Comparing Initial Wound Healing and Osteogenesis of Porous Tantalum Trabecular Metal and Titanium Alloy Materials
Porous tantalum trabecular metal (PTTM) has long been used in orthopedics to enhance neovascularization, wound healing, and osteogenesis; recently, it has been incorporated into titanium alloy dental implants. However, little is known about the biological responses to PTTM in the human oral cavity. We have hypothesized that, compared with conventional titanium alloy, PTTM has a greater expression of genes specific to neovascularization, wound healing, and osteogenesis during the initial healing period. Twelve subjects requiring at least 4 implants in the mandible were enrolled. Four 3 × 5mm devices, including 2 titanium alloy tapered screws and 2 PTTM cylinders, were placed in the edentulous mandibular areas using a split-mouth design. One device in each group was trephined for analysis at 2 and 4 weeks after placement. RNA microarray analysis and ingenuity pathway analysis were used to analyze osteogenesis gene expression and relevant signaling pathways. Compared to titanium alloy, PTTM samples exhibited significantly higher expressions of genes specific to cell neovascularization, wound healing, and osteogenesis. Several genes—including bone morphogenic proteins, collagens, and growth factors—were upregulated in the PTTM group compared to the titanium alloy control. PTTM materials may enhance the initial healing of dental implants by modifying gene expression profiles.
Surgical placement and retrieval of Ti alloy and porous tantalum trabecular metal (PTTM) devices. (a) Ti alloy and PTTM devices. (b) Placement of the control Ti alloy and PTTM devices. (c) Periapical radiograph taken 2 weeks after the placement showing the radiolucent bone remodeling around the Ti alloy devices. (d) Surgical retrieval of devices at 2 week post-placement visit showing bone adhering to the PTTM but not the Ti alloy devices. (e) Surgical retrieval of devices at 4 week post-placement visit. (f) Histological sections of Ti alloy and PTTM devices. (g) High resolution photomicrographies illustrating the histologic aspects observed in the bone implant contact.
Gene expression profiles of selected genes comparing porous tantalum trabecular metal to Ti alloy at 2 weeks (blue) and 4-week (red) visits. (a) Bone morphogenic protein and bone specific proteins. (b) Collagens. (c) Growth factors. (d) Genes with notably high expression. BMP indicates bone morphogenic proteins.
Proposed signaling model for porous tantalum trabecular metal (PTTM) and osseoincorporation. (a) Genes upregulated associated with PTTM at 2-week visit. (b) Genes upregulated associated with PTTM at 4-week visit. (c) Combined genes upregulated associated with PTTM at 2- and 4-week visits. Note that notably highly expressed genes are in bold.
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