Assessment of Human Gingival Fibroblast Proliferation after Laser Stimulation In Vitro Using Different Laser Types and Wavelengths (1064, 980, 635, 450, and 405 nm)-Preliminary Report

The photobiomodulation effects of continuous and pulsed blue diode laser on proliferation and osteogenic differentiation of periodontal ligament stem cells

This study investigated the photobiomodulation effect of pulsed and continuous blue diode laser on osteogenic differentiation and proliferation of periodontal ligament mesenchymal stem cells. Periodontal Ligament Stem cells were seeded in 96-well plates, and 450 nm blue laser irradiation procedure was performed a day after cell seeding. Each experimental group was divided into two subgroups according to their energy density and irradiation duration: Continuous wave (100 mW, 10s, 2 J/cm2 and 100 mW, 20 s, 4 J/cm2) and pulse wave (200 mW, 10 s, 2 J/cm2 and 200 mW, 20 s, 4 J/cm2 and duty cycle 50% for both). Then, all groups were evaluated with a cell viability test (MTT), cell apoptosis (Annexin V) on the second and fourth days after irradiation, Alizarin Red staining on the 14th day after irradiation based on genes. Real-time PCR was conducted 7 and 14 days after irradiation. GAPD gene primers were used as internal control, and OPN, OCN, ALP, and RUNX2 gene primers were used as tests. The one-way ANOVA statistical analysis revealed that cell proliferation in the continuous-irradiated groups was significantly higher than in pulsed groups. However, there is no significant difference in comparison with the control group. Also, pulsed-irradiated groups demonstrated a higher rate of necrosis. The osteogenic differentiation in the continuous groups was more substantial than in the pulsed and the control groups. In comparison to all other study groups, the group that received continuous mode irradiation at an energy density of 2 J/cm2, power of 100 mW, and a radiation time of 10 s exhibited significantly higher numbers of calcified nodules and increased expression of OPN, OCN, and ALP genes (p < 0.05). Overall, treating periodontal ligament stem cells with a continuous blue diode laser and appropriate parameters can enhance their osteogenic differentiation and proliferation, accelerating the regeneration of periodontal tissues.

Clinical Observations of Soft Tissue Dimensions Around Teeth and Implants After Free Gingival Graft

INTRODUCTION AND AIMS

The histological and morphological differences in soft tissue between natural teeth and peri-implant may result in different clinical effectiveness to free gingival graft (FGG). This research aims to investigate the different efficacy of FGG in augmenting keratinized tissue width (KTW) between tooth and implant sites while evaluating its medium-term stability over a 2- to 5-year follow-up.

METHODS

In this study, 29 patients underwent FGG to address insufficient clinical scenarios when KTW <2 mm at the buccal aspect, including 37 implant sites and 33 natural teeth sites both in posterior regions were included. The KTW and gingival margin position (GMP) of these sites was assessed by measuring the intra-oral photographs which were taken at 0 days (T0), 3-month (T1), 6-month (T2), 12-month post-surgery (T3), and 2 to 5 years follow-up (T4).

RESULTS

The results revealed that KTW increased significantly in both groups. However, the natural teeth group showed significantly less graft shrinkage (GS) than the implants group. (Teeth: 2.05 ± 0.51 mm and 25.42% ± 6.45%; Implants: 3.18 ± 0.65 mm and 38.92% ± 5.39%, P <.01). From T1 to T4. The gingival margin coronally advanced by 0.47 ± 0.51 mm and 0.18 ± 0.43 mm for the natural teeth and implants group, respectively (P<.05).

CONCLUSIONS

A greater KTW reduction after FGG was observed at implants versus natural teeth. And, the graft surrounding implants after crown restoration was stable for up to 2 to 5 years.

