In Vitro Photobiomodulation Effects of Blue and Red Diode Lasers on Proliferation and Differentiation of Periodontal Ligament Mesenchymal Stem Cells.

Introduction: This study aimed to assess the photobiomodulation effects of blue and red lasers on the proliferation and osteogenic differentiation of periodontal ligament mesenchymal stem cells (PDLMSCs). Methods: PDLMSCs were cultured and tested in 4 groups. The first two groups were exposed to 445 nm diode laser irradiation (200 mW, 6 and 12 J/cm2 ), and the third group was exposed to 660 nm diode laser irradiation (50 mW, 4 J/cm2 ). The fourth group was also considered as the control group without irradiation. Cell viability/proliferation was assessed by MTT assay. RUNX2, alkaline phosphatase (ALP), collagen type 1 (col1), and osteocalcin (OCN) were evaluated by RT-PCR, and Alizarin red was used to evaluate the colonization. The data were analyzed by means of one-way analysis of variance. Results: The results of our study showed that cell survival/proliferation in the second group was significantly lower than that in the control group on days 1 and 7 (P<0.05). RT-PCR showed a significant increase in osteogenic genes in all three laser groups compared to the control group (P<0.05). All groups showed a significant increase in calcium content compared to the control group (P<0.05). ALP activity also confirmed the osteoblastic differentiation of cells in laser groups. Conclusion: 445 nm and 660 nm lasers with the studied parameters showed positive effects on the proliferation and osteoblastic differentiation of PDLMSCs.

Surgical reconstruction of peri-implantitis with adjunctive antimicrobial photodynamic therapy: A case report with 5-year follow-up.

BACKGROUND: Peri-implantitis poses a significant challenge in dental implantology due to its potential to result in the loss of supporting tissue around dental implants. Surgical reconstruction is often recommended for intrabony defects, accompanied by various adjunctive therapies, such as antimicrobial photodynamic therapy (aPDT), for bacterial decontamination. However, the long-term efficacy of such treatments remains unclear. METHODS: This clinical report presents a case of peri-implantitis management in a healthy 55-year-old male using guided bone regeneration principles and surface decontamination via aPDT. The patient exhibited peri-implantitis with probing pocket depths (PPD) of 7 mm at buccal sites, 5 mm at palatal sites, and significant bone loss around implant #12. The reconstructive approach involved preservation of the existing implant and following a non-submerged healing protocol. The surgical phase included meticulous debridement, chemical detoxification with hydrogen peroxide, and aPDT using a 670 nm diode laser with methylene blue as the photosensitizer. Xenogenic bone graft and a resorbable collagen membrane were applied and the patient was followed up to through a 5-year period. RESULTS: Postsurgery the patient exhibited normal healing, and long-term follow-up at 5 years showed reduced PPD (2 mm buccally, 3 mm mid-palatally), complete intrabony defect fill, and stable bone levels, indicating successful treatment. CONCLUSIONS: This case report demonstrates the potential long-term success of a reconstructive approach with adjunctive aPDT in peri-implantitis management. However, it highlights the need for standardized protocols and further clinical trials to establish the clinical benefits of aPDT in surgical reconstruction of peri-implantitis defects, serving as valuable pilot data for future research. HIGHLIGHTS: Why is this case new information? Provides a rare 5-year insight into peri-implantitis intrabony defect reconstruction, offering extended success and outcomes not frequently documented. Demonstrates the efficacy of aPDT with a 670-nm diode laser in achieving successful long-term outcomes, contributing valuable evidence to existing literature.Keys to successful management of this case: Success involves initial non-surgical debridement followed by a reconstructive strategy, incorporating guided bone regeneration and surface decontamination via aPDT. Long-term success hinges on patient compliance with routine oral hygiene, emphasizing the importance of adherence to preventive measures post-reconstruction to minimize recurrence risk.What are the primary limitations to success in this case? Variability in photosensitizer uptake, and potential risks such as tissue damage and bacterial resistance pose challenges to the effectiveness of aPDT. The existing literature on aPDT in peri-implantitis treatment lacks standardization in methodology, laser parameters, and follow-up durations, making it challenging to establish a universally accepted protocol.

