Why doesn't a tooth come out completely? Dental ankylosis

You may have spent years watching your child's tooth trying to erupt but not quite coming through, and it feels like it's 'sunken in', or maybe it's happening to you and you think: what's wrong?

Most likely you have dental ankylosis.

What is dental ankylosis?

Occasionally some teeth, whether permanent or temporary, fuse with the surrounding bone because the periodontal ligament - the sheath that separates the bone and the tooth - has been disappearing. This is why complete eruption does not occur.

Although the causes of dental ankylosis are not fully defined, it is most commonly due to genetic factors, but it can also occur in anterior teeth that have suffered trauma.

To diagnose it, we base it on the difference in height with the other teeth; on percussion (they make a very characteristic dull sound that is quite different from that of any other tooth); on radiology (although it is not always clear) and on history (if the tooth has had dental trauma, even if it was years ago).

What are the consequences of dental ankylosis?

There are several problems associated with this anomaly, depending on which tooth is affected:

In deciduous or primary teeth

  • Low likelihood of it falling out on its own. Most likely to have to be removed in the clinic.
  • The permanent tooth that is to replace it cannot come out, as it is obstructed by the temporary tooth, so it looks for other ways and ends up coming out tilted to the other side.
  • Sometimes, when there is an ankylosed milk tooth, it is a sign that the permanent tooth that should replace it does not exist and in reality we are dealing with an agenesis. In these cases, we can find out with a simple X-ray.
  • Malocclusion, as this tooth is 'sunken in' and leaves a space between the upper and lower teeth, creating an infra-occlusion, which in turn causes the next molar to lean forward (mesial), leaving a malocclusion in that area.
  • Bone loss. The bone and gum accompany the growth of the tooth, so if the tooth does not grow, the bone does not grow either.

In permanent teeth

  • As with the primary teeth, it will be under-occluded and the adjacent teeth will be tilted, resulting in malocclusion and increased risk of caries due to food packing.
  • Immobilisation occurs, making it impossible to move these teeth to align them in case orthodontic treatment is needed.

And how is dental ankylosis treated?

Treatments for ankylosis vary depending on age, type of malocclusion, degree of malocclusion, possible bone defects and the presence or absence of agenesis.

For example, the correct option for primary teeth that do have a replacement is extraction. It is also recommended for mixed dentition, from 6 to 12 years of age.

This extraction is usually a little more complex, as some bone has to be removed so that the tooth can come out, but it is also necessary.

If a temporary tooth does not have its permanent tooth waiting (or if it is a well-positioned permanent tooth), but there is no bone defect, what should be done is a reconstruction, thus giving it the thickness and height necessary for good mastication and so that the adjacent teeth do not shift.