CLINICAL RELEVANCE

By comparing the changes in KTW around natural teeth and implants following FGG to investigate whether there are differences between them and the degree of differences. Additionally, this allows us to explore whether the restorations impact the effect of FGG. This research can assist clinicians in selecting an appropriate amount of soft tissue during surgery to achieve treatment goals, reduce postoperative discomfort for patients, and enhance predictability in clinicians' ability to increase keratinized tissue. Furthermore, by observing changes in the position of GMP around natural teeth and implants, the effectiveness of FGG in root coverage can be understood, thus improving the predictability of FGG for root coverage.

Effect of low-level laser therapy on proliferation and cytotoxicity of mouse fibroblasts and human fibroblasts: An in vitro study

Background

Diode laser is known for its biostimulatory effects on various cell populations such as osteoblasts and fibroblasts. The usage of low-level laser therapy for photobiomodulation depends on its type, emission wavelength, and energy selected. Previously performed in vitro studies have determined its effect on cell proliferation and cytotoxicity; however, the results were inconsistent.

Objectives

The objectives of this study were to evaluate and compare diode laser effect on mouse embryonic fibroblasts (MEFs) and human gingival fibroblasts (HGFs) for proliferation and cytotoxicity.

Materials and Methods

32 samples, 16 wells of MEF cells (Group I) and HGF cells (Group II) each with 8 subgroups containing control (no laser irradiation) and experimental (laser irradiated) groups were cultured after being seeded at 4000 cells/ well with 4cm inter-well distance. Experimental group cell cultures were irradiated with a single dose of 810 nm diode laser (energy 1J/cm2, 12.5 mW, 80 s/well) using continuous wave mode after 1 day of incubation. Spectrophotometric analysis was done after 24 h of laser irradiation for cell proliferation and cell cytotoxicity on the 2nd, 3rd, and 7th days on all groups.

Results

Human and mouse fibroblast groups showed positive results when irradiated with an 810 nm laser. A hundred percent proliferation was seen for MEF in 7 days and HGF in 2 days. Two percent cytotoxicity was seen on the 2nd and 3rd day in MEF. Increased cell proliferation and minimal cytotoxic effects were seen with diode laser usage.

Conclusion

Low-level laser irradiation indicates an increase in cell proliferation with less cytotoxicity on mouse and human fibroblasts.

Clinical and thermographic evaluation after lower third molar extractions and the application of different photobiomodulation protocols: double-blind randomised clinical trial

OBJECTIVES

to compare the parameters of pain, oedema, temperature, and soft tissue closure in dental sockets that received two different photobiomodulation (PBM) protocols following extractions.

MATERIALS AND METHODS

Thirty-one participants had their teeth 38 and 48 extracted. Subsequently, one of the dental sockets received PBM at a wavelength (WL) of 808 nanometers (808 group- nm) and the other dental socket received the PBM at WLs of 808 nm and 660 nm, simultaneously (808 + 660 group). The PBM was applied immediately after the surgical procedure and on the 3rd and 7th days.

RESULTS

The mean of Visual Analogue Scale (VAS) values for pain were 1.45 for the 3rd day and 0.52 for the 7th day in the 808 + 660 and 808 group, respectively. The mean the pogonion-tragus measurement, used to assess facial oedema on the 3rd day, was 15.38 cm (range 13.5-17.5) in the 808 + 660 group and 15.48 cm (range 14.0-17.5) in the 808 group. The mean facial temperatures in the 808 + 660 group were 34.9 degrees Celsius (ºC) (range 33.5-36.4) on the 3rd day and 35 ºC (range 33.4-36.4) on the 7th day. In the 808 group, the mean temperatures were 34.9 ºC (range 33.9-36.2) on the 3rd day and 34.9 ºC (33.7-36.2) on the 7th day. Regarding the dimensions of the dental socket, the mean were similar for both groups. Significant differences between the groups were only observed in the pain parameter and only on the 7th day, being greater for the 808 + 660 group (p = 0.031).

CONCLUSIONS

The association of the 660 nm with 808 nm, and the increase in energy did not showed more benefits in pain reduction oedema, or acceleration of the closure of the soft tissues of the dental sockets of lower third molars, in the protocols used here.

