Extensive research has been conducted to detect new approaches for the treatment of dentin root caries, as the prevalence of root caries is increasing. In addition, as post-radiation dental lesions develop mainly at cervical area, the concern for control dentin root caries in patients that received radiotherapy on head and neck area is high. Especially for high-risk population, the material-dentin interface integrity is of major concern to avoid secondary caries, however, the correlation between microleakage around restorations and artificial caries-like lesions adjacent to restorations generated is poor. The main aim of this in vitro study is to evaluate restorative materials to treat root caries in sound (S) and irradiated (I) dentin in terms of their polymerization shrinkage (PS) and the influence of the shrinkage stress (SS) in the performance of the restoration in a high cariogenic challenge. The effect of high-F toothpastes to prevent secondary caries around the restorations and their synergic effect with F-release material will be also evaluated. In phase 1, nano-hybrid and bulk-fill composites will be compared with a resin-modified glass ionomer cement (RMGIC) regarding their PS. To I specimens, a dose of 70 Gy of gamma radiation will be used in a Linear Accelerator. In phase 2, a subsurface lesion will be inducted in the specimens in two levels (S and I). Box-shaped cavities will be prepared in the centre of the lesion. The specimens will be randomly restored with the 4 materials tested (n=80) and distributed into 4 treatments groups, respectively (n=20): 1- demineralizing solution for 7 days, 2- non-F (negative control), 3- conventional concentration of F (1,450 µg F/g), 3- high-F toothpastes (5,000 µg F/g). Groups 1,2 and 3 will be tested in a dynamic pH-cycling regime, with daily challenges DES/RE. The response variables will be PS, SS, percentage of Energy-dispersive x-ray spectroscopy and percentage of hardness loss. For statistical analyses, data will be collected and analyzed by means of normal distribution and homogeneity to be evaluated with parametric analyses (p<0.05).
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