Molecular mechanisms of photobiomodulation related to its effectiveness in the treatment of dentinal hypersensitivity – a novel cell culture-based study

Abstract

Dentinal hypersensitivity is a common cause of chronic dental pain and affects around 30% of the general population. Photobiomodulation (PBM) is the delivery of low-intensity photons using a laser or light emitting diode (LED) within the infrared (600-700nm) or near-infrared (770-1200nm) spectrum to a target tissue, inducing reversible biochemical changes.

PBM delivered using GaAlAs 810nm laser is a promising treatment alternative to topical desensitising agents for dentinal hypersensitivity, producing both immediate and long-term pain relief. The aim of this thesis was to investigate the molecular mechanisms underlying the effectiveness of PBM in dentine hypersensitivity treatment.

A novel cell culture study simulating the clinical setting was developed to measure PBM, delivered at clinically relevant parameters, on Mitochondrial membrane potential (MMP) changes. Rat dorsal root ganglia (DRG) cultures were stained with JC-1 and exposed to either GaAlAs 810nm PBM (energy density 9J/cm2) or sham laser (sPBM) delivered through a suspended human tooth to cultured rat DRG neurons, Schwann cells, and fibroblasts.

Significant variability between teeth affects PBM delivery to the dental pulp and a possible method to address this aspect is by is utilising Cone Beam Computer Tomography (CBCT) imaging to measure tooth morphology, allowing for parameter adjustments and leading to more personalised dentinal hypersensitivity treatment. However, this has drawbacks as it involves ionising radiation and requires more time to take measurements of tooth thickness.

The findings of the study presented in this thesis were unable to determine that conduction block was the molecular mechanism of PBM treatment of dentinal hypersensitivity. Furthermore, PBM device parameters, tooth and delivery factors significantly impact photon delivery and should be considered to optimise PBM effectiveness and develop standardised guidelines for clinical practice.