In Vitro Cytological Responses against Laser Photobiomodulation for Periodontal Regeneration

Current status of Er:YAG laser in periodontal surgery

Lasers have numerous advantageous tissue interactions such as ablation or vaporization, hemostasis, bacterial killing, as well as biological effects, which induce various beneficial therapeutic effects and biological responses in the tissues. Thus, lasers are considered an effective and suitable device for treating a variety of inflammatory and infectious conditions of periodontal disease. Among various laser systems, the Er:YAG laser, which can be effectively and safely used in both soft and hard tissues with minimal thermal side effects, has been attracting much attention in periodontal therapy. This laser can effectively and precisely debride the diseased root surface including calculus removal, ablate diseased connective tissues within the bone defects, and stimulate the irradiated surrounding periodontal tissues during surgery, resulting in favorable wound healing as well as regeneration of periodontal tissues. The safe and effective performance of Er:YAG laser-assisted periodontal surgery has been reported with comparable and occasionally superior clinical outcomes compared to conventional surgery. This article explains the characteristics of the Er:YAG laser and introduces its applications in periodontal surgery including conventional flap surgery, regenerative surgery, and flapless surgery, based on scientific evidence from currently available basic and clinical studies as well as cases reports.

The comparative study of temperature rise, time consuming and cut quality among piezosurgery, conventional rotary instruments and Er: YAG laser in apicectomy

OBJECTIVES

This study aimed to compare the temperature rise, time consuming and cut quality of apicectomy using three different methods.

MATERIALS AND METHODS

Twenty-four single-rooted teeth were collected and divided into four groups operating apicectomy with a NINJA tip of a piezoelectric device (G1), a diamond bur with 300,000 rpm (G2), and Er: YAG laser at 200 mJ/ 30 Hz (G3) as well as 250 mJ/ 30 Hz (G4). The temperature elevation and time were recorded and the cut quality was evaluated via stereomicroscope and scanning electronic microscopy (SEM).

RESULTS

The temperature increases for G1 was significantly higher than for G2. However, there was no significant difference between G1 and G2 with laser groups respectively. The median time for apicectomy was: 100.14s for G1, 22.65s for G2, 33.58s for G3, and 21.80s for G4. G1 is the most time-consuming group and there was no statistically significance in the comparisons with G2, G3 and G4. Cut quality was assessed by crack occurrence, smear layer formation and dentinal tubules exposed. The percentage of cracked teeth in G1 and G2 was 33.33% and for laser groups the percentage was 16.67% each. SEM showed that no smear layer formed and almost all dentinal tubules were exposed on resected surfaces for G3&G4, surfaces from G2 were partly covered by smear layer, and surfaces from G1 were fully covered by smear layer and with no dentinal tubules exposed.

CONCLUSIONS

Er: YAG laser and conventional rotary instruments were safe and efficient for apicectomy and with a better cut quality when compared with piezoelectric equipment. Er: YAG laser could be a promising technique for apicectomy and further studies are necessary, especially larger sample in vivo investigations, to verify the feasibility of Er: YAG laser in endodontic surgery.

Enhanced periodontal tissue healing via vascular endothelial growth factor expression following low-level erbium-doped: yttrium, aluminum, and garnet laser irradiation: In vitro and in vivo studies

BACKGROUND

This study aimed to investigate the effects of low-level erbium-doped: yttrium, aluminum, and garnet (Er:YAG) laser irradiation on periodontal tissue healing and regeneration through angiogenesis in vivo and in vitro studies.

METHODS

Intrabony defects were surgically created in the bilateral maxilla molar of rats. The defects were treated by open flap debridement (OFD) with Er:YAG laser, including low-level laser irradiation (LLLI) to bone and blood clot surfaces, or conventional procedures. The mRNA expression of vascular endothelial growth factor (VEGF) in the surgical sites was quantified using real-time polymerase chain reaction. The decalcified specimens were prepared for histometric analysis. Also, LLLI was performed on human umbilical vein endothelial cells to evaluate the effects on angiogenesis. Cell proliferation, VEGF expression, and tube formation were assessed. In addition, capsazepine (CPZ), a selective inhibitor of transient receptor potential vanilloid 1 (TRPV1), treatment was performed before LLLI for the same assays.

