Chronic Pain–Related Jaw Muscle Motor Load and Sensory Processing

Abstract

Chronic pain associated with temporomandibular disorders (TMDs) may reflect muscle mechanoreceptor afferent barrage and dysregulated sensory processing. This observational study tested for associations between Characteristic Pain Intensity (CPI), physical symptoms (Patient Health Questionnaire–15 [PHQ-15]), and cumulative jaw muscle motor load (mV*s). In accordance with institutional review board oversight and Strengthening the Reporting of Observational Studies in Epidemiology guidelines, adult subjects gave informed consent and were identified via Diagnostic Criteria for TMD (DC-TMD) examination and research protocols. Subjects were assigned to ±Pain groups using DC-TMD criteria for myalgia. CPI scores characterized pain intensity. PHQ-15 scores were surrogate measures of dysregulated sensory processing. Laboratory tests were performed to quantify masseter and temporalis muscle activities (mV) per bite force (N) for each subject. In their natural environments, subjects recorded day- and nighttime electromyography from which cumulative jaw muscle motor loads (mV*s) were determined for activities consistent with bite forces of >1 to ≤2 and >2 to ≤5 N. Data were assessed using univariate analysis of variance, simple effects tests, K-means cluster classification, and 3-dimensional regression analyses. Of 242 individuals screened, 144 enrolled, and 125 with complete data from study protocols, there were 35 females and 15 males for +Pain and 35 females and 40 males for −Pain. Subjects produced 324 daytime and 341 nighttime recordings of average duration 6.9 ± 1.7 and 7.6 ± 1.7 h, respectively. Overall, +Pain compared to −Pain subjects had significantly higher (all P ≤ 0.002) CPI and PHQ-15 scores. Cumulative jaw muscle motor loads showed significant between-subject effects for time, diagnostic group, and sex (all P < 0.003), where motor loads tended to be higher for daytime versus nighttime, +Pain versus −Pain groups, and males versus females. Two clusters were identified, and regression relations showed associations of low-magnitude daytime masseter motor load, PHQ-15, and CPI scores for cluster 1 ( n = 105, R2 = 0.44) and cluster 2 ( n = 18, R2 = 0.80). Furthermore, these regression relations showed thresholds of motor load and PHQ-15 scores, above which there were nonlinear increases in reported pain.

Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets

“…Increased responsiveness of sensory neurons during TMD-M could occur in any muscle controlling temporomandibular joint (TMJ) articulation, including superficial and in the deep heads of masseter muscle (MM), temporal muscle (TM), medial pterygoid closing muscles (MPM) as well as gliding superior and inferior heads of the lateral pterygoid muscles (LPM) (Kucukguven et al, 2022; Nickel et al, 2022) ( Fig 1 ). Muscle tissues of the TMJ structure are innervated by the masseteric nerve (MN) for MM, the auriculotemporal nerve (ATN) for LPM, and temporal nerve (TN) for TM ( Fig 1 ).…”

Effect of acupuncture on the molar bite force in women with chronic neck pain

“…Moreover, bite force, influenced by the stomatognathic system's function, stands as a crucial oral health indicator. 11 Acupuncture has been widely employed for chronic pain management, including temporomandibular disorder-related pain, though its effectiveness varies. The comprehensive approach of acupuncture, by targeting specific points, aims to modulate pain perception and, by extension, could impact masticatory function, thus contributing to a more thorough management of these conditions.…”

Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets

“…Increased responsiveness of sensory neurons during TMDM could occur in any muscle types controlling temporomandibular joint (TMJ) articulation, including superficial and in the deep heads of masseter muscle (MM), temporal muscle (TM), medial pterygoid (MPM) closing muscles as well as gliding superior and inferior heads of the lateral pterygoid muscles (LPM) 11,12 (Fig. 1 adapted from Kucukguven and co-workers 12 ).…”