By LunaDNA Contributor
The causes of crooked teeth are varied. Our ancestry may have interesting clues to the genetics of crooked teeth. Learn about crooked teeth, and how DNA may play a role in overall teeth health.
According to the American Association of Orthodontists, an estimated 4 million people wear braces on their teeth. However, misaligned teeth are a recent development in human evolution. Early human fossils from cavemen usually have well-aligned, uniform teeth. Some anthropologists believe the development of misaligned teeth occurred when our jaws began shrinking over time due to changes in our diet that required less chewing. Today, we know that some genetic factors, such as jaw size and number of teeth, can affect misalignment, but behaviors and environmental causes are also involved.
Crooked teeth are common over the last few hundred years, yet skulls from humans that lived thousands of years ago have well-aligned teeth. Fossils show that cavemen didn’t have many dental problems despite the lack of toothpaste and floss. Today, dental consultations are recommended before the age of 8. Learn more about crooked teeth and its genetic connections, including:
- What Causes Crooked Teeth?
- Types of Crooked Teeth
- Are Crooked Teeth Genetic?
- Ancestry of Crooked Teeth
- Problems Associated With Crooked Teeth
What Causes Crooked Teeth?
Crooked teeth do not always happen by chance. Habits and maladies that may lead to undeveloped jaws and crowded teeth include:
- Tongue thrusting (also known as reverse swallowing)
- Thumb sucking
- Prolonged use of pacifiers
- Mouth breathing (due to allergies, asthma, and other conditions that cause a person to breath through his or her mouth)
- Open mouth posture
- Tumors of the mouth and jaw
These habits and maladies contribute to poor jaw growth, leaving many with misaligned teeth and undeveloped jaws. This improper development can limit the space available for teeth and can prohibit them from growing in the ideal position.
An undeveloped jaw can lead to a mouth of crowded teeth. Since orthodontia work does not usually start until all permanent teeth come in, teeth might be pulled, because the jaw is deemed too small to accommodate all the teeth.
Mouth breathing leads to the tongue not resting in the correct position on the roof of the mouth. This can in turn lead to an underdeveloped upper and lower jaw. An upper jaw improperly developed may restrict the airway further. This can keep the mouth open, which might exacerbate the problem.
Reverse swallowing, also known as tongue thrusting, occurs when the tongue pushes forward and the lips push back when swallowing. A child swallows at least a couple times a minute, so pushing the tongue forward against the teeth can, over time, create a condition called open bite.
Diet may be a factor too. In the 1930s, Weston Price, an American dentist, studied various groups around the world and found that those employing a primitive diet had little tooth decay, larger jaws, and straight teeth. Orthodontics became a specialty in 1900 in response to bad habits and maladies that children had during the Industrial Revolution. After the Industrial Revolution, people swapped out a natural diet, closer to what their ancestors had eaten, for one of more processed foods. It is possible that this softer diet hindered normal jaw growth because less jaw strength was required.
Types of Crooked Teeth
Crooked mouthfuls of teeth come in all shapes and sizes, but there are three general classes of malocclusions, which means misaligned teeth:
Class 1 occurs when the upper teeth slightly overlap the lower teeth, but the bite is normal. This is the most common type of crooked teeth.
Class 2 occurs when the upper teeth and jaw severely overlap the lower teeth and jaw and is sometimes called an overbite. Difficulties in chewing can be painful and can lead to headaches and temporomandibular joint dysfunction (TMJ), a painful condition of the joint that connects your jaw to the side of your head.
Class 3 occurs when the lower teeth project beyond the front of the upper teeth when the jaw closes and is sometimes called an underbite. Those with underbites can have trouble chewing and often suffer from headaches. Overtime, an underbite can cause TMJ.
Are Crooked Teeth Genetic?
Humans today are nearly identical to their ancestors who had straight teeth. This suggests that crooked teeth are partly a result of evolution. Some experts believe that the Industrial Revolution, which happened about 150 to 200 hundred years ago, triggered people to have crooked teeth.
Interestingly, most wild mammals have straight teeth. Some researchers believe that when culture shifted from rural to manufacturing, something went awry. Others think it happened thousands of years earlier, when humans transitioned from hunting and gathering to farming. Ancestral upper and lower jaws of hunter-gatherers were more often better aligned than those of later humans.
Ancestry of Crooked Teeth
With the introduction of the modern baby bottle in the mid-1800s, human populations became less reliant on breastfeeding their young. Research has shown that the muscles required for an infant to breastfeed are not used as extensively when a child is bottle-fed. At the end of the 1940s, German dental experts Dr. Wilhelm Balters and Dr. Adolf Müller discovered that babies who had been breastfed had significantly fewer crooked teeth. Studies continue to be conducted to determine if there is a link between the use of bottles and the impact it has on jaw development and crooked teeth.
Problems Associated With Crooked Teeth
Crooked teeth make it harder to chew and can put a strain on the jaw, increasing the risk of breaking a tooth. It is also harder to clean crooked teeth, leaving the opening for cavities and other dental maladies. Protruding teeth can rub against and wear down other teeth.
Beyond this, crooked teeth can impact overall health. This decreases the chance of bacteria going into the pockets of the gums, which can lead to gum disease. Some research suggests that, when bacteria is left untreated, it can enter the bloodstream and may lead to heart disease, diabetes, or stroke.
While we know some genetic causes for tooth issues, much is still unknown about the connections between genes and dental problems. Researchers are hopeful that recent discoveries will open the door for the development of new and improved dental- and orthodontic-care tactics and treatments.
Luna is bringing together individuals, communities, and researchers to better understand life, including genetic traits like crooked teeth. Directly drive health discovery by joining the Tell Us About You study. The more we come together to contribute health data for the greater good, the quicker and more efficient research will scale, and improve the quality of life for us all.