A baby tooth that never fell out: when no adult tooth is coming

Why a baby tooth stays

Normally the adult tooth dissolves the root of the baby tooth above it as it comes through, and the baby tooth falls out, usually by the age of 12–14. If the adult tooth never formed, or is stuck in the jaw (impacted), nothing dissolves the root and the baby tooth can stay. The commonest examples are baby molars with no premolar beneath them and a baby canine that stays because the adult canine is impacted.

Being born without one or more adult teeth is called hypodontia. Leaving out wisdom teeth, it affects around 6.4% of people worldwide, and most of them are missing only one or two teeth. It is often genetic and can run in families.

An X-ray shows what is underneath

You cannot tell from the outside whether there is an adult tooth under a baby tooth; a panoramic X-ray shows this and also how long the baby tooth's root is. If the adult tooth is impacted, its position, angle and closeness to the neighbouring roots matter, and a 3D scan is sometimes needed. In young people an impacted tooth can be guided into place with surgery and braces; in adults this is less likely, and the tooth is either monitored or removed. Because an impacted tooth can dissolve the roots of neighbouring teeth, this assessment should not be put off.

How long a baby tooth can last

There is no way to say for sure in advance. Some go at the usual time, others stay well into adult life, and a healthy one can last 20 years or more. In studies following baby molars with no premolar beneath them, around 82–89% were still in good condition after 5–13 years, and root resorption or sinking mostly did not increase much. Changes are reported to slow down after the age of 20. The studies are few, though, and the level of evidence is low. The most common reason these teeth are lost is decay.

Root resorption and sinking

Two things are watched. The first is root resorption: the root of a baby tooth can shorten over the years until the tooth becomes loose. The second is infraocclusion, meaning the tooth sits lower than its neighbours. A baby tooth sometimes fuses to the bone (ankylosis); as the neighbouring teeth and the jawbone keep growing, it stays put and looks more and more sunken. In mild cases the difference is about 1 mm; in severe cases the tooth sinks to gum level.

A sunken tooth is not only a matter of looks. The opposing tooth can over-erupt into the space, the teeth on either side can tip over it, and the room needed for a future replacement shrinks. The bone in that area may not develop fully either.

Keep it or take it out

If the tooth is decay-free and firm, less than half of its root has resorbed and it is not markedly sunken, keeping it is often sensible. While it stays, it holds the space, supports the bone and gum around it and puts off the decision about what replaces it. The biting surface of a sunken tooth can be built up with filling material or a crown, which helps stop the opposing tooth over-erupting and the neighbours tipping.

Removal is usually discussed when the tooth is badly sunken, when the root has become very short and the tooth is loose, when there is extensive decay or infection, or when an orthodontic plan relies on closing that space. The timing is chosen to fit the plan, because the bone in the area can gradually thin after an extraction.

When the baby tooth is lost

The options are the same as for a missing adult tooth: an implant, a bridge, sometimes closing the space with braces or, if there are several gaps, a removable denture. An implant needs growth to have finished and enough bone; where the adult tooth never formed, the bone can stay thin and extra bone work may be needed. For a single gap, a bonded bridge needs very little drilling of the neighbouring teeth and does not rule out an implant later. The width of the gap, the bite, the bone and the state of the neighbouring teeth decide which fits.

When several teeth are missing

Severe hypodontia, with six or more adult teeth missing, is less common but takes longer and is more complex to treat. Several baby teeth may still be in place, the teeth that did form may be small or pointed, and the bone may be underdeveloped where teeth are missing. If most back teeth are missing or the baby molars have sunk, the bite height can drop: when the teeth meet, the jaws come closer than they should, leaving less vertical room for new teeth. Filling gaps one by one is then not enough; the orthodontist, the prosthodontist (the dentist who replaces missing teeth with crowns, bridges and dentures) and the surgeon first plan the height of the bite together. Alongside fixed options, removable dentures are also considered, for a while or for the long term.

This content is for general information only and does not replace an examination.