Alveolar bone regeneration using sustainable eggshell-derived nano-hydroxyapatite and zinc oxide nanoparticles: an in vivo experimental study

Abstract

The present study focused on developing nanocrystalline hydroxyapatite (NHAP) from waste eggshells and assessed its role in bone regeneration after tooth extraction, with and without the addition of zinc oxide nanoparticles (ZnO NPs). Sixty adult male albino rats were used. The lower first molar was extracted, and the rats were divided into four groups (n = 15): Group I, control without treatment; Group II, bone socket loaded with ZnO NPs; Group III, bone socket loaded with NHAP; and Group IV, bone socket treated with both ZnO NPs and NHAP. Animal scarification was performed 4 weeks after extraction, and the results were assessed using histological, histomorphometric, and scanning electron microscopic assessment of bone. Also, energy dispersive X-ray analysis (EDXA) was performed for all animal groups and subsequently evaluated statistically. After 4 weeks of extraction, Group I exhibited complete healing with remnants of immature bone, while in Groups II and III, mature compact bone filled most of the socket, and cancellous bone occupied small areas. Group IV exhibited complete healing of the extraction socket, which was completely closed by mature bone. The combined use of NHAP derived sustainably from eggshells and laboratory-synthesized ZnO NPs proposes a potential, biocompatible, and economical approach for improving alveolar socket healing. These nanomaterials enhance osteoinduction and antibacterial properties and exemplify a novel application of locally obtained waste and cost-effective synthesis methods, rendering them highly appropriate for clinical utilization in resource-constrained environments, as in developing countries. Thus, dentists can access and benefit from state-of-the-art nanotechnological solutions without financial impediments, as in alveolar ridge preservation and rapid healing after extraction for future implant placement. Treatment modalities with ZnO NPs and NHAP administered separately could accelerate bone socket healing. However, combining ZnO NPs and NHAP resulted in a more rapid improvement of the histological and statistical results. This might be due to the enhancement of the early release of growth factors that increase angiogenesis and regeneration in healing sockets. However, additional studies are needed to evaluate this combination.