Jaw Locked or Can't Open Your Mouth? It Might Be Your Wisdom Tooth – London Emergency Guide
South Ken MD Team
If you find yourself unable to open your mouth fully, or your jaw feels locked or stiff alongside wisdom tooth pain, this can be a concerning experience. The clinical term for restricted mouth opening is trismus, and it is one of the most common reasons patients seek urgent dental care in London. Understanding what may be causing it—and when it requires prompt assessment—can help you make informed decisions about your care.
What Is Trismus?
Trismus refers to a restricted ability to open the mouth. In healthy adults, normal mouth opening is typically between 35 and 55 millimetres—roughly the width of three fingers stacked vertically between the upper and lower front teeth. When trismus is present, this range can be reduced to 20 millimetres or less, making eating, speaking and even swallowing uncomfortable or difficult.
Trismus is not a condition in itself but rather a symptom of an underlying problem. It occurs when the muscles responsible for jaw movement—primarily the masseter and medial pterygoid muscles—go into spasm. This spasm can be triggered by infection, inflammation, trauma or, in some cases, temporomandibular joint (TMJ) dysfunction.
In the context of wisdom teeth, trismus from a wisdom tooth is particularly common because the lower wisdom teeth sit in close proximity to these muscles. When infection or inflammation develops around an impacted or partially erupted wisdom tooth, the surrounding tissues swell and the muscles respond by tightening, restricting mouth opening.
Wisdom Tooth Infection and Jaw Locking
One of the most frequent causes of a locked jaw or restricted mouth opening in adults aged 17 to 30 is an infected or impacted wisdom tooth. The condition most commonly associated with this is pericoronitis—an infection of the gum tissue (operculum) overlying a partially erupted wisdom tooth.
Pericoronitis develops when bacteria become trapped beneath the gum flap covering a wisdom tooth that has not fully emerged. Food debris and bacteria accumulate in this space, leading to localised infection. As the infection progresses, the surrounding soft tissues swell, and the inflammation can spread to the muscles that control jaw movement.
When this happens, patients may notice a gradual reduction in how far they can open their mouth. In some cases, the restriction develops over 24 to 48 hours and can become severe enough that the patient struggles to eat solid food or even take medication orally. This is a clear indication that the infection may be worsening and that a dental assessment should be arranged promptly.
How Infection Causes Trismus
When a wisdom tooth becomes infected, the inflammatory response causes swelling in the tissues surrounding the jaw muscles. These muscles go into protective spasm, physically restricting how far the mouth can open. The more significant the infection, the greater the restriction tends to be.
TMJ vs Infection – How to Tell the Difference
Not all cases of jaw locking are related to wisdom teeth. Temporomandibular joint (TMJ) dysfunction is another common cause of restricted mouth opening, and it is important to understand the differences so that appropriate care can be sought.
Infection-Related Trismus
- Develops over hours to days
- Accompanied by swelling, redness or pus
- Often one-sided, near the wisdom tooth
- May be accompanied by fever or malaise
- Bad taste or discharge from the gum area
- Pain worsens progressively
TMJ-Related Jaw Locking
- May be intermittent or recurrent
- Clicking, popping or grinding sounds
- Often affects both sides of the jaw
- No swelling, fever or discharge
- Associated with jaw clenching or bruxism
- Pain may ease and return in episodes
The critical distinction is that infection-related trismus typically worsens over time and is accompanied by signs of infection such as swelling, heat, redness or discharge. TMJ dysfunction, by contrast, tends to fluctuate and is not accompanied by systemic symptoms such as fever. However, only a qualified dental professional can make a definitive assessment, and patients who are uncertain about the cause should seek clinical evaluation.
When Is It an Emergency?
Whilst not every case of restricted mouth opening constitutes an emergency, certain signs indicate that the situation may be worsening and that prompt dental assessment is advisable. The following red-flag indicators should be taken seriously:
Red-Flag Indicators Requiring Urgent Assessment
- Swelling spreading toward the cheek, eye or neck – this may suggest the infection is extending beyond the immediate tooth area into deeper tissue spaces
- Fever or feeling systemically unwell – a raised temperature alongside dental swelling can indicate the infection is producing a systemic response
- Difficulty swallowing (dysphagia) – swelling that affects the throat or floor of the mouth can compromise the airway and requires urgent assessment
- Increasing restriction of mouth opening – trismus that is getting progressively worse rather than improving suggests the underlying cause may be escalating
- Severe pain not relieved by over-the-counter analgesics – pain that does not respond to ibuprofen or paracetamol at recommended doses may indicate significant infection or abscess formation
If any of these signs are present, arranging a timely dental assessment is advisable. Untreated dental infection can, in rare but serious cases, spread to deeper tissue planes, potentially causing airway compromise or systemic infection. Early clinical intervention reduces the risk of complications and typically leads to more straightforward treatment.