Evaluation of the effect of photodynamic therapy with Curcumin and Riboflavin on implant surface contaminated with Aggregatibacter actinomycetemcomitans.

BACKGROUND: Peri-implantitis is a destructive inflammatory disease affecting both hard and soft tissues of the osseointegrated implant and causing bone loss and envelope surrounding the implant. The study aimed at evaluating the effect of Photodynamic therapy with Curcumin and Riboflavin on the level of decontamination of implant surface impregnated with Aggregatibacter actinomycetemcomitans (A.a) biofilm. MATERIALS AND METHODS: In this experimental and laboratory study, 42 implants (4.3 mm in diameter and 8 mm in length) were infected with A.a. bacterial suspension. Then, the implants carrying A.a biofilm were randomly divided into seven groups (n = 6). The groups included: 1- a negative control group (without treatment), 2- a positive control group of Chlorhexidine 0.12 %, 3- a Curcumin (5 mg/ ml) group, 4- a Riboflavin (0.5 %) group, 5- an LED irradiation group (390-480 nm), 6- a photodynamic therapy with Curcumin group, and 7- a photodynamic therapy with Riboflavin group. Then, the implants were sonicated and the amount of CFU/mL of each sample was calculated. One-way ANOVA and Tamhane tests were used to analyze the data. RESULTS: The lowest mean number of colonies of A.a (CFU/ mL) were seen in the following groups, respectively: the positive control group of Chlorhexidine 0.12 %, the photodynamic therapy with Curcumin group, the photodynamic therapy with Riboflavin group, the Curcumin (5 mg/ ml) group, the Riboflavin (0.5 %) group, the LED radiation group, and the negative control group. The use of photodynamic therapy with Curcumin significantly reduced the number of colonies of A.a (CFU/ mL) in comparison with the photodynamic therapy with Riboflavin group (p = 0.004), the Riboflavin group (p = 0.045), the LED radiation group (p = 0.012), and the negative control group (p = 0.007). CONCLUSION: aPDT with Curcumin and LED can reduce A.a biofilm on implant surfaces and can be used as a safe and non-invasive disinfection method to reduce A.a biofilm on implant surfaces.

The influence of different mode of power density during antimicrobial photodynamic therapy for photokilling of Streptococcus mutans.

BACKGROUND: The aim of this study was to evaluate the inactivation potency of riboflavin and curcumin plus blue diode laser against Streptococcus mutans with different power densities. MATERIALS AND METHODS: In this in vitro study, standard-strain S. mutans was exposed to curcumin and riboflavin plus blue diode laser with different power densities (0.4-1.0 W/cm2) as well as chlorhexidine (CHX). The colony forming units (CFUs)/mL was calculated. Data were analyzed by one-way ANOVA. RESULTS: Antibacterial analysis indicated that the blue diode laser irradiation with curcumin and riboflavin provided a satisfactory reduction of the S. mutans level. In addition, S. mutans was more affected by curcumin + blue diode laser when the power density was set to 1.0 W/cm2 (P < 0.0001). Meanwhile, bacterial suspensions treated with CHX showed maximum colony number reduction, compared with the control (P < 0.0001). CONCLUSION: This study showed the blue diode laser along with curcumin had strong bactericidal effect on S. mutans, and this effect improved by increasing the power density.

In Vitro Efficacy of Antimicrobial Photodynamic Therapy With Phycocyanin and Diode Laser for the Reduction of Porphyromonas gingivalis.

