Tooth sensitivity: why teeth hurt with cold
The most common cause is physical: the dentine, the layer beneath the enamel, has become exposed and transmits cold, sweetness or air directly to the nerve. In most cases it's managed with simple measures, but if the pain lasts more than a few seconds or also occurs with heat, it's worth having a dentist take a look.
What happens inside the tooth when you feel that twinge
Dentine, the layer beneath the enamel that also forms the tooth's root, is riddled with thousands of tiny microscopic tubules connected to the nerve. While enamel (on the crown) or gum (on the root) covers that dentine, those tubules stay protected. As soon as that barrier thins or disappears, a stimulus from cold, sweetness, acid or even air travels straight to the nerve and causes that sharp, brief pain we know as tooth sensitivity, as the Mayo Clinic explains.
The most common causes
- Enamel erosion: frequent consumption of acidic food and drink (citrus fruit, fizzy drinks, wine) wears down the tooth's surface over time.
- Bruxism: clenching or grinding your teeth wears down the enamel and can produce small cracks that expose the dentine.
- Gum recession: exposes the tooth's root, which has no enamel to protect it. It can be caused by brushing too aggressively or by periodontal disease.
- Cracks or fissures in the tooth, sometimes invisible to the naked eye but that let the stimulus reach the nerve.
- A recent dental treatment: it's normal to notice temporary sensitivity after whitening, a new filling or a professional clean; it usually settles on its own within a few days.
- Brushing with a hard brush or an aggressive technique: wears down the enamel over time instead of cleaning any better.
Is this normal sensitivity, or could it be something else?
A brief twinge when you have something cold or sweet, which disappears as soon as you remove the stimulus, is typical dentine sensitivity: uncomfortable but manageable. The warning sign is different: if the pain persists for several seconds after the cold has gone, if it also occurs with heat, if it wakes you up at night, or if it's always in the same tooth, the nerve is probably inflamed rather than simple dentine exposure. In that case, the tooth may need a root canal treatment, not just a desensitising toothpaste.
- The pain lasts more than a few seconds after removing the cold or sweetness
- It also hurts with heat
- It's always located in the same tooth, not several at once
- It wakes you up at night
- You notice swelling or a small pimple on the gum next to the tooth
None of these signs correspond to simple sensitivity: they may indicate that the tooth's nerve is affected, and the sooner it's assessed, the simpler the treatment tends to be.
What you can do in the meantime
Desensitising toothpastes (with potassium nitrate or similar compounds) are the usual first measure. It's worth being honest about how much they help: a Cochrane review of trials on potassium nitrate toothpastes found limited evidence of improvement in patients' subjective perception, although it did observe a significant effect on objective sensitivity tests after 6-8 weeks of continued use. Either way, they carry no risk and help many patients reduce the discomfort.
- Use a soft-bristled brush and a gentler brushing technique.
- Avoid brushing immediately after having something acidic: wait around 30 minutes, while saliva neutralises the acid.
- Cut down on frequent acidic drinks and food.
- If bruxism is an underlying cause, a night guard stops the enamel wear from progressing any further.
Frequently asked questions
- This article is for information purposes only and does not replace the assessment of a healthcare professional. Always consult your dentist.
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