Spectroscopic analyses reveal radiotherapy-induced variations in elemental composition and crystallite properties of human permanent teeth enamel.

Objective: To study the effect of radiation therapy on the structural and elemental composition of permanent teeth enamel in vitro.

Methods: Sections from 21 noncarious healthy human teeth were exposed to a cumulative radiation dose of 20-80 Gy. The sections were subjected to electron dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis to study the elemental composition, the ratio of inorganic and organic content, and the mineralization and crystalline properties of the hydroxyapatite crystal structure respectively. All measures were taken on specified areas of enamel surface before and after radiation exposure and compared.

Results: In FTIR and EDS studies, the calcium to phosphorus (Ca/P) and carbonate to phosphate (CO/PO) ratios were significantly different (P < 0.05) in teeth sections exposed to 80 Gy, indicating the deterioration of inorganic calcium and phosphorous content. The XRD spectrum data showed loss of peaks at seven specific 2θ coordinate areas, flattened peaks and an increase in the crystallite size in the radiation-exposed groups due to mineralization loss and alteration of the hydroxyapatite crystal matrix in the tooth enamel.

Conclusions: Radiotherapy can induce significant variations in the inorganic and organic functional groups constituting the tooth enamel surface; and these variations are dose dependent. The mechanism responsible for delamination and radiation caries needs to be explored by studying the protein lysis pattern, which might be a leading factor causing the enamel degradation and radiation caries.