Introduction: Implant surface disinfection is the most difficult phases in treatment of peri-implantitis. This study sought to assess the efficacy of antimicrobial photodynamic therapy (aPDT) with phycocyanin and diode laser for the reduction of Porphyromonas gingivalis. Methods: In this in vitro, experimental study, first the minimum inhibitory concentration (MIC) of phycocyanin, the sub-lethal exposure time of the diode laser, and the sub-lethal dose of aPDT were determined. The wells containing P. gingivalis suspension were randomly divided into three experimental groups for exposure to ½ MIC phycocyanin for 5 minutes, minimum lethal dose of diode laser (635 nm, 4 minutes), and aPDT with phycocyanin and diode laser. The positive control group was exposed to 0.2% chlorhexidine (CHX) for 5 minutes, and the negative control group received no treatment. The colony count was calculated in the five groups and compared using one-way ANOVA and t test. Results: aPDT with a diode laser (635 nm, 4 minutes) and 125 µg/mL phycocyanin caused a significantly greater reduction in P. gingivalis count (mean reduction of 44.24%) compared with other groups (P<0.0001). Minimum and maximum colony counts were noted in 0.2% CHX and negative control groups respectively. The reduction in the colony count was significant in all experimental groups, compared with the control group (P<0.0001). Conclusion: aPDT with 635-nm diode laser and phycocyanin can significantly decrease P. gingivalis count in vitro. Considering the conservative nature of this modality, it may be used for the decontamination of peri-implant.

Comparison of shear bond strength of rebonded brackets prepared with different methods of resin removal: an in vitro study.

AIM: Clinicians and researchers have always made every effort to achieve proper bonding between the surface of the tooth and the rebonded orthodontic brackets in order to prevent the re-fracture failure of orthodontic pressures throughout treatment. The aim of this study was to determine the bond strength of rebonded brackets by four adhesive removal methods.

In Vitro Effect of Photodynamic Therapy with Indocyanine Green Followed by 660 nm Photobiomodulation Therapy on Fibroblast Viability.

This in vitro study sought to assess the effect of repetitive PBMT on the viability of fibroblasts following aPDT with indocyanine green (ICG). In this in vitro experimental study, human gingival fibroblasts (HGFs) were obtained and incubated in a culture medium. After reaching 10 000 cells cm-2 , the cells were divided into five groups of control, aPDT with ICG and 808 nm (energy density of 24 J cm-2 ), PBMT immediately after aPDT, PBMT with 660 nm (energy density of 7.2 J cm-2 ) immediately and 24 h after aPDT and PBMT immediately and 24 and 48 h after aPDT in 48-well plates. Cell viability was evaluated using the methyl thiazolyl tetrazolium (MTT) assay after 1, 4 and 7 days of incubation. Statistical analyses were performed using one-way ANOVA. Cell viability significantly decreased in group 2 (P < 0.002). We observed no significant increase in cell viability at any time point in group 3 (P > 0.05). Cell viability significantly increased in groups 4 and 5 after the first day of incubation (P < 0.000). Emission of 660 nm as PBMT for two and three times along with passage of time would increase the viability of HGFs following aPDT with ICG.

Effect of Different Energy Densities of 915 nm Low Power Laser on the Biological Behavior of Human Gingival Fibroblast Cells In Vitro.

Photobiomodulation is recognized as an effective method for adjunct therapy in periodontal treatments. Our purpose in this study was to investigate the effects of different energy densities of 915 nm diode laser on the viability and viability capacity of human gingival fibroblast cells. Cell samples were examined in five groups, including four irradiation groups with low-level diode laser 915 nm, 1, 2, 3, 4 J cm-2 and a control group (no Laser irradiation). Cell viability and viability were measured 1, 3 and 5 days after irradiation by MTT and DAPI assay. Statistical differences between groups at any time were analyzed by one-way ANOVA and a post hoc Turkey's test. The cell viability and viability capacity increased on the third day at an energy density of 3 J cm-2 ; (P-value = 0.007) and the fifth day at energy densities of 2, 3 and 4 J cm-2 was recorded compared with the control group (P-value = 0.000). Also, a significant decrease in the viability and viability of irradiated cells with an energy density of 1 J cm-2 was found (P-value = 0.033). According to our results, Photobiomodulation with 915 nm diode laser has a positive stimulating effect on the viability and viability capacity of human gingival fibroblast cells.