CLINICAL RELEVANCE

There is no need to combine lasers at wavelengths of 660 and 808 nm to reduce oedema, pain and repair of soft tissues after extraction of lower third molars.

CLINICAL TRIAL REGISTRATION

This trial was registered in the Brazilian Registry of Clinical Trials (ReBEC) with the following code: RBR-66pyrh8, on 29th December, 2022.

Different wavelengths of laser: are they significant for treatment of denture stomatitis?: an in-vitro study

BACKGROUND

Denture stomatitis (DS) is an inflammatory disorder that affects the mucosal surface underneath the dentures and frequently causes oral mucosal irritation, discomfort, and altered taste perception, which prevents people from consuming enough nutrients. One of the main causes of DS is an overgrowth of the fungus Candida albicans (C. albicans). A possible alternative treatment for Candida infections is thought to be laser therapy. The aim of this study was to evaluate how different wavelengths of laser would affect growth and pathogenic properties of Candida albicans.

METHODS

A concentration of 106 viable cells/ml of Candida albicans were used in the preparation process. Four groups were created from the specimens. Culturing of the control group was completed with no intervention. The other 3 groups received laser radiation for 60 seconds at a power of 1W. The 2nd and 3rd groups were irradiated with diode laser at a wavelength of 940 nm and 980 nm respectively. The 4th group was irradiated with Nd-YAG laser at a wavelength of 1064 nm. Turbidimetric growth was defined as variations in the optical density of fungal growth. These measures were made at three different times: baseline, 48 hours, and 72 hours.

RESULTS

In both groups of diode laser, the growth of Candida albicans showed no remarkable differences at baseline, after 48 and 72 hours using a power of 1 W and duration of 60 seconds. The Nd-YAG group showed significant increase in optical density after 48 hrs then significant decrease after 72 hrs. The optical density values in the control group showed no notable difference between the control and diode study groups at different time periods. However, the Nd:YAG group showed a statistically significant difference compared to the control and the 2 diode laser groups.

CONCLUSIONS

Different laser parameters have a different effect on growth and pathogenic properties of Candida albicans. Diode laser therapy with wavelengths 940 and 980 nm used in continuous mode with power of 1 W for duration of 60 seconds can result in proliferation of Candida albicans instead of destroying them. Nd:YAG laser, used in pulsed mode, with power of 1 W for a duration of 60 seconds can be used to destroy Candida albicans and therefore, can be used as an effective treatment for denture stomatitis.

Photobiomodulation effects of pulsed and continuous wave near-infrared laser on the proliferation and migration of human gingival fibroblasts: An in vitro study

There are limited data on comparison of pulsed and continuous wave in photobiomodulation therapy (PBM). This study aimed to investigate the effect of PBM with 980 nm laser in pulsed and continuous wave on the proliferation and migration of human gingival fibroblasts (HGF) cells. Cultured HGF were divided into three main groups: (1) irradiated in pulsed mode (frequencies of 50 and 25 KHz; energy densities of 3 and 5 J/cm2 ), (2) irradiated in continuous mode (energy densities of 3.2 and 5.2 J/cm2 ), and (3) no irradiation as control group. HGF proliferation rate was measured by MTT assay at 24, 48, and 72 h post irradiation. In addition, HGF migration rate was measured by scratch test at 24 h post PBM. At 24 h, the group received continuous irradiation at 5.2 J/cm2 showed significantly higher proliferation compared with the control group (p = 0.012). At 48 and 72 h, the groups received continuous, and 50 Hz pulsed irradiation at energy densities of 5.2 and 5 J/cm2 respectively, had significantly higher HGF proliferation rates compared to the control (p < 0.05). Only the continuous irradiations were effective in significant increase of the cell migration. In conclusion, continuous PBM at energy density of 5.2 J/cm2 showed promising effect on HGF proliferation and migration.

