Sensitive Teeth: Why It Happens, and When It Is a Warning

Sensitivity is the symptom patients most often decide to live with. Sometimes that is reasonable. Sometimes it is the only warning you will get before a tooth needs a root canal. The useful question is not how bad the pain is — it is how long it lasts after the trigger is gone.

What sensitivity actually is

Under your enamel is dentine, and dentine is not solid. It is threaded with microscopic tubules that run to the nerve at the centre of the tooth. Where enamel is worn through or the gum has receded and left the root exposed, those tubules are open. Cold, heat, sweetness and air move fluid inside them, and the nerve reads that movement as pain.

The common causes

• Brushing too hard — a worn notch at the gum line, usually on the side you favour. The single most common cause we see.
• Gum recession — root surface has no enamel at all, so it is sensitive by nature the moment it is uncovered.
• Acid — citrus, cola, and also acid reflux, which erodes enamel from the inside of the mouth while you sleep.
• Night grinding — flattens the biting surface until the dentine underneath is exposed.
• A recent filling — mild sensitivity for a couple of weeks afterwards is expected and settles.
• A crack or a cavity — this is the one that matters, and it is why sensitivity in a single tooth is treated differently from sensitivity across a whole side.

The test that tells you which it is

Take something cold. Note what happens when you take it away.

• Pain stops within a few seconds — reversible. Dentine sensitivity. Desensitising toothpaste, a softer brush and a technique correction will usually handle it.
• Pain lingers for thirty seconds or more, or throbs afterwards — the pulp inside the tooth is inflamed. This does not resolve on its own and often ends in root canal treatment if left.
• Pain on biting down rather than on cold — think crack, or a high filling. Either way it needs looking at.
• Pain that wakes you at night — treat as urgent. Get it seen.

What to try first

1. Soft brush, small circles, no pressure. Let the bristles do it.
2. A potassium-nitrate or stannous-fluoride sensitivity toothpaste. Brush with it, then smear a little on the sensitive spot and leave it — do not rinse.
3. Give it a month. Genuinely. This is where most people quit too early.
4. Wait thirty minutes after anything acidic before brushing.
5. If you wake with a tight jaw or flattened teeth, ask about a night guard.

When to come in

One tooth rather than a region, pain that lingers, pain on biting, swelling, or sensitivity that has got worse over a month — those are examination cases, not toothpaste cases. Tooth pain assessment and root canal treatment are both services we provide, and finding out which one you need takes a single visit.