Radiotherapy in the head and neck region influences the chemical and mechanical properties of intraradicular dentin.

OBJECTIVES: To investigate the chemical and mechanical properties of intraradicular dentin submitted to radiotherapy. MATERIALS AND METHODS: Sixteen mandibular incisors were divided into two groups (n = 8): non-irradiated and irradiated. The irradiated teeth were obtained from head and neck radiotherapy patients, with a total dose ranging from 70.2 to 72 Gy divided into 1.8 Gy daily. After sample preparation, intraradicular dentin slices of each root third were evaluated by Raman spectroscopy, energy dispersive spectroscopy and Knoop microhardness test. Data were analyzed by Two-way ANOVA and Tukey's test (α = 0.05). RESULTS: In Raman spectroscopy, carbonate and amide III showed a significant difference for irradiation and third (carbonate p = 0.021 and p < 0.001; amide III p < 0.001 and p = 0.001, respectively). For amide I, there was a significant difference for third (p < 0.001). For carbonate/mineral ratio, there was a significant difference for irradiation (p = 0.0016) and third (p < 0.001), with the irradiated middle third showing the lowest values. For amide I/amide III ratio, there was a significant difference for irradiation (p = 0.005) in the cervical third. In energy dispersive spectroscopy, carbon (p = 0.004; p = 0.020), phosphorus (p < 0.001; p = 0.009) and calcium (p = 0.008; p = 0.007) showed differences for irradiation and third, with the irradiated groups presenting lower values in cervical and middle thirds. For calcium/phosphorus ratio, there was a significant difference for irradiation (p < 0.001) in cervical and middle thirds. Regarding microhardness, there was a significant difference for irradiation (p < 0.001), with all irradiated groups showing lower microhardness values. CONCLUSIONS: The radiotherapy altered the chemical and mechanical properties of intraradicular dentin, mainly in the cervical and middle root thirds.

Chemical analysis of irradiated root dentin and its interaction with resin cements.

OBJECTIVES: To investigate the chemical changes in root dentin submitted to ionizing radiation and how it affects the interaction with resin cements. MATERIALS AND METHODS: Forty human premolars were randomly divided into two groups (n = 20): non-irradiated and irradiated. They were randomly subdivided according to the type of resin cement (n = 10): conventional (RelyX ARC, 3 M ESPE) or self-adhesive (RelyX U200, 3 M ESPE). After cementation of the fiberglass posts, the roots were sectioned to be analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and confocal laser scanning microscopy (CLSM). The data obtained from FTIR and Raman were analyzed using two-way ANOVA followed Tukey's test (α = 0.05). For CLSM, a descriptive analysis was performed. RESULTS: In the FTIR, there was a significant difference between the non-irradiated and irradiated groups for phosphate (p = 0.011), carbonate (p < 0.001), amide III (p = 0.038), and carbonate/mineral ratio (p < 0.001). Regarding the root third, there was a difference for amide I (p = 0.002), mineral/matrix ratio (p = 0.001), and amide I/CH2 (p = 0.026) between the cervical and the others. Raman spectroscopy revealed no difference between groups for 961/1458 cm-1 in the diffusion zone. CLSM showed a different interaction pattern for the two cements with the irradiated dentin from the cervical third. CONCLUSIONS: Ionizing radiation altered the chemical composition of root dentin, especially in the cervical third. The resin cements showed less interaction with the irradiated root dentin. CLINICAL RELEVANCE: As radiotherapy alters the chemical composition of root dentin, the interaction of resin cement with dentin can compromise the success of rehabilitation with fiberglass posts.