Our teeth stay anchored to our jawbone, thanks to healthy tissue and ligaments. Normally, the roots and ligaments for primary ("baby") teeth will dissolve, allowing the baby teeth to come out and the permanent teeth to emerge from underneath.

Sometimes the roots don't dissolve properly, and instead they fuse directly to the jawbone. The fusion may occur because the ligament that normally surrounds the tooth in the jawbone is lost. This condition is called ankylosis (ang-kil-LO-sis).

Causes of ankylosis

The causes for ankylosis vary; for example, the healthy ligament cells may dry up and die because of:

• Inflammation or infection
• Problems with metabolism or normal bone growth
• Congenital tendencies
• Gaps in the membranes around the tooth
• Abnormal pressure from the tongue
• Crushing or other damage

Ankylosis also may develop in children or adults when an injury (such as with sports or accidents) causes the top of the tooth to be broken off, leaving the roots behind.

Some studies have indicated that 1 to 3 percent of children may have ankylosis with one or more primary teeth, while other studies have indicated more than 38 percent of children may have ankylosis. Studies also have shown that children or adolescents with 1 or 2 ankylosed teeth are more likely to have additional ankylosis later.

These variances in statistics may be due to different ways of diagnosing ankylosis, ethnic factors, or other reasons. (For example, a study at the Pediatric Dentistry Clinic of the University of Minnesota's School of Dentistry focused only on Caucasian children.) But the studies all come to the same conclusion: while it may not be an unusual condition, especially with lower first molars, ankylosis is a serious condition. To ensure the healthy development of your child's teeth, ankylosis must be addressed.

Signs and sounds of ankylosis

Some of the signs of ankylosis may include:

• The ankylosed tooth appears submerged because its roots don't grow at same rate as other teeth.
• The opposing tooth visibly loses alignment as it grows out of its socket.
• The permanent tooth is blocked out of position because the primary tooth's roots failed to dissolve normally.

Often we can diagnose ankylosis simply through observation. For example, a tooth noticeably lower in growth is a tell-tale sign of ankylosis. Also, with x-rays taken at regular checkups, we can view the development of permanent teeth that may be blocked by the primary teeth's roots.

Special, sophisticated instruments can be used to identify ankylosis. But one of the most reliable instruments is our ears! Simply by tapping on the teeth, we can hear a distinct difference between an ankylosed tooth and a normally growing tooth. That's why we may use the clean handle of a dental mirror to tap lightly on children's teeth as part of their regular dental exam. (An ankylosed tooth has a higher pitched or dulled sound as opposed to the more cushioned sound of a normal tooth.)

Solutions for ankylosis

We may recommend several solutions for ankylosis, depending on the specific tooth and your child's situation. For example, with younger children, we may simply recommend monitoring the situation for a period of time, to watch how the primary and permanent teeth develop.

Sooner or later we may recommend removing the ankylosed tooth, to ensure that your child's permanent teeth can develop straight and strong. We also may recommend surgery to expose, protect, or reposition the emerging tooth.

If we must remove a primary tooth before the permanent tooth is ready to emerge, we may use space maintainers to ensure that surrounding teeth do not crowd out the emerging permanent tooth. Sometimes orthodontic steps may be taken to ensure that your child's teeth align and the bite is correct. In general, the sooner we can deal with your child's ankylosed tooth, the fewer problems that are likely to develop later.

For more information

If you have questions or concerns about ankylosis affecting your child's or adolescent's teeth, please call our office. Also, you might find the following websites useful:

• "Ankylosis of Traumatized Permanent Incisors: Pathogenesis and Current Approaches to Diagnosis and Management" in the Journal of the Canadian Dental Association, November 2005 at http://www.cda-adc.ca/jcda/vol-71/issue-10/763.html
• "Ankylosed primary molars: Results and treatment recommendations from an eight-year longitudinal study" (messer-02-01.pdf), "Diagnosis and treatment planning for unerupted premolars" (burch-16-02.pdf), and "Early ankylosis of a primary molar with self-correction: case report" (belanger-08-01.pdf) in Pediatric Dentistry; PDFs available at the American Academy of Pediatric Dentistry at http://www.aapd.org