness. PMMA fracture load was also assessed and statistical analysis was performed for CFU/mL (log10) of exposed C. Albicans, S. aureus, S.mutans, and E.coli by one-way ANOVA and Tukey's multiple comparison test at a significance level of p < 0.05.

RESULTS

Intergroup comparison disclosed that denture disinfection with Er, Yag laser, autoclave, Chitosan, and CHX (control) validated comparable antimicrobial efficacy to denture against all inspected CFU/mL (log10) (p>0.05). The intragroup comparison revealed that DBP sanitization with Er, Yag laser, autoclave, Chitosan, RB, and CHX substantiated equivalent effective antimicrobial efficacy in plummeting CFU/mL (log10) of S. mutans and E. coli (p>0.05) but in consideration to S.aureus and C.albicans, all groups resulted in declining their count except 5µm RB activated by PDT(p < 0.05). No significant difference was perceived in fracture load of PMMA denture base among Er, Yag laser, RB, chitosan, and CHX (control) (p > 0.05) except autoclave decontamination procedure that indicated the least fracture strength of DBP when disinfected (p < 0.05).

CONCLUSION

Er, Yag laser, and Chitosan activated by PDT have the potential to be used as an alternative to chlorhexidine for disinfecting Polymethyl methacrylate denture base as they demonstrated the highest antimicrobial efficacy against E. coli, C. Albicans, S aureus, and S. mutans with optimal fracture load.

Comparative evaluation of combined efficacy of methylene blue mediated antimicrobial photodynamic therapy (a-PDT) using 660 nm diode laser versus Erbium-chromium-yttrium-scandium-gallium-garnet (Er, Cr: YSGG) laser as an adjunct to scaling and root planing on clinical parameters in supportive periodontal therapy: A randomized split-mouth trial

AIM

The aim of this study was to evaluate combined efficacy of methylene blue mediated antimicrobial photodynamic therapy (a-PDT) using 660 nm diode laser versus Er, Cr: YSGG laser as an adjunct to scaling and root planing on improving the Probing depth (PD), Clinical attachment level (CAL), Plaque Index (PI) and Gingival Index (GI).clinical parameters in Supportive periodontal therapy.

MATERIALS AND METHOD

In this split-mouth, double-blind, randomized controlled trial, we compared a-PDT versus Er,Cr:YSGG as an adjunct to scaling and root planning (SRP) with SRP alone in Supportive periodontal therapy. A total of 36 subjected were enrolled. In each patient, two quadrants constituted the control group (Group I - Scaling and root planing SRP alone), one site in other quadrant constituted the test group 1 (Group II - SRP followed by application of Er, Cr: YSGG laser), and another site in different quadrant constituted the test group 2 (Group III - SRP followed by antimicrobial Photodynamic therapy using diode laser). The diode laser was operated at a peak power of 70 mW using a 0.6 mm diameter fiber-optic tip. Each site was irradiated with a power density of 28 mW/cm², for 10 s, thus delivering a total energy of 16.72 J/cm² per tooth. Whereas, the Er,Cr:YSGG laser's parameters were set to 1 W of power, 10% air, and 15% water. The same procedure was repeated at 1st, 2nd and 3rd week for both the laser therapies. Plaque index (PI), Gingival index (GI), Probing depth (PD,) and Clinical attachment level (CAL) were measured by a single examiner at baseline and 3 months follow up. Inter group analysis of the parameters were done using One-way ANOVA and pairwise comparison was carried out by Tukey's post hoc test. Intra group analysis was performed using Students's paired t test. Statistical significance was set to p < 0.05.

RESULTS

There were no significant differences between participants for clinical parameters at baseline. PI, GI PD, and CAL significantly improved at 3 months follow up compared to baseline in both the study groups (Group II - SRP + Er,Cr:YSGG, Group III - SRP + a-PDT) with P < 0.05. Adjunctive use of Er,Cr:YSGG laser with SRP showed better clinical outcomes than a-PDT with SRP.

CONCLUSION

Nonsurgical periodontal therapy of chronic periodontitis using Er, Cr: YSGG, and a-PDT as an adjunct to SRP was significantly more effective than SRP alone in reducing PD, CAL, GI, and PI at 3 months follow up. Adjunctive use of Er,Cr:YSGG laser with SRP showed better clinical outcomes than a-PDT with SRP. However, the long-term positive benefits of the laser therapies are yet unknown and more research with longer follow-ups are required.

Comparative frenectomy with conventional scalpel and dual-waved laser in labial frenulum

Aim

The purpose of the study is to compare the labial frenectomy between the laser surgery (erbium yttrium aluminum garnet and neodymium-doped yttrium aluminum garnet (Er:YAG and Nd:YAG)) and the scalpel method.

Methods

The trial was a randomized controlled test. Thirty four patients aged from 5 to 10 years requiring the frenectomy were included in this study. Patients were randomly divided into two groups: group A: Er:YAG and Nd:YAG laser group and group B: scalpel group. In addition, this comparison considered the following factors: surgical time and Visual Analog Scale (VAS) pain score, which includes intraoperative pain, postoperative pain and complications, such as speaking and chewing, for 1 day and 7 days following labial frenectomy. After 3 months, we recorded the healing outcome by photos.

