We all like a visit from the tooth fairy, but isn't it kind of weird that we're born essentially toothless, a set of teeth grows in when we're babies, and then we lose those to make room for our comparatively giant adult teeth? The vast majority of mammals grow two sets of teeth during their lives. Our young are born toothless because mammals produce milk for their young, and mothers definitely don't want to be nursing babies with rows of sharp teeth. Losing our baby teeth — also called deciduous teeth because they fall out of our heads like autumn leaves — allows us to change our diet as we mature, and makes the most of the food-grinding capacity of our growing jaws.
So, what happens when we get our primary teeth as babies, but our adult teeth don't come in? Do we just keep our tiny baby teeth forever?
There are a few different conditions that could lead to someone not losing their primary teeth, and dentists have their ways of dealing with each, depending on whether the permanent teeth are sitting right up there waiting for the coach to put 'em in, or whether they just didn't make it to the game.
When Baby Teeth Leave the Nest
It's difficult to predict the lifespan of a baby tooth, since they're only supposed to do their job for about a decade, give or take a couple of years. That said, if a permanent tooth doesn't swoop in to take its place, a primary tooth may far outlast its life expectancy, or it could also just totally fail without warning. When a primary tooth is working way past its expiration date, a dentist will probably keep tabs on it to make sure it's healthy, but eventually it'll have to be removed and replaced.
If the permanent teeth are taking a little longer to develop than normal, or are sitting in the wings, but just aren't emerging, the dentist will usually want to wait to see what is going to happen. In the case of an ectopic tooth, a permanent tooth develops normally, but fails to erupt. In these cases, the position and angle of the tooth relative to the permanent teeth that have already erupted will help a dentist or orthodontist decide what to do. Oftentimes, an attempt is made to orthodontically drag a recalcitrant tooth into the correct position.
But having perfectly formed permanent teeth that are just kind of slow to emerge is definitely a best-case scenario. It's much harder to treat a patient who doesn't have any adult teeth to coax out.
Tooth agenesis is a congenital condition wherein a patient's mouth just didn't get directions to make some of their permanent teeth when they were born. This can range in severity from hypodontia, in which five or fewer teeth are missing, to oligodontia, when six or more permanent teeth are missing in action — this is uncommon, but often associated with genetic syndromes like Down syndrome, Van Der Woude syndrome, Reiger syndrome and ectodermal dysplasia. Anodontia is a rare recessive genetic disorder in which someone just doesn't get permanent teeth — it's also often associated with conditions like ectodermal dysplasia.
"Congenitally missing teeth are relatively uncommon," writes Jim Nickman, president of the American Academy of Pediatric Dentistry, in an email. "In the primary dentition, up to 2 percent of children will experience missing teeth, but in the permanent dentition, the range in various studies is from 0.15 percent to 16 percent. The most common missing permanent teeth are lateral incisors and premolars, and it's very common that a missing baby tooth also will not have a permanent successor."
Miracles of Modern Dentistry
So, let's say you don't have some of your permanent teeth. What can your dentist do about it?
It largely depends on what's wrong, but you can bet it's probably going to be expensive and time-consuming. In the case of a single missing tooth, your dentist might propose solutions ranging from a dental implant to some sort of fixed bridge. A treatment often used for children who are congenitally missing their incisors is to use orthodontics either to open up some space for a future implant or bridge, or shove another permanent tooth into the space to camouflage the gap.
According to Nickman, for multiple missing teeth (depending on their location), patients could end up with implants, fixed bridges or removable partial dentures. But for complete loss of teeth, the treatment would consist of removable or fixed dentures, depending on how well-developed the bone is around the missing teeth.
Sometimes a dentist will perform bone grafts to fill in a place where bone hasn't grown. But, although dentists can do all sorts of fancy patching and bridging and screwing things into your jaw, any treatment for tooth agenesis is going to have to be continually maintained. "For a young child with oligodontia or anodontia, this can be a lifelong burden requiring multiple 'temporary' partial or complete dentures until they are physically developed enough to undergo implant placement," says Nickman.
In summary, if you have all your permanent teeth in your head, take a moment to thank them for their service. Now go brush them. And don't forget to floss.