Why Does a Toothache Get Worse at Night?
Clinically reviewed by Dr. Abinaash Kaur, DDS, RCDSO, on 2026-09-14. Dr. Kaur is a general dentist in Toronto (Bloor West Village) registered with the Royal College of Dental Surgeons of Ontario.
A toothache gets worse at night because three things stack up at once. Lying down raises the blood flow inside your tooth, an inflamed nerve has almost no room to swell, and there's nothing left to distract you from it.
What I'd push back on is the conclusion people draw. A tooth that only bothers you at night isn't a tooth settling down.
First, the part that can't wait, and it splits into two. Trouble swallowing or breathing, swelling spreading under your jawline, a voice that sounds muffled, or a mouth you can't open properly means a hospital emergency room now, and call 911 if breathing is hard. Do not wait for a dental office to open for any of those.
Swelling in your face or under your eye, or a fever, means being seen tonight, at a dentist or an emergency room, whichever you reach first. The Canadian Dental Association is direct about that second group: once an infection has "progressed too far, resulting in swelling of the face or under the eye", antibiotics are likely needed and you should visit your dentist as soon as possible (Canadian Dental Association).
Everything below assumes you've ruled that out.
What's actually inside a tooth that can hurt this much?
Inside every tooth is a space called the root canal system. It's filled with soft dental pulp, made up of nerves and blood vessels that help the tooth grow and develop (Canadian Dental Association).
That pulp sits inside hard walls, and dentin doesn't flex. When you sprain an ankle it puffs up, because skin and soft tissue give way. Your pulp can't do that.
Researchers describe the pulp as having low compliance because it's enclosed between rigid dentin walls, so even a modest rise in fluid inside it will raise the pressure (Critical Reviews in Oral Biology and Medicine via PubMed). A separate review puts it in one line: the pulp "has relatively low compliance, because it is enclosed in hard tissue" (Japanese Dental Science Review via PubMed).
It isn't a sealed box, though, and that distinction matters. The same review notes that rising pressure can push fluid out through lymph flow and into nearby capillaries, which carries it away from the area and brings the pressure back down (Critical Reviews in Oral Biology and Medicine via PubMed).
So the setup isn't "no way out". It's no room to swell, and only slow ways to drain.
So why does lying down make it worse?
One study used a laser Doppler flowmeter to record blood flow inside teeth, in 21 premolars across 16 people aged 20 to 31. Changing from lying down to standing caused a significant reduction in blood flow in the pulp (Journal of Dental Research via PubMed).
Read that the way round it was measured. Standing up lowered the flow, which means lying down is the higher-flow state.
Now the limits, because they're real. Those were healthy teeth in healthy young adults, the study didn't measure pain at all, and the researchers hedged their own explanation, saying pulpal blood flow is affected by posture "presumably via the autonomic nervous system" (Journal of Dental Research via PubMed).
Joining those two findings together is my reasoning as a dentist, not something either paper claims. More blood arriving in a space that can't expand, in a pulp that's already inflamed, plausibly means more pressure and more pain. Nobody has tested that in a person with an actual toothache, so treat it as a good explanation rather than a proven one.
Is the night itself doing something, or is it just you?
Some of both, and the research on the clock is older and thinner than you'd expect.
In 136 healthy men, pain thresholds in front teeth were measured using a cold stimulus. The threshold was highest in the early afternoon and lowest in the early morning (International Journal of Chronobiology via PubMed).
A lower threshold means it takes less to register as pain. The authors noted their findings matched clinical experience about when toothache tends to start (International Journal of Chronobiology via PubMed). That study is from 1978, it used healthy teeth, and pain in general varies by time of day with studies disagreeing about when it peaks (Pharmacology and Therapeutics via PubMed).
The other half is the ordinary half. All day you're working, talking, driving, feeding somebody. At eleven at night there's nothing between you and that tooth.