Effects of Photobiomodulation Therapy with Various Laser Wavelengths on Proliferation of Human Periodontal Ligament Mesenchymal Stem Cells.

Several methods have been proposed to enhance the regeneration and healing time in periodontal therapy. Photobiomodulation therapy (PBMT) is a recently suggested novel technique for this purpose. This study aimed to compare the efficacy of PBMT with various laser wavelengths and energy densities on proliferation of human periodontal ligament mesenchymal stem cells (PDLMSCs). The wells containing PDLMSCs were subjected to laser irradiation at 635, 660, 808 and 980 nm wavelengths with 1, 1.5, 2.5 and 4 J cm-2 energy densities. Cell proliferation and viability were evaluated after 1, 3 and 5 days with the methyl thiazolyl tetrazolium (MTT) assay and 4,6-diamidino-2-phenylindole (DAPI) staining. No significant difference was observed among the experimental and the control groups on day 1 (P > 0.05). On day 3, 808 nm laser at 4 J cm-2 energy density and 980 nm laser at all densities had significant differences with control group. On day 5, the control group had significant differences in cell proliferation with 808 nm laser at 2.5 and 4 J cm-2 energy densities, and 980 nm laser at all densities. PBMT with 635, 660, 808 and 980 nm wavelengths increased the proliferation of PDLMSCs but the maximum cell viability was prominent after irradiation by 980 nm laser with energy density of 4 J cm-2 on day 3.

Efficacy of titanium brush, 915 nm diode laser, citric acid for eradication of Staphylococcus aureus from implant surfaces.

BACKGROUND: This study aimed to assess the efficacy of titanium brush, 915 nm diode laser, citric acid and the combination of latter two with titanium brush for decontamination of SLA surface mini-implants. METHODS: Seventy-five mini-implants contaminated with Staphylococcus aureus (S. aureus) were randomly divided into five experimental groups (n = 12) of titanium brush (TiB), laser, citric acid (CA), brush-laser, and brush-acid, positive [n = 12; chlorhexidine mouthwash (CHX)] and negative [n = 2; phosphate buffered saline (PBS)] control groups and one no-treatment group (n = 1). After counting the colony forming units (CFUs), data were analyzed using the Kruskal-Wallis and Dunn post-hoc tests. RESULTS: Regardless of the no-treatment and negative control groups, maximum and minimum CFUs were noted in the titanium brush and positive control groups. After CHX, minimum CFUs were noted in brush-acid group followed by brush-laser, laser, and acid groups. Generally, the Kruskal-Wallis test revealed a significant difference between the groups regarding the colony count (P < 0.001). Dunn post-hoc test showed that the difference between the titanium brush and acid-brush group was significant (P < 0.001) while the differences between the brush and laser groups with the brush-laser group were not significant (P > 0.077). CONCLUSIONS: Combined use of titanium brush and citric acid yielded superior results compared to other groups in reduction of S. aureus on implant surface.

Blue Light Photodynamic Therapy With Curcumin and Riboflavin in the Management of Periodontitis: A Systematic Review.

Introduction: The aim of this article was to evaluate reports in the scientific literature that used antimicrobial photodynamic therapy (aPDT) with a blue light source and curcumin and riboflavin as photosensitizers in the management of periodontitis. Methods: The search was conducted in electronic databases, including PubMed, Web of Science, and Scopus, with the keywords "photodynamic therapy", "antimicrobial photodynamic therapy", "laser activated disinfection", "photoactivated disinfection", "light activated disinfection" "LED", "Periodontitis", "Curcumin", "Riboflavin", and "periodontitis" from 2012 to 2020. Results: After evaluating a total of 24 relevant articles, 13 articles were selected, full texts were read, and the data were extracted and placed in a table. Conclusion: Reviewing articles showed that curcumin as a photosensitizer activated by a blue wavelength is effective in the elimination of the various bacterial species involved in periodontal disease, and to the best of our knowledge, there is no study that has shown this substance does not reduce bacteria. According to the result of the articles, riboflavin as a photosensitizer activated by blue light can reduce bacteria that are involved in periodontitis, but other studies have reported that blue light alone can also reduce bacteria significantly. Therefore, more in-vitro and clinical trial studies are needed to give a more conclusive opinion on the effectiveness of riboflavin as a photosensitizer in the treatment of periodontitis.

