Comparison of Pain-Generated Functional Outcomes in Experimental Models of Delayed-Onset Muscle Soreness and Nerve Growth Factor Injection of the Masticatory Muscles

To compare two pain models of myalgic TMD, delayed-onset muscle soreness (DOMS) and injections of nerve growth factor (NGF), in terms of pain-related and motor function outcomes, as well as activity-related temporal summation. Methods: Fifty age- and gender-matched healthy participants were recruited and randomized into one of three groups: to a repeated eccentric contraction task to cause DOMS (n = 20), to receive NGF injections into the masseter muscle (n = 20), or to a control group (n = 10). Mechanical sensitivity of masticatory muscles, chewing parameters, jaw function limitation, maximum bite force, and activity-related temporal summation were assessed at baseline and at days 1, 2, and 7 following the intervention. Results: Compared to baseline, both model groups showed increased mechanical sensitivity, jaw function limitation, pain on chewing, and decreased chewing efficiency, lasting longer in the NGF group than in the DOMS group (P .05). Conclusion: Both models produced similar pain- related outcomes, with the NGF model having a longer effect. Furthermore, the NGF model showed a more substantial effect on motor function, which was not seen for the DOMS model. Finally, neither of the models were able to provoke activity-related temporal summation of pain. J Oral Facial Pain Headache 2020;34:311–322. doi: 10.11607/ofph.2623