Electron microscopy analysis of the thermal phase transition from hydroxyapatita to β-TCP observed in human teeth

Samples of enamel and dentin from human molar teeth were heated in air from room temperature (25°C) up to 1200°C and the phase transition from hydroxyapatite (HAP) to tricalcium phosphate (β-TCP) was recorded. The changes produced in morphology and chemical composition in the tooth during heating were analysed by light microscopy, scanning electron microscopy (SEM), characteristic x-ray energy dispersion spectroscopy (EDS), x-ray diffraction (XRD), electron diffraction, transmission electron microscopy (TEM) and high-resolution electron microscopy (HRTEM). The results indicated a high correlation relationship among Ca content, P content, O content and Na content, and the existence of the Kirkendall effect during the HAP- β-TCP phase transition. LAY DESCRIPTION: This work is related with tooth materials. Samples of enamel and dentine from human molar teeth were heated in air from 25°C up to 1200°C and the phase transition from hydroxyapatite (HAP) to tricalcium phosphate (β-TCP) was recorded. The β-TCP phase is also known as whitlockite. The changes produced in morphology and chemical composition in the tooth during heating were analysed by electron microscopy and X-ray diffraction. The results indicated a high correlation relationship among Ca, P, O and Na contents, and the existence of the Kirkendall effect, the atomic diffusion producing voids, during the HAP- β-TCP phase transition.