Assessment of the effect of Botulinum toxin injection on the frequency of luxation and TMJ Pain in patients with TMJ dislocation either chronic recurrent dislocation or subluxation

Diagnostic procedure:

1. Patient questionnaire: a questionnaire will be recorded by the examiner including the Chief complaint, Personal data, and Medical history.

2. Consent: Informed consent will be obtained from patients to participate in the study.

3. Clinical examination: TMJ examination with specific emphasis on the TMJ regarding pain, clicking, maximum inter-incisal mouth opening, lateral excursions, and muscle examination is done (Inspection and palpation).

   o operative procedures:

   • The surgical field will be scrubbed and prepared in a standard sterile fashion using alcohol and topical anesthesia is applied at point of needle insertion

   A-Botulinum Toxin Type A injection:

   BTX-A vial will be reconstituted with normal saline to obtain a 10 U/0.1 ml solution, 0.25 ml of this solution containing 25 U BTX-A will be loaded in a 1-ml insulin syringe attached to a needle with 27 Gauge and 31 mm length.

   B-The placebo comparator Injection:

   Patients in the placebo arm will receive equivalent volumes of placebo solution (Normal Saline).

   • Procedure

   - With the patient sitting in an upright position on the dental chair, the lateral ptreygoid muscle will be approached extra orally through the space formed by the zygomatic arch and the sigmoid notch of the mandible below the center of the zygomatic arch. The needle will be advanced perpendicular to the skin with the mouth closed. The muscle is approximately 3 to 4 cm deep. Aspiration will be carried out to avoid unintentional intravascular injection.

   According to the assigned group, the inferior head of Lateral pterygoid muscle will be injected with BTX-A or normal saline

   - The patient will be instructed to remain in an upright position for 6 h (to reduce diffusion into pharyngeal muscles which may cause dysphagia and nasal regurgitation).

   - Patients will be recalled weekly during the first month, then monthly after 3 months

   • Post-operative care:

   Paracetamol 1000 mg will be prescribed as needed Any excessive mouth opening should be avoided Soft diets are advised in the first 48 hours after injection

Inclusion Criteria:

1. patients with TMJ habitual or recurrent dislocation
2. Age ≥ 18 years
3. The willingness of the patient to receive relative painful injections and to follow instructions

Exclusion Criteria:

1. Patients with neurogenic cause of TMJ Hypermobility.
2. Drug-induced TMJ Hypermobility