Comparative study of hydroxyapatite from eggshells and synthetic hydroxyapatite for bone regeneration

Bone regeneration remains a challenge in clinical settings. Prior research has shown that synthetic hydroxyapatite (sHA) is widely used in bone grafting due to its osteoconductive properties. However, the availability and cost of sHA have led to interest in alternative sources. Natural sources such as eggshells have been proposed as potential substitutes. This gap motivated the investigation of hydroxyapatite derived from eggshells (eHA) as a viable material. It was already known that eHA contains calcium compounds, but its effectiveness in bone regeneration had not been fully evaluated. The physical properties of eHA, including purity and granule size, were not well characterized in prior studies. No prior work had resolved whether eHA could match or exceed sHA in promoting bone healing. This uncertainty drove the need for a comparative study using animal models. The study aimed to address these limitations by analyzing both materials in a controlled setting.

This study aimed to compare the physical and biological properties of synthetic hydroxyapatite (sHA) and eggshell-derived hydroxyapatite (eHA) for bone regeneration. The specific problem was to determine whether eHA could serve as a cost-effective and biologically active alternative to sHA. The motivation was to assess the feasibility of using a natural, abundant material for bone grafting. Researchers wanted to evaluate the structural characteristics of both materials using analytical techniques. They also sought to determine the regenerative capacity of eHA in a rabbit calvarial defect model. The study focused on histomorphometric analysis to measure new bone formation. The goal was to compare the performance of eHA and sHA at two time points after grafting. This approach allowed for a direct assessment of their regenerative potential.

The researchers used Fourier-transform infrared spectroscopy (FT-IR) and x-ray diffraction (XRD) to analyze the physical properties of sHA and eHA. These techniques provided insights into the crystallinity and chemical composition of the materials. Scanning electron microscopy (SEM) was also used to observe granule size and surface morphology. sHA was obtained from a commercial supplier, while eHA was sourced from a research institution. Sixteen New Zealand white rabbits were used in the animal study. Bilateral parietal bone defects were created in each animal, and either sHA or eHA was grafted into the defects. A control group had no graft material placed in the defect. Histomorphometric evaluation was conducted at 4 and 8 weeks post-surgery to assess bone regeneration. The data were analyzed using statistical methods to compare the groups.

At 4 weeks, the control group showed 17.11 ± 10.24% new bone formation. The sHA group had 28.81 ± 12.63%, and the eHA group had 25.68 ± 10.89%. These differences were not statistically significant (P > 0.05). At 8 weeks, the control group had 27.50 ± 10.89% new bone. The sHA group showed 38.62 ± 17.42%, and the eHA group had 41.99 ± 8.44%. The eHA group was significantly different from the control (P = 0.038). The sHA group did not show a significant difference from the control (P > 0.05). The eHA group also did not differ significantly from the sHA group (P > 0.05). XRD results showed that sHA had a smaller granule size than eHA. SEM confirmed this observation, showing broader peaks for eHA. The eHA contained impurities such as CaO and Ca(OH)₂, as identified by ICDD codes.

The study found that both sHA and eHA promoted more bone formation than the unfilled control at 8 weeks. The eHA group showed a statistically significant increase in new bone compared to the control. However, the eHA group did not significantly outperform the sHA group. The presence of impurities in eHA did not appear to hinder its regenerative ability. The physical properties of eHA, such as granule size and crystallinity, were different from sHA. These differences may affect the long-term performance of the materials. The authors propose that eHA is a viable alternative to sHA for bone grafting. They suggest that further studies are needed to evaluate the long-term effects of eHA in larger animal models. The findings support the use of eHA as a cost-effective and biologically active material.