LLLT Effects on Oral Keratinocytes in an Organotypic 3D Model

An organotypic model of oral mucosa cells for the biological assessment of 3D printed resins for interim restorations

STATEMENT OF PROBLEM

Three-dimensionally (3D) printed resins have become popular as a new class of materials for making interim restorations. However, little is known about how the fabrication parameters can influence biological compatibility with oral tissues.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of the postpolymerization time on the cytotoxicity of resins for printing interim restorations by using a 3D organotypic model of the oral mucosa.

MATERIAL AND METHODS

Cylindrical specimens were prepared with conventional acrylic resin (AR), computer-aided design and computer-aided manufacture (CAD-CAM) resin (CC), composite resin (CR), and 2 resins for 3D printing (3DP) marketed as being biocompatible. The 3DPs were submitted to postpolymerization in an ultraviolet (UV) light chamber for 1, 10, or 20 minutes (90 W, 405 nm). Standard specimens of the materials were incubated for 1, 3, and 7 days in close contact with an organotypic model of keratinocytes (NOK-Si) in coculture with gingival fibroblasts (HGF) in a 3D collagen matrix, or directly with 3D HGF cultures. Then, the viability (Live/Dead n=2) and metabolism (Alamar Blue n=6) of the cells were assessed. Spectral scanning of the culture medium was performed to detect released components (n=6) and assessed statistically with ANOVA and the Tukey post hoc test (α=.05).

RESULTS

Severe reduction of metabolism (>70%) and viability of keratinocytes occurred for 3DP resin postpolymerized for 1 minute in all periods of analysis in a time-dependent manner. The decrease in cell metabolism and viability was moderate for the 3D culture of HGFs in both experimental models, correlated with the intense presence of resin components in the culture medium. The resins postpolymerized for 10 and 20 minutes promoted a mild-moderate cytotoxic effect in the period of 1 day, similar to AR. However, recovery of cell viability occurred at the 7-day incubation period. The 3DP resins submitted to postpolymerization for 20 minutes showed a pattern similar to that of CR and CC at the end of the experiment.

CONCLUSIONS

The cytotoxic potential of the tested 3DP resins on oral mucosa cells was influenced by postprinting processing, which seemed to have been related with the quantity of residual components leached.

Comparison of different dual-wavelength photobiomodulation protocols application in third molar extractions. A split-mouth randomized controlled trial

OBJECTIVE

To compare the use of PBMT in the soft tissue and bone healing after third molar extraction using the dual-wavelength laser directly into the post-extraction alveoli (PBMT-I), or PBMT with a red laser directly into the alveoli and with an infrared laser externally on the patient's face (PBMT-IE).

METHODS

Twenty patients underwent extraction of four third molars were involved in this split-mouth double-blind randomized controlled trial. The Post-extraction alveoli were treated with the following protocols: PBMT-IE: Application of a red laser directly into the alveolus, and infrared laser irradiation transcutaneously and PBMT-I: Application of dual-wavelength laser intraorally. Patients were clinically evaluated 3, 7, 14, 30, and 90 days after the surgical procedure. The analyses in this study were divided into qualitative (centered on the patient's report and on the evaluators' analysis), and quantitative analyses (measurement of the vertical and horizontal dimensions of the face with the objective of measuring post-surgical edema and radiographic analyses for evaluation of the density and structure of the newly formed bone).

RESULTS

A progressive improvement was observed in all parameters evaluated in this study, however, this improvement was time dependent, with no distinct effect observed between the PBMT treatments applied.

CONCLUSION

The different dual-wavelength PBMT protocols induced a similar postoperative clinical course in third molar extraction surgeries, with a reduced occurrence of complications and a good healing pattern of hard and soft tissues.