Results

There was a statistically significant difference in mean surgical time between laser surgery (mean=224±59 s) and scalpel surgery (mean=740±168 s). According to VAS scores of the intraoperative period (3 hours after the operation and 1st postoperative day of pain), chewing and speaking were statistically higher in group B than those in group A; but in the 7th postoperative day of pain, there was no significant difference in speaking and chewing. After 1 month, all of the patient results were recorded, including the healing of wound and scar. Except for one patient in group B who had a scar, all patients achieved good results.

Conclusion

Based on the results of this study, it can be concluded that Nd:YAG laser is an efficient and more comfortable alternative to the scalpel for a frenectomy in upper lip frenulum.

Efficacy of Er:YAG laser irradiation for decontamination and its effect on biocompatibility of different titanium surfaces

Background

Erbium yttrium–aluminum–garnet (Er:YAG) laser have been shown to be suitable for decontamination of titanium surfaces at a wide range of energy settings, however, high intensity of laser irradiation destroy titanium surface and low intensity cannot remove enough microbial biofilm. The aim of this study was to investigate the optimal energy setting of Er:YAG laser for decontamination of sandblasted/acid-etched (SLA) and hydroxyapatite (HA) titanium surfaces.

Material and methods

After supragingival biofilm construction in vivo, SLA and HA titanium discs were divided into three groups: blank control (BC, clean discs), experimental control (EC, contaminated discs) and experimental groups (EP, contaminated discs irradiated by Er:YAG laser at 40, 70, and 100 mJ/pulse). Scanning electron microscopy (SEM), live/dead bacterial fluorescent detection, and colony counting assay were used to detect the efficacy of laser decontamination. To investigate the effect of laser decontamination on titanium surface biocompatibility, MC3T3-E1 cell adhesion and proliferation activity were examined by SEM and CCK-8 assay.

Results

Er:YAG laser irradiation at 100 mJ/pulse removed 84.1% of bacteria from SLA titanium surface; laser irradiation at 70 and 100 mJ/pulse removed 76.4% and 77.85% of bacteria from HA titanium surface respectively. Laser irradiation improved MC3T3-E1 cell adhesion on both titanium surfaces. For SLA titanium discs, 100 mJ/pulse group displayed excellent cellular proliferation activity higher than that in BC group (P < 0.01). For HA titanium discs, 70 mJ/pulse group showed the highest activity comparable to BC group (P > 0.05).

Conclusions

With regards to efficient microbial biofilm decontamination and biocompatibility maintenance, Er:YAG laser at 100 mJ/pulse and 70 mJ/pulse are considered as the optimal energy settings for SLA titanium and HA titanium surface respectively. This study provides theoretical basis for the clinical application of Er:YAG laser in the treatment of peri-implantitis.

Decontamination and Biomodification of Periodontally Affected Root Surface for Successful Regeneration: Is There Room for Improvement?

Periodontitis is a multifactorial inflammatory condition associated with an oral microbiome dysbiosis that results in gingival inflammation and clinical attachment loss. Periodontal therapies are based on scaling and root planing to disturb the bacterial biofilm mechanically and remove calculus and contaminated cementum. Research does not support the use of root modifiers for decontamination and biomodification of periodontally affected root surfaces. Standardized clinical trials in large populations, assessing biological and patient-reported outcome measures, are necessary to evaluate candidate biomaterials for decontamination and biomodification of periodontally affected root surfaces.

Erbium, chromium-doped: yttrium, scandium, gallium, garnet and diode lasers in the treatment of peri-implantitis: clinical and biochemical outcomes in a randomized-controlled clinical trial

This study aims to evaluate the effects of 940 nm diode laser and 2780 nm erbium, chromium-doped: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser used in addition to mechanical therapy in the non-surgical treatment of peri-implantitis on clinical parameters and matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels in the peri-implant crevicular fluid. A total of 50 patients with peri-implantitis were randomized into three groups to receive peri-implant treatment. The control group (n = 17) only received conventional non-surgical mechanical therapy. The trial groups [(diode group (n = 16) and Er,Cr:YSGG group (n = 17)] received dental laser in addition to mechanical therapy. Gingival index (GI), plaque index (PI), bleeding on probing, probing depth (PD), MMP-9, and TIMP-1 levels were assessed at baseline (T0) and at 6 months after treatment (T1). The GI, PI, and PD significantly decreased in all groups at T1, compared to T0 (p < 0.05). The decrease in the PD was similar between the control and diode groups with Er,Cr:YSGG providing more reduction (1.16 ± 0.64 mm) than either method (p = 0.032). A significant intra-group decrease in MMP-9 level was only observed in the Er,Cr:YSGG group (p = 0.009). The decrease in TIMP-1 level from T0 to T1 was similar between the control and the diode groups (p > 0.05) and it was significantly lower than the decrease in the Er,Cr:YSGG group (p < 0.05). Addition of diode laser to non-surgical mechanical therapy does not provide any additional benefit for treatment outcomes. The Er,Cr:YSGG laser seems to be more efficient both at clinical and molecular levels. ClinicalTrials, ID: NCT04730687. Registered 13 April 2021. Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04730687.

