If your jaw will not open properly after dental work, the most likely explanation is trismus, a temporary tightening or spasm of the jaw muscles, and most cases settle in under 2 weeks. Normal adult mouth opening is generally around 40 to 60 mm between the front teeth, and anything under about 35 mm is usually regarded as restricted. A rough home check is whether you can fit two to three stacked fingers vertically between your front teeth. This article explains why trismus happens after dentistry, what helps, and the specific signs that mean you should be seen urgently rather than waiting it out.
Key Takeaways
- Trismus means restricted mouth opening caused by spasm or tightening of the jaw muscles, and it is a recognised, expected consequence of some dental procedures.
- The most common triggers are surgical removal of impacted wisdom teeth, a lower jaw nerve block injection near the medial pterygoid muscle, prolonged wide opening during a long appointment, and infection.
- Most post-dental trismus resolves in less than 2 weeks, with many cases easing in about a week.
- Under about 35 mm of opening is generally considered restricted. Two to three stacked fingers between the front teeth is a rough home guide.
- Management is conservative: ice in the first 48 hours, moist heat after that, gentle controlled stretching, soft diet and suitable anti-inflammatory pain relief.
- Fever, spreading facial or neck swelling, difficulty swallowing or breathing, drooling, or rapidly worsening restriction need urgent review, not watchful waiting.
Why Your Jaw Tightens Up After Dental Treatment
The muscles that open and close your jaw sit in a fairly confined space. When any of them become inflamed or swollen, there is simply less room for them to move, and the result is a jaw that feels stiff and will not open as far as usual.
Wisdom tooth surgery
This is the most common cause by a wide margin. Removing an impacted lower wisdom tooth involves working close to the muscles at the back of the jaw, and the surgery itself creates inflammation and swelling. That swelling limits the space the muscles have to move, which creates tension and restricts jaw motion for roughly two weeks in many cases.
This is expected. It is not a sign that anything went wrong. Our guide to wisdom teeth removal and anaesthetic options and the article on dissolvable stitches after wisdom teeth cover the rest of the recovery picture.
The lower jaw injection
An inferior alveolar nerve block, the injection used to numb the lower teeth, passes through or near the medial pterygoid muscle. If the needle irritates that muscle, or if there is a small amount of bleeding into it, the muscle can respond by tightening. This can start a day or two after the appointment rather than immediately, which catches people off guard.
Holding your mouth open for a long time
A long appointment means sustained wide opening. Muscles held stretched for an extended period can become sore and stiff afterwards, in much the same way any muscle does after unaccustomed work. This is more likely if you already clench or grind, and our article on jaw clenching versus teeth grinding explains why those muscles may already be working hard.
Infection
Infection is the cause that changes the plan. When infection spreads into the tissue spaces around the jaw muscles, restricted opening is one of the signs. This is why trismus that is worsening rather than improving, especially alongside fever or spreading swelling, is treated as urgent. See our articles on facial swelling from spreading dental infection and pericoronitis.
How Long Has Your Jaw Been Stiff?
| Time since treatment | What is usually going on | What to do |
|---|---|---|
| First 48 hours | Peak swelling and inflammation from the procedure itself. Stiffness is usually at its worst here. | Ice packs on the outside of the cheek, soft diet, anti-inflammatory pain relief if suitable for you, rest the jaw. Do not force stretching yet. |
| 3 to 7 days | Swelling starting to subside. Muscles still guarding. Many people notice gradual improvement day by day. | Switch to moist heat. Begin gentle, controlled opening exercises within a comfortable range. Keep eating soft food. Contact your dentist if it is not improving at all. |
| 1 to 2 weeks | Most cases are resolving or resolved. Some residual tightness at the end of the range is common. | Continue gentle stretching and heat. Gradually return to normal diet. Book a review if opening is still clearly limited. |
| Beyond 2 weeks or getting worse | Not the usual pattern. May indicate ongoing infection, a joint issue, or muscle problems needing specific management. | Arrange professional evaluation. Do not keep waiting. If there is fever, spreading swelling or difficulty swallowing, seek urgent care the same day. |
The Self-Check At Home
You do not need a ruler, though one helps. Stack your index, middle and ring fingers on top of each other and try to slide them vertically between your upper and lower front teeth.
- Three fingers comfortably: opening is likely within a normal range.
- Two fingers: restricted, but within the range commonly seen after wisdom tooth surgery.
