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Effects of low-level laser therapy and epidermal growth factor on cell metabolism in titanium and zirconia surfaces

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Taisa Nogueira Pansani
Total Authors: 1
Document type: Doctoral Thesis
Press: Araraquara. 2019-11-18.
Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araraquara
Defense date:
Advisor: Carlos Alberto de Souza Costa; Fernanda Gonçalves Basso

The attachment of the connective tissue to abutment surface of dental implants prevents the apical migration of the junctional epithelium and the bone crest reabsorption, normally caused by the peri-implant inflammation, which compromises the aesthetics and the success of the rehabilitation procedure. The use of therapies to promote cell adhesion in order to induce effective biological sealing can improve aesthetic and functional conditions in prosthetic rehabilitation. The aim of this study was to evaluate the effects of low-level laser therapy (LLLT) and surfaces coating of titanium (Ti) and zirconia (ZrO2) with epidermal growth factor (EGF) on adhesion and metabolism of oral mucosa cells exposed or not to tumor necrosis alpha (TNF-α) inflammatory stimuli. Gingival fibroblasts and epithelial cells were isolated and seeded on surface Ti or ZrO2 surfaces, simulating the in vitro biological sealing. In EGF-coated groups, this growth factor was applied to Ti and ZrO2 surfaces prior to cell culture. After seeding cells, they were irradiated 3 times with LLLT (LaserTABLE, InGaAsP, 780 ± 3 nm) at 24 h intervals at doses of 0.5 J/cm2, 1.5 J/cm2 and 3.0 J/cm2, according to the established groups and then, TNF-α was applied to them for 24 h. Discs surface roughness analyzes were performed by confocal microscopy (n=8), EGF release of the coated substrates and cell adhesion by direct fluorescence. Cell viability (AlamarBlue, n=8), IL-6, IL-8 and VEGF (qPCR, n=5) gene expression, IL-6, IL-8 (ELISA, n=6) synthesis, as well as cell morphology and adhesion (SEM and Fluorescence, n=2) were evaluated. For fibroblasts, 3D culture in collagen matrix and morphological evaluation under Confocal Microscopy were performed (n=2). Quantitative data obtained were submitted to ANOVA statistical test complemented by Tukey or Games-Howell at 5% of significance level. It was observed an increase of roughness average (Ra) after the EGF-coating, but with immediate release of this growth factor and its incorporation after 1 h of contact with the cells. For all experimental groups, the viability of fibroblasts and epithelial cells was increased when cells were seeded onto Ti surface compared to the control group. When cells were seeded onto ZrO2 surfaces only LLLT-treated epithelial cells demonstrated increased viability. Increased IL-6 and IL-8 synthesis were observed in the TNF-α treated groups and the LLLT tested, especially 3.0 J/cm2 laser dose inhibited the interleukin expression regardless of cell type and surface. Increased IL-6 gene expression in both cells seeded onto Ti and ZrO2 discs and treated with TNF-α, and down modulation in this interleukin synthesis when cells were submitted to LLLT and EGF treatments. Similar results were observed for IL-8 expression by epithelial cells submitted to TNF- α and EGF. There was also an increase in VEGF gene expression by fibroblasts submitted to EGF and LLLT with decreased VEGF gene expression in TNF-α-treated groups. Regardless of the groups evaluated, there was uniform spread of cells throughout the Ti and ZrO2 discs when SEM was performed. However, alterations in the cells’ cytoskeleton were very evident in the presence of inflammatory stimulus when fibroblast 3D culture in collagen matrix was performed by Confocal Microscopy. According to the methodologies used in this laboratorial study, it was possible to demonstrate that EGF and specific LLLT parameters can biomodulate some inflammatory cell responses, improving the recovery of cell exposed to inflammatory conditions. (AU)

Grantee:Taisa Nogueira Pansani
Support type: Scholarships in Brazil - Doctorate