Abstract
The advent of neuroimaging in dental research provides exciting opportunities for relating excitation of trigeminal neurons to human somatosensory perceptions. Cold air sensitivity is one of the most frequent causes of dental discomfort or pain. Up to date, devices capable of delivering controlled cold air in an MR-environment are unavailable for quantitative sensory testing. This study therefore aimed at constructing and evaluating a novel MR-compatible, computer-controlled cold air stimulation apparatus (CASA) that produces graded air puffs. CASA consisted of a multi-injector air jet delivery system (AJS), a cold exchanger, a cooling agent, and a stimulus application construction. Its feasibility was tested by performing an fMRI stimulation experiment on a single subject experiencing dentine cold sensitivity. The novel device delivered repetitive, stable air stimuli ranging from room temperature (24.5°C ± 2°C) to −35°C, at flow rates between 5 and 17 liters per minute (l/min). These cold air puffs evoked perceptions similar to natural stimuli. Single-subject fMRI-analysis yielded brain activations typically associated with acute pain processing including thalamus, insular and cingulate cortices, somatosensory, cerebellar, and frontal brain regions. Thus, the novel CASA allowed for controlled, repetitive quantitative sensory testing by using air stimuli at graded temperatures (room temperature down to −35°C) while simultaneously recording brain responses. No MR-compatible stimulation device currently exists that is capable of providing non-contact natural-like stimuli at a wide temperature range to tissues in spatially restricted areas such as the mouth. The physical characteristics of this novel device thus holds promise for advancing the field of trigeminal and spinal somatosensory research, namely with respect to comparing therapeutic interventions for dentine hypersensitivity.
Highlights
Temperature perception and discrimination are part of the body’s homeostatic control system that evaluates and integrates internal and external body states
The cold air stimulation apparatus (CASA) was designed to include four tube-connected components (Figure 1): (1) An air source that does not condense at very low temperatures and that feeds into a computer-controlled air jet delivery system, (2) a cold exchange system (CE), and (3) an air switch that directs the cold stimulus to and away from the target tooth
Since transduction mechanisms are determined by stimulus characteristics, quantitative sensory testing (QST) of a specific stimulus type is an ideal method to assess sensory function and dysfunction
Summary
Temperature perception and discrimination are part of the body’s homeostatic control system that evaluates and integrates internal and external body states. Sodium channels Nav1.8 and transient 4-AP-sensitive K+ currents are involved in cold related cellular activation and inhibition (McKemy, 2013) Some of these ion channels have been detected in dental tissue (Story et al, 2003; Patapoutian et al, 2009; Chung et al, 2013). In molars of transgenic mice, a portion of TRPM8 labeled axons were observed below the odontoblast layers and more interestingly, another subset of TRPM8 fibers crossed the odondoblast layer to extend into dentinal tubules This observation, taken with functional recordings in animals and psychophysical data in humans suggest that direct stimulation of TRPM8 neurons may play a more important role in dentine cold hypersensitivity than the more popular “hydrodynamic theory.”. By presenting a microscale model of tooth physiology, Lin M. et al (2014) presented a synthesis of possible thermal transduction mechanisms in teeth from an engineering perspective, highlighting the activation of stress-sensitive ion channels on nociceptors by cooling effects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
