FLUID DYNAMICS ANALYSIS OF SHEAR STRESS ON NERVE ENDINGS IN DENTINAL MICROTUBULE: A QUANTITATIVE INTERPRETATION OF HYDRODYNAMIC THEORY FOR DENTAL PAIN

Abstract

Noxious thermal and/or mechanical stimuli applied to dentine can cause fluid flow in dentinal microtubules (DMTs). The fluid flow induces shear stress (SS) on intradental nerve endings and may excite pulpal mechanoreceptors to generate dental pain sensation. There exist numerous studies on dental thermal pain, but few are mathematical. For this, we developed a computational fluid dynamics (CFD) model of dentinal fluid flow (DFF) in innervated DMTs. Based on this model, we systematically investigated the effects of various parameters (e.g., biological structure, DFF velocity, and fluid properties) on the SS experienced by intradental nerve endings and thus provide a quantitative interpretation to the hydrodynamic theory. The dimensions of biological structures, odontoblastic process (OP) movement, dentinal fluid velocity, and viscosity were found to have significant influences on the SS while dentinal fluid density showed negligible influence under conditions studied. The results indicate that: (i) dental pain study of animal models may not be directly applied to human being and the results may even vary from one person to another and (ii) OP movement caused by DFF changes the dimension of the space for the fluid flow, affecting thus the SS on nerve endings. The present work enables better understanding of the mechanisms underlying dental pain sensation and quantification of dental pain intensity resulted from clinical procedures such as dentine sensitivity testing and dental restorative processes.