The effects of re-irradiation on the chemical and morphological properties of permanent teeth.

Abstract Objectives Evaluate in vitro, simulating a radiotherapy retreatment of HNC, the effects of re-radiation on the properties of enamel and dentin. Materials and Methods Forty five human permanent molars were divided in five groups: non-irradiated; irradiated up to a dose of 60 Gy and re-irradiated up to doses of 30, 40 and 50 Gy, through the analysis of Raman spectroscopy, Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS). Raman spectroscopy was analyzed comparatively, according to the intensity, general area of the spectra and peaks of interest. Kolmogorov – Smirnov test, followed by the One-Way ANOVA test and Tukey's post-test, with the significance level were adopted for all analyzes being 5%. Results There were significant changes in the peaks of irradiated, non-irradiated and re-irradiated enamels, with the presence of phosphate (438nm), hydroxyapatite (582nm), phosphate (960nm) and carbonate (1070nm) (p  0.05), with degradation of the interprismatic region, destruction of enamel prisms and hydroxyapatite crystals. In dentin, it caused obliteration of the tubules, formation of cracks and progressive fragmentation of collagen fibers. EDX indicated an increase in the percentage of oxygen and a decrease in phosphorus and calcium after re-irradiation. Conclusion The chemical and morphological changes in the permanent irradiated teeth are progressive and directly proportional to the escalation of the radiation dose. Clinical relevance Re-irradiation causing even more damage to enamel and dentin of permanent teeth.