I can't point you to a study that measured distraction in toothache specifically. It's the common explanation rather than a proven one, and in 25 years of listening to people describe this, I'd still put it near the top.
Why is the second night usually worse than the first?
Pain costs you sleep, and lost sleep lowers your pain threshold. A review of 29 studies found that sleep deprivation leads to increased pain sensitivity, and that recovery sleep mostly resets it (Neuroscience and Biobehavioral Reviews via PubMed).
Did you know about this? Most people don't, and it explains something patients tell me constantly.
Night two was worse than night one. The tooth costs you a night, the lost night lowers your threshold, and the same tooth hurts more the next time you lie down. That's a loop, and waiting it out is what keeps it running.
Is it your tooth, your jaw, or your sinuses?
The one that catches people out is the sinus. Your upper back teeth sit directly under the sinus floor, so when it's congested the ache can spread across several upper teeth at once, and it gets worse lying flat or bending forward.
That's the pattern I look for first in a "worse at night" story, because it imitates the real thing so closely. A cold or congestion alongside the pain is the clue.
Then there's grinding. If you wake with a sore jaw, tender cheek muscles, or a dull ache across several teeth rather than one sharp source, night-time clenching is a likelier explanation than a dying nerve, and it's a different problem with different fixes.
Two more worth naming. A partly erupted wisdom tooth with a sore gum flap over it has its own pattern. A cracked tooth usually gives a sharp jab when you release a bite rather than a throb that builds on its own.
Sensitivity is its own category too. Pain that spikes with cold and stops within seconds behaves differently from pain that lingers, and sudden sensitivity has its own list of causes.
Pretty much all of it comes down to three things. Which teeth, what kind of pain, and what sets it off.
Is a toothache that wakes you up serious?
It tells me the pain is spontaneous, and that word carries weight.
Pain that arrives with nothing touching the tooth is called spontaneous unprovoked pain. It's one of the defining features of symptomatic irreversible pulpitis, meaning an inflamed nerve that isn't going to recover on its own, alongside lingering pain to hot or cold and pain that spreads to other areas (Pediatric Dentistry via PubMed).
That doesn't mean a tooth waking you up is automatically that diagnosis. I can't diagnose you from one symptom, and neither can a search result. What it means is that "it only hurts at night" isn't the reassuring detail people treat it as. It's the detail I'd want to hear about.
Most people think pain that comes and goes means a tooth is sorting itself out. Here's what worries me more than the throbbing.
When the pain stops on its own, people relax. A pulp can die and go quiet while the infection underneath carries on, and the Canadian Dental Association is plain about where that leads: left untreated, an abscessed tooth "can cause serious oral health problems" (Canadian Dental Association).
If the nerve is past saving, root canal treatment is how the tooth gets kept rather than pulled. It's the process of removing the infected or injured pulp from inside the crown and roots, and the Canadian Dental Association calls it "an effective and safe treatment for teeth whose pulp has become inflamed or infected" (Canadian Dental Association). We've written about what that treatment involves here.
What helps a toothache at night?
Have no fear, there are sensible things to do, and one common mistake worth undoing.
No heat. The Ontario Dental Association says not to put a heating pad, a hot water bottle, or any other source of heat on your jaw, because "the heat will make things worse instead of better" (Ontario Dental Association).
Don't put pills on the tooth either. The same guidance says not to put the pills on your sore tooth (Ontario Dental Association). They're meant to be swallowed.
On pain relief, the Canadian Dental Association says ibuprofen and acetaminophen, "used individually or in combination, can be very effective for managing dental pain", and adds that you should "always take any medication exactly as directed by your dentist or pharmacist" (Canadian Dental Association). I'm not going to hand out doses in a blog post. Your pharmacist can tell you what suits you, which matters if you take anything else.
Antibiotics usually aren't the answer people are hoping for. Most toothaches are treated by removing the original source of the pain and early infection, without antibiotics at all (Canadian Dental Association).
