Crowded teeth: where the missing millimetres come from, and how space is created

Crowding (Engstand) is a space problem: the teeth are wider, in total, than the jaw that has to hold them. That is why teeth overlap, twist or stand out of the arch — and why no amount of careful brushing changes it. Correcting crowding always comes down to the same question: where do the missing millimetres come from? There are only four real answers — filing tiny amounts between the teeth, widening the arch, moving the back teeth backwards, or removing a tooth — and the size of the shortfall decides which of them your plan uses. Statutory health insurance (gesetzliche Krankenversicherung, GKV) contributes only where the crowding reaches grade 3 of the German KIG grading system, which for crowding means a displacement of more than three millimetres, and only for treatment beginning before the eighteenth birthday. For adults, treating crowding is a private matter in essentially every case.

Two numbers explain every crowded mouth. The first is the space available: the length of the dental arch, from the back tooth on one side round to the back tooth on the other. The second is the space required: the combined width of all the teeth that have to fit into it.

When the second number is bigger than the first, the teeth have to go somewhere. They rotate, they overlap, they push forward or fall back out of line. The teeth themselves are usually perfectly healthy and normally shaped — they simply have nowhere to stand.

As a rough guide, orthodontists talk about a shortfall of a couple of millimetres as mild, roughly four to eight millimetres as moderate, and more than that as severe. It sounds trivially small until you realise that a lower incisor is only about five millimetres wide. A four-millimetre shortfall is most of a tooth.

Where does the mismatch come from? Overwhelmingly from inheritance — you can inherit your father’s tooth size and your mother’s jaw size, and the combination does not always cooperate. Beyond that:

Milk teeth lost too early. This one is preventable and worth knowing. A baby molar removed early because of decay lets the teeth behind it drift forward into the gap. When the permanent tooth underneath finally arrives, its space has been occupied. A great deal of childhood crowding traces back to exactly this, which is why a space maintainer after an early extraction is not fussiness.

Milk teeth that stay too long. The opposite problem. A baby tooth that will not come out sends the permanent one erupting off to the side.

Habits and breathing patterns. Long-term mouth breathing, often from enlarged adenoids or persistent allergies, changes how the tongue rests, and the tongue is part of what shapes the upper arch during growth.

The natural forward drift of teeth. Teeth migrate slightly forward through life. Over decades that drift alone tightens the front of the arch.

A specific and very common story: your teeth were straight, or were straightened as a teenager, and now the lower front teeth are overlapping again. It is one of the most frequent reasons adults come to an orthodontic consultation, and it has a name — late lower incisor crowding.

Two things are worth saying about it.

First, it is normal in a statistical sense. Lower front teeth tend to crowd gradually through adult life, in treated and untreated mouths alike. It is part of how a bite ages, along with the slow forward drift mentioned above and continued small growth of the lower jaw well beyond the teenage years.

Second, it is probably not your wisdom teeth. This is the most persistent myth in the field. The intuitive picture — wisdom teeth (Weisheitszähne) erupting at the back and shoving everything forward like a shunting train — is not supported by the evidence, and late lower crowding is seen just as readily in people whose wisdom teeth never developed at all. There are good reasons to remove wisdom teeth in individual cases: recurrent infection around a partly erupted one, decay that cannot be treated, a cyst. Preventing front-tooth crowding is not, on its own, a reliable one. If removal is suggested purely to protect your alignment, it is fair to ask what else speaks for it in your particular case.

The practical consequence of both points is retention, and we come back to that below — because for crowding specifically, retention is the whole ball game.

Let us be even-handed here. Mild crowding in a mouth that is cleaned well can cause nothing at all for a lifetime, and there are plenty of people for whom the honest recommendation is to leave it alone. The problems are real, but they are probabilistic rather than automatic.

Cleaning becomes harder in exactly the places that matter. Where two teeth overlap, the surface underneath the overlap is hard to reach with a brush and awkward with floss. Decay between the front teeth in an otherwise low-risk mouth is very often found precisely at an overlap.

The gum reacts to what stays behind. Plaque that sits undisturbed at a crowded contact point produces gum inflammation (Zahnfleischentzündung), which bleeds when you brush. Left long enough in a susceptible patient, chronic inflammation is the entry point to gum disease (Parodontitis) and the bone loss that comes with it. German dental associations consistently flag hard-to-clean tooth positions as a risk factor for exactly this reason.

A tooth standing outside the arch has thin bone in front of it. Thin bone means the gum above it recedes more readily, exposing root surface that is more sensitive and more prone to decay.

Rotated teeth take odd loads. A tooth turned sideways in the arch meets its opposite number at an angle it was not designed for, and edges chip more easily.

Speech and chewing are rarely affected by mild to moderate crowding, whatever the internet suggests. If your only complaint is appearance, that is a legitimate reason to treat — it is simply a private one in the German system, and worth naming honestly rather than dressing up as a medical necessity.

Every crowding plan is a combination of these, in proportions decided by how many millimetres are missing and where.

A few notes that matter in practice.

Slenderising is not damaging when it is planned. It removes a thin layer of enamel from the contact surface between two teeth — a surface that is naturally worn down through life anyway. It is measured, done in stages and kept well within the thickness available. Concern is reasonable; alarm is not.

Arch widening in an adult has a ceiling. Teeth can only be tipped outwards as far as the bone that houses their roots allows. Push beyond that and you trade crowding for gum recession, which is a poor exchange. It is the honest limit behind any promise of alignment without creating space somewhere.

Extraction is not a defeat. Where the shortfall is large, taking out two premolars and closing the space produces a stable, well-supported result that no amount of expansion would achieve. It is a considered decision, discussed in advance, not a shortcut.