Photobiomodulation Effect of Different Diode Wavelengths on the Proliferation of Human Gingival Fibroblast Cells.

This study is focused on comparing the effect of various energy densities and wavelengths of diode lasers on the proliferation of human gingival fibroblast (HGF) cells in vitro. In this study, 204 sample cells were examined in 4 test groups (laser radiation) and 1 control group (non-laser radiation). The proliferation rate of radiated cells with wavelengths of 635, 660, 808 and 980 nm and the densities of 1, 1.5, 2.5 and 4 J cm-2 was measured after 1, 3 and 5 days using the MTT assay. The proliferation rate of human gingival fibroblast (HGF) cells in test groups was increased on day 1 at wavelengths of 635, 808 and 980 nm and on day 3 at the wavelength of 980 nm compared with the control group. Our findings denoted that the photobiomodulation therapy increased the proliferation rate of HGF. The most desirable laser radiation setting, which led to the highest proliferation rate of the cells, included 980 nm wavelength with 1, 1.5 and 4 J cm-2 energy densities and 635 nm wavelength with 4 J cm-2 energy density.

Cytotoxicity and Antibacterial Activity of Toothpastes and Mouthwashes Available in the Iranian Market.

Objectives: Toothpastes and mouthwashes contain chemicals that may be harmful to oral tissues. This study assessed the cytotoxicity and antibacterial activity of toothpastes and compare the Iranian and foreign toothpastes and mouthwashes available in the Iranian market in this respect. Materials and Methods: Twenty samples (13 toothpastes and 4 mouthwashes) were selected. The cytotoxicity of 1, 10, and 50 mg/mL of toothpastes and 0.05, 2 and 10 µL of mouthwashes was measured after 1, 15 and 30 min of exposure to human gingival fibroblasts, each in triplicate. The methyl thiazolyl tetrazolium (MTT) assay was used for cytotoxicity testing. The serial dilution method was utilized to determine the minimum inhibitory concentration (MIC) of each sample against Lactobacillus acidophilus (L. acidophilus) and Streptococcus mutans (S. mutans). Two-way ANOVA and Tukey's test were used for data analysis. Results: A significant difference in cytotoxicity was noted among different products (P=0.00). The difference in cytotoxicity of each sample was not significant at 1, 15 and 30 min (P=0.08). The obtained MIC for all toothpastes and mouthwashes was between 0.0039 mg/mL and 0.0156 mg/mL, except for Sensodyne toothpaste and Oral B mouthwash. Conclusion: Some brands of toothpastes have higher cytotoxicity due to their composition, and their cytotoxicity should not be overlooked. The antibacterial activity of the samples was almost equal when they were in contact with L. acidophilus and S. mutans except for the Irsha mouthwash, Sehat, Darugar and Bath toothpastes. The antibacterial effect of toothpastes and mouthwashes increased with an increase in exposure time.

Bacterial Colonization on Different Suture Materials Used in Oral Implantology: A Randomized Clinical Trial.

