Why can't I open my mouth after a dental injection?
Not being able to open your mouth fully after a dental injection is called trismus. It usually happens when the needle for a lower-jaw injection passes through a chewing muscle or causes a small bruise, so the muscle tightens in a protective spasm. It typically settles within two weeks with warmth, soft food and gentle exercises. Stiffness that worsens after two to three days, with swelling or fever, needs prompt review; Creative Arts in Dubai can assess it.
Who treats you here Dr. Firas Osman Oral & Maxillofacial Surgeon & Implantologist · Dr. Valeriia Kozachenko Specialist Orthodontist
Every dentist’s licence can be checked on the DHA Sheryan medical directory.
What is trismus, and how much should your mouth open?
Trismus is restricted mouth opening caused by spasm, inflammation or injury of the jaw-closing muscles. It is sometimes called lockjaw, although after dental treatment it is a local muscle problem, not the infection that name is often associated with. The jaw feels tight and sore, opening stops part way, and yawning, eating or brushing the back teeth becomes awkward.
Most adults can open wide enough to fit roughly three of their own fingers, stacked, between the front teeth. If you can fit only one or two after dental work, that is trismus. Measuring with your fingers each day is a simple way to tell whether it is improving.
The key muscles involved are the medial pterygoid, on the inside of the lower jaw, and the masseter, the large chewing muscle on the outside of the cheek. Both are close to where dentists work on the lower back teeth.
Why is my jaw stiff after the dentist? The common causes
When the stiffness started and what came with it are the most useful clues.
| Cause | When it starts | What you notice | What it usually needs |
|---|---|---|---|
| Injection into the muscle | Within hours to a day of a lower-jaw injection | Tight, sore jaw on the injection side; little or no swelling | Warmth, soft food, gentle exercises; settles over days |
| Bruise (haematoma) from the injection | Same day or next day | Stiffness, sometimes a bruise inside the mouth or on the cheek | Time and warmth after the first day; review if it grows |
| Needle-track infection | Often two to three days after the injection | Stiffness and pain getting worse, not better; swelling, fever | Prompt dental review; treatment of the infection |
| After wisdom tooth removal | First day or two after surgery | Stiffness with swelling that peaks around day two or three | Usual post-operative care; improves as swelling settles |
| Long appointment | Straight after treatment | Tired, achy jaw joint and muscles after keeping the mouth open | Rest, warmth and soft food for a few days |
| Infected wisdom tooth (pericoronitis) | With a painful, swollen gum at the back | Stiffness, pain swallowing, bad taste, sometimes fever | Dental treatment of the infection; urgent if swelling spreads |
Ordinary swelling after surgery has its own pattern; our guide to swelling after oral surgery covers it day by day.
How long does trismus last after a dental injection?
Trismus after dental treatment is usually temporary. Most cases from an injection or a long appointment improve noticeably within a few days and typically settle in less than two weeks. After wisdom tooth surgery, stiffness tends to follow the swelling: worst around the second or third day, then easing over the following week.
The direction matters more than the exact day. A jaw that opens a little further each day is healing. A jaw that is getting tighter and more painful after the second or third day, especially with swelling or a raised temperature, suggests infection and should be checked promptly, not treated with exercises.
Normal recovery or a reason to be seen?
Use this to decide whether to wait, call the clinic, or go to hospital.
| Usually normal | Call the clinic | Hospital emergency department | |
|---|---|---|---|
| Opening | Improves a little each day | No better after two to three days, or getting worse | Cannot open enough to drink, or the jaw is stuck open |
| Pain | Achy, controlled by pain relief as directed | Increasing or throbbing pain | Severe pain with spreading swelling |
| Swelling | Mild, peaks by day two or three after surgery | Swelling that keeps increasing after day three | Swelling spreading to the eye or neck |
| General | Feeling well | Fever, bad taste or pus | Difficulty breathing or swallowing |
The clinic is open daily, 10:00–20:00, without an overnight service.
What are the exercises to open the jaw?
Once the first sore day or two has passed and infection has been ruled out, gentle movement helps the muscle relax and stops it stiffening further. Exercises should be slow and comfortable: stretching that causes sharp pain makes the spasm worse.
- Warmth first. Hold a warm, moist cloth against the stiff side of the face for 15 to 20 minutes before exercising. After surgery, use cold packs on the first day and switch to warmth from the second day, or as your dentist advises.
- Open and close. Slowly open as far as is comfortable, hold for a few seconds, then close. Repeat about ten times.
- Side to side. With the mouth slightly open, slide the lower jaw gently left and right.
- Gentle stretch. Place a thumb on the upper front teeth and a finger on the lower ones and ease them apart a little at the end of an opening movement, without forcing.
- Little and often. Several short sessions a day work better than one long one.
Eat soft food cut into small pieces, avoid gum and very chewy food, and take pain relief only as directed on the label or by your dentist or pharmacist. Measure your opening with your fingers each morning so you can see progress.
Jaw still tight days after an extraction or injection? The oral surgery team at Creative Arts can check for infection and plan the next step.
Oral surgery at Creative ArtsWhat if my jaw locks closed or open?
Two jaw-joint problems can feel like trismus but behave differently. In a closed lock, the cartilage disc inside the jaw joint slips forward and blocks the joint, so opening stops suddenly, often after years of clicking that then stops. It is a joint problem rather than a muscle one, and it needs a TMJ assessment rather than forced stretching.
A jaw that is locked open and cannot close, usually after a very wide yawn or a long appointment, may be dislocated. Do not try to force it shut: go to a hospital emergency department, where it can be put back safely. If the jaw also aches on one side when it is working normally, see our page on jaw pain on one side.
Can trismus be prevented, and who treats it at Creative Arts?
Trismus cannot always be avoided, because the injection for the lower teeth has to pass near the chewing muscles. Telling the dentist if you have had jaw stiffness or clicking before, asking for short breaks during long appointments, and using a soft bite rest to support the jaw all reduce strain. After surgery, following the written aftercare and keeping the area clean lowers the chance of infection, the cause of trismus that matters most.
At Creative Arts, Dr. Firas Osman, Oral & Maxillofacial Surgeon & Implantologist, reviews stiffness after extractions and surgery and checks for infection. Dr. Valeriia Kozachenko, Specialist Orthodontist with a focus on TMJ and jaw function, assesses jaws that lock, click or stay stiff because of the joint. Numbness lasting longer than expected is a separate issue; see how long dental numbness lasts, and for a swollen lip after treatment, swollen lip after the dentist.
Who assesses a stiff jaw after dental treatment
Dr. Firas Osman checks stiffness after injections, extractions and surgery, including signs of infection; Dr. Valeriia Kozachenko assesses the jaw joint when it locks, clicks or stays stiff.
