Photobiomodulation in the parotid and submandibular glands: a Monte Carlo simulation of photon penetration using 525-nm, 660-nm, and 850-nm wavelengths.

There are ongoing questions about the most effective wavelength for photobiomodulation (PBM) on major salivary glands due to the specific anatomical location and unique optical properties of the tissues surrounding the glands. The aim of this study was to analyze the photon propagation in the major salivary glands region of humans and rats using Monte Carlo (MC) stochastic simulation. Phantoms were designed to replicate the tissues surrounding the parotid and submandibular glands in humans and rats. Simulations were carried out using a MC online platform with wavelengths of 525 nm, 660 nm, and 850 nm. An experimental assay in rats was conducted to evaluate if the wavelength with the best performance could enhance the salivary flow. The 525 nm photons were primarily absorbed by the skin and fat tissue of humans and rats. Only in rats, this wavelength reached the salivary glands. The 660 nm photons reached the human glands but were more absorbed in the submandibular gland than in the parotid gland. The 850 nm photons had a higher absorption in both human and rat parotid glands. PBM using 850 nm wavelength improved the salivary flow in rats. The 660 nm and 850 nm wavelengths were more effectively absorbed in the human parotid and submandibular glands, respectively, compared to the 525 nm. The increased salivary flow observed in rats following treatment with 850 nm suggests a beneficial effect of this wavelength on salivary gland function. Clinical trial number: Not applicable.