In children, growth is itself a method. Widening the upper jaw at its growth seam creates space that simply is not available later, which is one of the arguments for having crowding assessed while it can still be treated cheaply.

Both correct crowding. The choice depends less on the crowding itself than on how much rotation and root movement is needed.

Clear aligners (Aligner) are strong on tipping and on mild to moderate crowding, and they make cleaning easier during treatment because they come out. They are more demanding of the patient: worn for fewer hours than agreed, they simply do not deliver the movements planned. Severely rotated teeth, teeth that need substantial root movement, and cases requiring space closure after extraction are territory where fixed braces (feste Zahnspange) remain very efficient.

Our clear aligner treatment is offered in three variants — 1,049 €, 2,800 € or 3,699 € — and which one applies depends on the scope of the case. Whether aligners are the right tool for yours is a question for the examination, not the price list; the detailed comparison lives in a separate article, linked at the end.

A measured space analysis. We scan both arches with Primescan — a digital scan, so no impression trays and nothing to gag on — and measure the shortfall in millimetres rather than describing it as “a bit crowded”. That number determines which of the four methods above your plan needs.

Where the gum and bone currently stand. Thin gum, existing recession or previous gum disease change what is safe to do. Crowding cannot sensibly be treated in an actively inflamed mouth: moving teeth through inflamed tissue risks losing attachment. Stabilising the gums first is standard, and it is not a delaying tactic.

Root positions and anything unerupted. An X-ray shows whether roots are already close together, whether wisdom teeth are present and how they lie, and whether a tooth is stuck. Where a three-dimensional view genuinely changes the plan — an impacted canine, for example — a 3D X-ray (DVT) costs 178 € with us; it is not routine and we say so when it is not necessary.

What you actually want. A patient bothered by one twisted upper incisor and a patient who wants the whole arch aligned need different plans, different durations and different budgets. Both are legitimate. The written plan should say which one you are getting.

If you remember one thing from this article, make it this. Crowding is the misalignment with the strongest tendency to return. Teeth that were rotated remember their old position through the fibres in the gum around them; the lower front teeth drift on their own account throughout adult life; and the forces that produced the crowding in the first place have not gone anywhere.

The answer is retention, and there are two standard forms, usually combined:

A fixed retainer — a thin wire bonded behind the front teeth, invisible from outside, working around the clock without any effort from you. It needs checking periodically and cleaning carefully, since it is a plaque trap by design.

A removable retainer — a clear tray worn at night. Simple, replaceable, and entirely dependent on being worn.

The realistic expectation is long-term, usually nightly, usually indefinitely for the removable option. Anyone who tells you the result is permanent without retention is not describing how teeth behave. Our retainers and splints are made in our own in-house master laboratory (Meisterlabor), which keeps replacements quick if one is lost or breaks.

Cover for orthodontics in Germany is settled by a fixed catalogue rather than by a case-by-case judgement. Its name is KIG, short for Kieferorthopädische Indikationsgruppen — orthodontic indication groups.

Every type of misalignment belongs to a lettered group, and inside that group the finding is scored from 1 to 5 on the basis of measurements taken at the examination. Grades 1 and 2 are not covered by statutory funds; treatment is possible, but you pay for it. Grades 3, 4 and 5 are covered, provided treatment starts before the eighteenth birthday.

Crowding sits in group E (Engstand), and the measurement is the displacement at the contact point between neighbouring teeth:

• a displacement of up to three millimetres stays at grade 1 or 2 — mild crowding, not covered;
• a displacement of more than three millimetres reaches grade 3 and is covered.

Three millimetres is not much. It is roughly half the width of a lower incisor. But it is the line, it is measured with an instrument, and the measurement goes into the file that is submitted to the fund. This is also why two children whose teeth look similarly crooked to a parent can get different answers from the same insurer.

Where cover applies, the fund pays 80 % of the standard treatment as it goes, and you advance the remaining 20 % — refunded by your fund once treatment is completed as planned, and reduced to 10 % for a second child in treatment simultaneously. It is a deposit, not a fee, so keep the paperwork.

Two further limits. Adults are outside the statutory system for orthodontics, except in severe skeletal cases treated together with jaw surgery. And anything beyond the standard catalogue is private even for a covered child — aligners, ceramic brackets and some retainers included. That is entirely legitimate; it simply needs to be in writing before treatment, not discovered afterwards.

Private health insurance (private Krankenversicherung, PKV) and supplementary dental cover (Zahnzusatzversicherung) frequently reimburse a tariff-dependent share depending on the tariff. As a rule, such policies do not pay for treatment that was already recommended before the policy started, so check the terms rather than assuming. Instalment payment (Ratenzahlung, subject to a credit decision) is available with us, and the first consultation is free.

If you have had gum disease. Crowding can absolutely be treated after periodontal treatment, but only once the gums are stable and being maintained. Teeth with reduced bone support move faster and with lighter forces, and the plan has to reflect that. Professional cleaning (professionelle Zahnreinigung, PZR) at agreed intervals is part of the treatment, not an add-on.

If you are pregnant. Orthodontic treatment can generally continue during pregnancy. Gums become more reactive under hormonal changes, so cleaning and check-ups matter more, and elective X-rays are postponed. Tell us — it changes what we do and when.

If you have moved to Germany recently. Bring records from your previous dentist or orthodontist, ideally digitally: old models or scans, X-rays, and any retainer you were given. If you had braces abroad and stopped wearing your retainer during the move, that is a very common story and worth mentioning early. We treat in English, and patients travel to us from Düsseldorf, Cologne and Bonn as a matter of routine — and for treatment of this kind from well outside NRW. What that looks like in practice is described in English-Speaking Dentist in NRW.