One mechanism explains almost all of it
Dentine is not solid. It is a dense weave of microscopic channels running from the outer surface of the tooth inward towards the pulp, the living core containing the nerve. Those channels are filled with fluid.
When something makes the fluid move sharply — cold, a rush of air, sugar, an acidic mouthful — the movement tugs on nerve endings at the inner end of the channel. The nerve has only one language, and it says pain. That explains the distinctive character of the sensation: instantaneous, sharp, over almost as soon as it started. Dentists call it dentine hypersensitivity, and international dental bodies describe it as one of the most common complaints in people with otherwise healthy mouths.
Enamel normally caps this system and blocks it. So the real question is never “why is my nerve so sensitive” but “where has the covering gone”.
Where the covering goes: six common reasons
1. The gums have moved
Gum recession (Zahnfleischrückgang) is the most frequent reason by far. The root surface underneath was never covered by enamel at all, and its paper-thin layer of cementum wears away quickly. Recession creeps up on people: it progresses over years, rarely hurts while it is happening, and is often noticed first as a tooth that “suddenly” reacts to cold.
2. Brushing like you are cleaning a pan
Hard bristles, heavy pressure and a horizontal scrubbing motion wear a smooth notch into the tooth at the gum line. Right-handed people usually have it worse on the left, which is a useful clue. This wear is entirely mechanical, entirely preventable, and does not repair itself.
3. Acid
Enamel softens below a certain acidity, and the modern diet supplies acid all day: citrus, sparkling water, energy and sports drinks, wine, vinegar dressings, fruit teas. Acid also comes from inside — reflux, frequent vomiting, morning sickness. Erosion does not drill holes the way decay does; it dissolves the surface evenly, so teeth become sensitive and the edges of the front teeth start to look transparent, all without a single cavity.
4. Grinding and clenching
Bruxism (Bruxismus) applies forces the tooth was never designed for. It flattens chewing surfaces, flexes the tooth at the neck and can craze the enamel with fine cracks. Many people who grind have no idea they do — the clues are a tight jaw in the morning, headaches at the temples, an indented ridge along the side of the tongue, and teeth that ache at breakfast and settle by lunchtime.
5. Right after dental treatment
A new filling, a professional cleaning (professionelle Zahnreinigung, PZR) or gum treatment can leave teeth temporarily sensitive, usually improving over two to four weeks. After gum treatment in particular, tooth necks previously covered by swollen tissue become exposed as the inflammation resolves — a sign the treatment worked, even though it feels like the opposite. Sensitivity after whitening belongs in the same category: Sensitive teeth after whitening: how long the twinges last.
6. A crack
A cracked tooth is the awkward one, because it hides from X-rays. The typical story is a tooth that is fine most of the time but produces a sharp jolt when you bite on something hard — or, oddly, when you release the bite. Cracks are common in teeth carrying large old fillings.
Sensitivity, or something more serious?
This distinction matters more than any other on this page, and you can make a first assessment yourself.
| What you notice | Ordinary sensitivity | The nerve inside the tooth |
|---|---|---|
| How long the pain lasts | Seconds; stops with the trigger | 30 seconds to minutes; continues on its own |
| Number of teeth | Several, often on both sides | One tooth you can point to |
| Trigger | Cold, air, sweet, acidic | Heat, chewing, or nothing at all |
| At night | Rarely a problem | Often worse lying down |
| Over time | Fluctuates, better on some days | Steadily worse over days |
A tooth in the right-hand column needs an appointment, not a different toothpaste — and decay under an old filling, an inflamed nerve and a crack are all far simpler to treat early.
How a dentist finds the cause
The examination is more detective work than technology. We map which teeth react and to what, using a controlled cold stimulus and gentle air rather than guesswork. We test whether the tooth hurts when tapped, and ask you to bite on a small wedge, one cusp at a time — the classic way to expose a crack. Small bitewing X-rays show decay between teeth and under existing fillings, where the eye cannot reach, and working under a microscope makes fine cracks and leaking filling edges visible that would otherwise be missed. Where a 3D X-ray (DVT) is genuinely needed — usually for a suspected fracture rather than routine sensitivity — it costs 178 € with us, and we say so before we take it.