In vitro efficacy of biofilm removal from titanium surfaces using Er:YAG laser: Comparison of treatment protocols and ablation parameters

BACKGROUND

The aims of the present study were to compare the antibacterial effect of Er:YAG laser with other acceptable decontamination methods and to single out the optimal laser device parameters for effective bacterial elimination.

METHODS

A multispecies biofilm which was composed of Streptococcus sanguis, Actinomyces naeslundii, Porphyromonas gingivalis, and Fusobacterium nucleatum was grown on sandblasted and acid-etched (SLA, homogeneous moderately microrough, and nanosmooth surface) titanium disks. The biofilm was removed from the coated disks by hand curets, ultrasonic device, nylon brush (dental polishing prophy cup), or Er:YAG. Additionally, different parameter combinations of the laser machine were examined to reach an optimal lasing power for bacterial elimination/reduction. Residual biofilm samples were stained with bacterial live/dead staining and quantified using a fluorescent microscope.

RESULTS

A multispecies biofilm was accumulated on the SLA titanium surfaces exhibiting cluster distribution next to bacteria-poor areas. Hand curets, nylon brushes, and the ultrasonic device showed limited capability to effectively remove the biofilm from the SLA surfaces as opposed to the Er:YAG which displayed a superior ability to remove the biofilm. All Er:YAG parameter combinations that were evaluated as well as the tested "tip to target" distances showed similar excellent anti-biofilm effects. Furthermore, we observed that the Er:YAG capability of biofilm removal is not only due to its light emission, but depends on its water irrigation as well.

CONCLUSIONS

Er:YAG laser has an excellent biofilm removal capability compared with hand curets, ultrasonic devices, or nylon brushes even when low energy parameters and low power settings are used. Additionally, an excellent antibacterial effect can be reached using a non-contact mode of 1 to 5 mm "tip to target" distance.

In Vitro Cytological Responses against Laser Photobiomodulation for Periodontal Regeneration

Periodontal disease is a chronic inflammatory disease caused by periodontal bacteria. Recently, periodontal phototherapy, treatment using various types of lasers, has attracted attention. Photobiomodulation, the biological effect of low-power laser irradiation, has been widely studied. Although many types of lasers are applied in periodontal phototherapy, molecular biological effects of laser irradiation on cells in periodontal tissues are unclear. Here, we have summarized the molecular biological effects of diode, Nd:YAG, Er:YAG, Er,Cr:YSGG, and CO₂ lasers irradiation on cells in periodontal tissues. Photobiomodulation by laser irradiation enhanced cell proliferation and calcification in osteoblasts with altering gene expression. Positive effects were observed in fibroblasts on the proliferation, migration, and secretion of chemokines/cytokines. Laser irradiation suppressed gene expression related to inflammation in osteoblasts, fibroblasts, human periodontal ligament cells (hPDLCs), and endothelial cells. Furthermore, recent studies have revealed that laser irradiation affects cell differentiation in hPDLCs and stem cells. Additionally, some studies have also investigated the effects of laser irradiation on endothelial cells, cementoblasts, epithelial cells, osteoclasts, and osteocytes. The appropriate irradiation power was different for each laser apparatus and targeted cells. Thus, through this review, we tried to shed light on basic research that would ultimately lead to clinical application of periodontal phototherapy in the future.

Effect of implant cleaning on titanium particle dissolution and cytocompatibility

BACKGROUND

Peri-implantitis treatments are mainly based on protocols for teeth but have not shown favorable outcomes for implants. The potential role of titanium dissolution products in peri-implantitis necessitate the consideration of material properties in devising treatment protocols. We assessed implant cleaning interventions on (1) bacterial removal from Ti-bound biofilms, (2) Ti surface alterations and related Ti particle dissolution, and (3) cytocompatibility.

METHODS

Acid-etched Ti discs were inoculated with human peri-implant plaque biofilms and mechanical antimicrobial interventions were applied on the Ti-bound biofilms for 30 seconds each: (1) rotary nylon brush; (2) Ti brush; (3) water-jet on high and (4) low, and compared to sterile, untreated and Chlorhexidine-treated controls. We assessed colony forming units (CFU) counts, biofilm removal, surface changes via scanning electron microscopy (SEM) and atomic force microscopy (AFM), and Ti dissolution via light microscopy and Inductively-coupled Mass Spectrometry (ICP-MS). Biological effects of Ti particles and surfaces changes were assessed using NIH/3T3 fibroblasts and MG-63 osteoblastic cell lines, respectively.

RESULTS

Sequencing revealed that the human biofilm model supported a diverse biofilm including known peri-implant pathogens. WJ and Nylon brush were most effective in reducing CFU counts (P < 0.01 versus control), whereas Chlorhexidine was least effective; biofilm imaging results were confirmatory. Ti brushes led to visible streaks on the treated surfaces, reduced corrosion resistance and increased Ti dissolution over 30 days of material aging as compared to controls, which increase was amplified in the presence of bacteria (all P-val < 0.05). Ti particles exerted cytotoxic effects against fibroblasts, whereas surfaces altered by Ti brushes exhibited reduced osteoconductivity versus controls (P < 0.05).