Then call. For constant or severe pain the Ontario Dental Association's advice is to call your dentist immediately, describe your symptoms, and ask to be seen as soon as possible (Ontario Dental Association).
When does a bad night become an emergency?
Fever or swelling on the outside of your face changes the category. The Ontario Dental Association uses exactly that line as the point where antibiotics come into it (Ontario Dental Association), and the Canadian Dental Association adds swelling under the eye (Canadian Dental Association).
From me, not from a guideline: swelling spreading under your jawline, trouble swallowing or breathing, a voice that sounds muffled, or a mouth you can't open properly means a hospital emergency room, not a morning appointment. Those are the ones where hours matter. If you're unsure what counts, we've laid out what's a true dental emergency and what can wait.
Some days the schedule pushes me, and even then I'd rather find room for somebody who hasn't slept in two nights than leave them waiting a week. You don't have to wait for the second night to call, either. One is plenty.
Frequently Asked Questions
Q: Why does my tooth only hurt at night? Lying down is the higher blood flow state for the pulp inside your tooth. Standing up caused a significant reduction in pulpal blood flow in a study of 21 premolars across 16 healthy adults (Journal of Dental Research via PubMed). Combine that with a pulp that has "relatively low compliance, because it is enclosed in hard tissue" (Japanese Dental Science Review via PubMed) and nothing to distract you, and night is when you notice it most. Pain with nothing touching the tooth is worth an appointment rather than another night of waiting.
Q: Does a toothache at night always mean I need a root canal? No. Spontaneous unprovoked pain is one of the defining features of symptomatic irreversible pulpitis, an inflamed nerve that won't recover on its own (Pediatric Dentistry via PubMed), but it can also come from a sinus, a cracked tooth, a gum flap over a wisdom tooth, or night-time clenching. A dentist sorts those out with an examination, and the treatment is completely different for each.
Q: Can I put a hot water bottle on my jaw to settle it? No. The Ontario Dental Association says not to put a heating pad, hot water bottle, or any other source of heat on your jaw, because "the heat will make things worse instead of better" (Ontario Dental Association). It's one of the most common things people reach for at 2am and one of the few that can actively set you back.
Q: My toothache stopped by itself. Am I fine now? Not necessarily, and it's the answer on this page worth taking most seriously. A pulp can die and stop hurting while the infection underneath continues, and left untreated an abscessed tooth "can cause serious oral health problems" (Canadian Dental Association). Pain stopping is not the same as a problem resolving, so book the visit anyway.
Q: Why was the second night worse than the first? Because the first night cost you sleep. A review of 29 studies found sleep deprivation leads to increased pain sensitivity, with recovery sleep mostly resetting it (Neuroscience and Biobehavioral Reviews via PubMed). The pain disrupts your sleep, the lost sleep lowers your threshold, and the same tooth then feels worse. Breaking that loop generally means treating the tooth, not toughing out another night.
Q: Should I go to the emergency room for a toothache? For pain alone, a dentist is the right call, and the Ontario Dental Association advises phoning immediately and asking to be seen as soon as possible (Ontario Dental Association). Go to a hospital instead if you have facial swelling with fever, swelling under your eye (Canadian Dental Association), swelling spreading under your jawline, trouble swallowing or breathing, or you can't open your mouth. Those need care the same night.
Reviewed by Dr. Abinaash Kaur, B.Sc., DDS (University of Toronto Faculty of Dentistry), who has practised general and family dentistry in Bloor West Village for about 25 years. This article is general oral health information, not a diagnosis or a substitute for an examination.
Kept awake by a tooth two nights running? Come in and we'll find out which tooth it is and why, with an examination and an x-ray rather than a guess. If it turns out to be your sinus or your jaw muscles instead, we'll tell you that too. We're at 750 Annette Street in Bloor West Village, serving the Junction, High Park, and Baby Point. Book a visit with The Village Dentist and we'll take a proper look.
