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Description
Introduction
In addition to the osseointegration of the implant’s surface, a sufficient adhesion of the abutment's surface to the soft tissue is a crucial factor for the longevity of the implant. The soft tissue seal surrounding natural teeth acts as a barrier against deleterious stimuli in the oral cavity, thus preventing bacteria penetration and protecting the underlying alveolar bone. However, the peri-implant mucosa around the abutment is different from the mucosa around natural teeth, which can result in a poorly bacterial resistance. To overcome this limitation, this study proposes a novel method to biofunctionalize abutment material surfaces through the covalent conjugation of specific proteins to enable a stable soft tissue adhesion.
Materials and Methods
A silane monolayer was applied on the established abutment materials (Y-TZP and Ti6Al4V) with subsequent coupling of proteins of the extracellular matrix (ECM), fibronectin and laminin, via a bifunctional crosslinker. The successful application was proved by XPS, AFM, and immunostaining. Preserved biofunctionality of the ECM proteins after surface coupling was shown in a centrifugation-assay. Proliferation, cell adhesion, and migration behavior of human gingival cells on the ECM-modified and non-modified specimens as a control was investigated additionally. Moreover, integrin expression of gingival cells on the individually modified surfaces was determined via confocal microscopy and flow cytometry. Stability of the applied substances on both specimens was tested via mechanical exposure, acid and heat resistance and was examined using XPS, SEM, and AFM.
Results
The centrifugation-assay showed that gingival cells seeded onto the ECM-protein-coupled surfaces exhibited significantly higher adhesion (p < 0.001) in comparison to non-functionalized controls. In addition, a proliferation assay (CCK-8) showed that significantly more cells (p < 0.05) were evident after seven days on ECM-modified surfaces compared to non-functionalized surfaces. Confocal microscopy revealed a much higher cell area (up to threefold) and enhanced expression of pFAK-Y397 and vinculin on ECM protein-coated surfaces compared to the controls. Moreover, the wound healing assay demonstrated, that cells seeded on ECM-modified surfaces exhibited significant more migration activity compared to untreated specimens. Stable attachment of the ECM proteins over 21 days was confirmed via ELISA.
Conclusion
Covalent conjugation of ECM proteins by cross-linking on the abutment material surfaces Y-TZP and Ti6Al4V enables improved adhesion, proliferation, and migration of human gingival cells. Therefore, in future clinical applications, this novel approach could lead to improved soft tissue adhesion and thus potentially prevent bacterial penetration through the soft tissue-abutment interface. Finally, this biofunctionalization approach could contribute to reduce or even prevent peri-implant diseases.
Acknowledgments
We acknowledge the financial support of the German Research Foundation, DFG (grants FI 975/30-1+2 and WO 1576/6-1+2).
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