Comparative study of tissue structure and composition of human and dog supragingival tartar

Objective: Only a few anatomical studies have compared tartar between humans and animals. This study aimed to compare the structure and chemical composition of human and dog supragingival tartars using histological and analytical methods.Design: Supragingival tartar samples were obtained from humans and indoor dogs with advanced periodontal disease. Tartar samples were analysed using X-ray micro-computed tomography, scanning electron microscopy, transmission electron microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, electron probe X-ray microanalysis, and X-ray diffraction.Results: Layered structures and cavities were found inside the tartar; however, cavities were more common in dogs than in humans. Ca and P were distributed throughout the human tartar; however, P was not detected in some internal regions in dog tartar. The Ca/P ratio of dog supragingival tartar was 1.98 +/- 0.10, which was higher than that of hydroxyapatite (1.67) and human supragingival tartar (1.73 +/- 0.16). Needle-like crystals were observed in human tartar, such as carbonate apatite (CO3Ap). Numerous plate-like crystals were observed in the dog tartar, and it contained both calcite (calcium carbonate; CaCO3) and CO3AP.Conclusions: Dog supragingival tartar contains more organic matter than human supragingival tartar. The crystal structure of dog tartar differs from that of humans and contains mixed calcite and CO3AP.