Impact Age in Treatment Myofacial Pain with Temporomandibular Joint Disorders by Botox Injection

Background: Temporomandibular joint disorder is defined as a dysfunctional temporomandibular joint resulting from myoarthropathy of the masticatory system because of possible multifactorial nature of the disorder. Use of botulinum toxin A injections in treatment temporomandibular joint disorder that caused locally reduction of muscle activity by inhibiting acetylcholine release at the neuromuscular junction leading to decreases the muscle contractions, relief of myofacial pain and relieve the tenderness and restore functions of the temporo mandibular joint. The current study aim to evaluate the effect and duration of botulinum toxin type A (BTX-A) injections in the masseter, temporalis and lateral pterygoid muscles to treat Temporomandibular joint disorder symptoms in terms of pain intensity, maximum mouth opening, joint click and deviation on opening, with correlation of the patients age during three months following injection.

Materials and Method: The human sample consists of 28 patients suffered from myofacial pain, trismus, and TMJ sounds related to temporo mandibular joint dysfunction, males and females, with age range of (16-42) years. The subjects recruited for the study were patients attending and whose get treatment with 100 U dose of botulinum toxin type A (BTX-A) was injected with 100 mL at sites per masseter, temporalis and lateral pterygoid muscles that carried out at the dental clinics. The subjects were divided into four groups: Group I : consisted of 7 males and females patients, with age 16-22. Group II : consisted of 7 males and females patients with age 23-29. Group III : consisted of 7 males and females patients with age 30-36. Group IV : consisted of 7 males and females patients with age 37-43, all of these patients had symptoms of myofacial pain with Temporo mandibular joint disorders of whole groups. The clinical evaluation: An intraoral examination was performed to assess the dental occlusion and teeth and periodontal damage caused by bruxism or parafunction. The existence of dentoskeletal dysmorphosis was also evaluated. The initial and follow-up reports after the BTX-A injection identified four main TMD symptoms: pain intensity, maximum mouth opening, joint click, and deviation on opening, and clinical evaluation of efficacy and tolerance was performed at 10 days, 1 month and 3 months after the injection. Patients were re-examined to assess the pain intensity, maximum mouth opening, joint click, and deviation on opening, the symptom release, and average duration of the BTX effect.

Results: The mean age of patients was 29.4 ± 7.879 years (ranged from 16.2 to 42.0 years). A detailed sex and age distribution . Highest mean and ± SD (standard deviation) values of the pain intensity, maximum mouth opening, joint click and deviation on opening were recorded in Group IV (older age ), followed by Group III then Group II and Group I (younger age) in the initial (pre-treatment visit) and follow-up visits after the BTX-A injection. Inter study visits comparisons of each group regarding of the pain intensity, maximum mouth opening, joint click, and deviation on opening revealed, HS differences between the initial (pre-treatment visit) and follow-up visits after the BTX-A injection.

Conclusions: Aging process leads to change physiology of neuromuscular junctions and distinct muscle mass and strength loss. The decline of the effectiveness and duration of BTX-A used as same dosage in the older group than the younger group, so that mean BTX-A dosages of the older group was little higher required than those used of the younger group in treatment of temporomandibular joint disorders and pain relief.