He Could Only Open His Mouth Two Centimetres

Quick answer: A jaw that will not open because of a tooth infection is called trismus, and it is a warning sign. It means the infection has spread into the chewing muscles. Below about two centimetres of opening, the infection is deep enough that hospital assessment is usually the right call.

The call

Amir, 29, works near Tzomet HaMesila and phoned on a Monday morning barely able to speak clearly. He had had a sore wisdom tooth for a week. Over the weekend it had become impossible to eat, and by Monday he could get two fingertips between his teeth and no more.

Measured properly, his opening was 21mm. Normal is 40 to 55mm.

What we found

Lower left wisdom tooth, partly erupted, with an infection that had clearly spread beyond the gum flap. Firm, tender swelling extending backwards along the jaw and up towards the ear rather than out into the cheek. Temperature 38.1. Tender lymph nodes. He felt genuinely unwell.

Crucially: no swelling in the floor of the mouth, tongue sitting normally, swallowing intact, voice normal, breathing normal.

Trismus is not simply pain limiting movement. It happens when infection tracks into the spaces around the muscles that close the jaw — the submasseteric and pterygomandibular spaces — and those muscles go into spasm. The significance is anatomical: infection that has reached those planes has left the confines of the gum and bone and entered the deep tissues of the face and neck, where it can travel further.

The degree of opening is a rough but useful measure of depth:

• 30 to 40mm — sore, guarded, usually still a dental-chair problem.
• 20 to 30mm — deeper spread. Urgent, and the threshold for referral depends on the other findings.
• Under 20mm — deep space infection. Hospital.
• Any trismus with difficulty swallowing, a raised tongue, a changed voice or neck swelling — hospital immediately, regardless of the number.

There is a practical dimension too. You cannot safely operate on a mouth that will not open. Access for anaesthesia, drainage and extraction all become marginal.

What we did

We drained what we could reach: an incision into the accessible part of the swelling under local anaesthetic, releasing pus, plus irrigation under the gum flap. That bought immediate relief.

But with 21mm of opening, a temperature and involvement of the deep spaces, we referred him to the maxillofacial unit the same day rather than attempting the extraction. We phoned ahead, sent his x-ray and a written summary, and made sure he understood he was going now, not tomorrow.

He was admitted overnight for intravenous antibiotics, scanned, and had a formal drainage and extraction under general anaesthetic the following morning.

The outcome

Discharged after two nights. His opening returned to normal over about three weeks, helped by gentle jaw exercises — trismus takes time to resolve even after the infection has gone, because the muscle has been inflamed.

He had the opposite wisdom tooth removed electively four months later.

What to do if this happens to you

1. Measure your opening. Stack your fingers vertically between your front teeth. Three fingers is roughly normal; one is not.
2. Go to hospital immediately if you also have difficulty swallowing, drooling, a changed voice, neck swelling or any breathing difficulty.
3. Do not delay because you can still manage soft food. Trismus worsens over hours.
4. Do not force the jaw open.
5. Keep taking fluids. People with trismus become dehydrated quickly.
6. Expect a slow recovery of opening even after the infection resolves, and do the exercises you are given.

Struggling to open your mouth? Call Ramat Beit Shemesh Urgent Dental Care immediately on 055-985-8845 · WhatsApp https://wa.me/972559858845 · Harav Kook 28/1, Beit Shemesh.

Based on real cases treated at the clinic. Names have been changed.