Why Are My Teeth Suddenly Sensitive?

Most advice on sensitive teeth treats sensitivity as a single condition with a single set of causes. It is more useful to split it by timescale, because sensitivity that develops gradually over years and sensitivity that appears within days point in quite different directions.

Gradual sensitivity usually reflects slow processes: recession creeping down, enamel thinning, dentine gradually exposed. Sudden sensitivity almost always has a specific, recent trigger — and identifying it is usually straightforward once you look at what changed.

Dentine, the layer beneath enamel, is perforated by tens of thousands of microscopic tubules per square millimetre, each containing fluid and running inwards towards the nerve.

The accepted explanation for sensitivity is hydrodynamic. A stimulus — cold, a sugary drink, a blast of air — causes rapid movement of the fluid within those tubules. That movement deforms nerve endings at the inner end, and the nerve interprets the deformation as a sharp, brief pain. The nerve is not being touched by the cold; it is responding to fluid shifting.

This explains the characteristic quality of dentine sensitivity: sharp, immediate, and gone within seconds of the stimulus being removed. It also explains why sealing the tubules works, which is what desensitising toothpastes are designed to do.

Enamel has no tubules and no sensation. For a tooth to be sensitive, dentine must be exposed somewhere — at the gum line, under a chipped edge, through wear, or beneath a leaking restoration.

A recent dental appointment. Sensitivity after a new filling is common, usually settles within a few weeks, and generally reflects the tooth reacting to being worked on. Sensitivity after a professional clean is also common and typically brief, particularly where calculus that had been insulating exposed root surfaces has been removed. Our articles on whether a filling should hurt weeks later and whether cleaning damages enamel cover both.

Teeth whitening. Peroxide passes through enamel and dentine to reach internal pigment, and in doing so it temporarily increases tubule permeability. Sensitivity during and shortly after whitening is expected, is usually transient, and responds to desensitising products and to spacing out sessions. Our article on whitening sensitivity and how long it lasts sets out what is typical.

An acid episode. This is the most under-recognised cause. A period of reflux, morning sickness, a stomach bug with vomiting, a new habit of drinking sparkling water or citrus through the day, or a fitness regime involving sports drinks can soften enamel and expose dentine surprisingly quickly. Silent night-time reflux often presents as sensitivity on the inner surfaces of the upper back teeth with no heartburn at all. Our articles on acidic foods and enamel and drinks that harm enamel cover the mechanism.

A change in brushing. A new firm-bristled brush, a switch to a more abrasive whitening toothpaste, or simply brushing harder after a dental telling-off can strip the thin cementum at the gum line and expose dentine within weeks. Brushing immediately after anything acidic compounds it, since the softened surface is removed rather than cleaned. Our article on whether brushing harder cleans better covers the point.

A period of stress. Increased clenching and grinding loads teeth in ways they are not designed for. The flexing at the neck of the tooth can crack away enamel at the gum line, producing small wedge-shaped notches that are often exquisitely sensitive. A stressful few months can produce sensitivity that appears entirely mysterious. Our article on stress and grinding covers the link.

A crack. A cracked tooth produces a distinctive pattern: sharp pain on releasing a bite rather than on biting down, often localised to one tooth, and frequently accompanied by cold sensitivity. It is worth taking seriously because a crack confined to the crown can usually be stabilised, while one that has travelled below the bone often cannot. Our article on cracked tooth syndrome describes the presentation.

A lost or failing restoration. A filling that has come out, chipped, or developed a gap at its margin exposes dentine directly. Sometimes the loss is not obvious to the patient, particularly at the back. Our article on sharp pain after losing a restoration covers what to do.

• Sensitivity is caused by fluid movement in dentine tubules, not by cold reaching the nerve.

• Sudden onset usually points to a recent change — whitening, a new filling, an acid source, a brushing habit or a crack.

• Sensitivity confined to one tooth is more concerning than generalised sensitivity.

• Pain that lingers more than thirty seconds, or occurs spontaneously, suggests the nerve rather than dentine.

• Night-time reflux commonly presents as dental sensitivity without any heartburn.

Most sudden sensitivity is dentine sensitivity and settles. Certain features suggest the pulp itself is involved and warrant assessment rather than a desensitising toothpaste.

Pain that lingers well beyond the stimulus — thirty seconds or more — rather than disappearing immediately. Pain that starts on its own, without anything triggering it. Pain that is worse lying down or wakes you at night, which reflects the change in blood pressure within the tooth when horizontal. Sensitivity to heat rather than cold, which is a more ominous sign than cold sensitivity. Pain that is clearly localised to one tooth. And any accompanying swelling, a bad taste, or a tender lump on the gum.

Sensitivity that fades after a period of severe pain is also worth reporting rather than welcoming. It sometimes indicates the pulp has died rather than recovered, and discomfort can return later as infection develops. Our article on deep decay reaching the nerve covers this.

One other pattern worth knowing: sinusitis can produce aching in several upper back teeth at once, typically worse when bending forward, often with nasal congestion. Where multiple upper molars on one side are tender simultaneously, a dental cause is less likely than a sinus one.

While waiting for an appointment, several things genuinely reduce dentine sensitivity.

Switch to a desensitising toothpaste containing potassium nitrate or stannous fluoride, and use it consistently for at least two weeks — these work cumulatively rather than immediately. Smearing a small amount onto the sensitive area with a fingertip last thing at night, without rinsing, is more effective than brushing with it alone.

Use a soft brush and reduce pressure. Stop using any whitening or "extra cleaning" toothpaste temporarily; higher abrasivity works against you here.

Identify and reduce acid exposure. Frequency matters more than quantity, so sipping something acidic across an hour is worse than drinking it at once. Rinse with water afterwards and wait at least thirty minutes before brushing.

Avoid extremes of temperature short-term, not as a treatment but to interrupt the cycle while the surface remineralises.

Our article on managing sensitive teeth sets out the routine in more detail.

Beyond identifying the cause, there are several effective in-practice options: fluoride varnish applied to the sensitive areas, which is quick and often noticeably effective; bonding agents or desensitising resins sealing exposed root surfaces; composite restorations to cover wedge-shaped notches at the gum line, as described in our article on bonding to fix a notch at the gum line; a night guard where grinding is contributing; and treatment of any underlying cause such as a crack, a failing restoration or recession.

Where recession is progressive and extensive, gum grafting is sometimes appropriate, and our receding gums page covers the options.

If sensitivity has appeared suddenly, is localised to one tooth, or is not settling, an examination will identify the cause rather than just the symptom. Arrange an appointment through our contact page.

You can read more on our dental check-up page, our receding gums page, our white fillings page, our night guards page and our teeth whitening page.

This article is for general information only and does not constitute dental or medical advice. The cause of tooth sensitivity can only be determined by clinical examination and, where appropriate, radiographs. Always consult a registered dental professional. If you have severe pain, facial swelling or fever, seek urgent dental care.

Next review due: 4 August 2027