RAMAN-SPECTRA OF HUMAN DENTAL CALCULUS

Raman spectra of human dental calculus have been observed for the firs t time by use of micro-Raman spectroscopy. The spectral features of ca lculus were influenced easily by heating caused by laser irradiation. Therefore, the measurements were carried out at relatively low power ( 5 mW, 1-mu m spot size). The spectra could be characterized as phospha te vibrational bands due to the nu(1), nu(2), nu(3) and nu(4) modes. T he overall spectral features did not resemble those of pure minerals s uch as brushite, octacalcium phosphate, and hydroxyapatite. There were spectral differences among mixed calculus particles obtained from 18 adults, probably due to variations in local mineral composition and di fferences among patients. However, the averaged spectral features did not vary significantly with formation period from 1 to 6 months. Fresh ly removed and stored (5-11 months) calculus also gave comparable Rama n spectra. Measurements on a fractured sample indicated that Raman spe ctra at saliva and dentin interfaces are nearly identical, and major m ineral constituents may not vary significantly along the growth axis o f calculus.