Surface properties of irradiated and non-irradiated dentin following pH cycling and fluoride toothpaste exposure: An in vitro study.

OBJECTIVE

To investigate the effects of irradiation on the surface properties of demineralized human dentin following pH cycling and toothpaste exposure.

DESIGN

Twenty sound human third molars were randomly assigned to control and irradiated groups (n = 10 each). Dentin samples were demineralized to induce artificial caries, then subjected to pH cycling and immersion in a toothpaste slurry. Surface changes were assessed using Knoop microhardness (KHN), atomic force microscopy (AFM), and scanning electron microscopy (SEM).

RESULTS

At baseline, irradiated dentin showed significantly lower KHN values than control (p = 0.04). After demineralization, both groups exhibited a significant reduction in microhardness (p = 0.04). Following pH cycling and toothpaste exposure, KHN decreased further; however, no significant between-group differences were observed (p > 0.99). Significant intragroup changes occurred across all evaluation periods (p < 0.05). AFM analysis showed no significant intergroup differences in surface roughness; however, roughness increased significantly from baseline to the final evaluation in both groups, with no significant difference between the baseline and demineralized stages. AFM and SEM images demonstrated smooth surfaces at baseline, loss of peritubular material post-demineralization, and increased roughness with mineral deposition after pH cycling, particularly in irradiated dentin.

CONCLUSIONS

Under the in vitro conditions evaluated, irradiated and non-irradiated dentin demonstrated comparable microhardness and surface roughness following pH cycling and fluoridated toothpaste exposure. These findings indicate similar surface responses between groups under the experimental conditions tested. Further research is warranted to evaluate the influence of the oral environment, dietary factors, and mechanical abrasion.