RESULTS

OFD using Er:YAG laser did not generate thermal damage on bone or root surfaces. LLLI accelerated hemostasis by coagulation of the superficial layers of blood clots in the laser-treated group. Postoperative healing was sound in all animals in both groups. VEGF expression and bone formation were significantly increased in the laser-treated group compared to those in the conventional treatment group. In vitro, cell proliferation and VEGF expression were significantly increased in the LLLI group compared to the control group. Tube-formation assays showed that LLLI significantly promoted angiogenesis. CPZ treatment significantly suppressed VEGF expression and tube formation following LLLI.

CONCLUSIONS

This study suggests that Er:YAG laser irradiation may promote periodontal tissue healing by enhancing angiogenetic effect of endothelial cells via TRPV1.

Evaluating the effect of strontium ranelate and photobiomodulation on cementogenic and osteogenic differentiation of buccal fat pad-derived stem cells: An in vitro study

This study aimed to analyze the impact of strontium ranelate (Str), photobiomodulation (PBM), or their combination of the proliferation, osteogenic differentiation, and cementogenic differentiation of buccal fat pad-derived stem cells. BFPdSCs were exposed to one of the following interventions: (1) PBM (660 nm), (2) PBM (660 nm) + Str, (3) PBM (880 nm), (4) PBM (880 nm) + Str, (5) Str. All study groups had significantly higher osteogenic differentiation than the control group (p < 0.05), and no significant difference existed between the 660 and 808 nm groups (p = 0.97). Compared to the Str group, 660 nm and 880 nm group samples had significantly lower osteogenic differentiation (p < 0.0001), while other groups did not show a significant difference. Regarding cementogenic differentiation, the 660 nm group showed higher values than the 808 nm group (p < 0.01). Compared with the Str group, 660 nm, 660 nm + Str, and 808 nm + Str groups showed significantly higher gene expression (p < 0.05). In the case of osteogenic differentiation, although photobiomodulation alone had a lower inducing effect than strontium ranelate, combining 808 nm diode lasers and strontium ranelate may provide the best results. Moreover, using a 660 nm diode laser and exposing stem cells to strontium ranelate can be the most effective approach to induce cementogenic differentiation.

Effects of photobiomodulation on different phases of in vitro osteogenesis

The present study aimed to evaluate the effect of photobiomodulation therapy (PBM) on different stages of osteogenesis in vitro. For this, osteoblastic-like cells (Saos-2 cell lineage) were irradiated in two different periods: during the Proliferation phase (PP; from the second to the fourth day) and during the Differentiation phase (DP; from the seventh to the ninth day). The energy density used in the study was 1.5 J/ cm2. The following parameters were evaluated: 1) quantification of collagen type 1 (COL 1), osteopontin (OPN), and bone morphogenetic protein 2 (BMP-2); 2) quantification of alkaline phosphatase (ALP) activity; and 3) quantification of  extracellular matrix (ECM) mineralization. Non-irradiated cultures were used as controls. The data were analyzed using the Student's t-test or one-way ANOVA, considering a significance level of 5%. The results indicated that COL 1 and BMP-2 quantification was higher in Saos-2 irradiated during the DP in relation to the control group at day 10 (p < 0.05). No differences were observed for other comparisons at this time point (p > 0.05). OPN expression was greater in PP compared with the other experimental groups at day 10 (p < 0.05). Irradiation did not affect ALP activity in Saos-2 regardless of the exposure phase and the time point evaluated (p > 0.05). At day 14, ECM mineralization was higher in Saos-2 cultures irradiated during the DP in relation to the PP (p < 0.05). In conclusion, the results suggested that the effects of PBM on osteoblastic cells may be influenced by the stage of cell differentiation.

High-frequency low-intensity semiconductor laser irradiation enhances osteogenic differentiation of human cementoblast lineage cells

PURPOSE

Laser irradiation activates a range of cellular processes in the periodontal components and promotes tissue repair. However, its effect on osteogenic differentiation of human cementoblast lineage cells remains unclear. This study aimed to examine the effects of high-frequency semiconductor laser irradiation on the osteogenic differentiation of human cementoblast lineage (HCEM) cells.

