The Tissue Implant Response Surrounding Subcutaneous TCP, HA, And ALCAP Bioceramics

The objective of this investigation was to quantify and further elucidate the tissue-implant response in the fibrous tissue surrounding tricalcium phosphate (TCP), hydroxyapatite (HA), and aluminum calcium phosphate (ALCAP) implants when implanted subcutaneously. Sixteen animals in four experimental groups (n = 4/group) were implanted with one implant each: Group I (control, TCP), Group II (HA), and Group III (ALCAP). At 90 days post-implantation, the fibrous tissue surrounding the implants was harvested. Sections of stained fibrous tissue were evaluated for the presence of macrophages, fibrocytes, neutrophils, vascularity and thickness for all three groups using semi-automated quantitative methods. The analysis indicated Group III demonstrated a significantly higher number of neutrophils but fewer macrophages and blood vessels per high power field and had a substantially thinner fibrous tissue capsule thickness compared to Groups I and II (alpha=0.05). Group II elicited a greater response of fibroblasts compared to Groups I and III suggesting HA may provide a slightly higher degree of stability to the implant. In total, these findings suggest both TCP and HA behave similarly in vivo when compared to ALCAP and may be better choices for subcutaneous soft-tissue application compared to ALCAP.