Why Are Teeth Sensitive to Hot or Cold?

Tooth sensitivity to temperature is one of the most common dental complaints we see at Tooronga Family Dentistry, and one of the most misunderstood. Many people accept it as normal, manage it with sensitive toothpaste, and never investigate further.

Why teeth become sensitive to temperature

At the centre of every tooth is the pulp — a living tissue containing nerves and blood vessels. Surrounding it is dentine, a softer mineralised layer riddled with microscopic fluid-filled channels called dentinal tubules. Enamel covers the crown of the tooth, and cementum covers the root. Both act as insulating barriers.

When these barriers are compromised — through enamel loss, gum recession, cracks, or decay — dentinal tubules become exposed. Temperature changes cause the fluid inside these tubules to expand or contract, stimulating the nerve and producing that sharp, brief pain. The thinner the remaining barrier, the more pronounced the sensitivity.

The most common causes of temperature sensitivity

Enamel erosion Dietary acid from soft drinks, citrus, wine and vinegar gradually dissolves enamel, thinning the insulating layer over the dentine. Sensitivity from erosion tends to affect multiple teeth and worsens progressively without dietary and clinical intervention.

Gum recession When gums recede — through aggressive brushing, gum disease, or natural ageing — the root surface becomes exposed. Unlike the crown, roots have no enamel covering, only thin cementum. Exposed roots are acutely sensitive to both temperature and touch. Recession-related sensitivity is often localised to specific teeth.

Tooth grinding (bruxism) Grinding wears enamel from the biting surfaces and edges of teeth at an accelerated rate. Patients who grind often notice broad, generalised sensitivity across multiple teeth — particularly to cold. The wear pattern is typically visible clinically even when patients are unaware they grind.

Cracked tooth syndrome A crack in a tooth that doesn’t show on an X-ray can cause sharp, highly localised sensitivity — often to cold, and sometimes with a distinct pain on biting that releases suddenly when pressure is removed. This is one of the trickier diagnoses in dentistry, but an experienced clinician can identify it with targeted testing.

Tooth decay A cavity that has reached or is approaching the pulp produces sensitivity — initially to cold and sweet, and eventually to heat as well. Heat sensitivity that lingers after the stimulus is removed is a significant warning sign of pulp involvement requiring prompt assessment.

Recent dental treatment Sensitivity following a filling, crown preparation, or whitening treatment is common and usually temporary. The tooth has been disturbed and requires time to settle. If sensitivity from a recent procedure is worsening rather than improving after two to three weeks, review is warranted.

Gum disease Active periodontal disease causes bone and tissue loss around teeth, leading to root exposure and sensitivity. Treating the gum disease addresses both the infection and, in many cases, the sensitivity.

Receding fillings or leaking margins Old or worn fillings can develop gaps at their margins, allowing temperature, bacteria and fluid to reach the dentine beneath. This type of sensitivity is typically localised to one tooth with a specific restoration.

When sensitivity is a warning sign you should not ignore

Not all sensitivity is equal. These patterns require prompt dental assessment rather than watchful waiting:

• Sensitivity to heat, or heat sensitivity that lingers after the stimulus is removed — this suggests pulp inflammation or infection
• Spontaneous toothache with no stimulus
• Sensitivity combined with visible swelling, a pimple on the gum, or a bad taste
• Sensitivity in a single tooth that is progressively worsening
• Pain on biting combined with cold sensitivity — possible cracked tooth

Prolonged heat sensitivity in particular is one of dentistry’s more urgent signals. It can indicate irreversible pulpitis — inflammation of the pulp that will not resolve without root canal treatment or extraction.

How we diagnose and treat sensitivity at Tooronga Family Dentistry

Diagnosing the cause of sensitivity requires clinical examination, targeted testing with cold and heat stimuli, bite testing, transillumination for cracks, and X-rays where indicated. We do not guess — we test systematically until the cause is clear.

Treatment depends entirely on the cause:

• Fluoride application: In-chair fluoride varnish for erosion and generalised sensitivity — strengthens and partially remineralises exposed dentine
• Dentine bonding agents: A thin layer of bonding resin sealed over exposed dentinal tubules for immediate and durable relief
• Gum grafting: For significant recession exposing root surfaces — restores gum coverage and eliminates the underlying cause
• Nightguard: Custom occlusal splint for grinding-related sensitivity — prevents further enamel loss while protecting restorations
• Fillings or crowns: For decay, cracked teeth, or failing restorations contributing to sensitivity
• Root canal treatment: Where the pulp is irreversibly inflamed or infected — eliminates the source of pain definitively
• Dietary counseling: For erosion-driven sensitivity — identifying and modifying the acid load in your diet

We see patients across Glen Iris, Malvern, Hawthorn, Hawthorn East and Ashburton with sensitivity ranging from mild and manageable to severe and urgent — and the approach we take is always guided by an accurate diagnosis first.

Experiencing sensitivity to hot or cold? Don’t just mask it with sensitive toothpaste and hope it resolves. Book an assessment at Tooronga Family Dentistry — finding the cause is the only way to find the right solution.