Effects of ultraviolet treatment and alendronate immersion on cellular behavior of MG-63 osteoblast-like cells and human gingival fibroblasts cultured on titanium substrata

Abstract

Titanium is widely used as a dental implant material due to its biocompatibility and excellent physical properties. However, when exposed to the external environment over time, the titanium surface becomes contaminated, leading to decreased bio-responses related to osseointegration of the implant surface and the mucosal seal around the abutments. As a part of approach to overcome the above phenomenon, this study aimed to investigate the effects of ultraviolet (UV) irradiation and alendronate (ALN) immersion on the response of osteoblast-like cells and gingival fibroblasts cultured on the titanium surface, as a part of approach to overcome the above phenomenon. Titanium discs were fabricated with a diameter of 10 mm and a thickness of 2 mm, using grade 4 titanium. Titanium substrates were classified as sandblasted with large grit and acid-etched (SLA) surface or machined (MA) surface, and further sub-divided into the following four categories to produce a total of eight groups (n = 12 per group): no treatment, only UV irradiation, only ALN immersion, and UV irradiation with ALN immersion (dual application). MG-63 osteoblast-like cells and gingival fibroblasts were cultured on the SLA surface groups and the MA surface groups, respectively. The morphology and attachment of cells and the extent of proliferation, differentiation, and attachment were examined using a scanning electron microscope, WST-8 (water-soluble tetrazolium-8) analysis, alkaline phosphatase (ALP) activity assay, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Statistical analyses were performed using a one-way analysis of variance for cell proliferation, differentiation, and attachment-related gene expression. Proliferation of MG-63 cells significantly decreased in ALN-treated groups compared to the non-ALN-treated groups (P < 0.05). However, in dual application group, there was a significant increase in ALP activity of MG-63 osteoblast-like cells, compared to the control group (P < 0.05). Proliferation of gingival fibroblasts was decreased in the dual application group compared to UV or ALN-only groups (P < 0.05). The mRNA (messenger ribonucleic acid) expression related to the attachment of gingival fibroblasts significantly increased in the UV-only group, compared to the other groups (P < 0.05). Accordingly, dual application of UV irradiation and ALN immersion on the SLA surface augmented the differentiation of MG-63 osteoblast-like cells, and UV irradiation on the MA surface promoted the expression of factors related to the attachment of gingival fibroblasts. Further studies are required to verify the clinical usefulness of these findings.