Effects of the Saliva of Patients Undergoing Orthodontic Treatment with Invisalign and Brackets on Human Gingival Fibroblasts and Oral Epithelial Cells

The transient worsening of oral health sometimes accompanies orthodontic treatment (OT), and the extent of this effect might depend on whether the patients are treated with traditional brackets or clear aligners. Saliva is an important tool for monitoring oral health and influences the functional properties of various oral cells. This study aimed to compare the effects of saliva from patients undergoing OT with Invisalign aligners and brackets on human gingival fibroblasts and oral epithelial cells in vitro. Unstimulated saliva was collected from 15 patients treated with Invisalign and 16 patients treated with brackets before and 3 and 6 months after therapy began. The saliva was used to stimulate primary human gingival fibroblasts and the oral epithelial Ca9-22 cell line, and the resulting cell response was investigated. Saliva did not exhibit any toxic effect on investigated cells, as shown by the proliferation/viability assay with the MTT method. In human gingival fibroblasts, saliva increased gene expression of various proinflammatory mediators, such as interleukin (IL)-6, IL-8, and monocyte chemoattractant protein-1, assessed by qPCR. In epithelial cells, saliva increased the production of IL-8 measured by ELISA and decreased gene expression of various proteins involved in the barrier function. During the therapy, the saliva-induced production of IL-8 tended to be decreased, and the saliva-induced decrease in the expression of barrier protein was partially improved. No difference between aligners and brackets was observed in either cell type. Saliva affects the functional properties of oral cells, but this effect is not influenced by the type of OT.