Radiotherapy alters the composition, structural and mechanical properties of root dentin in vitro.

OBJECTIVES: Post-radiation dental lesions affect mainly the cervical area of the tooth. Until now, there are quite few evidences regarding the effects of radiation exposure on root dentin breakdown. To better understand this effect, we used human root dentin specimens obtained from third molars from similarly aged individuals. MATERIALS AND METHODS: Twenty specimens were analyzed by the surface hardness (SH), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) to evaluate the baseline properties of their root dentin. Other six human teeth were prepared and analyzed by scanning electron microscopy (SEM). Then the specimens were randomly distributed between two groups (n = 13 per group) and irradiated with a total dose of 55 or 70 Gy in a linear accelerator. The percentage of EDX and surface hardness loss (%SHL) were determined based on measurements before and after irradiation. The specimens were also analyzed after irradiation by SEM and XRD. The Ca/P weight ratio was calculated. RESULTS: Based on SEM analysis, radiation exposure induced dehydration of the dentin. The Ca/P weight ratio decreased (p = 0.0045). The %SHL of specimens irradiated with 70 Gy was higher than that of the 55-Gy group (p < 0.05), although even the lower dose induced root dentin breakdown. CONCLUSIONS: Overall, we can state that radiation exposure changes the composition and structure of human root dentin, which detrimentally affect its hardness. CLINICAL RELEVANCE: The changes reported herein might influence the selection of the dental materials and will bring new knowledge in this field to prevent radiation-related caries in root dentin.

Profile of high-fluoride toothpastes combined or not with functionalized tri-calcium phosphate on root dentin caries control: An in vitro study.

PURPOSE: This in vitro study was conducted in two regimens hypothesizing that high-fluoride (F) toothpaste (5,000 µg F/g) with or without functionalized tri-calcium phosphate (f TCP) would provide additional protection against (1) root caries development and (2) progression. For both regimens, bovine root dentin specimens were used. METHODS: In regimen 1, 60 specimens were subjected daily to alternate immersions between demineralizing and remineralizing solutions for 7 days. The specimens were randomly distributed into four treatment groups (n=15) : non-F toothpaste; Colgate Total 12 (CT) (1,450 µg F/g); Colgate Prevident (CP) (5,000 µg F/g); and Clinpro 5000 (CL) (5,000 µg F/g) associated with (f TCP), and treated with toothpastes/water slurries (1:3 w/w) (5 minutes), twice a day. In regimen 2, the efficacy of the toothpastes to inhibit the progression of the developed lesions was assessed, using the previously described pH-cycling model without additional treatment. The response variables were based on the percentage of surface hardness change (ΔSH), cross-sectional hardness (ΔCSH), mineral content/lesion depth by transversal microradiography (TMR) and the alkali-soluble F uptake. RESULTS: Both high-F toothpastes reduced initial dentin demineralization and increased the F uptake compared to non-F and conventional toothpastes (P< 0.05). In terms of caries lesion progression, all tested toothpastes were able to promote this protection. CLINICAL SIGNIFICANCE: High-F toothpastes, regardless of the presence of f TCP, were more effective than conventional F toothpaste in inhibiting initial root dentin demineralization.