If you are experiencing increasing jaw restriction or facial swelling, arranging a prompt dental assessment is advisable. Our South Kensington clinic provides urgent wisdom tooth assessments seven days a week, subject to clinical triage and availability.
Arrange an AssessmentWhat Happens at an Emergency Assessment
When a patient presents with a locked jaw or restricted mouth opening, an emergency dentist in London will follow a structured assessment process to determine the cause and severity of the problem.
Clinical history
The dentist will ask about the onset of symptoms, their duration, severity and progression. They will also ask about any recent dental treatment, medication use and relevant medical history.
Clinical examination
The dentist will examine the mouth, jaw and face, assessing the degree of mouth opening, palpating the muscles of mastication, and checking for swelling, redness, discharge or lymph node involvement.
Radiographic assessment
An X-ray (typically a dental panoramic tomograph or periapical radiograph) is usually taken to assess the position and condition of the wisdom tooth, check for abscess formation and evaluate the surrounding bone.
Clinical diagnosis
Based on the findings, the dentist will determine whether the trismus is caused by infection (pericoronitis or abscess), TMJ dysfunction, or another condition, and will explain the findings clearly to the patient.
Treatment Options
Treatment will depend on the clinical findings and the severity of the presentation. Common approaches include:
- Irrigation and debridement – cleaning beneath the gum flap (operculum) to remove trapped debris and reduce bacterial load; this can provide significant relief in cases of pericoronitis
- Antibiotics – where clinically indicated, antibiotics may be prescribed to manage active infection; antibiotics alone do not treat the underlying cause and are used alongside other interventions
- Pain management advice – guidance on appropriate analgesic use, including ibuprofen and paracetamol, to manage discomfort during the acute phase
- Wisdom tooth extraction – if the wisdom tooth is impacted, recurrently infected or unlikely to erupt into a functional position, extraction may be recommended; this is typically performed once the acute infection has been managed
- Referral for complex cases – if the tooth is deeply impacted, close to the inferior alveolar nerve, or the infection involves deep tissue spaces, referral to an oral surgeon may be appropriate
It is important to understand that extraction is only recommended when it is clinically indicated. Not every wisdom tooth requires removal, and the decision is based on clinical examination, radiographic findings and the patient’s individual circumstances.
Why Prompt Assessment Matters
Dental infections, particularly those involving impacted wisdom teeth, have the potential to worsen if left without clinical assessment. The tissues around the lower jaw contain several anatomical spaces into which infection can spread, including the submandibular, sublingual and parapharyngeal spaces.
Whilst the majority of wisdom tooth emergencies are managed straightforwardly with appropriate clinical care, delayed assessment can result in more extensive infection, increased pain and more complex treatment. Seeking timely dental advice allows the condition to be assessed at an earlier stage, when management is typically simpler and more predictable.
A Calm Perspective
Most cases of wisdom tooth-related trismus are manageable with prompt clinical care. The purpose of seeking assessment is not to assume the worst, but to ensure the right treatment is provided at the right time. Early intervention almost always leads to better outcomes.
Conclusion
If you can’t open your mouth fully and suspect a wisdom tooth may be the cause, understanding the difference between infection-related trismus and TMJ dysfunction is an important first step. Whilst many cases resolve with appropriate treatment, the presence of spreading swelling, fever, difficulty swallowing or worsening restriction should prompt a timely dental assessment.
A structured clinical examination, supported by X-rays and a thorough history, allows your dentist to identify the cause and recommend appropriate management—whether that involves irrigation, antibiotics, extraction or onward referral.
Patients experiencing wisdom tooth symptoms can find further information on our wisdom tooth emergency page.
Need an assessment? Our South Kensington clinic provides urgent wisdom tooth assessments seven days a week, subject to clinical triage and availability. Patients can contact the team on 020 7183 2362 to arrange an appointment.
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