Kusp Pediatric Dentistry

Over Retained Primary

Why are my child’s permanent teeth growing behind the baby teeth?

Ah, the good old “shark teeth ”…my daughter Mia had this phenomenon. What am I talking about? Shark teeth are a very common occurrence in children where the permanent front teeth start growing behind the baby teeth. Even though the baby teeth may be loose, they are not loose enough to fall out and the permanent teeth are fully growing behind them. There are two technical terms for this 1) over-retained primary teeth (teeth that just really love your kid’s mouth and never want to come out) 2) ectopic eruption (this just means the permanent teeth do not come in the correct orientation or location in the mouth).  Most children start having loose teeth between 5 to 7 years of age (some as early as 4 years old), and usually by 6 or 7 years of age most kids have lost at least one tooth. Usually children that are taller and larger for their age, like above the 95th percentile may lose teeth earlier, while leaner, more petite children may lose their teeth later.  I get a lot of parents who notice that their child has permanent teeth growing behind their baby teeth. We call a permanent tooth that is replacing a baby tooth a succedaneous tooth.

Over-retained Baby Teeth and how do baby teeth get loose?

The most common place that I see over-retained baby teeth (or baby teeth that just don’t want to come out) is usually in the lower front teeth. By five or six years of age most children may start having some loose teeth. The reason baby teeth become loose is that because as the permanent tooth develops in the bone, and its roots grow longer, it starts having some momentum moving into the mouth. Imagine the roots of a plant, as they grow and establish we start seeing a little sprout in the soil, teeth are very similar. In the process of the permanent tooth growing, there are enzymes in the follicle (or the little bud) of the permanent tooth that eat away at the baby tooth root causing it to “resorb” or disintegrate as the permanent tooth grows under the baby tooth. When the baby tooth root resorbs, there is nothing holding that little tooth in the bone and it falls out. Occasionally, a permanent tooth does not  come in directly under the baby tooth it is replacing. On many occasions, the permanent tooth will come in behind the baby teeth. This does not allow the full resorption of the baby tooth root and as a result, the baby tooth will remain in place and the permanent tooth grows behind it.

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frenectomies close up - Kusp Pediatric Dentistry in Beverley Hills, CA

So, what do we do about this? Do we have to extract the baby teeth? The short answer is, no. Usually we try to let the body do what it knows how to do. Usually, when we see permanent teeth growing behind the baby teeth – we give the body a chance to self-correct the path of eruption. MOST of the time (with the help of eating lots of carrots and apples), the baby teeth in the front will come out on their own and the permanent teeth will naturally drift into that space. 

Here are some examples of two rows of teeth that end up coming out on their own:

Here is my daughter Mia. I noticed the bulging happening behind her baby teeth and knew long before her permanent teeth started peeking that we were going to have a problem. I knew her case would be problematic because well, she is the daughter of a dentist so naturally, she has dental issues BUT also because despite being on the brink of having new permanent teeth, her baby teeth were barely loose. I started documenting the eruption of those teeth and realized after 8 weeks that mama was going to have to take out those baby teeth (AND BOY WAS I HEARTBROKEN). Those cute little teeth that developed in my womb were going to be pulled out by, well…ME! I am lucky that this child is such a trooper and did so well. Here is how it went:

So as you can generally see, not ALL kids have to have their baby teeth pulled out/extracted in this case. Most of the time, the teeth are loose enough to make their way out on their own or with a little wiggling!

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Lastly, sometimes our older kids/teens sometimes have this same phenomenon in the back molars. There are four baby molars in the upper arch and four on the lower (see our link on primary teeth here). These molars also are replaced by the permanent premolars. Baby molars on the lower arch usually have two roots, unlike the front teeth that only have one. Similarly, the upper baby molars have three roots, much like their permanent counterparts. In some cases, the premolar that is replacing the baby tooth does not come into the mouth directly below the baby molar and comes in slightly to the side. Because there are so many baby tooth roots for the permanent molar to munch through it comes in angled or on the side of the baby tooth leaving the baby molar anchored to the mouth. Sometimes, these baby molars get so stuck, that the permanent tooth comes ALL the way in, leaving a shell of a baby tooth on the side. This little shell fills with the gum tissue and turns PINK! Yep, a PINK tooth! When we see pink teeth – usually, it is time for us to step in and intervene so that the gums can stay healthy and that the kid is comfortable when eating, chewing, and talking. Further, we may recommend to extract an overretained baby molar to prevent a permanent premolar from coming in totally to the side and out of alignment of the rest of the permanent teeth. Here are some image of overretained primary molars:

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Happy Brushing!