METHODS

HCEM cells were cultured to reach 80% confluence and irradiated with a gallium-aluminum-arsenide (Ga-Al-As) semiconductor laser with a pulse width of 200 ns and wavelength of 910 at a dose of 0-2.0 J/cm2. The outcomes were assessed by analyzing the mRNA levels of alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), and type I collagen (COLL1) using real-time polymerase chain reaction (PCR) analysis 24 h after laser irradiation. Cell mineralization was evaluated using ALP activity, calcium deposition, and Alizarin Red staining.

RESULTS

The laser-irradiated HCEM cells showed significantly enhanced gene expression levels of ALP, RUNX2, and COLL1 as well as ALP activity and calcium concentration in the culture medium compared with the non-irradiated cells. In addition, enhanced calcification deposits were confirmed in the laser-irradiated group compared with the non-irradiated group at 21 and 28 days after the induction of osteogenic differentiation.

CONCLUSION

High-frequency semiconductor laser irradiation enhances the osteogenic differentiation potential of cultured HCEM cells, underscoring its potential utility for periodontal tissue regeneration.

Infrared diode laser enhances human periodontal ligament stem cells behaviour on titanium dental implants

Low level laser treatment (LLLT) is known for its photobiostimulatory and photobiomodulatory characteristics, which stimulate cell proliferation, increase cellular metabolism, and improve cellular regeneration. The objective of the present research was to assess the possible influence of infrared diode laser irradiation on the behaviour, attachment, and osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) seeded on different types of dental implants. Two distinct types of implants, one subjected to laser surface treatment and the other treated with acid etching, were longitudinally divided into two halves and submerged in six wells culture plates. Both implants were subjected to infrared diode laser treatment, and subsequently, the morphology and attachment of cells were examined using scanning electron microscopy (SEM) after 14 and 21 days. The behaviour of (hPDLSCs) towards two types of implants, when exposed to osteogenic medium and low-level laser therapy (LLLT), was assessed using quantitative real-time polymerase chain reaction to measure the expression of stemness markers and osteogenic markers. The scanning electron microscopy (SEM) demonstrated that the application of infrared diode laser irradiation substantially improved the attachment of cells to both types of implants. The stemness gene markers were significantly down regulated in cells seeded on both surfaces when challenged with osteogenic media in relation to control. At 14 days, early osteogenic markers, were upregulated, while late osteogenic markers, were downregulated in both challenged groups. At the 21-day mark, hPDLSCs seeded on an acid-etched implant exhibited increased expression of all osteogenic markers in response to stimulation with osteogenic media and infra-red diode laser, in contrast to hPDLSCs seeded on a laser surface treated implant under the same conditions. Finally, the findings of our research revealed that when subjected to infrared diode laser, human periodontal ligament stem cells cultured on both types of implants demonstrated improved cellular attachment and differentiation. This suggested that infrared diode laser enhanced the activity of the cells surrounding the implants. Hence, the use of infrared diode laser could be pivotal in improving and expediting the clinical osseointegration process around dental implants.

Effects of low-level Er:YAG laser irradiation on proliferation and gene expression in primary gingival fibroblasts isolated from mouse maxilla

We investigated the effects of low-level Er:YAG laser irradiation on proliferation and alternations in early gene expression of gingival fibroblasts. Mice primary gingival fibroblasts were irradiated with an Er:YAG laser (1.8, 3.9, and 5.8 J/cm2 ). Irradiation at 3.9 J/cm2 promoted cell proliferation without significant changes in lactate dehydrogenase or Hspa1a expression. Three hours after irradiation at 3.9 J/cm2 , the Fn1 expression level was significantly increased. RNA-seq identified 15 differentially expressed genes between irradiated and non-irradiated cells, some of which belonged to immediate early genes (IEGs). Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated MAPK pathway enhancement, and gene set enrichment analysis showed enrichment in the TGF-β signaling gene set. Enhanced proliferation via laser irradiation disappeared upon inhibition of Dusp4, Dusp5, and Tgfr1 expression. Low-level Er:YAG laser irradiation, especially at 3.9 J/cm2 without a major temperature elevation, enhanced fibroblast proliferation, via TGF-β and the MAPK signaling pathway following IEG expression.