The Use of 810 and 1064 nm Lasers on Dental Implants: In Vitro Analysis of Temperature, Surface Alterations, and Biological Behavior in Human Gingival Fibroblasts

Objective: The primary objective of this study was to evaluate the safety of 810 and 1064 nm laser treatment on dental implants. Background: Peri-implantitis is a challenge for clinicians and researchers. Methods: A pig mandible model was used to evaluate temperature increases during laser irradiation. Surface alterations on processed pure titanium discs were analyzed via scanning electron microscopy and measurement of surface contact angles. Processed titanium discs were cocultured in vitro with human gingival fibroblasts; subsequently, cell proliferation was measured. Results: The maximum temperature and time to reach each threshold were comparable. No surface alterations were detected after 810 nm laser irradiation, whereas surface cracks were observed after 1064 nm laser irradiation under the parameter setting of 31.84 W/cm2. Compared with unaltered processed pure titanium discs, the proliferation of human gingival fibroblasts was significantly greater on altered processed pure titanium discs. Conclusions: The use of either 810 or 1064 nm laser treatments may increase the risk of thermal damage in terms of increased temperature if the parameter setting is not warranted. In addition, the use of 1064 nm laser treatment could lead to changes in pure titanium discs that do not negatively affect cell proliferation. Further investigations of laser-assisted therapy are necessary to improve guidelines concerning the treatment of peri-implantitis. Clinical trial registration number: 2021-P2-098-01.

Effectiveness of photobiomodulation for people with age-related cognitive impairment: a systematic review and meta-analysis

The increasing incident of age-related cognitive impairment worldwide and the lack of pharmaceutical treatments emphasizes the value of non-pharmaceutical therapy. Emerging evidence suggested photobiomodulation (PBM) is a popular intervention to brain disorder; however, it remains unclear the efficacy of PBM for patients with age-related cognitive impairment. The purpose of this systematic review is to compare the different parameters used in PBM, analyze the beneficial effects of PBM as a potential therapy for age-related cognitive impairment. Five electronic database, PubMed, Web of Science, Cochrane Library, CINAHL, and PsycINFO, were systematically searched from inception to November 2021. Relevant randomized controlled trials (RCTs) were screened and assessed for risk of bias. Eleven RCTs evaluating PBM interventions were included. The systematic review and meta-analysis has been registered in PROSPERO(CRD42022374562). Results showed that PBM had a significant moderated effect on global cognition function (SMD=0.51, 95% CI [0.162, 0.864], p=0.004). We found that multiple wavelength PBM (SMD=0.648, 95% CI [0.220, 1.075], p=0.003) had significant effects while single wavelength PBM was non-significant (SMD=0.385, 95% CI [-0.168, 0.987], p=0.172). Laser effect (SMD=0.682, 95% CI [0.37, 0,994], p<0.001) was larger than LED effect (SMD=0.582, 95% CI [0.269, 0.895], p<0.001). PBM in clinical setting (SMD=0.468, 95% CI [0.050, 0.887], p=0.028) had significant effect, but there was no significant effect of home-used PBM (SMD=0.616, 95% CI [-0.121, 1.354], p=0.101). The pool effect of multi-modality PBM (SMD=0.720, 95% CI [0.027, 1.414], p=0.040) was significantly higher in the studies of transcranial irradiation (SMD=0.616, 95% CI [-0.121, 1.354], p=0.010). Cumulative irradiation time was a moderator between the PBM and cognitive function improvement. Photobiomodulation have the potential to improve cognitive function in aging adults. Cumulative irradiation duration, light source, device type, penetration modality, and intervention site can affect the effectiveness of PBM intervention.

