A malocclusion is any misalignment between your upper and lower teeth when your jaw is closed. Roughly 56% of people worldwide have some form of malocclusion, making it one of the most common dental conditions. It ranges from mild crowding to significant jaw misalignment that affects chewing, speaking, and long-term oral health.
Unlike most medical problems, malocclusions usually result from variations in normal development rather than a disease process. Your teeth, jaw bones, surrounding muscles, and soft tissues all interact as you grow, and small deviations in any of those can shift your bite out of alignment.
How Dentists Classify Malocclusion
Orthodontists group malocclusions into three main classes based on how your first molars (the large teeth toward the back of your mouth) line up.
- Class I: Your molars align correctly, but individual teeth are crooked, crowded, or spaced too far apart. This is the most common type.
- Class II: Your upper jaw and teeth sit noticeably forward of your lower jaw. This creates what people often call an overbite. Within Class II, one subtype involves protruding front teeth with a deep overlap, while another features a broad upper arch with less protrusion but still a deep vertical overlap of the front teeth.
- Class III: Your lower jaw juts forward past your upper jaw, sometimes causing a crossbite where lower front teeth sit in front of the upper ones. This is commonly called an underbite.
Beyond these classes, specific bite problems have their own names. An open bite means your front teeth don’t touch when you close your mouth. A crossbite means one or more upper teeth sit inside the lower teeth instead of outside. Crowding happens when your jaw doesn’t have enough room for all your teeth, while spacing is the opposite, with gaps between teeth. Overjet refers to how far forward your upper front teeth extend past the lower ones horizontally. In an ideal bite, that distance is only 1 to 2 millimeters.
What Causes a Misaligned Bite
Genetics plays a major role, though researchers note that genetic and environmental factors are so intertwined they’re difficult to separate cleanly. The shape of your dental arch is determined by your underlying bone structure, the path your teeth take as they erupt, the muscles around your mouth, and how your tongue and lips press against your teeth over time. A mismatch between tooth size and jaw size, which is largely inherited, is one of the most direct causes of crowding or spacing.
Childhood habits are a significant environmental factor. Pacifier use and thumb sucking push the front teeth forward and can hold the jaw in an open position, encouraging the back teeth to over-erupt and creating an open bite. The critical threshold appears to be around age three. Children who stopped using a pacifier before three had substantially lower rates of bite problems, while those who continued past three saw open bite rates jump from roughly 19% to 65% in one study. Extending pacifier use beyond 18 months increased the risk of developing an open bite by more than three times.
Other contributing factors include early loss of baby teeth (which lets neighboring teeth drift into the gap), jaw injuries, and TMJ disorders that change how the jaw moves and rests.
Signs You Might Notice
Some malocclusions are obvious in the mirror: crowded or overlapping teeth, a visible gap when you close your mouth, or a lower jaw that looks like it sits too far forward or back. Others are subtler. You might notice a lisp or difficulty pronouncing certain sounds. Chewing might feel uneven, or you might catch yourself biting the inside of your cheek regularly. Jaw pain, clicking, or headaches can also trace back to a bite that forces your jaw muscles to compensate.
Why It Matters Beyond Appearance
Left untreated, malocclusion tends to cause problems that worsen with age. Crowded teeth trap food in spots your toothbrush and floss can’t easily reach, raising your risk of cavities and gum disease. Gum recession is another common complication, particularly when teeth are pushed out of their ideal position in the bone. Over time, an uneven bite distributes chewing forces unevenly, which can wear down certain teeth faster and strain your jaw joints.
In more severe cases, difficulty chewing can limit the foods you’re able to eat comfortably, potentially affecting nutrition. Speech issues tied to tooth position sometimes persist into adulthood if the underlying alignment isn’t addressed.
How Malocclusion Is Diagnosed
A dentist or orthodontist starts with a visual exam and moves to imaging when they need precise measurements. The standard tool is a lateral cephalometric radiograph, essentially an X-ray of your skull from the side. It reveals the relationship between your upper jaw, lower jaw, and the base of your skull by measuring specific angles. For example, the angle between the upper jaw and skull base averages about 81 degrees, while the lower jaw averages 78 degrees. The difference between these two angles tells the orthodontist whether your jaws are in a Class I, II, or III skeletal pattern.
A front-facing X-ray can also be taken to assess jaw width and symmetry. Many offices now use digital tracing software or 3D intraoral scans to map your teeth precisely, replacing the old method of biting into a tray of impression material.
Treatment Options and What to Expect
Treatment depends on severity, but most malocclusions are correctable. For mild to moderate cases, traditional braces or clear aligners gradually shift teeth into better positions. A typical course of treatment runs about two and a half years. One study of Class II patients found average treatment times of roughly 30 months, and interestingly, the amount of crowding didn’t significantly affect how long treatment took.
Children and teens sometimes benefit from interceptive treatment, devices like palatal expanders that widen a narrow upper jaw while the bones are still growing. This can prevent more complex correction later. For severe skeletal malocclusions in adults, where the problem is the jaw bones themselves rather than just tooth position, orthodontics may be combined with surgery to reposition the upper jaw, lower jaw, or both.
After active treatment ends, retainers are standard. Teeth have a natural tendency to drift back toward their original positions, so most people wear a retainer at night long-term to maintain their results.
When Children Should Be Screened
The American Association of Orthodontists recommends children have their first orthodontic evaluation by age seven. At that age, a mix of baby and permanent teeth is present, and an orthodontist can spot developing problems with jaw growth or tooth eruption early enough to intervene simply. Most children evaluated at seven won’t need immediate treatment, but early screening catches the cases where waiting would make correction harder.
Prevalence stays remarkably consistent across age groups. A large meta-analysis found that about 54% of children have some degree of malocclusion in both their baby teeth and permanent teeth, suggesting that bite issues identified early tend to persist rather than self-correct. Regional rates vary widely, from 48% in Asia to 81% in Africa, likely reflecting differences in genetics, diet, and access to early intervention.