Low-level laser therapy alleviates periodontal age-related inflammation in diabetic mice via the GLUT1/mTOR pathway

Diabetes mellitus (DM) is a chronic age-related disease that was recently found as a secondary aging pattern regulated by the senescence associated secretory phenotype (SASP). The purpose of this study is to detect the potential efficacy and the specific mechanisms of low-level laser therapy (LLLT) healing of age-related inflammation (known as inflammaging) in diabetic periodontitis. Diabetic periodontitis (DP) mice were established by intraperitoneal streptozotocin (STZ) injection and oral P. gingivalis inoculation. Low-level laser irradiation (810 nm, 0.1 W, 398 mW/cm2, 4 J/cm2, 10 s) was applied locally around the periodontal lesions every 3 days for 2 consecutive weeks. Micro-CT and hematoxylin-eosin (HE) stain was analyzed for periodontal soft tissue and alveolar bone. Western blots, immunohistochemistry, and immunofluorescence staining were used to evaluate the protein expression changes on SASP and GLUT1/mTOR pathway. The expression of aging-related factors and SASP including tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 were reduced in periodontal tissue of diabetic mice. The inhibitory effect of LLLT on GLUT1/mTOR pathway was observed by detecting the related factors mTOR, p-mTOR, GLUT1, and PKM2. COX, an intracytoplasmic photoreceptor, is a key component of the anti-inflammatory effects of LLLT. After LLLT treatment a significant increase in COX was observed in macrophages in the periodontal lesion. Our findings suggest that LLLT may regulate chronic low-grade inflammation by modulating the GLUT1/mTOR senescence-related pathway, thereby offering a potential treatment for diabetic periodontal diseases.

Optimization of a Photobiomodulation Protocol to Improve the Cell Viability, Proliferation and Protein Expression in Osteoblasts and Periodontal Ligament Fibroblasts for Accelerated Orthodontic Treatment

Numerous pieces of evidence have supported the therapeutic potential of photobiomodulation (PBM) to modulate bone remodeling on mechanically stimulated teeth, proving PBM's ability to be used as a coadjuvant treatment to accelerate orthodontic tooth movement (OTM). However, there are still uncertainty and discourse around the optimal PBM protocols, which hampers its optimal and consolidated clinical applicability. Given the differential expression and metabolic patterns exhibited in the tension and compression sides of orthodontically stressed teeth, it is plausible that different types of irradiation may be applied to each side of the teeth. In this sense, this study aimed to design and implement an optimization protocol to find the most appropriate PBM parameters to stimulate specific bone turnover processes. To this end, three levels of wavelength (655, 810 and 940 nm), two power densities (5 and 10 mW/cm2) and two regimens of single and multiple sessions within three consecutive days were tested. The biological response of osteoblasts and periodontal ligament (PDL) fibroblasts was addressed by monitoring the PBM's impact on the cellular metabolic activity, as well as on key bone remodeling mediators, including alkaline phosphatase (ALP), osteoprotegerin (OPG) and receptor activator of nuclear factor κ-B ligand (RANK-L), each day. The results suggest that daily irradiation of 655 nm delivered at 10 mW/cm2, as well as 810 and 940 nm light at 5 mW/cm2, lead to an increase in ALP and OPG, potentiating bone formation. In addition, irradiation of 810 nm at 5 mW/cm2 delivered for two consecutive days and suspended by the third day promotes a downregulation of OPG expression and a slight non-significant increase in RANK-L expression, being suitable to stimulate bone resorption. Future studies in animal models may clarify the impact of PBM on bone formation and resorption mediators for longer periods and address the possibility of testing different stimulation periodicities. The present in vitro study offers valuable insights into the effectiveness of specific PBM protocols to promote osteogenic and osteoclastogenesis responses and therefore its potential to stimulate bone formation on the tension side and bone resorption on the compression side of orthodontically stressed teeth.

The effect of adjunctive LASER application on periodontal ligament stem cells

Periodontal regeneration involves the composite action of cell, scaffolds and signaling molecules. There are numerous autologous sources of regenerative cells which are present close to the vicinity of the periodontally debilitated site, the primary one being the periodontal ligament stem cell, which is believed to have a key role in regeneration. Various methods can be harnessed to optimize and enhance the regenerative potential of PDLSCs such as the application of LASERs. In the last few years there have been various studies which have evaluated the effect of different types of LASERs on PDLSCs and the present review summarizes the photo-biomodulative activity of LASERs in general and its beneficial role in the stimulation of PDLSC specifically.

