* Roughness and Hydrophilicity as Osteogenic Biomimetic Surface Properties

Abstract

Successful dental and orthopedic implant outcomes are determined by the degree of osseointegration. Over the last 60 years, endosseous implants have evolved to stimulate osteogenesis without the need for exogenous biologics such as bone morphogenetic proteins. An understanding of the interaction between cells and the physical characteristics of their environments has led to development of bioactive implants. Implant surfaces that mimic the inherent chemistry, topography, and wettability of native bone have shown to provide cells in the osteoblast lineage with the structural cues to promote tissue regeneration and net new bone formation. Studies show that attachment, proliferation, differentiation, and local factor production are sensitive to these implant surface characteristics. This review focuses on how surface properties, including chemistry, topography, and hydrophilicity, modulate protein adsorption, cell behavior, biological reactions, and signaling pathways in peri-implant bone tissue, allowing the development of true biomimetics that promote osseointegration by providing an environment suitable for osteogenesis.

Keywords: biomimetic; implant; mesenchymal stem cell; osteoblast; osteoclast; titanium.

FIG. 1.

The growth of MG63 osteoblast-like cells on bone wafers pretreated with osteoclasts decreases cell proliferation, but increases production of local factors that promote osteogenesis. Bone wafers were treated for 0, 10, and 20 days with osteoclasts and compared with tissue culture plastic. *p < 0.05 vs. plastic; ^#p < 0.05 vs. bone wafers not pretreated with osteoclasts; ^•p < 0.05 vs. bone wafers treated with osteoclasts for 10 days. Adapted from a study by Boyan et al. PGE₂, prostaglandin E2; TGFβ1, transforming growth factor beta-1.

FIG. 2.

Scanning electron micrograph of an osteoclast-resorbed bone surface and a Ti surface that has been sandblasted with large-grit corundum and acid etched (SLA). SLA, sandblasted, large grit, and acid etched.

FIG. 3.

Schematic illustrating the steps of implant osseointegration. Osseointegration involves formation of a fibrin clot (A), recruitment of monocytes and macrophages and migration of MSCs along the clot (B), osteoblastic differentiation of MSCs and woven bone formation, as well as vasculogenesis (C), and ultimately, osteoclast-mediated bone remodeling (D), leading to mature lamellar bone (E). MSCs, mesenchymal stem cells.

FIG. 4.

Cell signaling mechanisms among osteoblast lineage cells and osteoclasts involved in osseointegration lead to release of local regulatory factors in the peri-implant space. 1,25(OH)2D3, 1α,25-Dihydroxy vitamin D3; OPG, osteoprotegerin; RANKL, receptor activator of NFκB ligand.

FIG. 5.

Ti surfaces modulate the mRNA levels and protein production of BMP ligands in MSCs cultured on microstructured Ti surfaces. The surfaces used were able to distinguish among the basic surface features such as smooth PT, microrough/hydrophobic SLA, and microrough/hydrophilic modSLA. *p < 0.05 vs. TCPS; ^#p < 0.05 vs. PT; ^$p < 0.05 vs. SLA. Substrates were provided by Institut Straumann AG. Adapted from a study by Olivares-Navarrete et al. BMP, bone morphogenetic protein; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; mRNA, messenger RNA; PT, pretreatment; TCPS, tissue culture polystyrene.