Enhancing epithelial tissue sealing of titanium alloy implants through CaCl₂-based hydrothermal treatment

The long-term stability of dental implants is significantly influenced by their resistance to foreign factors in the peri-implant epithelium (PIE). Despite this, enhancing the sealing properties at the implant-PIE interface continues to be an unmet clinical need. Ti-6Al-4V (Ti64) alloy has higher tensile strength and hardness than pure titanium. This study was to verify whether hydrothermal treatment of Ti64 alloy implants with distilled water (HT-DW) or calcium chloride (CaCl₂) solution (HT-Ca) could improve the sealing of the PIE around Ti64 implants. The existence of calcium (Ca) on the surface of HT-Ca implants was confirmed using x-ray photoelectron spectroscopy and synchrotron-based x-ray absorption fine structure techniques. These data showed that the surface was oxidized, and Ca existed in the form of anhydrous CaCl₂ and calcium titanate. Laminin-332 (Ln), which is an essential component of epithelial adhesion structures, was observed between all types of implants and the PIE, 4 weeks after implantation in rat maxillae. Ln distribution over the entire epithelial interface was similar for the HT-Ca implant and a natural tooth. Moreover, the HT-Ca implant inhibited foreign body penetration, which indicated stronger gingival sealing at the implant-PIE interface, compared with the untreated and HT-DW implants. We also investigated the attachment of mouse-derived gingival epithelial cells (GE1). GE1 adherence was stronger and Ln expression levels were higher for HT-Ca plates compared with the untreated and HT-DW plates. Our results demonstrate that hydrothermal treatment of Ti64 implants with CaCl₂ solution facilitates the growth of an effective soft tissue seal around the implant.