Effect of red and near-infrared irradiation on periodontal ligament stem cells: ROS generation and cell cycle analysis

Reconstruction of lost tooth structures and the periodontium with the help of tissue engineering has found a special place in dentistry in recent years with reports of great therapeutic success. Stem cells from the periodontal ligament have the potential for high differentiation into the bone and periodontal ligament cells and are therefore a suit candidate for regenerative therapies of the periodontium and other tissues. In this regard, the use of photobiomodulation on these cells by light irradiation can be effective in increasing the efficiency of these regenerative methods. The effect of red and near-infrared lasers was investigated in pulsed and continuous modes on the cell viability, ROS production and the cell cycle of Periodontal Ligament Stem cells (PDLSCs) using MTT assay and flowcytometry techniques. The result shows that both red and near-infra-red (NIR) irradiations at 3 J/cm2 maintain cell viability. ROS generation assay indicated that in PDL stem cells irradiated with NIR laser (940 nm), ROS production was greater than in the red (660 nm) irradiated groups. Cell cycle analysis revealed that NIR irradiation can enhance the proportion of S-phase cells and declinedecline the proportion of G1-phase cells compared to the red laser irradiation groups. Moreover, this enhancement was greater in the pulsed group compared to the continuous mode group. Overall, the current study results showed that photobiomodulation can support the cell viability of PDLSCs and could affect the ROS production and cell cycle. This effect was more with 940 nm (NIR) irradiation pulsed mode compared to 660 nm (red).Communicated by Ramaswamy H. Sarma.

Exosomes Derived from Adipose Tissue-Derived Mesenchymal Stromal Cells Prevent Medication-Related Osteonecrosis of the Jaw through IL-1RA

Medication-related osteonecrosis of the jaw (MRONJ) is a severe disease with unclear pathogenesis. Adipose tissue-derived mesenchymal stromal cells (MSC(AT)s) serve as a special source for cell therapy. Herein, we explored whether exosomes (Exo) derived from MSC(AT)s promote primary gingival wound healing and prevent MRONJ. An MRONJ mice model was constructed using zoledronate (Zol) administration and tooth extraction. Exosomes were collected from the conditioned medium (CM) of MSC(AT)s (MSC(AT)s-Exo) and locally administered into the tooth sockets. Interleukin-1 receptor antagonist (IL-1RA)-siRNA was used to knock down the expression of IL-1RA in MSC(AT)s-Exo. Clinical observations, micro-computed tomography (microCT), and histological analysis were used to evaluate the therapeutic effects in vivo. In addition, the effect of exosomes on the biological behavior of human gingival fibroblasts (HGFs) was evaluated in vitro. MSC(AT)s-Exo accelerated primary gingival wound healing and bone regeneration in tooth sockets and prevented MRONJ. Moreover, MSC(AT)s-Exo increased IL-1RA expression and decreased interleukin-1 beta (IL-1β) and tumor necrosis factor-α (TNF-α) expression in the gingival tissue. The sequent rescue assay showed that the effects of preventing MRONJ in vivo and improving the migration and collagen synthesis abilities of zoledronate-affected HGFs in vitro were partially impaired in the IL-1RA-deficient exosome group. Our results indicated that MSC(AT)s-Exo might prevent the onset of MRONJ via an IL-1RA-mediated anti-inflammatory effect in the gingiva wound and improve the migration and collagen synthesis abilities of HGFs.

In vitro effects of photobiomodulation on cell migration and gene expression of ALP, COL-1, RUNX-2, and osterix in cementoblasts

The aim of this study was to evaluate the effects of photobiomodulation (PBM) on cell migration and alkaline phosphatase (ALP), type I collagen (Col-1), runt-related transcription factor 2 (RUNX-2), and Osterix (OSX) gene expression in a cementoblast culture (OCCM-30), in a microenvironment mimicking an injury on the cementoblast layer, such as it occurs during root resorption. For this, OCCM-30 cells were cultured in 6-well plates and the following parameters were assayed: (1) migration by scratch assay and ALP, Col-1, Runx2, and Osx by real-time PCR. PBM was performed in two protocols using a LED device emitting light at 660 nm (± 30 nm). OCCM-30 cementoblasts were grown and divided into four groups: (1) negative control; (2) positive control (scratch); (3) scratch + PBM with a total energy of 36 J and energy density 1.6 J/cm²; and (4) scratch + PBM with a total energy of 72 J and energy density of 3.2 J/cm². Data were statistically analyzed, with the level of significance set at 5%. Cementoblasts migrated from the edge of the scratch toward the center, and the wound closed after 24 h, with the PBM3.2J/cm² group showing the higher cell migration compared with the other groups at 2 h, 6 h, 8 h, and 13 h (p < 0.05). The control and PBM1.6J/cm² groups showed similar levels of cell migration, with no significant differences (p > 0.05). PBM3.2J/cm² group exhibited greater ALP, Col-1, OSX, and RUNX2 in comparison with the other experimental groups (p < 0.05). Similar levels of all genes evaluated were observed between the PBM1.6J/cm² group and the positive control group (p > 0.05). In conclusion, our findings support the effectiveness of photobiomodulation on cementoblast migration and gene expression, which may contribute to the formation of a new cementum layer.

