Physical and biochemical shifts of irradiated dentin during caries progression

This study investigated the physical and chemical changes in carious dentin lesions between irradiated and non-irradiated teeth to understand the impact of radiotherapy on caries progression.

Using an in vitro model, 26 human maxillary canines were divided into irradiated and control groups (n = 13). Carious lesions were induced with S. mutans, and the carious dentin was analyzed for mineral density via microcomputed tomography, biochemical composition through Raman spectroscopy, lesion depth and porosity using confocal microscopy, and collagen ultrastructure via histological staining.

Irradiated dentin exhibited reduced mineral density in the superficial layer of coronal dentin (p = 0.029), and in the middle (p = 0.007) and deep (p = 0.006) layers of radicular dentin. Raman spectroscopy revealed chemical differences mainly in root caries, including a decrease in pentosidine (p < 0.001) and an increase in amide I (p < 0.001) in the irradiated group compared to the control, suggesting altered collagen structure and resistance to degradation. No significant differences in lesion depth or porosity were observed among groups (p > 0.05). Histological analysis showed that the irradiated root dentin was more resistant to collagen degradation, while no structural differences in collagen were observed between the groups.

Radiotherapy-induced tissue changes affected the dentin caries progression as demonstrated mainly by differences in mineral density and susceptibility of the root collagen matrix to caries-induced degradation in irradiated teeth.

This study provides a better understanding of the response of irradiated dentin to caries progression and supports a strict evidence-based caries management in patients undergoing radiotherapy.