Influence of titanium surfaces on attachment of osteoblast-like cells in vitro

Abstract

Implant surface topography influences osteoblastic proliferation, differentiation and extracellular matrix protein expressions. Studies on preliminary interactions of osteoblast-like cells on implant interface through in vitro systems, can give lucid insights to osseo-integrative efficacies of when in vivo implants. In the present investigation two titanium surfaces of dental implants, a sandblasted and acid-etched surface and an experimental grooved surface were compared through in vitro systems. The titanium implants were seeded with osteoblast-like primary cells and maintained for a period of 1–7 days. Expressions of fibronectin and osteonectin were assessed through immunogold labelling by scanning electron microscopy. The grooved surface, supported better osteoblastic cell adhesion and proliferation than the rough surfaces. Further, osteoblastic cells on the grooved surfaces also displayed a strong labelling for fibronectin at the cytoplasmic extensions coupled with intense osteonectin expression in comparison to the rough surfaced implants. In conclusion, grooved surfaces offered better cell attachment and proliferation than the other rough surfaces studied.

Introduction

Cell–matrix interaction is dependent on cytoskeletal organization, transmembrane integrin receptor expression and most importantly, the nature of the extracellular matrix (ECM) [1], [2]. In bone, the ECM is largely composed of ECM proteins, such as collagen [3], fibronectin, laminin [4], vitronectin, osteopontin, osteonectin and other glycoproteins [5], [6]. The ECM is crucial in mediating cell adhesion to biomaterials, its organization and production modulates the degree of cell attachment to the materials. Success of non-biodegradable implants will first and foremost depend on biocompatibility, followed by the capacity of the surface topography of the implants to evince, desired cell matrix, surface–cell matrix interactions. Although it is well accepted that surface topography of the implants has marked influence in osseointegration, little is known about the effect of surface roughness on cell metabolism or differentiation of osteoblastic cells interacting with the implants. Controlled roughness values of titanium surfaces in dental implants have been associated to increase bone-to-implant contacts [7]. Further, a mineralized osteoblast ECM is necessary for dental implant osseointegration, however, the molecular mechanisms (cytokines, factors up-regulating synthetic activity of osteoblastic cells) associated with osseointegration of osteoblasts to dental implant surfaces are not fully understood. Osseointegration is not only dependent on wound healing process but also on the potential of osteogenic cells to form bone.

The use of endosseous dental implants as transmucosal devices necessitates the successful integration of three different tissues: bone, connective tissue, and epithelium. Previous studies have demonstrated in short-term experiments that sandblasted and acid-etched (SLA) titanium implant had a greater bone-to-implant contact than a titanium plasma-sprayed (TPS) implant in non-oral bone [8], [9]. Studies done have also shown that surface roughness of titanium implants cannot only have a profound influence on proliferation, differentiation and matrix production of osteoblastic cells but also influence the cytokines and growth factors in the milieu thereby modulating the healing process [10]. The effects of surface roughness on proliferation, matrix synthesis, differentiation, local factor production, cell morphology can also aid in giving valuable insights into implant–cell interface interactions.

In vitro systems offer a model tandem to in vivo applications while studying cell–biomaterial interface interactions. Further, primary osteoblastic cells are better candidates for evaluations of implants as in vitro models to comprehend integrative efficacies of the same when implanted in vivo [11]. In the present study, surface efficacies of two different titanium implants, a SLA surface was compared with a grooved surface.