Influence of Three Laser Wavelengths with Different Power Densities on the Mitochondrial Activity of Human Gingival Fibroblasts in Cell Culture

Phototherapy plays a key role in wound healing and tissue regeneration. The use of lasers has the potential to become an effective and minimally invasive treatment in periodontal and peri-implant disease. The aim of this study was to evaluate the influence of three laser wavelengths with the combination of parameters such as power density and energy density on human gingival fibroblasts (hGFs) in vitro culture. Isolated cells were seeded in 96-well plates with culture medium (DMEM, Dulbecco's modified Eagle's medium) supplemented with 10% fetal bovine serum (FBS). After 24 h cells were irradiated (1064, 980 and 635 nm, various energy density value). After 24, 48 and 72 h, cells were evaluated for viability. Data were analyzed by ANOVA followed by Tukey's HSD test. We found the best outcomes for hGFs irradiated with laser 1064 nm for all combinations of power output (50/400/1000 mW) and energy dose (3/25/64 J/cm²) after 48 h and 72 h compared with control group. Cell viability increase ranged from 0.6× (3 J/cm², 50 mW) to 1.3× (64 J/cm², 1000 mW). Our findings indicate that the appropriate use of low-level laser irradiation (LLLI) can increase the proliferation rate of cultured cells. The use of LLLI can be extremely useful in tissue engineering and regenerative medicine.

Photobiomodulation Reduces the Cytokine Storm Syndrome Associated with COVID-19 in the Zebrafish Model

Although the exact mechanism of the pathogenesis of coronavirus SARS-CoV-2 (COVID-19) is not fully understood, oxidative stress and the release of pro-inflammatory cytokines have been highlighted as playing a vital role in the pathogenesis of the disease. In this sense, alternative treatments are needed to reduce the level of inflammation caused by COVID-19. Therefore, this study aimed to investigate the potential effect of red photobiomodulation (PBM) as an attractive therapy to downregulate the cytokine storm caused by COVID-19 in a zebrafish model. RT-qPCR analyses and protein-protein interaction prediction among SARS-CoV-2 and Danio rerio proteins showed that recombinant Spike protein (rSpike) was responsible for generating systemic inflammatory processes with significantly increased levels of pro-inflammatory (il1b, il6, tnfa, and nfkbiab), oxidative stress (romo1) and energy metabolism (slc2a1a and coa1) mRNA markers, with a pattern similar to those observed in COVID-19 cases in humans. On the other hand, PBM treatment was able to decrease the mRNA levels of these pro-inflammatory and oxidative stress markers compared with rSpike in various tissues, promoting an anti-inflammatory response. Conversely, PBM promotes cellular and tissue repair of injured tissues and significantly increases the survival rate of rSpike-inoculated individuals. Additionally, metabolomics analysis showed that the most-impacted metabolic pathways between PBM and the rSpike treated groups were related to steroid metabolism, immune system, and lipid metabolism. Together, our findings suggest that the inflammatory process is an incisive feature of COVID-19 and red PBM can be used as a novel therapeutic agent for COVID-19 by regulating the inflammatory response. Nevertheless, the need for more clinical trials remains, and there is a significant gap to overcome before clinical trials can commence.

