Trouble Opening Your Mouth After Surgery

Almost everyone who has a lower third molar removed loses some mouth opening afterwards. The surgical term is trismus, and in the ordinary case it is not a complication at all — it is the predictable result of retracting and stretching the masseter and medial pterygoid muscles for twenty or forty minutes, plus a needle passing through the medial pterygoid on the way to the inferior alveolar nerve. Muscle that has been held open and injected through responds by guarding.

That is why the absolute number of millimetres you can open on any single day tells you very little on its own. Two people can both open twenty millimetres on day three and have completely different problems. What separates them is what the same measurement did over the preceding forty-eight hours. Ordinary post-surgical trismus is a curve that bottoms out and then rises. Infective trismus is a curve that keeps falling.

So the useful question after wisdom tooth surgery is never "how tight is my jaw?" It is "is my jaw tighter or looser than it was yesterday, and than the day before?" That single comparison, repeated daily, is the most informative thing a patient can bring to a phone call, and it is something no one but you can observe.

Most people open between 40 and 55 millimetres normally, and lose a substantial share of that in the first days after lower third molar surgery. Twenty to thirty millimetres on day two — roughly two stacked fingers — is a common finding after a straightforward lower removal, and a bony impaction requiring more retraction and bone removal can restrict further still.

A practical home measure is the finger test. Stack your own index, middle and ring fingers vertically and see how many fit between your upper and lower front teeth. Three of your own fingers is approximately normal opening. Two is meaningful restriction. One, or less than one, is severe restriction and is worth a call on its own regardless of the trend.

Record it the same way at the same time each day, ideally in the morning before you have eaten or taken anything. The point is not clinical precision. The point is a comparable series, so that on day five you can say "two fingers on Tuesday, one and a half on Wednesday, one today" instead of "it feels bad." The first version tells a surgeon what to do. The second does not.

The lower third molar sits at a crossroads of tissue spaces. Immediately medial to it is the pterygomandibular space, containing the medial pterygoid muscle and the inferior alveolar nerve. Lateral and above is the buccal space; below and forward, the submandibular and sublingual spaces; behind, the parapharyngeal and retropharyngeal spaces that run down the neck alongside the airway.

When infection escapes the socket, it does not spread randomly. It follows those planes, and the muscles it reaches respond by contracting. Involvement of the medial pterygoid produces exactly the picture this article is about: a jaw that will not open, with pain deep and behind rather than at the surface, often with less visible cheek swelling than the severity would lead you to expect. That last point is the trap. A face that does not look dramatic can still be housing a deep space infection, because the swelling is medial where you cannot see it.

This is also why worsening trismus is taken so seriously as a sign rather than a symptom. Progressive restriction is one of the few external clues that infection has moved from the socket into muscle and fascia, and the same spaces continue downward toward the airway. Trismus is the early part of a sequence whose late part is airway compromise, which is the reason a surgeon will want to see you today rather than at your scheduled review.

Worry when the restriction is going the wrong way. Opening that is tighter today than yesterday after day three, opening that had improved and has now closed down again, or restriction arriving together with fever, growing swelling, foul taste, or pain on swallowing — each of those is a reason for a same-day call rather than a wait-and-see. Any breathing or swallowing difficulty escalates it to 911.

Timing carries information of its own. Trismus present from the moment the anaesthetic wore off, tracking with a swollen face and steadily loosening, behaves like surgical trauma. Trismus that appears or deepens on day four to day seven, after you had begun to feel better, is a late arrival — and late arrivals in this recovery are usually infective, whether that is a localised infection in the socket or something spreading beyond it.

Fever is the single most useful thing to pair with the trend. A jaw that is tightening with no temperature and no new swelling may still need to be seen, but a jaw that is tightening with a temperature above 38°C is a different urgency, and the two facts together should be the first two sentences of your phone call.

Ordinary stiffness is a recovery event with a shape. It appears early, deepens for two to three days as swelling peaks, and then unwinds over one to two weeks. It responds to warmth from about day three, to gentle stretching, and to the simple passage of time. It does not come with a temperature, it does not migrate, and it does not interfere with swallowing. Nothing about it requires an antibiotic, and nothing about it requires an operation.

Progressive restriction has no such shape. It does not resolve on its own, it does not respond to stretching, and stretching an infected pterygomandibular space is uncomfortable without being useful. It needs the source dealt with — irrigation and debridement of the socket, drainage where a collection has formed, imaging where the spread is not obvious from outside, and antibiotics chosen for the organisms that live around a third molar. A patient at home cannot do any of those things, which is precisely why the distinction is worth the effort of measuring.

There is a third possibility that sits between the two and is neither dramatic nor benign: dry socket. Alveolar osteitis typically declares itself on day three to five with severe, radiating pain out of proportion to what you see, sometimes with a foul taste, and it can add its own guarding to the jaw. It is not an infection and it does not spread, but it does need to be seen and dressed, because the pain rarely settles unaided. The distinguishing feature is that dry socket brings pain without fever and without progressive swelling.