Three dimensional (3D) gingival models in periodontal research: a systematic review

The aim of this study is to systematically appraise the evidence on available full thickness 3D gingival and mucosal models (3D culture in scaffold base system) and their application in periodontal and peri-implant research. This study involved a systematic review of twenty-two studies obtained from searching from five electronic databases: MEDLINE-OVID, EMBASE, EBSCOhost, Web of Science Core Collection and LILACS, as well as a hand search of eligible articles up to September 2022. A total of 2338 studies were initially identified, after removal of duplicates (573), abstracts/title selection (1765), and full text screening (95), twenty-two studies were included, thirty-seven models were identified. Several cellular markers were reported by the studies included. The expression of keratinocytes differentiation markers (K4, K5, K10, K13, K14, K16, K17, K18, K19, involucrin, laminin5), proliferation marker (Ki67, CD90), and vimentin, Type I, II and IV collagen produced by fibroblasts were investigated in thirty models. No quantitative analyses were performed, and results of the review confirmed a substantial level of heterogeneity across experiments. In conclusion, there is currently insufficient evidence to conclude that the available 3D gingival and mucosal models can entirely recapitulate the human gingival tissue/mucosa and provide a useful research tool for periodontal and peri-implant research. This review also highlighted the lack of a standardized protocol to construct and characterize 3D gingival models. A new protocol is proposed for the characterization of in vitro gingival models for future research.

High density of CD8 T cell and immune imbalance of T lymphocytes subsets are associated with proliferative verrucous leukoplakia

Oral leukoplakia (OL) and proliferative verrucous leukoplakia (PVL) are oral potentially malignant disorders (OPMDs) that microscopically show no or varying degrees of dysplasia. Even sharing clinical and microscopic aspects, PVL shows a more aggressive clinical behaviour, with a malignant transformation rate greater than 40%. Inflammatory infiltrate associated with dysplastic lesions may favour malignant transformation of OPMDs. This study aimed to evaluate the density of T cells and cytokines in dysplastic lesions from OL and PVL patients. Additionally, we evaluated whether soluble products produced in vitro by dysplastic keratinocytes are capable of modulating apoptosis rates and Th phenotype (Th1, Th2, Th17 and Treg) of peripheral blood mononuclear cells. The density of CD3, CD4 and CD8 T cells was assessed by immunohistochemistry. Cytokines and chemokines profile from frozen tissue samples were analysed using the LUMINEX system. Apoptosis rates and Th phenotype modulation were evaluated by flow cytometry. Our results showed an increase in the number of CD8 T cell in the subepithelial region from PVL dysplastic lesions in relation to OL samples. PVL showed increased levels of IL-5 and a decrease in IL-1β and IFN-γ levels compared to OL. Soluble products of PVL and oral carcinoma cell cultures were able to reduce apoptosis rate and promote an imbalance of Th1/Th2 and Th17/Treg. The high-subepithelial density of CD8 T cells and immune imbalance of T lymphocytes subsets probably play an important role in the pathogenesis of PVL and may explain its more aggressive behaviour in relation to OL.

Hormesis: Wound healing and keratinocytes

Hormetic dose responses (i.e., a biphasic dose/concentration response characterized by a low dose stimulation and a high dose inhibition) are shown herein to be commonly reported in the dermal wound healing process, with the particular focus on cell viability, proliferation, and migration of human keratinocytes in in vitro studies. Hormetic responses are induced by a wide range of substances, including endogenous agents, numerous drug and nanoparticle preparations and especially plant derived extracts, including many well-known dietary supplements as well as physical stressor agents, such as low-level laser treatments. Detailed mechanistic studies have identified common signaling pathways and their cross-pathway communications that mediate the hormetic dose responses. These findings suggest that the concept of hormesis plays a fundamental role in wound healing, with important potential implications for agent screening and evaluation, as well as clinical strategies.

