Crooked teeth are teeth that grow in misaligned, overlapping, twisted, or spaced unevenly within the jaw. The medical term is malocclusion, and the World Health Organization ranks it as the third most common oral health problem worldwide, behind only cavities and gum disease. Most people have some degree of misalignment, and it ranges from a mild cosmetic concern to a significant functional issue that affects chewing, breathing, and long-term dental health.
Types of Crooked Teeth
Not all misalignment looks the same. Orthodontists group it into broad categories based on how the upper and lower teeth relate to each other, plus several specific patterns you might recognize in your own mouth.
- Crowding: The most common form. Teeth overlap or twist because there isn’t enough room in the jaw for them to line up.
- Overbite (deep bite): The upper front teeth overlap the lower front teeth more than they should. About 22% of people with permanent teeth show a significant deep bite.
- Overjet: The upper front teeth jut forward noticeably, sometimes called “buck teeth.” This is different from a standard overbite because the teeth project outward rather than simply overlapping downward.
- Underbite: The lower front teeth extend beyond the upper front teeth, often linked to a jaw that grows further forward than usual.
- Crossbite: Some upper teeth sit inside the lower teeth instead of outside them. This affects roughly 9 to 12% of people depending on age.
- Open bite: The front teeth don’t meet when the back teeth are closed together, leaving a visible gap.
- Spacing: Gaps appear between teeth, either from missing teeth or from a jaw that’s larger than the teeth can fill.
Globally, about 75% of people fall into the mildest classification where the jaw itself aligns properly but the teeth are still crowded or slightly off. Around 20% have a more significant forward positioning of the upper jaw, and roughly 6% have the reverse pattern where the lower jaw sits too far forward.
Why Teeth Grow In Crooked
Genetics is the biggest driver. The genes that control tooth size, tooth number, and jaw dimensions don’t always coordinate perfectly. You can inherit large teeth from one parent and a narrow jaw from the other, leaving your teeth with nowhere to go but sideways or on top of each other. Researchers have identified specific genes involved: mutations in one gene family affect whether teeth develop at all, while another set controls where teeth erupt in the arch. Conditions like ectodermal dysplasia, which causes small, misshapen, or missing teeth along with underdeveloped upper jaws, follow clear inherited patterns.
Canine teeth that drift into the roof of the mouth instead of dropping into their correct position are a good example of genetic influence. This happens even when there’s plenty of room in the arch, and it tends to run in families, suggesting the positioning error is coded into development rather than caused by crowding alone.
Childhood Habits
Thumb sucking and prolonged pacifier use physically reshape the growing jaw. The repeated pressure pushes the front teeth forward, narrows the upper arch, and can create an open bite where the front teeth no longer touch. Pacifier use beyond 36 months is particularly associated with both open bites and crossbites, because the object sitting in the mouth alters tongue position and muscle dynamics during a period when the bone is still soft and responsive to force.
The Modern Diet Factor
People in industrialized societies have measurably higher rates of crooked teeth than people in non-industrialized communities, and the leading explanation is food texture. Softer, more processed diets put less mechanical stress on the jaw muscles during chewing. Over time, and potentially across generations, this reduced stimulation appears to produce narrower upper jaws and shorter lower jaws. Animal studies confirm the pattern: subjects raised on soft diets develop narrower, more recessed jaws compared to those eating harder food. A smaller jaw with the same number of teeth means crowding, impacted wisdom teeth, and in some cases restricted airways.
How Crooked Teeth Affect Your Health
Mild misalignment is extremely common and doesn’t always cause problems. But when teeth are significantly crowded, overlapping, or mispositioned, the consequences go beyond appearance.
Overlapping teeth create tight spots that are difficult or impossible to clean properly with a toothbrush and floss. Plaque builds up in these areas, raising the risk of cavities and gum disease over time. Teeth that don’t meet evenly distribute chewing forces unevenly, which can wear down enamel on certain teeth faster than others. A misaligned bite also forces the jaw joints and muscles to compensate, which can contribute to jaw pain, clicking, headaches, and difficulty opening the mouth fully. In more severe cases, protruding front teeth are more vulnerable to injury during falls or contact sports.
How Misalignment Is Diagnosed
A dentist or orthodontist evaluates crooked teeth through a combination of visual examination, dental molds or digital scans, standard X-rays, and sometimes a specialized lateral skull X-ray called a cephalometric radiograph. That lateral image lets the orthodontist measure precise angles between the upper jaw, lower jaw, and skull base to determine whether the problem is purely dental (teeth in the wrong position) or skeletal (the jaws themselves are mismatched in size or position). This distinction matters because it determines whether braces alone will work or whether the jaw itself needs to be addressed.
Treatment Options
The two most common approaches are traditional braces and clear aligners, and both work by applying sustained, gentle pressure that gradually moves teeth through bone over months.
Traditional braces use brackets bonded to each tooth, connected by a wire that an orthodontist tightens or replaces at regular appointments. They remain the most versatile option, capable of handling everything from mild crowding to complex bite corrections. Clear aligners use a series of custom-made plastic trays instead. You wear each set for one to two weeks, then switch to the next tray in the sequence. They’re effective for mild to moderate cases and are less visible, but they require discipline since they need to stay in your mouth for 20 to 22 hours a day to work properly.
For severe skeletal misalignment, where the jaws themselves are significantly different sizes, orthodontics alone can’t fully correct the bite. These cases sometimes require surgical repositioning of the upper jaw, lower jaw, or both, typically done after the jaw has finished growing.
How Long Treatment Takes
The average duration of orthodontic treatment with braces is about 18.5 months, though individual cases can be shorter or longer depending on several factors. Cases that require tooth extractions to create space average close to 20 months, while non-extraction cases average about 17.5 months. Interestingly, age at the start of treatment doesn’t significantly affect how long it takes.
The biggest factor within your control is showing up to appointments. Patients who missed more than one scheduled visit had significantly longer treatment times. Broken brackets also extend treatment, since each repair session interrupts the planned tooth movement. The most efficient path to straight teeth is keeping your scheduled visits and being careful with hard or sticky foods that can pop brackets off.
When Treatment Starts
Children are typically first evaluated by an orthodontist around age 7, when enough permanent teeth have come in to spot developing problems. Early treatment during childhood can take advantage of jaw growth to guide the bones into better alignment, potentially simplifying or shortening treatment later. But orthodontic correction works at any age. Adult treatment has become increasingly common, and the biological process of moving teeth through bone responds to pressure regardless of whether you’re 14 or 44. The timeline is similar, though adults may have additional considerations like existing dental work or gum recession that influence the treatment plan.