One more group deserves naming: people whose restriction has nothing to do with the socket at all. A joint that was already clicking before surgery, held wide open for an hour under general anesthesia, can be sore and limited afterwards from the joint rather than the wound. That presentation is usually bilateral, sits in front of the ear rather than behind the last tooth, and is not accompanied by intraoral swelling.

The assessment is short and mostly physical. A surgeon measures your interincisal opening in millimetres so there is an objective number to compare against the next visit, takes your temperature, palpates the floor of the mouth and under the jaw for firmness, checks whether the swelling is soft or tense, looks at the socket itself for food packing, exposed bone or discharge, and asks you to swallow while watching how you do it.

Imaging follows if the picture suggests spread. A panoramic film shows the socket, retained root fragments and the bone; it does not show a soft tissue collection, so a CT is what answers the question of whether pus has formed in a space and where. That distinction matters to patients who arrive expecting an x-ray to settle everything and find it does not.

Treatment then follows the finding, not the symptom. A socket packed with debris is irrigated. A localised infection at the socket may be managed with irrigation and oral antibiotics. A collection in a fascial space needs drainage, and drainage in a patient who can barely open may not be practical in an office chair — some of these cases belong in a hospital, under general anesthesia, with an airway secured by an anaesthetist. Being told your care is moving to a hospital is not a sign that something has gone wrong with your treatment; it is the correct answer to a deep space infection in a jaw that will not open.

1. Say the trend first: what your opening was two days ago, yesterday and today, in fingers or millimetres.
2. Say your temperature, the actual reading and when you took it.
3. Say whether swallowing has changed, and whether your voice sounds different to you.
4. Say the date of your surgery and which teeth were removed.
5. Say what medication you have taken, including any antibiotic, the dose and how many doses you have missed.

Gentle stretching helps ordinary muscular trismus and is reasonable from around day three, once the initial swelling has peaked. Slow controlled opening to the point of stretch but not pain, a few repetitions several times a day, alongside warm compresses. What stretching does not do is treat infection, and forcing an infected, guarded jaw open causes pain without changing the underlying problem.

The rule of thumb is that stretching is for a jaw that is already improving, to help it improve a little faster. A jaw that is tightening is telling you something, and the answer to that message is a phone call rather than more force. If stretching that was comfortable yesterday has become impossible today, that change is itself the finding.

Two cautions on technique. Do not use stacked tongue depressors or a screw device without being shown how, because aggressive mechanical stretching of a healing socket can disturb the clot and reopen bleeding. And do not stretch into the first 48 hours — during the peak swelling window it adds pain and achieves nothing that the following week will not achieve on its own.

Most people are close to their usual opening within seven to fourteen days after uncomplicated lower third molar surgery, with the largest gains between days four and eight. Deep bony impactions, long operations and cases that involved a haematoma in the muscle can take three to four weeks. Restriction still meaningfully present at six weeks is outside the usual pattern and deserves reassessment rather than more waiting.

Recovery is rarely a straight line. A day of slightly less opening after a day of talking or chewing more than usual is not a change of direction, and a single flat day means little. The signal is a trend across two or more days combined with something else — temperature, swelling, taste, swallowing — rather than a bad afternoon in isolation.

Where opening has plateaued short of normal without any sign of infection, the cause is more often the muscle or the joint than the socket. Persistent guarding, muscle scarring after a needle-track haematoma, or a temporomandibular joint that was already symptomatic can all leave a jaw that is comfortable but limited. Those are worth naming out loud at a review, because they are managed with time, physiotherapy-style exercises and joint assessment, not with antibiotics.

Everything above assumes an otherwise well adult recovering from third molar removal. Some people cannot rely on the trend, because the signs this page depends on are blunted in them, and they should have a lower threshold for being seen.

• Anyone immunosuppressed — chemotherapy, long-term corticosteroids, biologic therapy, transplant medication — in whom fever and swelling can be muted while infection spreads normally.
• People with poorly controlled diabetes, in whom odontogenic infections progress faster and glycaemic control deteriorates as the infection advances.
• Anyone already taking an antibiotic for something else, which can partially suppress the signs without treating the source.
• People who cannot reliably report change — a patient with cognitive impairment, or a teenager who has told nobody how bad it has become.
• Anyone who has had a previous deep space infection in the head or neck, where the fascial planes are already known to be a route.
• Anyone living alone with no one to observe overnight deterioration, where a plan of watching another day carries a different risk.

Nothing on this page diagnoses anything. It describes a pattern, and patterns exist so that people know when to ask. If your jaw is closing down instead of opening up, ask early rather than late, and ask the practice that operated on you first, because they know what was done and how difficult it was.