Low-Level Erbium-Doped Yttrium Aluminum Garnet Laser Irradiation Induced Alteration of Gene Expression in Osteogenic Cells from Rat Calvariae

Objective: The aim of this study was to investigate the effect of low-level erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiation on gene expression in osteogenic cells from rat calvariae. Background: Previous studies showed beneficial effects of laser irradiation on bone-related cells. However, few studies have examined the gene expression alteration by laser irradiation on osteogenic cells in a calcified condition. Materials and methods: Osteogenic cells were prepared by culturing rat calvarial osteoblast-like cells in osteoinductive medium for 21 days. The cells at the bottom of the culture dish were irradiated with Er:YAG laser (wavelength: 2.94 μm, energy density: 3.1 and 8.2 J/cm²) positioned at distance of 25 cm. Lactate dehydrogenase (LDH) assay of the irradiated cells was performed. After screening for genes related to bone formation, mechanotransduction, and thermal effect by quantitative polymerase chain reaction (qPCR), gene expression at 3 h after 3.1 J/cm² irradiation was comprehensively analyzed using microarray. Results: No dramatical increase in surface temperature and LDH activities after laser irradiation were observed. Sost expression was significantly reduced at 3 h after 3.1 J/cm² irradiation. Bcar1 and Hspa1a expression was significantly increased following 8.2 J/cm² irradiation. Microarray analysis identified 116 differentially expressed genes. Gene set enrichment analysis showed enrichment of histone H3-K9 methylation and modification gene sets. Conclusions: Er:YAG laser irradiation, especially at 3.1 J/cm², showed positive effect on the expression of genes related to bone formation in osteogenic cells, without inducing significant cell damage. These findings may represent critical mechanisms of early bone formation after Er:YAG laser irradiation.

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.

Asperuloside ameliorates lipopolysaccharide-induced primary human periodontal ligament cell injury by decreasing TLR4 expression and NF-κB activation

OBJECTIVE

The mechanism underlying lipopolysaccharide (LPS)-induced primary human periodontal ligament (PDLC) cell injury is unclear. In this study, we focused on the therapeutic function of asperuloside (ASP) on LPS-induced cell injury.

DESIGN

The study enrolled 41 participants, including 18 healthy controls and 23 CP patients. Western blotting was used to measure the expression of Toll-like receptor 4 (TLR4), phosphorylated p65 (p-p65) and cyclin D1. Enzyme-linked immunosorbent assays (ELISAs) were utilized to evaluate the protein levels of proinflammatory factors interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor alpha (TNF-α). MTT assays and 5-ethynyl-2'-deoxyuridine (EdU) staining were performed to investigate cell proliferation. Immunohistochemistry was used to detect TLR4 and p65 expression in gingival tissues.

RESULTS AND CONCLUSIONS

Asperuloside ameliorates lipopolysaccharide-induced PDLC cell injury by decreasing TLR4 expression and NF-κB activation, while this protective effect of ASP was reversed by TLR4 overexpression.

A novel minimally-invasive approach for metal tattoo removal with Er:YAG laser

OBJECTIVE

Few effective and established treatment methods can remove gingival metal or amalgam tattoos. With this case series, we aimed to demonstrate the use of a novel minimally invasive technique to remove metal tattoos using an erbium-doped yttrium aluminum garnet (Er:YAG) laser.

MATERIALS AND METHODS

We retrospectively collected clinical data from 18 patients who had undergone Er:YAG laser treatment to remove metal tattoos. Minimal gingival ablation using an Er:YAG laser directed towards the pigmented area was performed, which exposed metal debris within the connective tissue that was carefully removed. A dental microscope was employed to identify the metal debris, for accurate irradiation, and to minimize wounding by reducing invasion. Postoperative gingival color and morphology, and visual analog scale as a patient-reported outcome assessing postoperative pain were evaluated.

RESULTS

All patients' metal tattoos were removed completely and safely during short procedures. Considerable esthetic improvements and favorable wound healing were achieved with almost no postoperative pain or complications.

CONCLUSION

The findings from this case series suggest that this novel minimally invasive therapy for metal tattoo removal that involved the Er:YAG laser is effective and safe, is associated with successful outcomes, and contributes greatly to patients' esthetic satisfaction.

CLINICAL SIGNIFICANCE

Metal tattoo removal using an Er:YAG laser safely and successfully improved gingival esthetics. This novel technique is much simpler and less invasive than conventional periodontal plastic surgery, and it may be more reliable regarding esthetic gingival improvements as it is associated with favorable wound healing, and it could offer significant benefits to patients by alleviating physical and mental stresses via reduced chair time and postoperative pain.