Dual therapy with nanohydroxyapatite and vitamin E restores irradiated dentin via remineralization and collagen protection.

Background: Radiotherapy-induced head and neck cancer harms the structural and biochemical integrity of dentin and causes mineral loss, breakdown of collagen, and increased sensitivity to radiation-induced caries and restorative failure.

Objective: To evaluate the therapeutic effectiveness of nanohydroxyapatite (nHAp) and vitamin E-individually and in combination-for remineralization and collagen matrix preservation of irradiated dentin.

Methods: Forty human third molars (n = 8 per group) were allocated into five groups randomly: non-irradiated control, irradiation-only (60 Gy linear accelerator, LINAC), irradiation + nHAp treatment, irradiation + vitamin E treatment, and irradiation + combination treatment (nHAp + vitamin E). Dentin samples were analyzed using Fourier transform infrared spectroscopy (FTIR), X‑ray diffraction (XRD), scanning electron microscopy with energy-dispersive X‑ray spectroscopy (SEM-EDX), and Vickers microhardness testing.

Results: Radiotherapy caused widespread microstructural loss and amide I and II band intensity decreases (mean of 41.3% and 47.7%, respectively) as well as a 33% loss in crystallinity. The nHAp treatment recovered phosphate peak intensity to 82.1% of the control mean, and vitamin E retained amide I and II bands at 91.3% and 88.9% of the control means, respectively. The combined treatment achieved the best recovery, with the crystallinity returning to 89.5% of the control, near full recovery of the intensities of amide and phosphate bands, normalization of the Ca/P ratio, and microhardness values that were not significantly different from the non-irradiated control (p > 0.05).

Conclusion: Nanohydroxyapatite and vitamin E have synergistic actions, promoting organic as well as mineral phases of irradiated dentin. Their combined application significantly increases microhardness, chemical composition, and ultrastructure, promoting a double-therapy strategy for the restorative rehabilitation of head and neck cancer patients after radiotherapy.