We also ask about things that sound unrelated: brushing technique, what you drink and when, reflux, medication that dries the mouth, whether anyone has told you that you grind at night. Sensitivity without decay is usually a habits problem wearing a dental disguise.
What genuinely helps
Change the toothpaste, and how you use it. Toothpastes for sensitive teeth work either by calming the nerve response (potassium compounds) or by plugging the open channels (stannous fluoride, arginine and similar). Both need two to four weeks of consistent use before you can judge them. Two habits double the effect: rub a little paste onto the sensitive spot with a fingertip before bed, and after brushing spit without rinsing.
Fix the brushing, and wait after acid. A soft brush, or an electric brush with a pressure sensor; small circles, not horizontal sawing. If your brush head splays outwards within weeks, you are pressing far too hard. Enamel also stays temporarily softened after anything acidic, and brushing in that window scrubs the softened layer away — rinse with water and brush later, and keep acidic drinks to mealtimes rather than sipping them across the afternoon.
Use fluoride regularly. A gel once a week at home, or a varnish applied in the practice, hardens the surface and narrows the exposed channels — undramatic, and reliably effective.
Seal the exposed necks. A notch that has already worn into the tooth can be filled with tooth-coloured composite — a small treatment, usually without anaesthetic, that often removes the sensitivity in one appointment.
Deal with the grinding, and treat the gums. A custom night guard (Knirscherschiene) takes the load off the teeth. And if the gums are inflamed because of gum disease, the gum treatment is the sensitivity treatment.
What is normal — and when to book an appointment
The last one is easy to talk yourself out of. Sensitivity that has been stable for years and then changes character is telling you something new is happening.
Special situations
Pregnancy. Hormonal changes make gums more reactive, and morning sickness adds stomach acid — rinse with water rather than brushing straight after being sick. Check-ups and treatment of inflammation are entirely appropriate during pregnancy; the second trimester is the most comfortable window for anything planned.
Diabetes. Poorly controlled blood sugar makes gum inflammation more likely and more persistent, and receding gums follow inflammation. If your gums bleed, sensitivity is the smaller of the two problems.
You are new to Germany. Sensitivity is one of the hardest complaints to describe in a second language, because the diagnosis rests on nuance. Here you can describe it in English, and we work through the causes with you rather than handing over a tube of toothpaste. English-Speaking Dentist in NRW explains how examinations and insurance work for newcomers.
Yes, and it is the most common situation of all. Sensitivity is about exposed dentine, not about holes. Gum recession, worn tooth necks, acid erosion and grinding all expose dentine while leaving the tooth structurally sound, which is why a check-up can be clear and your teeth can still react to cold.
Usually because a threshold was crossed rather than because something new happened. Recession or wear progresses invisibly for years until the last protective layer over one spot gives way — and a cold drink finds it. Medication that dries the mouth, a change in diet, or a stressful period of clenching can tip a borderline tooth over the edge.
For dentine hypersensitivity, yes, for most people — but it needs two to four weeks of daily use, and it treats the symptom rather than the cause. If it has made no difference after a month, that is useful information in itself: it suggests the problem is not simple exposed dentine, and the tooth should be examined.
The examination is ordinary dental care, so the statutory health insurance (gesetzliche Krankenversicherung, GKV) covers it, along with treatment of the underlying problems — decay, gum disease, a filling at an exposed neck. Purely preventive extras such as a professional cleaning are usually private, though some funds contribute. Ask us to write down what falls where before you agree to anything.
Healthy teeth that hurt are not a mystery and not a personal quirk. They are dentine doing exactly what dentine does once its cover is gone. Work out which cover went missing — gums, enamel worn by brushing, enamel dissolved by acid, or enamel cracked by grinding — and the treatment usually follows, often starting with a softer brush rather than anything in a chair. Seconds of sharp pain is sensitivity; lingering, throbbing or biting pain belongs to the nerve.
Zahnarztpraxis Tsypin · Wuppertal. This article was medically reviewed and is provided for information; it does not replace an examination. Updated August 2026.