CONCLUSIONS

Present findings support that mechanical treatment strategies selected for implant biofilm removal may lead to Ti dissolution. Ti dissolution should become an important consideration in the clinical selection of peri-implantitis treatments and a necessary criterion for the regulatory approval of instruments for implant hygiene.

Early Creeping Attachment Noted after Mandibular Labial Frenuloplasty

Recession of the mandibular central incisors is frequently associated with high frenum insertion. Often times, this recession is accompanied by a lack of sufficient amount of keratinized tissue and absence of attached gingiva. In this case report, an ASA I patient presented with Cairo Recession Type 2 (RT2) and a minimal amount of keratinized tissue on the mandibular central incisors and underwent frenuloplasty in the anterior mandible with the use of a conventional scalpel technique due to high frenum attachment. The results demonstrated creeping attachment of 1.0 mm as early as 10 days postoperatively resulting in complete root coverage and closure of the interproximal space between teeth #24 and 25. A second soft tissue surgery was avoided due to complete root coverage which remained stable at the 6-month follow-up appointment.

First Investigation of Dual-Wavelength Lasers (2780 nm Er,Cr:YSGG and 940 nm Diode) on Implants in a Simulating Peri-Implantitis Situation Regarding Temperature Changes in an In Vitro Pocket Model

Objective: This study aimed to investigate the temperature changes and question the safe laser settings and protocols for laser-assisted peri-implantitis treatment in an in vitro environment. Materials and methods: Three types of implants (Neoss, Dentegris, and Camlog) were implanted in an artificial bone model (n = 15). The model was placed into a 37°C water bath to simulate the in vivo oral condition. Throughout the laser irradiation, K-type thermocouples were used to record the real-time temperature measurements at different anatomically important locations in the artificial bone. Results: In all of the temperature measurements, no temperature rise above the critical safe limit, that is, >47°C, was observed. Conclusions: Within the limitations of this in vitro study, the use of the dual-wavelength protocol [Er,Cr:YSGG (1 and 1.5 W, 25, 50, 75 Hz)] and the 940 nm diode (peak power 2 W, duty cycle 50%) can be considered a safe method in the treatment of peri-implantitis, regarding its thermal safety.

Photobiomodulation of inflammatory-cytokine-related effects in a 3-D culture model with gingival fibroblasts

The aim of this study was to assess the effects of IL-6 and IL-8 cytokines on human gingival fibroblasts (HGF) cultured in a 3-D model and the possible photobiomodulation (PBM) of such effects by low-level laser therapy. In complete culture medium (DMEM), HGF from a healthy patient were seeded in a type I collagen matrix inserted into 24-well plates. After 5 days of incubation, the cytokines were added or not to serum-free DMEM, which was applied to the cell-enriched matrices. Then, PBM was performed: three consecutive irradiations using LaserTable diode device (780 nm, 0.025 W) at 0.5 J/cm² were delivered or not to the cells. Twenty-four hours after the last irradiation, cell viability and morphology, gene expression, and synthesis of inflammatory cytokines and growth factors were assessed. The histological evaluation demonstrated that, for all groups, matrices presented homogeneous distribution of cells with elongated morphology. However, numerous cytokine-exposed cells were rounded. IL-6 and IL-8 decreased cell viability, synthesis of VEGF, and gene expression of collagen type I. PBM enhanced cell density in the matrices and stimulated VEGF expression, even after IL-6 challenge. Reduced TNF-α synthesis occurred in those cells subjected to PBM. In conclusion, PBM can penetrate collagen matrix and stimulate HGF, highlighting the relevance of this research model for further phototherapy studies and in vitro biomodulation of the healing process.

Er:YAG Laser Irradiation Reduces Microbial Viability When Used in Combination with Irrigation with Sodium Hypochlorite, Chlorhexidine, and Hydrogen Peroxide