Photobiomodulation using LLLT and LED of cells involved in osseointegration and peri-implant soft tissue healing

This study evaluated the influence of photobiomodulation (PBM) using low-level laser therapy (PBM/LLLT) or light-emitting diode (PBM/LED) therapy on peri-implant tissue healing. A laboratory model was used to assess the adhesion and metabolism of osteoblasts (SaOs-2), human gingival fibroblasts (HGF), and normal oral keratinocytes (NOK) seeded on a titanium (Ti) surface. After seeding the cells on disks of Ti placed in wells of 24-well plates, three irradiations were performed every 24 h at energy density of 3 J/cm². For PBM/LLLT, a LaserTABLE device was used with a wavelength of 780 nm and 25 mW, while for PBM/LED irradiation, a LEDTABLE device was used at 810 nm, 20 mW, at a density of 3 J/cm². After irradiations, the number of cells (NC) attached and spread on the Ti surface, cell viability (CV), total protein (TP), and collagen (Col) synthesis were assessed. Alkaline phosphate activity (ALP) was evaluated only for SaOs-2. Data were submitted to ANOVA complemented by Turkey statistical tests at a 5% significance level. PBM significantly increased adherence of NOK to the Ti surface, while no significant effect was observed for SaOs-2 and HGF. PBM positively affected CV, as well as Col and TP synthesis, in distinct patterns according to the cell line. Increased ALP activity was observed only in those cells exposed to PBM/LLLT. Considering cell specificity, this investigation reports that photobiomodulation with low-power laser and LED at determined parameters enhances cellular functions related to peri-implant tissue healing in a laboratory model.

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

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

Photobiomodulation Enhances Cisplatin Cytotoxicity in a Culture Model with Oral Cell Lineages

Cisplatin plays a central role in cancer chemotherapy, but resistance to this drug remains a major obstacle in treatment. Drawbacks related to cisplatin failure may be associated with cell energy metabolism. This study investigated whether photobiomodulation (PBM) can potentiate the effects of cisplatin on keratinocytes (HaCat) and cancer cells (SCC25 and HN12). Cells were treated with laser (GaAlAs; 660 nm; 60 mW; 0.33 J; 2.14 W cm^-2 ; 11.7 J cm^-2 and 6 s) and cisplatin (7.8 μg mL^-1 ) to evaluate cell viability, Ki-67, VEGF, TGF-β1, EGF expression and ROS production. Observations were validated in the SCC25 cell lineage, where the type of cell death (necrosis/apoptosis) and the amount of ATP were assessed. Cell lineages showed increased sensitivity to cisplatin associated with PBM (Cis-PBM). Ki-67 was augmented in all cell lineages treated with Cis-PBM when compared to cisplatin alone (Cis). Cis or Cis-PBM significantly decreased VEGF expression in cancer cells, while no changes were seen in the expression of TGF-β1 or EGF compared to control. ROS levels were similar in the Cis and Cis-PBM groups. Cells treated with Cis-PBM died by apoptosis, leading to greater consumption of ATP. These observations suggest that PBM may potentiate the effects of cisplatin, leading to increased drug cytotoxicity and enhanced cell death.

A brief literature review and own clinical experience in prophylaxis of oral mucositis in children using low level laser therapy

OBJECTIVE

The article describes the experience of clinical application of low level laser therapy in pediatric oncology for the prevention and treatment of chemotherapy complications such as oral mucositis.

BACKGROUND

For this purpose, for the first time in the world non-invasive laser blood illumination is used on the sinocarotid zone (on the projection of the common carotid artery symmetrically) and popliteal fossa in order to stimulate the phagocytic activity of leukocytes.

METHODS

25 children with different oncological diseases were given non-invasive laser blood illumination treatment (904 nm, pulse mode, 100 ns, 50-150 Hz, 5-7 W, 4 cm², 1-2 minutes daily per each procedure) 1-3 days before the beginning of chemotherapy. For the objectification of the results of treatment, the phagocytic activity of leukocytes was evaluated.

RESULTS

None of the children who underwent low level laser therapy course had any complications and no cases of oral mucositis developed.

CONCLUSIONS

Clinical experience has shown high efficacy and safety of low level laser therapy aimed at preventing the development of complications of chemotherapy, primarily oral mucositis, and stimulating the phagocytic activity of leukocytes.