Trismus, often called “lockjaw,” is characterized by the limited ability to open the mouth. This restriction occurs when the muscles used for chewing (muscles of mastication) become stiff, inflamed, or go into spasm. A normal mouth opening is typically 40 to 60 millimeters; less than 35 millimeters is considered trismus. Trismus is a symptom, not a disease, and its duration depends heavily on its root cause. Determining the origin of the jaw restriction is the first step in determining the expected recovery timeline.
Identifying the Underlying Cause
Determining the specific trigger is important because the mechanism of injury directly influences the severity and duration of the symptom. The most frequent cause of temporary trismus is inflammation following routine dental or oral surgery, often occurring after a difficult lower wisdom tooth extraction. The irritation causes the muscles to tighten as a protective response, limiting movement.
Infection is another common source, such as an abscess or pericoronitis. Swelling from the infection irritates nearby jaw muscles, inducing a spasm. Trismus may also arise from direct trauma to the face or jaw, causing internal bleeding or damage to the temporomandibular joint (TMJ). TMJ disorders can lead to chronic or intermittent trismus due to joint derangement or muscle hypertonicity.
A more challenging category is trismus associated with head and neck cancer treatment, specifically radiation therapy. Radiation causes fibrosis, the formation of permanent scar tissue in the masticatory muscles. This fibrotic change results in a physical, structural shortening of the muscle, distinct from temporary inflammation or spasm.
Typical Recovery Timelines
The prognosis for trismus varies significantly based on the cause, ranging from a few days to lifelong management. Restriction resulting from post-surgical inflammation (e.g., after wisdom tooth removal or a dental injection) is typically acute and self-limiting. Most patients experience substantial improvement within three days, with nearly full resolution often occurring within one to two weeks. If the limited opening persists past two weeks, it may indicate a secondary complication like a low-grade infection.
When the condition is due to an odontogenic infection or abscess, the duration is tied to the successful treatment of the underlying issue. Once antibiotic therapy is initiated and the infection is eliminated, the associated muscle spasm and swelling usually subside quickly. Full recovery often occurs within a few days to two weeks following the start of appropriate medical care.
Restriction caused by trauma or chronic TMJ disorders presents a highly variable timeline, sometimes requiring sustained intervention. Recovery can take weeks to several months, depending on the extent of damage to the joint or muscle tissue. This type of restriction often requires ongoing physical therapy to restore the full range of motion.
The most challenging and chronic form is radiation-induced trismus, which is often permanent and requires lifelong management. Fibrotic tissue changes continue to develop for months after radiation treatment concludes, and the condition may worsen before improvement begins. Recovery is measured in gradual functional gains over several months or years, focusing on consistent management to prevent further loss of mobility rather than full restoration.
Strategies for Promoting Jaw Mobility
The recovery timeline is best met or improved through active, consistent intervention. Physical therapy, focusing on gentle jaw stretching exercises, forms the foundation of treatment for almost all forms of trismus. These exercises aim to slowly increase the maximum mouth opening, often involving repeated passive stretching with the fingers or specialized mechanical devices. Consistency is necessary, with exercises performed multiple times daily, holding the stretch for several seconds each time.
The application of warm compresses to the affected area is an effective technique. Warmth helps relax the contracted muscles of mastication and increases blood flow, which can improve elasticity before stretching exercises. Gentle massage of the jaw muscles can also help relieve tension and promote relaxation.
For managing discomfort and reducing inflammation, non-steroidal anti-inflammatory drugs (NSAIDs) are frequently recommended. In cases of severe muscle spasm, a physician may prescribe muscle relaxants to ease tightness. Throughout the recovery period, patients should adhere to a soft diet to minimize strain on the jaw muscles.