The erbium-doped yttrium aluminum garnet (Er:YAG) laser is used to treat periodontal disease; however, its effectiveness at killing oral bacteria is not well known. Furthermore, the compounding effect of the combination of a laser treatment and irrigation methods with antimicrobials on bacterial viability is yet to be determined. The purpose of this in vitro study was to evaluate the effect of the Er:YAG laser with irrigation using chlorhexidine (CHX), hydrogen peroxide (H₂O₂), or sodium hypochlorite (NaOCl) on the viability of oral bacteria. Three bacterial species were used in our study: Streptococcus gordonii, Fusobacterium nucleatum, and Porphyromonas gingivalis. Bacteria were grown in an anaerobic chamber in brain heart infusion broth and incubated at 37 °C. Bacterial samples with an OD of 0.5 were irradiated with the Er:YAG laser at 2940 nm using a 400-µm Varian tip. The experiment was repeated four times using these parameters: 40 mJ, 40 Hz, and 1.6 W for 20 seconds with the 300 µs short pulse duration in contact mode. Treatment groups consisted of the following: (1) no treatment, (2) 0.5% H₂O₂ alone, (3) 0.5% NaOCl alone, (4) 0.03% CHX alone, (5) Er:YAG irradiation alone, (6) Er:YAG irradiation with 0.5% H₂O₂, (7) Er:YAG irradiation with 0.5% NaOCl, and (8) Er:YAG irradiation with 0.03% CHX. Microbial viability was determined through plating and colony counts and calculated into CFU/ml. Statistical analysis was done using a two-tailed paired t-test. The use of the Er:YAG laser alone failed to show statistically significant antibacterial activity against any of bacteria. The most effective mono-treatment with irrigation solutions for all three bacteria were 0.5% H₂O₂ and 0.5% NaOCl (p < 0.001 for each solution). Irrigation with 0.03% CHX was most effective against F. nucleatum (p < 0.01) and less against P. gingivalis and S. gordonii and showed the least antibacterial action alone but improved significantly in combination therapy (p < 0.05). The combined treatment with the Er:YAG showed the greatest and most significant improvement in the reduction of bacterial viability compared to any other treatment group (p < 0.05 for each combined treatment). Irradiation with the Er:YAG laser with the addition of 0.5% H₂O₂, 0.5% NaOCl, or 0.03% CHX under a short working time (20 s) resulted in a significant reduction of bacterial viability for all three bacterial species compared with any single treatment option. The combination of irradiation with the Er:YAG laser with the addition of 0.5% H₂O₂, 0.5% NaOCl, or 0.03% CHX resulted in a larger reduction of bacterial survival when compared to monotherapies with antimicrobial solutions or laser. The combination of the Er:YAG laser with a low concentration irrigant solution of 0.5% H₂O₂, 0.5% NaOCl, or 0.03% CHX could be an effective treatment protocol for the reduction of periodontal pathogens and thus suitable treatment for non-surgical periodontal therapy.

Preservation of keratinized gingiva around dental implants using a diode laser when uncovering implants for second stage surgery

PURPOSE

The aim of the present study was to assess if a 940-nm diode laser or a traditional scalpel approach is more effective in minimizing patient comfort and postoperative sequelae, preserving peri-implant keratinized mucosa, and in enhancing impression quality after uncovering dental implants.

MATERIALS AND METHODS

We designed a prospective, split mouth, single blinded, randomi¬zed controlled trial with patients who needed uncovering of dental implants. Our analysis included 388 implants in 73 patients. Split mouth technique was used to compare two approaches for uncovering implants: laser study group vs. scalpel control group. Patients were evaluated for intra- and post-operative pain and bleeding. At 1, 2, and 3 weeks post procedure patients in both groups were rechecked for postoperative sequelae, keratinized mucosal thickness quality and quantity, and accuracy of the implant emergence profile.

RESULTS

The laser study group showed that there was a reduction in postoperative pain and bleeding that was statistically significant in comparison to the control group. There were also statistically significant differences in gingival color and presence or absence of soft tissue edema and in the gingival was emergency profile between the laser and scalpel sides at 1, 2, and 3 weeks' post-procedure. Statistically significant differences (p< 0.001) were observed between the two groups in the criteria of ideal or satisfactory soft tissue projection in the gingival emergency profile, which indicates that impressions can be taken immediately or within 1 week after laser surgery.

CONCLUSION

Uncovering dental implants using a diode laser operating at the wavelength of 940 ±10 nm, and a power output of 0.4-10 W is recommended for preparing an accurate implant emergence profile. Laser treatment can also effectively preserve keratinized mucosa around implants in comparison to the conventional scalpel technique.

Frenectomy with conventional scalpel and Nd:YAG laser technique: A comparative evaluation

BACKGROUND

Frenectomy is complete excision of the frenum attachment to the underlying bone. Conventional frenectomy with blade has been widely used; however, laser-assisted frenectomy is the most recent alternative.

AIM

The present study aims to compare two methods of frenectomy for the pain experienced, intraoperative bleeding, healing outcome, and need for analgesics.

MATERIALS AND METHODS

Twenty patients with high labial frenum attachment requiring frenectomy were included in this study. Patients were randomly divided into Group A: scalpel group and Group B: neodymium-doped yttrium aluminum garnet (Nd:YAG) laser group. Visual Analog pain score, intraoperative bleeding, number of analgesics used, and healing outcome 3 months postoperatively were recorded.

RESULTS

Group B patients experienced less pain (P = 0.016), less bleeding (P = 0.016), and required fewer number of analgesics (P = 0.008). Healing outcome at 3 months showed no significant difference between the two groups (P = 0.095).

CONCLUSION

Based on the results of this study, it can be concluded that Nd:YAG laser is an efficient and a more comfortable alternative to scalpel for frenectomy.

