Combined PIXE and optical microscopy characterization of calcium compounds in dental calculus

A combined PIXE and optical microscopy approach was applied to examine the dental calculus of patients with periodontal disease. PIXE was performed with the Bucharest 3 MV Tandetron with 3 MeV protons and a HPGe detector, using hydroxyapatite (HA) and other standards. Sections 30 mu m thick were prepared and observed using polarization microscopy and histochemical techniques. Both methods revealed the heterogeneous nature of dental calculus. Two main types (I and II) were postulated based on Ca/P ratios (p < 0.00001). Type I consisted mainly of whitlockite and octacalcium phosphate, whereas type II was mainly HA with some calcium carbonate. They correlated with rodlet masses and amorphous areas with a powdery appearance, observed using microscopy and histochemistry. PIXE also detected two rare forms of calculus (I' and II'). The traces of Zn and S were highly variable. The different types of calculus were probably formed by different biomineralization pathways.

Automated summary

The study examined dental calculus using a combination of PIXE and optical microscopy, revealing the heterogeneous nature of the calculus and identifying different types based on their Ca/P ratios and composition, suggesting they were formed by different biomineralization pathways.