Introduction: Tooth pulp tissue may undergo a pathological process of mineralization, resulting in formation of pulp stones. Pulp stones are clinically identified on radiographic routine exams, in close relationship with deep restoration or related with a succession of long time mild tooth injuries. While the prevalence of pulp stones in dental caries is significant but remains unclear (from 4% to 78% of endodontic teeth), their development and histopathology are poorly understood and their precise composition has never been established. The aim of the present study was to investigate the physicochemical properties of the pulp stones by comparison with sound mineralized tissues of teeth to elucidate the pathological origin of pulp stones.
Materials and Methods: Areas of carious and healthy dentin of eight decayed teeth intended for extraction were analysed and compared. In addition, six pulp stones were recovered from five teeth requiring root canal treatment. The samples were embedded in resin, sectioned and observed by scanning electron microscopy and energy-dispersive spectroscopy. X-ray diffraction was performed to identify phases and crystallinity. X-ray fluorescence provided information on the elemental composition of the samples.
Results: Spherical calcifications were identified within pulpal calcification. In sections, the chemical structure was highly heterogeneous, showing concentric electron dense areas. Tubular areas were evident in regions sparse in pulp stones, suggesting the existence of tubular dentin-like matter. Diffraction diagrams led to the identification of partially carbonated apatite both in pulp stones samples and dentine. Moreover, X-ray fluorescence identified P, Ca, Cu, Zn, and Sr within dentin and pulp stones with higher concentration of Zn and Cu in pulp stone and carious dentin compared to healthy dentin.
Conclusions: Taken together our results showed that pulpal cells produce unstructured apatitic mineralizations containing abnormally high Zn and Cu levels and adopt an odontoblastic behaviour. Zn is already described as an evidence of inflammation. We hypothesize that the high concentrations of Cu and Zn detected in pulp stones, but not in physiological dentin, may be related to elevated superoxide dismutase enzyme activity occurring in an inflammatory context.xide dismutase enzyme activity occurring in an inflammatory context.