Does laser therapy improve the wound healing process after tooth extraction? A systematic review

Laser therapy could amplify the oral wound healing process by stimulating cell regeneration after injury, attenuating pain, and modulating the immune system. The purpose of this systematic review was to evaluate whether the application of laser therapy improved alveolar healing after tooth extractions. Eight electronic databases were screened: MedLine (PubMed), The Cochrane Library, Web of Science, Scopus, Lilacs, Ibecs, Scielo, and BBO. Three reviewers independently assessed the title and abstracts of potentially relevant studies. Only clinical trials and animal experiments that evaluated the wound healing effect of laser therapy after tooth extraction were included. A total of 16 studies fulfilled all criteria, thus 8 animal experiments and 8 clinical trials were included. Different types of laser were evaluated, such as CO₂ , GaAlAs, Nd:YAG, Diode Laser, HeNe, and High-frequency Pulsed Diode Laser. Although HF, Diode and GaAs lasers were able to enhance wound healing process in clinical studies, four trials and one animal experiment showed no improvement in wound healing with laser therapy after tooth extractions. In general, the current available evidence in the literature showed that laser therapy improved the wound healing process, but these findings were limited to the type of laser applied and its specific settings. Further well-designed and randomized controlled trials are needed to support a benefit effect of using laser therapy after tooth extraction. PROSPERO registration number: CRD42014007509 (2014).

LLLT Effects on Oral Keratinocytes in an Organotypic 3D Model

Several in vitro studies evaluated the cellular and molecular events related to interactions between phototherapy and target tissues, including oral keratinocytes and fibroblasts, providing elucidative data about phototherapy-induced healing. However, these interactions were limited to the application of a bidimensional cell culture model of oral mucosal cells. Thus, thisstudy evaluated the use of an organotypic oral epithelium model to elucidate the morphological and phenotypic responses of cells subjected to low-level laser therapy (LLLT). Oral keratinocytes were seeded in the ex vivo-produced oral mucosal equivalent (EVPOME) model, with a porcine acellular dermal matrix. LLLT was applied by means of the LaserTABLE device (780 nm, 25 mW) at 0.5, 1.5 and 3 J cm^-2 . After three irradiations, morphology, proliferation and gene expression of growth factors were assessed. LLLT and control groups presented similar morphological features, characterized by the formation of a stratified, differentiated and keratinized epithelium. LLLT enhanced the cell proliferation and gene expression of keratinocytes (hKGF) as well as epidermal (hEGF) growth factors. In general, analysis of these data shows that the three-dimensional cell culture model can be applied for phototherapy studies and that the positive effects of LLLT were confirmed by the use of an organotypic model.

Cultured Human Fibroblast Biostimulation Using a 940 nm Diode Laser

Background: Fibroblasts are the main cells involved in regeneration during wound healing. The objective was to determine the effect of 940 nm diode laser on cultured human fibroblasts using different irradiation regimens. Methods: The CCD-1064Sk human epithelial fibroblast cell line was treated with a 940 nm diode laser at different energy doses (power: 0.2–1 W and energy density: 1–7 J/cm²) using different transmission modes (continuous or pulsed). The effect on cell growth at 24 and 72 h post-treatment was examined by measuring the proliferative capacity, the impact on the cell cycle, and the effect on cell differentiation. Results: fibroblast proliferative capacity was increased at 24 and 72 h post-treatment as a function of the energy dose. The greatest increase was observed with a power of 0.2 or 0.5 W and energy density between 1 and 4 J/cm²; no difference was observed between continuous and pulsed modes. There were no significant differences in cell cycle between treated groups and controls. α-actin expression was increased by treatment, indicating enhanced cell differentiation. Conclusion: The 940 nm diode laser has biostimulating effects on fibroblasts, stimulating proliferative capacity and cell differentiation without altering the cell cycle. Further researches are necessary to explore its potential clinical usefulness in wound healing.

Effects of high power-pulsed Nd:YAG laser irradiation on the release of transforming growth factor-beta (TGF-β) and vascular endothelial growth factor (VEGF) from human gingival fibroblasts

The purpose of this study was to investigate the effect of different high-power energy settings of a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (1064 nm) on cell viability of human gingival fibroblasts (GFs) and release of transforming growth factor-beta (TGF-β) and vascular endothelial growth factor (VEGF) on these cells. GFs were isolated from human gingival connective tissues during the crown lengthening procedure. GFs were irradiated with different laser parameters as follows: group 1: 1 W (100 mJ, 10 Hz) 10 seconds; group 2: 1.5 W (150 mJ, 10 Hz) 10 seconds; group 3: 2 W (200 mJ, 10 Hz) 10 seconds; group 4: 1 W (100 mJ, 10 Hz) 20 seconds; group 5: 1.5 W (150 mJ, 10 Hz) 20 seconds; and group 6: 2 W (200 mJ, 10 Hz) 20 seconds. Cell viability/cell proliferation was analyzed with XTT (tetrazolium salt, cell proliferation kit) staining. The release levels of TGF-β and VEGF were analyzed by the enzyme-linked immunosorbent assay. No significant differences were observed in the different laser irradiation groups compared to the control group in terms of cell viability (p > 0.05). The release of TGF-β was not affected by different laser irradiation settings (p > 0.05). Only group 6 promoted significantly higher VEGF release from GFs in 24 hours compared to the control group (p ˂ 0.05). These findings suggest that high-power Nd:YAG laser is probably safe but has a very limited effect for wound healing.

