As orthodontists, we really do get the privilege of watching our patients grow and change for many years. One thing that is obvious very early on is that people, as a whole, show a great deal of variation. Even within the same family, siblings and parents present us with a myriad of interesting challenges that keeps what we do interesting. That being said, there are some basic trends, rules of thumb if you will, that we can rely upon when planning your course of treatment.
One particular set of norms I have been questioned about recently is the eruption patterns of the permanent and baby teeth. Common questions I get include: When should my child start losing teeth? How many baby/permanent teeth should he/she have? Am I too old to still have baby teeth? So, in an attempt to break things down, Im going to address the norms of tooth eruption in this blog.
Let me begin by showing a diagram, and then I will explain it thoroughly.
The upper diagram describes the eruption pattern and exfoliation (when they are lost) pattern for the primary, or baby, teeth. Most of us know already that we are born without teeth, and live the first 6 months or so of our lives that way. Then, at around 6 months, the first primary teeth make their appearance into the mouth. These are normally the lower central incisor teeth, followed by the upper central incisors at around 8 months. Continuing, we will then, on average, see the upper and lower lateral incisors, upper and lower 1st molars, upper and lower canines, and finally the lower and upper 2nd molars before the child turns 3 years of age. For those of you counting, that finishes us at a grand total of 20 primary teeth.
Now I want to point out that all the times presented in this chart are given as a time span as opposed to as an exact month. This once again comes back to what I mentioned at the beginning of the blog, that people show variation. So, if your child is 5 months older than the neighbors, and the neighbors child has 4 more teeth erupted than yours, should you panic? No, your children are just demonstrating my point that everyone is different, and most likely this is normal for them. As dentists, in regards to tooth eruption and loss, we are really just looking for symmetry in the mouth. What I mean by this is that if you get or lose a tooth on one side of the mouth, I would expect the same tooth on the other side to come in/fall out around the same time. Its when this doesnt happen that red flags go up in my mind, but Ill discuss this later on.
More pertinent to orthodontics is the next part of the diagram; when the baby teeth are shed, or lost. From the ages of 3-6, our teeth take a break from change, at least from any changes that we can see in the mouth. At around 6, however, things begin to take off and we not only lose 8 teeth in rapid succession, but also gain 4 more through eruption. Our first teeth to become loose are normally the same as those that erupted into the mouth first, the lower central incisors. Also at around 6 years of age, the 1st permanent molars (also known as the 6 year old molars) will begin to erupt behind the 2nd primary molars. These 1st molars are not replacing any baby teeth, and therefore no teeth are lost as they come in. At around 6 the upper central incisors are lost as the permanent centrals take their place, followed by the lower and then upper lateral incisors between 7 and 8.
At this point there is another pause in tooth loss/eruption that may surprise many parents that have been caught up in the excitement of teeth being lost every few months. Dont worry, this is normal. In fact, we even have a technical name for it in dentistry, the mixed dentition. In the mixed dentition, for those who did the math, we now have 12 baby teeth remaining and 12 erupted permanent teeth in the mouth for a grand total of 24 teeth!
At about age 10, we normally start to lose teeth again. At 10, the lower primary canines become loose, followed by the upper and then lower primary1st molars at around 10 . Just as an aside, primary molars are replaced by permanent teeth called premolar or bicuspid teeth. All the other baby teeth are replaced by permanent teeth of the same name. Permanent molars erupt into the mouth behind the baby teeth, and dont replace a lost tooth, adding to the total number of teeth we have as adults. Tooth loss usually concludes between the ages of 11 and 12, with the upper and lower 2nd primary molars and upper primary canine teeth. Their permanent counterparts, along with the permanent 2nd molars are normally erupted into the mouth at about 12 years of age. That leaves us with 28 permanent teeth in the mouth which, barring extraction, will stay that way until the 3rd molar (wisdom teeth) erupt at around 18 years of age. That leaves us with a grand total of 32 teeth in the permanent dentition!
If you are still with me after all of that, please take note that these norms covered are averages of normal tooth progression, and not set in stone. I present them to you as a reference of what may be happening in your childs mouth. Remember, there is still that pesky variation from case to case. It is not at all uncommon for me to see a 9 year old without a baby tooth left, or a fifteen year old still holding on to a few stragglers. The actual age teeth come out is not as important as the pattern in which they do. Remember symmetry? Overall, dont worry, this is most likely what is normal for you.
That being said, sometimes things dont go according to plan. Like I mentioned earlier, losing a tooth without losing the same tooth on the other side of the mouth soon after sends up a red flag for me as an orthodontist. Other common problems include teeth prematurely lost to trauma or decay, or a tooth that has been lost more than three months ago without a permanent replacement coming in. These signs could mean many things, such as missing or malformed permanent teeth, lack of spacing necessary for permanent tooth eruption, ankylosed teeth (the tooth is fused to the bone), or permanent teeth erupting away from where it should be, just to name a few. Luckily, these are all conditions that we look for during an initial orthodontic evaluation. Treating these orthodontic problems is ideally done while the child is young. We recommend a child be screened by an orthodontist at around age 7. Because the permanent teeth havent yet erupted completely, its possible to evaluate the relationship of the teeth to each other and to act on any potential problems at the earliest stage. Any correction that is needed can be addressed at this point, and make future orthodontic treatment easier and more expedient.