Crooked teeth are partly genetic, but genes are only one piece of the puzzle. Twin studies estimate that crowding in the lower jaw has a heritability range of 35 to 81 percent, while upper jaw shape (its width, length, and overall form) shows even stronger genetic influence. That said, childhood habits, breathing patterns, and diet also play major roles in how your teeth line up.
What Genetics Actually Controls
The strongest genetic influence is on the size and shape of each individual jaw. Your upper jaw’s width, length, and arch shape all show high heritability, with estimates ranging from 16 to 100 percent for width and 42 to 100 percent for length, depending on the study. The shape of your lower jaw and the amount of crowding in it are also significantly heritable, though somewhat less so than upper jaw dimensions.
Here’s the key mechanism: you inherit tooth size and jaw size somewhat independently. You might get large teeth from one parent and a narrow jaw from the other. When your teeth are too big for the jaw holding them, crowding is the result. The jaw essentially acts as a placeholder for the teeth, and if it isn’t long or wide enough, teeth get pushed out of alignment as they compete for limited space.
Interestingly, the way your upper and lower jaws relate to each other (whether your bite sits too far forward, too far back, or off to one side) appears to be less genetically determined. A systematic review of twin studies found that traits like overbite depth, the degree of horizontal overlap between upper and lower front teeth, back crossbites, and the front-to-back relationship of molars did not show strong genetic patterns. This suggests that while each jaw’s individual shape is heavily inherited, how the two jaws fit together depends more on growth and environment.
The Jaw Size Problem in Modern Humans
One reason crooked teeth are so common today is that human jaws have been shrinking for thousands of years, while teeth have stayed roughly the same size. This mismatch traces back to major shifts in diet. Hunter-gatherer populations ate tough, unprocessed foods that demanded heavy chewing. That mechanical load stimulated jaw growth during childhood and kept jaws wide and long enough to accommodate a full set of teeth.
As humans shifted to agriculture, cooking, and eventually modern processed diets, the forces acting on the jaw during development dropped dramatically. Cooked and soft foods require far less chewing effort. Animal experiments confirm this relationship directly: mice raised on soft food develop shorter, narrower jaws with misaligned incisors compared to mice fed harder diets. The same principle applies to children. A kid who grows up chewing soft, processed food simply doesn’t get the mechanical stimulus needed to grow a jaw large enough for all 32 teeth.
This doesn’t erase genetics. Rather, there’s a genetic predisposition that environment then amplifies or dampens. Your genes set a range of possible jaw sizes, and your diet and chewing habits during childhood help determine where in that range you land.
Childhood Habits That Shift Teeth
Several non-genetic factors during childhood can directly push teeth out of alignment or reshape the jaw during critical growth periods.
- Thumb and pacifier sucking: Prolonged sucking habits push the upper front teeth forward and can narrow the upper jaw. The tongue sits low in the mouth during sucking, removing its natural outward pressure on the palate, while the cheek muscles press inward. This combination often leads to a narrow upper arch and back crossbites.
- Mouth breathing: Children who chronically breathe through the mouth, often due to allergies, enlarged adenoids, or nasal obstruction, develop a recognizable pattern: a long face, narrow upper jaw, high-arched palate, and open bite where the front teeth don’t touch. Mouth breathing forces the tongue into a low resting position, removing the pressure that normally helps the upper jaw widen.
- Tongue thrusting: An abnormal swallowing pattern where the tongue pushes forward against the front teeth can cause them to flare outward and create gaps or an open bite over time.
These habits are particularly damaging during early childhood when the jaw bones are still soft and actively growing. The same habit in a teenager or adult, whose bone has largely hardened, has far less impact on jaw shape.
When Genetics Makes the Biggest Difference
Some dental alignment problems are overwhelmingly genetic. A severe underbite where the lower jaw juts far forward, for instance, often runs in families and has been linked to specific chromosomal influences. The Habsburg dynasty is a famous historical example of inherited jaw protrusion passed through generations of intermarriage.
There’s also a rare genetic condition called primary failure of eruption, where certain teeth simply cannot erupt into the mouth properly. It follows a distinct pattern: all teeth behind the first affected tooth are partly or completely stuck. Family members often have a history of baby teeth fusing to the bone. This condition doesn’t respond to braces the way typical crowding does. Applying orthodontic force to these teeth often causes them to lock into the bone permanently rather than move.
Severe skeletal discrepancies, where the upper and lower jaws are dramatically different sizes, tend to have a stronger genetic component than mild crowding. If both of your parents needed jaw surgery to correct their bite, your risk of a similar skeletal mismatch is substantially higher than average.
What This Means for Treatment
Whether your crooked teeth stem primarily from genetics or environment doesn’t change the fact that orthodontic treatment works for both. Braces and aligners move teeth through bone regardless of why those teeth ended up misaligned. The distinction matters more for predicting how stable your results will be after treatment and whether braces alone will be enough.
Mild to moderate crowding caused by a mix of genetic and environmental factors typically responds well to braces or aligners, with retainers keeping the results in place afterward. Severe jaw size discrepancies rooted in genetics, however, sometimes require surgical correction of the jaw bones themselves, because no amount of tooth movement can compensate for a jaw that’s fundamentally too large or too small.
Relapse after treatment also has a genetic dimension. The muscles around your jaw have a composition partly determined by your genes, and those muscles constantly exert forces on your teeth. If the underlying muscle pattern favors the original tooth positions, teeth will tend to drift back without long-term retention. This is one reason many orthodontists now recommend permanent or semi-permanent retainers rather than ones you wear for just a year or two.
For parents wondering whether their children will inherit their dental problems: it’s likely but not guaranteed. If you had significant crowding, your child has a higher chance of crowding too, but early intervention like addressing mouth breathing, limiting pacifier use past age two, and encouraging a diet that includes harder, chewier foods can influence how the jaw develops within its genetic potential.