Dental implant surface physicochemistry controls Keratinocytes’ proliferation and hemidesmosome formation

Abstract

Objectives: Epithelial attachment around implants is marked by parafunctional junctional epithelium and reduced expression of epithelial cell adhesive hemidesmosomes (HD), adhesive structures that anchor the gingiva to implants. Previous research on osseointegration has shown that hydrophilic/hydrophobic surfaces stimulate/hinder cell adhesion by promoting/disfavoring expression of cell adhesion proteins. We hypothesized that control of surface physicochemistry, through application of common biological functional groups, could similarly determine epithelial cell hemidesmosome formation and oral keratinocytes proliferation (OKs). Enhanced epithelial cell function may promote soft tissue-implant integrity extending the service life of implants. Methods: Silanization chemistry was applied to functionalize model implant surfaces with relevant biological functional groups (-H, -NH2, -OH, and -CH3). Non-functionalized plasma-cleaned surfaces served as a control. X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) assessed surface modifications. The amount of adsorbed bovine serum (BSA) and fibrinogen (Fg) were evaluated, as well as BSA layer thickness. Proliferation and metabolic activity of OKs on all surfaces were assessed after 1, 3, and 5 days. HD formation was quantified using immunofluorescence for collagen XVII (Col17) and integrin β4 (Intβ4). ANOVA with Tukey post-hoc analysis assessed statistical significance (p<0.05) Results: XPS and WCA demonstrated the successful synthesis of all surfaces. Plasma-cleaned control and -CH3 functionalized surfaces were the most hydrophilic and hydrophobic substrates, respectively. All groups with -OH functional motifs were the most hydrophilic among all groups tested. OK metabolic activity, proliferation, andexpression of hemidesmosomal proteins was significantly higher on -OH functionalized surfaces after 3 and 5 days compared to other groups. Conclusions: Modification of implant surfaces with polar chemical groups, like -OH, improved epithelial cell attachment and thereby may enable reduction of peri-implantitis rates.