Objectives: This study aimed to compare the colonization of Enterococcus faecalis (E. faecalis), Escherichia coli (E. coli), Streptococcus mutans (S. mutans) and Staphylococcus aureus (S. aureus) isolated from the oral cavity on different suture materials used in oral implantology. Materials and Methods: Patients scheduled for implant surgery were included in this study. After flap approximation, the surgical site was sutured using silk, nylon, polyglactin 910 (Vicryl®) and triclosan-coated polyglactin 910 (Vicryl® Plus) sutures in a randomized order. Seven days after surgery, the sutures were removed and incubated in bile esculin agar (for E. faecalis), MacConkey agar (for E. coli), mitis salivarius agar (for S. mutans), and mannitol salt agar (for S. aureus) at 37°C for 24 h. The colonies were then counted. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Results: Vicryl® sutures showed the highest accumulation of E. faecalis, followed by Vicryl® Plus, nylon, and silk. There was no significant difference between nylon and silk (P=0.5) or between Vicryl® and Vicryl® Plus (P=0.4). Vicryl® Plus sutures showed the highest accumulation of E. coli followed by Vicryl®, silk and nylon (P<0.01). Vicryl® sutures showed the highest accumulation of S. mutans, followed by Vicryl® Plus, silk, and nylon. Vicryl® Plus sutures showed the highest accumulation of S. aureus, followed by Vicryl®, nylon, and silk. Conclusion: Nylon sutures showed the least microbial accumulation. Vicryl® and triclosan-coated Vicryl® Plus sutures had no advantage over the commonly used silk sutures in decreasing the number of bacteria.

In vitro effect of antimicrobial photodynamic therapy with phycocyanin on Aggregatibacter actinomycetemcomitans biofilm on SLA titanium discs.

BACKGROUND AND PURPOSE: The aim of this in vitro study was to evaluate antimicrobial photodynamic therapy (aPDT) with phycocyanin on Aggregatibacter actinomycetemcomitans biofilm formed on sandblasted, large-grit, and acid-etched (SLA) titanium discs. MATERIALS AND METHODS: In this in vitro experimental study, the minimum inhibitory concentration (MIC), sublethal dose of diode laser irradiation time, and sublethal dose of aPDT were first determined. Next, 30 SLA titanium discs with 8 mm diameter and 2 mm thickness were incubated with A. actinomycetemcomitans in order for the bacterial biofilm to form, and were randomly divided into 5 groups (n = 6): (I) negative control with no treatment, (II) positive control, immersed in 0.2 % chlorhexidine (CHX) for 5 min, (III) phycocyanin alone with ×2 MIC concentration for 5 min, (IV) diode laser alone (635 nm wavelength, 220 mW power), and (V) PDT with diode laser and phycocyanin. The samples were then sonicated, and the number of colony-forming units (CFUs) on each disc was calculated. Data were analyzed using one-way ANOVA, t-test, and a post-hoc test. RESULTS: aPDT with 125 µg/mL phycocyanin and 4 min irradiation of 635 nm diode laser decreasedA. actinomycetemcomitans biofilm by 40.07 %. The lowest mean colony count (CFUs/mL) was noted in 0.2 % CHX group (0.0 × 105 CFU/mL) while the highest mean was observed in the negative control group (4.55 ± 0.08 × 105 CFUs/mL). Using phycocyanin alone significantly decreased the A. actinomycetemcomitans count by 27.54 % (3.29 ± 0.06 × 105 CFUs/mL) compared with the negative control group (P < 0.0001). Significant differences were noted between the negative control and other groups (P < 0.0001). CONCLUSION: aPDT with phycocyanin and diode laser can decrease the A. actinomycetemcomitans biofilm on SLA titanium implant surfaces and can be used as a safe and non-invasive decontamination method for reduction of A. actinomycetemcomitans biofilm on implant surfaces.

In vitro evaluation of shear bond strength of orthodontic metal brackets to aged composite using a self-adhesive composite: Effect of surface conditioning and different bonding agents.