Nd:YAG laser therapy on postoperative pain, swelling, and trismus after mandibular third molar surgery: a randomized double-blinded clinical study

This study aims to evaluate the effect of Nd:YAG laser therapy (NdLT) on postoperative pain, swelling, and trismus after mandibular third molar (M3) surgery. Three hundred patients were randomly divided into the Nd group (n = 100), medication group (n = 100), and Nd+medication (Nd+m) group (n = 100). The WHARFE classification system was used to assess surgical difficulty. After surgery, the Nd group was irradiated by the Nd:YAG laser in very long-pulsed mode (VLP, pulse duration 1 ms, 20 Hz, 4 W, R21-C3) in 6 regions of the extraction socket with a total energy of 300 J. For the medication group, dexamethasone 0.75 mg and loxoprofen 60 mg were prescribed immediately and every 12 h thereafter for 3 days. The Nd+m group received both treatments mentioned above. Pain assessment was performed at 6, 24, 48, and 72 h postoperatively using the visual analog scale (VAS). Swelling was evaluated by changes in the distance from (1) the tragus to the labial commissure, (2) the tragus to the pogonion, and (3) the mandibular angle to the lateral canthus preoperatively and 72 h postoperatively. Trismus was assessed by the change in maximum mouth opening. Groups Nd and Nd+m had lower VAS scores at 6 h, 24 h, and 48 h (F = 13.80, p = 0.00), but the difference between the two groups was not significant (F = 1.34, p = 0.11). However, no significant difference was observed at 72 h (p = 0.10). There was no significant difference in swelling or trismus among the three groups (p > 0.05). NdLT is an effective approach to improve complications after M3 surgery.

TCPP/MgO-loaded PLGA microspheres combining photodynamic antibacterial therapy with PBM-assisted fibroblast activation to treat periodontitis

Bacteria eradication and subsequent periodontal tissue reconstruction is the primary task for periodontitis treatment. Commonly used antibiotic therapy suffers from antibiotic resistance. Meanwhile, promoting fibroblast activity is crucial for re-establishing a damaged periodontal structure. In addition to the fibroblast activation property of Mg²⁺, photobiomodulation (PBM) has recently attracted increasing attention in wound healing. Using the same 635 nm laser resource, PBM could simultaneously work with antibacterial photodynamic therapy (aPDT) to achieve antibacterial function and fibroblast activation effect. Herein, multifunctional microspheres were designed by employing poly (lactic-co-glycolic acid) (PLGA) microspheres to load tetrakis (4-carboxyphenyl) porphyrin (TCPP) and magnesium oxide (MgO) nanoparticles, named as PMT, with sustained Mg²⁺ release for 20 days. PMT achieved excellent antibacterial photodynamic effect for periodontal pathogens F. nucleatum and P. gingivalis by generating reactive oxygen species, which increases cell membrane permeability and destroys bacteria integrity to cause bacteria death. Meanwhile, PMT itself exhibited improved fibroblast viability and adhesion, with the PMT + light group revealing further activation of fibroblast cells, suggesting the coordinated action of Mg²⁺ and PBM effects. The underlying molecular mechanism might be the elevated gene expressions of Fibronectin 1, Col1a1, and Vinculin. In addition, the in vivo rat periodontitis model proved the superior therapeutic effects of PMT with laser illumination using micro-computed tomography analysis and histological staining, which presented decreased inflammatory cells, increased collagen production, and higher alveolar bone level in the PMT group. Our study sheds light on a promising strategy to fight periodontitis using versatile microspheres, which combine aPDT and PBM-assisted fibroblast activation functions.

Comparative evaluation of postoperative pain and tissue response in patients undergoing conventional flap surgeries with or without 940 nm diode laser exposure - A randomized clinical study

BACKGROUND

Over the past few years, a growing body of evidence has allowed us to ascertain that the initiation of periodontitis stems from the existence of oral microbial biofilm and that this requires definitive treatment. Owing to its exceptional usability, affordability, and antibacterial activity, the "diode laser" (DL) has increasingly become a popular and important tool in a dentist's armamentarium. However, there is a scarcity of scientific evidence on the utility and advantages of using "diode laser" in periodontal flap surgery. The study aimed to determine the efficacy of 940 nm diode laser exposure in combination with conventional periodontal flap surgery for the treatment of chronic periodontitis to evaluate postoperative discomfort and clinical parameters.

