Mechanisms of Effectiveness of Photobiomodulation on Somatosensory Neurons and the Peripheral Nervous System – Review of Clinical Relevance for Treatment of Pain and Dental Anaesthesia

The use of light (photons) delivered clinically from laser or light-emitting diodes (LED), is referred to as photobiomodulation therapy (PBMt). Increasingly PBMt is accepted particularly in dental practice for pain or pre-emptive anaesthesia. Understanding its mechanism of effectiveness is the key to its increasing acceptance. Of major importance to this is how PBMt affects not only the neurons but also the Schwann cells and fibroblasts of the peripheral nervous system which are unique in morphology and function. The specific roles of the neuronal cells of the dorsal root and trigeminal ganglia, now include consideration of the axon initial segment responsible for the initiation of the action potential and the T junction from which the distal and proximal axons arise which are complex but central to normal function. This cellular complexity, organization and function is discussed leading to a review of the mechanism of effectiveness of PBMt demonstrated by clinical trials in both medicine and dentistry. This review provides evidence of the involvement of the cytoskeleton, mitochondrial organization particularly related to fast and slow axonal flow and mitochondrial membrane potential in response to light in somatosensory neurons and nerves.