Objectives: For oncologic patients undergoing head and neck radiotherapy (HNRT), the rapid and chronic progression of radiation-related caries (RRCs) signifies an abrupt deterioration in oral health. This study investigated the in vitro effectiveness of silver diamine fluoride (SDF) at arresting carious lesions in irradiated teeth, and compared to the preventive topical therapy being clinically implemented at the Dental Oncology Program at the Northeast Cancer Centre of Health Sciences North.

Methods: Randomly assigned extracted tooth samples were subjected to in vitro irradiation comparable to typical HNRT treatment protocols, followed by a series of controlled chemical pH cycling to mimic artificial lesions. Experimental groups (N = 15) comprised of: controls (N = 10); positive control subjected to in vitro irradiation only; and treatment applications of: SDF; and nano medical hydroxyapatite remineralization paste with topical neutral fluoride gel (mHAP+F).

Results: Baseline Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy identified characteristic hydroxyapatite (HAp) functional groups: hydroxyl; carbonate (CO32-); and phosphate (PO43-). pH cycling suggested water removal, and relative CO32- and PO43- loss. It was clear from X-ray Photoelectron Spectroscopy survey analyses of major minerals that SDF altered enamel microstructure simply with application; fluorapatite (FAp) formation at 10 and 100nm, with calcium fluoride at 30nm. While mHAP+F, which inundated the surface with calcium at baseline, remained unchanged and formed increased FAp across profile depths. Interestingly, Scanning Electron Microscopy images of both treatments demonstrated restoration of surface destruction associated with irradiated and demineralized enamel. This restoration remained evident with pH cycling. Energy-Dispersive X-ray Spectroscopy spectra confirmed large, bright clusters of variously sized silver precipitates on the surface of group SDF. Additional analysis verified atomic percentage (At.%) F after mHAP+F application. 3-way ANOVA comparison showed a significant interaction of At.%Ag and O between group and with condition (<0.0001). Mechanical properties were investigated with Vickers hardness, demonstrating SDF significantly increased surface hardness. However, when comparing between groups, there was no significant difference. Findings of Micro-Computed Tomography indicated no difference in Relative Enamel Density.

Conclusion: SDF has equal in vitro benefits in the prevention and arresting RRCs as current mHAP+F treatment. This research provides evidence worthy of the recommendation for further investigations and future clinical studies.