MATERIALS AND METHODS

A total of 10 subjects (7 males and 3 females) with generalized chronic periodontitis were recruited and completed the study without any dropouts. For this split-mouth study, 40 sample sites with pocket probing depth (PPD) 5-7 mm post periodontal Phase I therapy were selected. The quadrants were randomly allocated to Groups A, B, C, and D using the fish bowl lottery method. Kirkland flap surgery with laser and modified Widman flap (MWF) with laser were performed in Group A and C, respectively, while Kirkland flap surgery and MWF surgery were performed in Group B and Group D. Clinical parameters including visual analog scale (VAS) score and gingival inflammation were determined at 3^rd and 7^th day postoperatively while PPD, clinical attachment level (CAL), and sulcus bleeding index (SBI) were recorded at baseline and 6 months following treatment. Wilcoxon signed-rank test and Kruskal-Wallis test were used for intra-group and inter-group comparison of parameters, respectively.

RESULTS

Statistically significant difference was attained with postoperative discomfort in laser-assisted groups on 1^st and 3^rd day postoperatively (P < 0.001). There was no significant difference in the proportion of subjects with gingival inflammation. A statistically significant reduction in mean PPD at 6 months postoperatively was seen among all study groups (P < 0.05) but the inter-group difference was not statistically significant. SBI score reduced significantly from baseline to 6 months follow-up among all four groups (P < 0.05). However, we did not find the inter-group difference to be statistically non-significant.

CONCLUSION

Diode laser as an adjunct to the surgical procedure can demonstrate appreciable benefits by increasing the CAL and minimizing the postoperative pain and the probing pocket, but such additional effects were not observed with gingival inflammation.

Molecular Research on Oral Diseases and Related Biomaterials: A Journey from Oral Cell Models to Advanced Regenerative Perspectives

Oral diseases such as gingivitis, periodontitis, and oral cancer affect millions of people worldwide. Much research has been conducted to understand the pathogenetic mechanisms of these diseases and translate this knowledge into therapeutics. This review aims to take the reader on a journey from the initial molecular discoveries to complex regenerative issues in oral medicine. For this, a semi-systematic literature search was carried out in Medline and Web of Science databases to retrieve the primary literature describing oral cell models and biomaterial applications in oral regenerative medicine. First, an in vitro cell model of gingival keratinocytes is discussed, which illustrates patho- and physiologic principles in the context of oral epithelial homeostasis and carcinogenesis and represents a cellular tool to understand biomaterial-based approaches for periodontal tissue regeneration. Consequently, a layered gradient nonwoven (LGN) is described, which demonstrates that the key features of biomaterials serve as candidates for oral tissue regeneration. LGN supports proper tissue formation and obeys the important principles for molecular mechanotransduction. Furthermore, current biomaterial-based tissue regeneration trends, including polymer modifications, cell-based treatments, antimicrobial peptides and optogenetics, are introduced to represent the full spectrum of current approaches to oral disease mitigation and prevention. Altogether, this review is a foray through established and new concepts in oral regenerative medicine and illustrates the process of knowledge translation from basic molecular and cell biological research to future clinical applications.

Photodynamic Therapy (PDT) in Prosthodontics: Disinfection of Human Teeth Exposed to Streptococcus mutans and the Effect on the Adhesion of Full Ceramic Veneers, Crowns, and Inlays: An In Vitro Study

The use of PDT in prosthodontics as a disinfection protocol can eradicate bacteria from tooth surfaces by causing the death of the microorganisms to which the photosensitizer binds, absorbing the energy of laser light during irradiation. The aim of the study was to investigate the capacity of PDT to increase the bond strength of full ceramic restorations. In this study, 45 extracted human teeth were prepared for veneers, crowns, and inlays and contaminated with Streptococcus mutans. Tooth surfaces decontamination was performed using a diode laser and methylene blue as a photosensitizer. The disinfection effect and the impact on tensile bond strength were evaluated by scanning electron microscopy (SEM) and pull-out tests of the cemented ceramic prosthesis. Results show that the number of bacteria was reduced from colonized prepared tooth surfaces, and the bond strength was increased when PDT was used. In conclusion, the present study indicates that using PDT as a protocol before the final adhesive cementation of ceramic restorations could be a promising approach, with outstanding advantages over conventional methods.