Periodontal and peri-implant wound healing following laser therapy

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

Commentary: Is There Clinical Benefit From Using a Diode or Neodymium:Yttrium-Aluminum-Garnet Laser in the Treatment of Periodontitis?

Despite a quarter of a century of laser research, there is a persistent debate regarding the efficacy of dental lasers in the treatment of periodontitis or periodontal maintenance therapy. There are many claims and much hyperbole surrounding the use of lasers, either as a monotherapy or adjunctive to scaling and root planing, to treat periodontitis. There is little evidence that using a diode or neodymium:yttrium-aluminum-garnet laser adds clinical value over and above conventional non-surgical or surgical periodontal treatment. There is a significant need for better designed human clinical trials. Data from such trials should be analyzed according to initial probing depth and characteristics of the treated sites, such as non-molar, molar flat surfaces, and molar furcations, and evaluated for long-term post-treatment results.

Non-surgical treatment of peri-implant mucositis and peri-implantitis at zirconia implants: a prospective case series

OBJECTIVES

To assess the efficacy of non-surgical therapy for the management of peri-implant diseases at a two-piece zirconium implant system.

MATERIAL & METHODS

Thirty-four patients with 45 implants participated in this study. Seventeen patients (24 implants) were diagnosed with peri-implant mucositis and received mechanical debridement + local antiseptic therapy using chlorhexidine digluconate (MD + CXH), while 17 patients (21 implants) diagnosed with peri-implantitis were assigned to Er:YAG laser therapy. In both groups, post-operative maintenance care included supramucosal plaque removal and local pocket irrigation using CHX. The primary endpoint was defined as disease resolution at 6 months (i.e. absence of bleeding upon probing (BOP) at mucositis sites/absence of BOP and probing pocket depths (PD) ≥6 mm at peri-implantitis sites).

RESULTS

Resolution of peri-implant mucositis and peri-implantitis was obtained in 9/17 (52.9%) (p = 0.001) and 5/17 (29.4%) (p = 0.02) of the patients respectively.

CONCLUSION

Non-surgical treatment of either peri-implant mucositis using MD + CHX or peri-implantitis using ERL at zirconia implants was associated with significant short-term clinical improvements. A complete disease resolution, however, was not achieved in the majority of the patients.

Health, Maintenance, and Recovery of Soft Tissues around Implants

BACKGROUND

The health of peri-implant soft tissues is one of the most important aspects of osseointegration necessary for the long-term survival of dental implants.

PURPOSE

To review the process of soft tissue healing around osseointegrated implants and discuss the maintenance requirements as well as the possible short-comings of peri-implant soft tissue integration.

MATERIALS AND METHODS

Literature search on the process involved in osseointegration, soft tissue healing and currently available treatment modalities was performed and a brief description of each process was provided.

RESULTS

The peri-implant interface has been shown to be less effective than natural teeth in resisting bacterial invasion because gingival fiber alignment and reduced vascular supply make it more vulnerable to subsequent peri-implant disease and future bone loss around implants. And we summarized common procedures which have been shown to be effective in preventing peri-implantitis disease progression as well as clinical techniques utilized to regenerate soft tissues with bone loss in advanced cases of peri-implantitis.

CONCLUSION

Due to the difference between peri-implant interface and natural teeth, clinicians and patients should pay more attention in the maintenance and recovery of soft tissues around implants.

Different laser wavelengths comparison in the second-stage implant surgery: an ex vivo study

The implant surgery consists of two distinct techniques, the transmucosal, also known as "one-stage" and the "two-stage" technique. Lasers represent a possible aid in implant dentistry, especially in the two-stage technique and its main characteristics are represented by a decreased trauma to bone and soft tissues, a reduction of pain as well as a reduction of the risk of postoperative infections. The aim of this study was to analyze in an animal model the thermal elevation induced by four different laser wavelengths (diode, Nd:YAG, Er:YAG, KTP) during the implant uncovering. Four pig jaws were used to carry out this study. Five implants were placed in each anatomical specimen for a total of 20 fixtures. Four wavelengths (532, 810, 1,064 and 2,940 nm) were used to uncover the implants. Two thermocouples were used to measure temperature changes during laser irradiation at bone level, peri-implant tissues and on the fixture surface The thermocouples were connected with two probes of 1.5 mm in diameter, in order to simultaneously recording two temperature variations. Surface temperature was also checked during all procedures with a thermal camera (Thermovision A 800, Flyr Systems, Stockolm, Sweden) connected to a PC. The mean temperatures of each specimen (five fixtures) were calculated (TM1, mean temperature at the beginning; TM2, mean peak temperature). Furthermore, a record of the temperature at 1 min after the end of the surgical procedure was taken (mean: TM3). All the recorded values were statistically evaluated by one-way analysis of variance (ANOVA). The thermocouples recorded a lower increase in temperature for Er:YAG and KTP laser; Nd:YAG and diode laser produced similar increases characterized by higher values. The thermo-camera pointed out the lower increase for Er:YAG and higher for diode laser. KTP laser resulted faster in uncovering implants and diode laser was the one that needed more time. This ex vivo study showed that laser utilization with the recommended parameters gives no risks of dangerous thermal elevation to the tissues and implants.

