Apatite pastes derived from eggshell waste (BAp) were implanted onto the calvarial bone of rats, and bone formation was evaluated using X-ray μ-computed tomography (CT) and histological evaluation. BAp was mixed with distilled water to prepare a paste. Monoclinic hydroxyapatite of mineral resources (HAp) was used as a control. A 5 mm diameter PTFE (polytetrafluoroethylene) tube was filled with apatite pastes and implanted in the calvarial bone of 9-week-old Sprague Dawley rats for 8 weeks. A larger radiopaque area, similar to that of native bone, was observed in the BAp paste-implanted specimens than that of HAp paste. The bone mineral density (BMD) value of the BAp paste was significantly higher than that of the HAp paste (p < 0.05). In the histological evaluation, new bone formation was noticed from the calvarial side for both apatite specimens, and HAp remained in the PTFE unlike BAp. The bone mass (BM) value of the BAp paste was significantly higher than that of the HAp paste (p < 0.05). SEM and XRD analyses revealed that BAp was microcrystalline and poorly crystalline. The promotion of new bone formation may contribute to the crystallinity and Mg content of BAp. BAp was found to be useful as a bone regeneration material.
Keywords: apatite; bone formation; eggshell; magnesium; μ-computed tomography (CT).