- Less than two fingers, or one finger: significantly restricted. Worth reporting to your dentist, particularly if it is not improving.
If you want a number, measure the gap between the biting edges of your upper and lower front teeth at maximum comfortable opening. Around 40 to 60 mm is generally normal for adults, and under about 35 mm is usually regarded as restricted. Measuring every couple of days is more useful than one reading, because the trend matters.
What Actually Helps
Temperature, in the right order
Ice in the first 48 hours, applied to the outside of the cheek in short spells, helps limit swelling. After 48 hours, switch to moist heat. A warm damp face washer held against the cheek helps relax the muscles. Using heat too early can increase swelling, so the order matters.
Gentle stretching, not forcing
Once past the first couple of days, controlled opening exercises help restore range. The principle is gentle and frequent, not hard and occasional. Open to the point of mild stretch, not pain, hold briefly, then relax. Repeat a handful of times, several times a day. Some people use stacked tongue depressors or a purpose-made device as a guide.
Forcing your jaw open past the point of pain is counterproductive. It provokes more muscle guarding. Our article on TMJ jaw exercises and self-help covers technique in more detail.
Soft diet
Not because chewing is dangerous, but because repeatedly asking sore muscles to work hard delays settling. Avoid anything requiring a wide bite, such as a thick burger or a whole apple.
Pain relief
Anti-inflammatory pain relief, if it is suitable for you, addresses both pain and the inflammation limiting movement. Check with your pharmacist or doctor if you take other medications or have conditions that make anti-inflammatories unsuitable.
Physiotherapy
For cases that are slow to settle, a physiotherapist experienced in jaw problems can add targeted soft tissue work and a structured exercise programme.
Red Flags That Need Urgent Review
Most trismus after dentistry is temporary and settles on its own. These signs are the exceptions, and they warrant being seen the same day rather than waiting.
- Fever or feeling generally unwell
- Swelling spreading across the face, under the jaw, or down into the neck
- Difficulty swallowing, or pain on swallowing
- Any difficulty breathing, which is a medical emergency
- Drooling, or inability to manage saliva
- Restriction that is rapidly getting worse rather than slowly better
- Severe pain alongside the restricted opening
These can indicate infection spreading into the tissue spaces around the jaw and airway. Our dental emergency guide covers when to attend a hospital emergency department rather than a dental practice, and antibiotics for tooth infection explains where medication fits.
When there was no dental treatment
If your jaw has become restricted without any recent dentistry, the possible causes are broader, including jaw joint problems, disc displacement, arthritis or trauma. That needs its own assessment rather than being managed as post-treatment trismus. Our articles on TMJ disorder and jaw clicking when you open are a starting point.
Common Questions
How long does trismus last after wisdom teeth removal?
Most cases settle in less than 2 weeks, and many ease noticeably within about a week. Stiffness is usually worst in the first 48 hours and then improves gradually. If your opening is still clearly limited past two weeks, or is getting worse rather than better, arrange a review.
Is it normal that my jaw is worse two days after the injection, not straight after?
Yes, this pattern is recognised. Muscle irritation from a nerve block injection can take a day or two to build, so the stiffness may peak after you have already started to feel otherwise better. It generally follows the same settling timeline as other causes.
Should I be forcing my jaw open to stretch it?
No. Gentle stretching to the point of mild resistance is helpful, forcing past pain is not. Sore muscles respond to being pushed hard by tightening further. Little and often is the approach that works.
Can trismus become permanent?
Prolonged restricted opening can lead to scar tissue and lasting stiffness in some cases, which is exactly why persistent trismus should be evaluated rather than tolerated indefinitely. The great majority of post-dental cases resolve fully with conservative management.
Does numbness that has not worn off relate to trismus?
They are separate issues that can occur after the same appointment. Restricted opening is a muscle problem, while lingering numbness relates to the nerve. If numbness has persisted well beyond the expected time, see our articles on how long dental numbness lasts and post-extraction nerve numbness.
This article is general information only and is not a substitute for individual dental or medical advice. If you have concerns about restricted jaw opening, particularly with fever, spreading swelling or difficulty swallowing or breathing, seek prompt professional care. Please speak with a qualified practitioner about your situation.
If your jaw is stiff after treatment and you are not sure whether it is settling as expected, the team at Lumi Dental can assess it and give you a clear plan. You can see current offers on our current deals page or read more on the general dentist page. Lumi Dental is open Monday to Saturday, with Sunday by appointment.
