Although the limitation of movement associated with post-injection trismus is usually minor, it is possible for much more severe limitation to develop.
The average inter-incisal opening in case of trismus is 13,7mm (range 5 to 23 mm)
- In the acute phase of trismus, pain produced by hemorrhage leads to muscle spasm and limitation of movement.
- The second, or chronic, phase usually develops if treatment is not begun.
Chronic hypo-mobility is secondary to organization of the hematoma, with subsequent fibrosis and scar contracture.
Infection also may produce hypo-mobility through increased pain, increased tissue reaction (irritation)ans scarring.
Extraction / Surgery
- Patients who have had mandibular third molars surgically removed frequently have mild to moderate trismus.
- This inability to open the mouth interferes with the patient’s normal oral hygiene and eating habits.
- Patients should be warned that they will be unable to open their mouths normally after surgery.
- The trismus gradually resolves, and the ability to open the mouth should return to normal by 7-10 days after surgery.
- If pain, edema, and trismus have not greatly improved by 7 days after surgery, the surgeon should investigate why
- Local Anesthetic Administration
- Use a sharp, sterile, disposable needle.
- Properly care for and handle dental local anesthetic cartridges.
- Use aseptic technique. Contaminated needles should be changes immediately.
- Practice atraumatic insertion and injection technique.
- Avoid repeat injections and multiple insertions into the same area through knowledge of anatomy and proper technique.
- Use minimum effective volumes of LA
- Extraction / Surgery (Minimizing Effect)
- Practice atraumatic surgical technique
- Educate the patient properly (post-operative care instructions)
Trismus is not Always preventable
- With mild pain and dysfunction (the patient reports minimum difficulty opening his or her mouth)
- Arrange an appointment for examination.
- In the intrim, prescribe
- Heat therapy
- Warm saline rinses
- Muscle relaxants (if necessary) to manage the initial phase of muscle spasm.
Heat Therapy: consists of applying hot, moist towel to the affected area for approximately 20 min every hour.
Warm Saline Rinse: a teaspoon of salt is added to a 12 ounce glass of warm water and held in the mouth on the involved side (and spit out) to help relieve the discomfort of trismus.
- Aspirin (325 mg) is usually adequate as an analgesic in managing pain associated with trismus. Its anti-inflammatory properties also are beneficial.
- On rare occasion, Codeine may be necessary (30 to 60 mg q6h) if the discomfort is more intense
Muscle Relaxant: Diazepam (approximately 10 mg bid) or other benzodiazepine is used if deemed necessary
- The patient should be advised to initiate physiotherapy consisting of opening and closing the mouth, as well as lateral excursions of the mandible for 5 min every 3-4 hours.
- Chewing gum (sugar free) is yet another means of providing lateral movement of the TMJ.
Avoid further dental treatment in the involved region until symptoms resolve and the patient is more comfortable.
If continued dental care in the area is urgent, as with infected painful tooth, it may prove difficult to achieve effective pain control when trismus is present. The vazirani-Akinosi mandibular nerve block usually provides relief of the motor dysfunction, permitting the patient to open his/her mouth and allow the administration of the appropriate injection for clinical pain control, if needed.
In virtually all cases of trismus related to intra-oral injections that are managed as described, patients report improvement within 48-72 hours.
Therapy should be continued until the patient is free of symptoms.
If pain and dysfunction continue unabated beyond 48 h consider the possibility of infection. Antibiotic should be added to the treatment regimen described and continued for 7 full days.
Complete recovery from injection-related takes about 6-weeks, with a range of 4 to 20 weeks.
For severe pain or dysfunction, if no improvement is noted within 2-3 days without antibiotics or within 5-7 days with antibiotics, or if the ability to open the mouth has become limited, the patient should be referred to an oral and maxillo-facial surgeon for evaluation.
Tempromandibular join involvement is rare in the first 4-6 weeks after injection.
Surgical intervention to correct chronic dysfunction may be indicated in some instances
- Handbook of Local Anesthesia 5th edition (Malamed)
- Contemporary Oral and Maxillofacial Surgery 5th edition (Hupp. Tucker. Ellis)