Minimally-invasive non-surgical periodontal therapy

Periodontitis is a complex disease that has both oral and systemic consequences. The treatment of periodontitis may be both surgical and non-surgical but, in recent years, there has been a shift towards managing disease non-surgically in preference to surgery. Fundamental to all types of therapy is the patient's role in disease control, in the form of self-performed plaque control, and it is important that the patient understands this. Non-surgical periodontal therapy has a long history and has traditionally been carried out using a variety of hand and powered instruments, the objective being root surface disinfection by the removal of plaque, calculus and contaminated root cementum. However, over the last 30 years or so, it has become apparent that calculus does not cause disease, cementum does not become significantly infected and bacteria and their toxins are only loosely adherent to the diseased root surface. This has led to the development of less invasive instrumentation principles which may be better for patients, more cost-effective and more easily applied in different clinical settings.

CLINICAL RELEVANCE

This paper aims to describe and justify a minimally-invasive approach to the management of the diseased root surface in periodontitis, to clarify the terminology used and to suggest how these principles may be applied in general practice.

Low-cost periodontal therapy

Periodontitis is a complex infectious disease that affects low-income individuals disproportionately. Periodontitis is associated with specific bacterial species and herpesviruses, and successful prevention and treatment of the disease is contingent upon effective control of these pathogens. This article presents an efficacious, highly safe, minimally invasive, practical and low-cost periodontal therapy that involves professional and patient-administered mechanical therapy and antimicrobial agents. The major components are scaling for calculus removal, periodontal pocket irrigation with potent antiseptics, and treatment with systemic antibiotics for advanced disease. Povidone-iodine and sodium hypochlorite have all the characteristics for becoming the first-choice antiseptics in the management of periodontal diseases. Both agents show excellent antibacterial and antiviral properties, are readily available throughout the world, have been safely used in periodontal therapy for decades, offer significant benefits for individuals with very limited financial resources, and are well accepted by most dental professionals and patients. Four per cent chlorhexidine applied with a toothbrush to the most posterior part to the tongue dorsum can markedly reduce or eliminate halitosis in most individuals. Systemic antibiotics are used to treat periodontopathic bacteria that are not readily reached by topical therapy, such as pathogens within gingival tissue, within furcation defects, at the base of periodontal pockets, and on the tongue, tonsils and buccal mucosae. Valuable antibiotic therapies are amoxicillin-metronidazole (250 mg of amoxicillin and 250 mg of metronidazole, three times daily for 8 days) for young and middle-aged patients, and ciprofloxacin-metronidazole (500 mg of each, twice daily for 8 days) for elderly patients and for patients in developing countries who frequently harbor enteric rods subgingivally. Scaling to remove dental calculus and the prudent use of inexpensive antimicrobial agents can significantly retard or arrest progressive periodontitis in the great majority of patients.

Lasers in periodontics

Laser is one of the most captivating technologies in dental practice since Theodore Maiman in 1960 invented the ruby laser. Lasers in dentistry have revolutionized several areas of treatment in the last three and a half decades of the 20^th century. Introduced as an alternative to mechanical cutting device, laser has now become an instrument of choice in many dental applications. Evidence suggests its use in initial periodontal therapy, surgery, and more recently, its utility in salvaging implant opens up a wide range of applications. More research with better designs are a necessity before lasers can become a part of dental armamentarium. This paper gives an insight to laser in periodontics.

Effects of 405 nm diode laser on titanium oxide bleaching activation

OBJECTIVE

The objective of this study was to evaluate the effects of a 405 nm diode laser on bleaching reaction of H(2)O(2) and VL-TiO(2) on methylene blue (MB) dye.

BACKGROUND DATA

Visible light activating titanium dioxide photocatalyst (VL-TiO(2)) may improve efficacy of hydrogen peroxide (H(2)O(2)) bleaching agents used in dentistry while contributing to their safety by lowering the required concentration of peroxide.

METHODS

The experimental solution was prepared with H(2)O(2), VL-TiO(2), MB, and pure water. The final concentration of H(2)O(2) was 3.5% and that of MB was 10 ppm. The experimental solution of 3 mL in a quartz cell was irradiated by a 405 nm diode laser with various powers, duty cycles, and pulse durations for 7 min.

RESULTS

In all irradiation conditions, the increase in laser irradiation time gradually decreased the MB concentration. Irradiation by higher output power showed more reduction of MB concentration. Pulse durations as short as 5 ms with duty cycle reduced to 25% did not affect the degree of the reduction in MB concentration compared with continuous wave irradiation at the same average output power.

CONCLUSIONS

It was concluded that using 405 nm diode laser, the bleaching effects of VL-TiO(2) depended upon the irradiation time and the average output power, regardless of pulse duration or duty cycle.