The small tooth right next to your two front teeth, called the lateral incisor, is one of the most commonly missing teeth in humans. If you’ve noticed that you, a friend, or seemingly everyone around you has a gap or a small peg-shaped tooth in that spot, there’s a good reason: somewhere between 2% and 5% of people never develop one or both of these teeth. That makes it common enough that you’ll spot it regularly once you start looking.
This isn’t caused by injury or decay. The tooth simply never formed beneath the gum. The permanent tooth bud that should have developed during childhood was absent from the start, a condition dentists call congenital absence or hypodontia. And the upper lateral incisor is one of the teeth most vulnerable to this.
Why the Lateral Incisor Specifically
Not all teeth are equally likely to go missing. After wisdom teeth (which a huge portion of the population lacks), the most commonly absent permanent teeth follow a consistent pattern: lower second premolars rank first, followed closely by upper lateral incisors. Lower front teeth, lower canines, and upper second premolars trail behind in frequency.
The lateral incisor’s vulnerability comes down to its position in the developmental sequence. Teeth form from clusters of cells called tooth buds during fetal development and early childhood. The lateral incisor sits at the end of a developmental field in the upper jaw, essentially on the boundary between two zones of tooth formation. Teeth at these boundary points are the most likely to fail to develop, because they receive the weakest developmental signals. Think of it like being at the edge of a WiFi signal: sometimes you connect, sometimes you don’t.
Genetics Drive Most Cases
Missing lateral incisors run strongly in families. If one of your parents is missing a lateral incisor, your chances of also missing one are significantly higher than the general population. Researchers have identified mutations in specific genes involved in tooth development that contribute to hypodontia, and these mutations can be passed down through generations. Some of these same genetic variations also influence overall tooth size, which explains why family members of someone with a missing tooth often have smaller-than-average teeth themselves.
The genetic nature of the condition also explains why it’s sometimes bilateral: if you’re missing the lateral incisor on one side, there’s a meaningful chance the one on the other side is also absent or unusually small. A common variation is the “peg lateral,” where the tooth does form but comes in much smaller and more cone-shaped than normal. This represents a partial expression of the same genetic tendency. The tooth bud started to develop but didn’t receive enough of the right signals to reach full size.
Human Jaws Are Getting Smaller
There’s a bigger evolutionary story behind missing teeth. Over the course of human evolution, our jaws and faces have been shrinking. As our diets shifted from tough, raw foods to softer, cooked meals, the functional demand on our jaws decreased. Smaller jaws meant less room for teeth, and over hundreds of thousands of years, tooth number and tooth size both declined in response. Meanwhile, human brains and skulls grew larger, further compressing the space available for the lower face.
Research published in Scientific Reports suggests this process may still be active, with common gene regulatory mechanisms coordinating both jaw size and tooth number. In other words, missing lateral incisors may not be a defect so much as a continuation of a long-running trend in human development. This could help explain why prevalence varies across populations: a meta-analysis found hypodontia rates of 5.5% in Europe, 6.3% in Australia, and lower rates in North America.
How to Know If a Tooth Never Formed
Most people discover a missing lateral incisor in childhood, when the baby tooth in that position either falls out and nothing replaces it, or simply refuses to fall out at all. When a permanent tooth is absent, the baby tooth above it has no reason to loosen, because there’s nothing pushing it from below. These retained baby teeth can sometimes last well into adulthood, though they tend to be smaller than the surrounding permanent teeth and may eventually wear down or develop problems.
A dental X-ray is the definitive way to confirm what’s happening. The X-ray will show whether a permanent tooth bud exists beneath the gum. Dentists typically take these images around age 7 to 10, which is when the absence becomes clear. If you’re an adult who still has a noticeably small tooth in the lateral incisor position, it may actually be your baby tooth hanging on, with no permanent successor behind it.
When Missing Teeth Signal Something Bigger
For most people, a missing lateral incisor is an isolated trait with no broader health implications. But when someone is missing several teeth (not just one or two), it can occasionally point to a group of conditions called ectodermal dysplasias. These are disorders affecting structures that develop from the same embryonic tissue layer: teeth, hair, skin, sweat glands, and nails. More than 180 types have been identified.
Dentists are often the first to suspect ectodermal dysplasia, particularly when a child has multiple missing teeth, teeth with unusual shapes, or widely spaced teeth combined with other signs like thin hair or dry skin. A single missing lateral incisor without other symptoms is almost never a cause for concern beyond the cosmetic and functional issues of the gap itself.
Filling the Gap
If you’re missing a lateral incisor, there are three well-established approaches to managing the space, and the best option depends on your bite, your age, and the position of your other teeth.
- Orthodontic space closure: Braces or aligners shift the canine tooth (the pointed “eye tooth”) forward into the lateral incisor’s spot. The canine is then reshaped to look more like the missing tooth. This approach avoids any prosthetic work entirely and can produce excellent long-term results, especially when started in adolescence.
- Implant after space opening: Orthodontics is used to create or maintain the correct amount of space, and then a dental implant with a crown is placed once jaw growth is complete (usually age 18 or older). This preserves the natural position of all remaining teeth.
- Resin-bonded bridge: A prosthetic tooth is bonded to the back of one or both adjacent teeth, filling the gap without surgery. This is less invasive than an implant and can be a good option when an implant isn’t feasible.
Each approach has trade-offs in terms of longevity, appearance, and cost. The space closure route avoids artificial teeth altogether but requires the canine to convincingly mimic a lateral incisor. Implants look natural but require surgery and can’t be placed until the jaw has finished growing. Bonded bridges are the least invasive prosthetic option but may need replacement over time. Many people with missing lateral incisors go through a combination of orthodontic treatment in their teens followed by a final restoration in early adulthood.