Background & Aims
The capsaicin model induces well-defined peripheral and central sensitization that plays an important role in the onset and persistence of pain. As such, it can improve the understanding of pain and nociception mechanisms. Thus, this case-control study compared the degree of secondary hyperalgesia induced by topical capsaicin between healthy participants and patients with chronic temporomandibular disorders (TMD) pain.
Methods
Thirty healthy participants [mean age (SD) of 28 (9) years, 28 women and 2 men] and 30 patients with chronic TMD pain [mean age (SD) of 29 (10) years, 28 women and 2 men] underwent a 45-minute application of 1% capsaicin cream to the skin overlying the middle portion of the right masseter and the distal part of the volar face of the right forearm. The applications were carried out in 2 sessions in a randomized order. Pain intensity during capsaicin application was measured using a 0-10 numerical rating scale every 5 minutes. The following outcomes were assessed before (baseline) and after capsaicin application: area of allodynia and pinprick hyperalgesia. Mixed ANOVA models were applied to the data (p=0.050).
Results
The area under the curve of the pain intensity during capsaicin application on both masseter [mean (SD) of 12.5 (17) for the healthy participants and 14.5 (18) for TMD patients) and forearm [11.5 (19) for the healthy participants and 9.8 (12) following capsaicin) sides showed no significant differences between the groups (p>0.050). Nonetheless, the area under the curve of the pain intensity during capsaicin was greater on the masseter when compared with the forearm (Tukey, p=0.023). However, the area of allodynia was smaller on the masseter when compared with the forearm in both groups (Tukey, p<0.001) and the TMD group showed larger areas (Tukey: p=0.016). The area of pinprick hyperalgesia was overall larger for the TMD group (Tukey: p=0.023) and smaller on the masseter when compared with the forearm only for the TMD group (Tukey, p=0.049).
Conclusions
The sensitization effects of capsaicin seem more pronounced in patients with chronic TMD pain. Additionally, the trigeminal and spinal regions differentiated in response to topical capsaicin, and such differences were more noticeable for TMD pain patients. Our findings suggest that exploring capsaicin-induced sensitization is an interesting mechanistic approach to investigating orofacial pain in humans.
References
LaMotte, R. H., Shain, C. N., Simone, D. A., & Tsai, E. F. P. (1991). Neurogenic hyperalgesia: Psychophysical studies of underlying mechanisms. Journal of Neurophysiology, 66(1), 190–211.
Torebjörk, H. E., Lundberg, L. E., & LaMotte, R. H. (1992). Central changes in processing of mechanoreceptive input in capsaicin?induced secondary hyperalgesia in humans. The Journal of Physiology, 448(1), 765–780.
Quesada, C., Kostenko, A., Ho, I., Leone, C., Nochi, Z., Stouffs, A., Wittayer, M., Caspani, O., Brix Finnerup, N., Mouraux, A., Pickering, G., Tracey, I., Truini, A., Treede, R. D., & Garcia-Larrea, L. (2021). Human surrogate models of central sensitization: A critical review and practical guide. European Journal of Pain, 25(7), 1389–1428.
Presenting Author
Yuri Costa
Poster Authors
Yuri M. Costa. DDS, Ph.D
University of Campinas
Lead Author
Camila Tagliari
School of Dentistry, Passo Fundo University
Lead Author
Micheline Trentin
School of Dentistry of Passo Fundo University
Lead Author
Leonardo Rigoldi Bonjardim
Bauru School of Dentistry, University of São Paulo
Lead Author
Topics
- Specific Pain Conditions/Pain in Specific Populations: Orofacial Pain