OBJECTIVES: Bracket bonding to composite surfaces is increasing. This study sought to assess the effect of different adhesives (acid etchant+Transbond XT™, acid etchant+Vertise Flow™, Vertise Flow™) with different surface treatments (no preparation, bur, sandblasting, Er:YAG laser) on shear bond strength (SBS) of metal brackets to aged composite. MATERIALS AND METHODS: In this in vitro, experimental study, Filtek™ Z250 composite discs were fabricated (10×4mm). After thermocycling (10,000 cycles between 5-55°C), the samples were randomly divided into three groups (n=48) based on the type of adhesive namely acid etchant+Transbond XT™, Vertise Flow™, and acid etchant+Vertise Flow™. Samples in each group were randomly divided into four subgroups (n=12) based on the surface treatment including no-treatment, diamond bur, sandblasting and Er:YAG laser. Samples in each group were randomly divided into three subgroups (n=12) based on the type of adhesive namely acid etchant+Transbond XT™, Vertise Flow™, and acid etchant+Vertise Flow™. After bracket bonding to composite discs, the samples underwent thermocycling (5000 cycles between 5-55°C), and their SBS was measured in a universal testing machine. The samples were then inspected under a stereomicroscope at x10 magnification to determine their mode of failure and adhesive remnant index (ARI). RESULTS: No significant difference was noted in SBS between adhesives in no-preparation and laser groups (P>0.05). In all adhesive groups, sandblast had highest SBS, but it was not significantly different in Vertise Flow™ groups, with and without etching. The SBS provided by acid etchant+Transbond XT™ was significantly higher than that of the other two adhesives (P<0.05). The SBS of sandblasted samples was significantly higher compared with other surface treatments in all adhesive subgroups (P<0.05). CONCLUSION: Bracket bonding to aged composite using Vertise Flow™ with or without surface treatment can serve as an alternative to the conventional orthodontic adhesives.

Shear Bond Strength of the Metal Bracket to Zirconium Ceramic Restoration Treated by the Nd: YAG Laser and Other Methods: An In Vitro Microscopic Study.

Introduction: Providing reliable bonding of the bracket base and the zirconia surface is required to apply orthodontic force. The purpose of this scientific experiment was to evaluate the efficacy of three different methods of surface preparation for Zirconia, including surface roughening, sandblasting and the Nd: YAG laser, in the shear bond strength (SBS) of the orthodontic brackets. Methods: Fifty-four discs of zirconia were divided into three groups of 18: A) Hydrofluoric acid etching, B) sandblasting, and C) Nd: irradiation using the power of 1.5 W for 10 seconds. After bonding the brackets, the samples were slowly thermo-cycled (1000 times) for 24 hours. The SBS test was performed by a universal testing machine at a head speed of 0.5 mm/min. The adhesive remnant index (ARI) was scored at a magnification of 10 in the stereo microscope. All data were collected and analyzed using the variance, Kruskal-Wallis, Tukey, Don, and Weibull tests (α = 0.05). Results: The HF acid etching group (6.11± 0.94 MPa) had the highest SBS, which was followed by the laser group (6 ± 0.61 MPa) and the sandblast group (3.1080 ± 0.82 MPa). There was a significant statistical difference between the laser and HF groups and the sandblast group (P < 0.05) and no significant difference between the HF group and the laser group (P = 0.03). Conclusion: Based on the obtained bond strength, the Nd: YAG laser with a power of 1.5 W could be a substitute treatment method for the HF acid-etching.

Assessment of the Photobiomodulation Effect of a Blue Diode Laser on the Proliferation and Migration of Cultured Human Gingival Fibroblast Cells: A Preliminary In Vitro Study.

Introduction: Photobiomodulation therapy (PBM) is emerging as an effective strategy for the management of wound healing. The application of red and near infra-red light sources in laser therapy has been the subject of most researches in recent literature. Considering the lack of sufficient evidence in assessing the blue light in PBM, we aimed to investigate the photobiomodulation effect of a blue diode laser on the proliferation and migration of cultured human gingival fibroblast cells as a preliminary in vitro study. Methods: Human gingival fibroblast cells were irradiated with a blue diode laser at a 445 nm wavelength. Irradiation was done using three different powers of 200 mW (irradiation times of 5, 10,15, and 20 seconds); 300 mW (irradiation times of 5, 10, and 15 seconds); and 400 mW (irradiation times of 5 and 10 seconds). The fibroblast cells without laser exposure were considered as control. After 24 hours of incubation, the MTT assay and the wound scratch test were performed on the cells to investigate the biomodulation effect of the blue laser on the proliferation and migration of the cells respectively. The results were analyzed by one-way ANOVA and a post-hoc Tukey test with a P value <0.05 as a statistical significance level. Results: PBM with blue diode laser at power densities of 400 mW/cm2 with irradiation times of 10 and 15 seconds corresponding to energy densities of 4 and 6 J/cm2 exerted the statistically significant positive effect on both proliferation and migration of gingival fibroblast cells. Conclusion: Considering the encouraging findings of this study, PBM with blue diode laser can promote proliferation and migration of human gingival fibroblasts, the key cells involved in the process of oral wound healing.

