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Abnormal Teeth

Double Tooth Gemination and Fusion
©Rachel Inbar

Many parents wait with great excitement and anticipation for the eruption of their baby’s first tooth.  Sadly, baby teeth don’t always look quite right.  This can cause extreme worry among parents.  Pictured to the left is one such scenario of a baby’s two upper teeth.  The tooth on the left is a “double tooth” while the one on the right is normal.

Double teeth are two teeth that are joined together by dentin or even by the pulp.  If you’re not sure what dentin and pulp are, take a look at the layers of a tooth.

There are two scientific terms for teeth that appear to be two teeth stuck together as one tooth: gemination and fusion.

Teeth Stuck Together: What is Gemination?

Tooth Twinning / Gemination - Close Up ViewGemination is when one developing tooth has split off into two distinct teeth that remain attached to each other and develop together.  Gemination comes from the latin word geminus which means twin.  You can think of gemination as two “twins” that are permanently attached.

When you count the geminated tooth as one tooth, there are a normal number of teeth in the mouth.  Rachel’s son (shown in the pictures) was shown to have gemination because he has all of his other teeth when you count the “double-tooth” as one tooth.

Teeth Stuck Together: What is Fusion?

Fusion is when two different developing teeth have joined together to create one tooth.  You can think of it as two teeth fusing together.  Gemination and fusion look very similar.  Sometimes the only way to tell them apart is to count the number of teeth.

When you count the fused teeth as one tooth, the person will be missing one tooth.

How Common Are Double Teeth?

Tooth Gemination
The same boy pictured above, a year or so later.  This boy has gemination. He has all four upper incisors including the double tooth. If he only had three upper incisors including the double tooth, it would be fusion.

Gemination and fusion have been reported to occur in the baby teeth in anywhere from 0.5% to 2.5% of Caucasian children.  It is more common in Asian children, where it has been reported to occur sometimes in excess of 5% of Asian kids.

Gemination and fusion occur most commonly in the upper front teeth.  However, it can also occur on the lower teeth as well.  As a general rule, if a double tooth is located in the upper teeth, it is probably gemination and if the double tooth is found in the lower teeth, then it is probably fusion.

Above and to the right, you can see the same boy’s twinned tooth now that he has gotten a little older.

Can Gemination and Fusion Happen with Permanent Teeth, Too?

Gemination and fusion do occur in permanent teeth, although it is not nearly as common as in baby teeth.  It reportedly occurs in one out of every 250 people.

Can Gemination and Fusion Cause Any Problems?

Gemination and fusion in the baby teeth can cause crowding, atypical spacing between the teeth, and can cause problems with or delay the eruption of the permanent teeth underneath.

Because of this, when a double tooth is found, you should have your dentist monitor the permanent teeth underneath it to ensure that they come in normal.  Sometimes, your dentist will have to remove the double tooth in order to allow the permanent tooth to erupt normally.

Rarely, there are no permanent teeth located under fused double teeth.  Your dentist will be able to provide more information about the permanent teeth through a simple x-ray.

One thing to watch out for is the propensity for fused and geminated teeth to have deep grooves between the “two” teeth.  This groove can be very susceptible to developing cavities as it is hard to get a toothbrush all the way down in the crevice to clean it properly.  You may want your dentist to put a sealant in this groove to help prevent a cavity.

How Are Gemination and Fusion Treated?

Sometimes, your dentist will be able to shave down and smooth the double tooth so that it doesn’t appear very obvious to the casual observer.  I say sometimes because the anatomy of twinned teeth can be complex.  If the pulp (click here to learn about the different layers of the tooth) is too close to the surface, then the dentist won’t be able to shave down very much of the surface.

Very rarely, the dentist may be able to surgically divide the teeth.  This often works best with fusion because both teeth usually have their own separate pulp chambers and root systems.  In any case, when surgically dividing the teeth, both teeth will need to have root canal treatment performed on them, which can end up being quite costly.

When Rachel gave me permission to use the photos of her son, she told me the following:

In case you’re curious – no one really notices it at all, even though it was obvious to me that we’d be constantly bombarded with questions about it. Maybe when he’s a little older (he’s almost 2-1/2 now).

Since kids will most likely lose all of their front teeth by the time they’re 9, you may elect to do nothing about the double tooth unless it’s a huge cosmetic concern.  Shannon W, one of the commenters on Rachel’s original post said to just “enjoy it’s cuteness”…and that may very well be sound advice!

Conclusion & Further Reading

For the record, I got my facts (the statistics) about gemination and fusion from this book: Oral and Maxillofacial Pathology by Neville.  If you want to read more on double teeth, that book is an excellent source.

Do you have any questions or comments about double teeth?  Do you or your child have double teeth?  If so, what did you do, if anything, to treat it?

Please share your experiences in the comments section below, so we can all learn from them.  Thanks for reading!

Updated Photos

Here’s a photo that Rachel recently shared with me showing her son with the double tooth still doing well a few years later!

Double Tooth

And a closeup of the double tooth:

Double Tooth Closeup

Extra Pictures of Tooth Twinning

Here’s an image of Deb’s son showing:

Gemination Tooth Twinning

You can read about his experience in this comment and this follow-up comment below.

If you would like to submit photos of twinned teeth, you can use this comment form or send me an email OralAnswers[at]gmail[dot]com.  Thanks!

I want to thank Rachel Inbar for allowing me to use two pictures of her son with a “double tooth” for this article.  Rachel runs a fertility blog and allows couples to share their fertility stories online.