Impact of radiotherapy on the morphological and compositional structure of intra-radicular dentin

Abstract

Considering the side effects in the oral cavity and dental structures of radiotherapy (RDT) for head and neck cancer, this study aimed to evaluate the effects of RDT on the root dentin concerning the obliteration of dentinal tubules, the inorganic composition of intra-radicular dentin, and the integrity of collagen fibers. Thirty human canines were selected from a biobank and randomly divided into two groups (n=15). The samples were sectioned buccolingually, and a hemisection was used for structural analysis by scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometer (EDS). Low-vacuum SEM images were obtained at 2000-x magnification to observe the obliteration of the dentinal tubules. Moreover, compositional evaluation was performed using EDS. After RDT, the SEM and EDS analyses were repeated using the same methodology. RDT was applied fractionally at 2 Gy per day, 5 days per week, for 7 weeks, resulting in a total dose of 70 Gy. The collagen integrity of the irradiated and non-irradiated samples was analyzed using Masson's trichrome and picrosirius red staining polarization microscopy. Samples subjected to RDT exhibited dentinal tubule obliteration (p < 0.001); low integrity of type I and III collagen fibers (p < 0.05); compositional reduction of calcium (p = 0.012), phosphorus (p = 0.001), and magnesium (p < 0.001); an increased Ca/P ratio (p < 0.001). RDT affects the structure of dentinal tubules, the inorganic composition of intra-radicular dentin, and the collagen fiber integrity in the root dentin, which may interfere with the effectiveness and durability of dental procedures.

Figure 1. Classification of dentinal tubules by scanning electron microscopy (SEM). A, regular; B, partially obliterated; C, totally obliterated.

Figure 2. Mineral composition analysis by Energy-Dispersive X-ray Spectrometer (EDS) in 3 points of intra-radicular dentin.

Figure 3. Evaluation of collagen fibers in the intra-radicular dentin of irradiated and non-irradiated teeth. Intense loss of integrity of collagen fibers of intra and peritubular dentin of an irradiated tooth (A) when compared to a non-irradiated tooth (B) (Masson's trichrome, 400x). Considerable loss of integrity of type I and III collagen fibers in the dentin of the irradiated tooth (C) when compared to the non-irradiated tooth (D) (Picrosirium red under polarization, 400x).