Effect of Er:YAG and Er,Cr:YSGG Lasers on Ceramic Bracket Debonding from Composite Blocks.

OBJECTIVES: This study aimed to assess the effect of erbium-doped yttrium aluminum garnet (Er:YAG) and erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) lasers on the shear bond strength (SBS) of ceramic brackets debonding from the surface of composite blocks. MATERIALS AND METHODS: Thirty-six composite blocks were fabricated using Filtek Z250 light-cure composite. Block surfaces were etched with 37% phosphoric acid for 30 seconds and then rinsed with water for 20 seconds and dried. Maxillary right central incisor ceramic orthodontic brackets were bonded to the surfaces of composite blocks using Transbond XT adhesive and were cured for 40 seconds. Twelve samples were irradiated with Er:YAG laser, while 12 samples were irradiated with Er,Cr:YSGG laser, and the brackets were then debonded using a universal testing machine. Twelve samples served as controls (debonding using the universal testing machine without using a laser). The adhesive remnant index (ARI) score and bracket or composite cracks were evaluated under a stereomicroscope. One-way analysis of variance (ANOVA) was used for the comparison of the three groups. Kruskal-Wallis test was used to compare the ARI scores. RESULTS: The mean SBS was 17.01±5.22 MPa with Er:YAG laser, 18.03±6.46 MPa with Er,Cr:YSGG laser, and 16.61±6.73 MPa in the control group; the difference of the three groups was not significant (P=0.835). The difference in the ARI scores and enamel and composite cracks was not significant either (P>0.05). CONCLUSION: This study did not show any reduction in the bond strength of ceramic bracket to composite blocks after Er:YAG and Er,Cr:YSGG laser irradiation.

Evaluation of the Shear Bond Strength and Adhesive Remnant Index in Debonding of Stainless Steel Brackets Assisted with Nd:YAG Laser Irradiation.

OBJECTIVES: The purpose was to compare shear bond strength (SBS), pulp temperature, and adhesive remnant index (ARI) in debonding of stainless steel brackets from enamel surface using neodymium-doped yttrium aluminum garnet (Nd:YAG) laser versus the conventional debonding method. MATERIALS AND METHODS: Forty-eight extracted premolars were bonded to stainless steel brackets. The samples were divided into three experimental groups and one control group. In the first three groups, Nd:YAG laser was used for debonding with the power of 1, 1.5, and 2 W, respectively, for 10 seconds. The SBS and ARI of the samples were assessed. Pulp temperature was recorded before and after irradiation. Two samples from each group were used for determining enamel morphology after debonding using scanning electron microscopy (SEM). RESULTS: The mean SBS in the groups was 33.05, 28.69, 24.37, and 31.53 MPa, respectively, with no statistically significant differences (P=0.205). Significant differences in post-irradiation temperature were noted among the lased groups (P=0.000). Debonding mainly occurred at the adhesive-enamel interface in the 1-W laser and control groups and at the bracket-adhesive interface in the 1.5-W and 2-W laser groups. Enamel structure was amorphous and irregular following laser irradiation. CONCLUSION: Based on the results of this study, the use of Nd:YAG laser could not significantly affect the SBS. Therefore, this laser would not be suitable for debonding of metal brackets. The use of a 2-W laser could significantly raise the pulpal temperature. Nd:YAG laser renders a more heterogeneous enamel morphology compared to conventional debonding methods.