Assessment of Electromyographic Changes in a Patient with Masseter Hypertrophy and Muscle Pain after Botulinum Injections: A Case Report and 5 Months Follow-up

J Contemp Dent Pract. 2022 Feb 1;23(2):226-231.


Aim: To determine if botulinum injections in masseters could be an option to avoid surgery and prolonged treatment with occlusal splints and/or drugs to care for both painful bruxism and cosmetic improvement in a patient with a square jaw, bruxism, and orofacial pain.

Background: Masseter muscle hypertrophy (MMH) is a benign, unilateral, or bilateral, painless enlargement in the lower face. It presents as a symmetrical or asymmetrical increase in the masseter muscle. Masseter muscle hypertrophy (MMH) sometimes can be related to bruxism symptoms like muscle and/or temporomandibular joint (TMJ) pain.

Case description: A 38-year-old woman complained of bilateral pain at palpation in the masseter body. She also complained about esthetics because of the prominent masseter muscle in the face and square face shape. A diagnosis of bruxism-related myalgia was performed, and treatment with botulinum injections into the masseter muscles was opted for. An oral electromyography was performed to detect the electrical muscular activity of masseter muscles over time.

Conclusion: After a drastic reduction in the mean electrical activity immediately after the botulinum injections, a progressive increase in strength over time was noted, testifying about the decrease in the effect of botulinum over time. The pain disappeared for 5 months after the injections of botulinum. The reduction of the masseter muscle mass led to a softening of the face shape.

Clinical significance: This case report shows that treatment with botulinum can lead, in the short term, to a reduction in orofacial pain due to a decrease in muscle electrical activity.

Keywords: Botulinum toxin; Dental esthetics; Masseter; Occlusion; Orofacial pain Sleep bruxism..

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Botulinum Toxins, Type A* / therapeutic use
  • Bruxism* / complications
  • Bruxism* / drug therapy
  • Esthetics, Dental
  • Facial Pain / drug therapy
  • Facial Pain / etiology
  • Female
  • Follow-Up Studies
  • Humans
  • Hypertrophy / drug therapy
  • Injections, Intramuscular
  • Masseter Muscle / abnormalities
  • Myalgia / chemically induced
  • Myalgia / drug therapy


  • Botulinum Toxins, Type A

Supplementary concepts

  • Masticatory Muscles, Hypertrophy of