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Letters to the Editor
Commentary on Manfredini et al. Funding source: None. The authors stated that there are no conflicts of interest to report.
URBANO SANTANA-MORA, DDS, and URBANO SANTANA-PENÍN, MD, DDS, PhD Department of Stomatology, Faculty of Medicine and Odontology, University of Santiago de Compostela, Santiago de Compostela, Spain
Dear Editor, We congratulate the authors for publishing their manuscript entitled “Surface Electromyography Findings in Unilateral Myofascial Pain Patients: Comparison of Painful vs Non Painful Sides” [1] in a recent issue of Pain Medicine. Future research strategies to elucidate the causes of temporomandibular joint (TMJ) disorders (TMD) will benefit from investigations of this complex initial TMD condition. The study assessed the muscular electromyographic activity in a clinical context and thus provided information that could be clinically valuable. Surprisingly, their results are in disagreement with previous reports showing intraindividual surface electromyography asymmetry in TMD patients [2–4]. We have some concerns regarding factors that could affect the interpretation of the study results. 1. Why didn’t the authors use any intraindividual asymmetry indexes? Differences that did not emerge from comparisons of mean data could emerge using asymmetry indexes [3,4]. 2. Because the null hypothesis was not rejected, type 2 error is possible and the lack of power could be a problem [5]. The study power should be reported. 3. This study does not consider the dental occlusion status of the participants. Because TMJ loads are a main factor for TMD [6], and dental occlusion can influence the TMJ loads [7], the dental occlusion status should be considered. 4. The chewing function, which can be a causal factor for TMD [8], should also be considered. In summary, there is the possibility of type 2, or beta, error in the study. Further studies, with surface electromyography recordings and the assessment of their variability, increased sample size, reporting of the dental occlusion status, masticatory function and affected side (body laterality could also be a factor), and using asymmetry indexes for intraindividual comparisons are recommended.
References 1 Manfredini D, Cocilovo F, Stellini E, Favero L, Guarda-Nardini L. Surface electromyography findings in unilateral myofascial pain patients: Comparison of painful vs non painful sides. Pain Med 2013;14:1848– 53. 2 Visser A, Kroon GW, Naeije M, Hansson TL. EMG differences between weak and strong myogenous CMD patients and healthy controls. J Oral Rehabil 1995;22: 429–34. 3 De Felício CM, Ferreira CL, Medeiros AP, et al. Electromyographic indices, orofacial myofunctional status and temporomandibular disorders severity: A correlation study. J Electromyogr Kinesiol 2012;22:266– 72. 4 Santana-Mora U, Cudeiro J, Mora-Bermúdez MJ, et al. Changes in EMG activity during clenching in chronic pain patients with unilateral temporomandibular disorders. J Electromyogr Kinesiol 2009;19(6):e543– 9. 5 Elwood M. Critical Appraisal of Epidemiological Studies and Clinical Trials. Oxford: Oxford Univ Press; 2007: 256–60. 6 Tanaka E, Detamore MS, Mercuri LG. Degenerative disorders of the temporomandibular joint: Etiology, diagnosis, and treatment. J Dent Res 2008;87:296–307. 7 del Palomar AP, Santana-Penín U, Mora-Bermúdez MJ, Doblaré M. Clenching TMJs-loads increases in partial edentates: A 3D finite element study. Ann Biomed Eng 2008;36:1014–23. 8 Santana-Mora U, López-Cedrún J, Mora MJ, Otero XL, Santana-Penín U. Temporomandibular disorders: The habitual chewing side syndrome. PLoS ONE 2013;8(4): e59980.
341
Letters to the Editor
Commentary on Manfredini et al. Funding source: None. The authors stated that there are no conflicts of interest to report.
URBANO SANTANA-MORA, DDS, and URBANO SANTANA-PENÍN, MD, DDS, PhD Department of Stomatology, Faculty of Medicine and Odontology, University of Santiago de Compostela, Santiago de Compostela, Spain
Dear Editor, We congratulate the authors for publishing their manuscript entitled “Surface Electromyography Findings in Unilateral Myofascial Pain Patients: Comparison of Painful vs Non Painful Sides” [1] in a recent issue of Pain Medicine. Future research strategies to elucidate the causes of temporomandibular joint (TMJ) disorders (TMD) will benefit from investigations of this complex initial TMD condition. The study assessed the muscular electromyographic activity in a clinical context and thus provided information that could be clinically valuable. Surprisingly, their results are in disagreement with previous reports showing intraindividual surface electromyography asymmetry in TMD patients [2–4]. We have some concerns regarding factors that could affect the interpretation of the study results. 1. Why didn’t the authors use any intraindividual asymmetry indexes? Differences that did not emerge from comparisons of mean data could emerge using asymmetry indexes [3,4]. 2. Because the null hypothesis was not rejected, type 2 error is possible and the lack of power could be a problem [5]. The study power should be reported. 3. This study does not consider the dental occlusion status of the participants. Because TMJ loads are a main factor for TMD [6], and dental occlusion can influence the TMJ loads [7], the dental occlusion status should be considered. 4. The chewing function, which can be a causal factor for TMD [8], should also be considered. In summary, there is the possibility of type 2, or beta, error in the study. Further studies, with surface electromyography recordings and the assessment of their variability, increased sample size, reporting of the dental occlusion status, masticatory function and affected side (body laterality could also be a factor), and using asymmetry indexes for intraindividual comparisons are recommended.
References 1 Manfredini D, Cocilovo F, Stellini E, Favero L, Guarda-Nardini L. Surface electromyography findings in unilateral myofascial pain patients: Comparison of painful vs non painful sides. Pain Med 2013;14:1848– 53. 2 Visser A, Kroon GW, Naeije M, Hansson TL. EMG differences between weak and strong myogenous CMD patients and healthy controls. J Oral Rehabil 1995;22: 429–34. 3 De Felício CM, Ferreira CL, Medeiros AP, et al. Electromyographic indices, orofacial myofunctional status and temporomandibular disorders severity: A correlation study. J Electromyogr Kinesiol 2012;22:266– 72. 4 Santana-Mora U, Cudeiro J, Mora-Bermúdez MJ, et al. Changes in EMG activity during clenching in chronic pain patients with unilateral temporomandibular disorders. J Electromyogr Kinesiol 2009;19(6):e543– 9. 5 Elwood M. Critical Appraisal of Epidemiological Studies and Clinical Trials. Oxford: Oxford Univ Press; 2007: 256–60. 6 Tanaka E, Detamore MS, Mercuri LG. Degenerative disorders of the temporomandibular joint: Etiology, diagnosis, and treatment. J Dent Res 2008;87:296–307. 7 del Palomar AP, Santana-Penín U, Mora-Bermúdez MJ, Doblaré M. Clenching TMJs-loads increases in partial edentates: A 3D finite element study. Ann Biomed Eng 2008;36:1014–23. 8 Santana-Mora U, López-Cedrún J, Mora MJ, Otero XL, Santana-Penín U. Temporomandibular disorders: The habitual chewing side syndrome. PLoS ONE 2013;8(4): e59980.
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