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.

Photobiomodulation with Red and Near-Infrared Light Improves Viability and Modulates Expression of Mesenchymal and Apoptotic-Related Markers in Human Gingival Fibroblasts

Photobiomodulation (PBM), also called low-level laser treatment (LLLT), has been considered a promising tool in periodontal treatment due to its anti-inflammatory and wound healing properties. However, photobiomodulation's effectiveness depends on a combination of parameters, such as energy density, the duration and frequency of the irradiation sessions, and wavelength, which has been shown to play a key role in laser-tissue interaction. The objective of the study was to compare the in vitro effects of two different wavelengths-635 nm and 808 nm-on the human primary gingival fibroblasts in terms of viability, oxidative stress, inflammation markers, and specific gene expression during the four treatment sessions at power and energy density widely used in dental practice (100 mW, 4 J/cm²). PBM with both 635 and 808 nm at 4 J/cm² increased the cell number, modulated extracellular oxidative stress and inflammation markers and decreased the susceptibility of human primary gingival fibroblasts to apoptosis through the downregulation of apoptotic-related genes (P53, CASP9, BAX). Moreover, modulation of mesenchymal markers expression (CD90, CD105) can reflect the possible changes in the differentiation status of irradiated fibroblasts. The most pronounced results were observed following the third irradiation session. They should be considered for the possible optimization of existing low-level laser irradiation protocols used in periodontal therapies.

Photobiomodulation of oral fibroblasts stimulated with periodontal pathogens

Photobiomodulation (PBM) utilises light energy to treat oral disease, periodontitis. However, there remains inconsistency in the reporting of treatment parameters and a lack of knowledge as to how PBM elicits its molecular effects in vitro. Therefore, this study aimed to establish the potential immunomodulatory effects of blue and near infra-red light irradiation on gingival fibroblasts (GFs), a key cell involved in the pathogenesis of periodontitis. GFs were seeded in 96-well plates in media + / - Escherichia coli lipopolysaccharide (LPS 1 μg/ml), or heat-killed Fusobacterium nucleatum (F. nucleatum, 100:1MOI) or Porphyromonas gingivalis (P. gingivalis, 500:1MOI). Cultures were incubated overnight and subsequently irradiated using a bespoke radiometrically calibrated LED array (400-830 nm, irradiance: 24 mW/cm² dose: 5.76 J/cm²). Effects of PBM on mitochondrial activity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and adenosine triphosphate (ATP) assays, total reactive oxygen species production (ROS assay) and pro-inflammatory/cytokine response (interleukin-8 (IL-8) and tumour growth factor-β1 (TGFβ1)) were assessed 24 h post-irradiation. Data were analysed using one-way ANOVA followed by the Tukey test. Irradiation of untreated (no inflammatory stimulus) cultures at 400 nm induced 15%, 27% and 13% increases in MTT, ROS and IL-8 levels, respectively (p < 0.05). Exposure with 450 nm light following application of P. gingivalis, F. nucleatum or LPS induced significant decreases in TGFβ1 secretion relative to their bacterially stimulated controls (p < 0.001). Following stimulation with P. gingivalis, 400 nm irradiation induced 14% increases in MTT, respectively, relative to bacteria-stimulated controls (p < 0.05). These findings could identify important irradiation parameters to enable management of the hyper-inflammatory response characteristic of periodontitis.