Figures and show the results of the crystallographic and chemical structure studies. For this research it is essential that the fillers have similar crystallographic and chemical structures to minimise the influence of these factors on the results of the study. Analysis of Figure shows that the diffraction patterns for both filler types are very similar. The main diffraction peaks identified from the literature correspond to specific crystallographic planes . The results confirm that the powders studied possess a hexagonal unit cell structure, typical of hydroxyapatite. Furthermore, the similarity in the shape of the curves suggests comparable phase composition and crystallite size. Similarly, ATR-FTIR analysis revealed similarities in the chemical structure (Fig. ). The largest band in the wavenumber range of approximately 900-1100 cm -1 consists of three signals arising from P-O stretching vibrations within the PO4 3-group (peaks at 1021 cm -1 , 1091 cm -1 and 983 cm -1 ). The presence of O-P-O bending vibrations in the PO4 3-group is indicated by a band with a maximum at 604 cm⁻¹. The spectra also show several minor bands characteristic of hydroxyapatite, including O-H stretching and H-O-H bending vibrations from surface-bound water (peaks at 3392 cm -1 and 1644 cm -1 , respectively), O-H stretching vibrations from OH -groups within the HAp structure (peaks at 3574 cm⁻¹ and 611 cm -1 ), and stretching vibrations from the CO3 2-group (peaks at 1499 cm -1 , 1458 cm -1 , and 1422 cm -1 ) .