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What Causes Overbite?

By WebMD Connect to Care Staff
From an overbite caused by thumb-sucking to adult overbite issues, it’s time to learn what causes an overbite.

An overbite is when the front teeth overlap the bottom teeth while the mouth is closed, according to the American Association of Orthodontists. When an overbite is abnormal, it can create crowded teeth and misalignment. But what causes an overbite? Read on for more details about the defining characteristics of an overbite, and the factors that could cause one. 

Normal Overbite

Is an overbite normal? Sometimes. According to the National Institutes of Health, an upper jaw that overlaps the lower one by 3 millimeters or less is considered normal.

To determine if you have a significant overbite, an orthodontist should check how far your top teeth extend over your bottom teeth. “It is critical to understand that straightening teeth without considering the effects on your bite, gums, and the bone that hold your teeth in can lead to negative effects,” Jeffery Schaefer, DDS, an orthodontist in San Diego, tells WebMD Connect to care. 

An orthodontist is a dentist with specific training in straightening teeth and will be able to properly evaluate your mouth and tell if you have an abnormal overbite. 


Scientists have been studying the genetic influence on the formation of overbites for decades. A 2019 article published by the International Journal of Applied Dental Sciences reviewed this research and summarized studies dating back to as early as 1949. Each of these studies found that genetics and hereditary factors had an influence on whether a person has an overbite or not. 

Additionally, the shape of your jaw is in part determined by the shape of your parent’s jaws. A small lower jawwhich can also result from geneticsis another common cause of overbites, according to the American Association of Orthodontists.

Nonnutritive Sucking in Children

According to the Cleveland Clinic, several factors can cause an overbite. Prominent among these is thumb-sucking or, as it’s clinically known, nonnutritive sucking behavior. 

Using pacifiers is also considered nonnutritive sucking and it, too, can contribute to an overbite, particularly if pacifier use extends beyond the time that the child reaches age 3. Even sippy cups with spill-proof valves might increase the risk of developing an overbite.

Nonnutritive sucking leads to an increased risk of having an overbite, according to the American Dental Association. In fact, the ADA recommends that your child’s first dental visit be no later than their first birthday, and after their first teeth have come in. At this time, any teeth alignment issues, including an overbite, can be addressed.

Unusual Biting Habits in Adults

Teeth-grinding, nail-biting, and clenching your jaw are unusual biting habits that can lead to an overbite in adults. According to the U.S. National Library of Medicine, other causes of overbites include:

  • Crowns or fillings that don’t fit well
  • Improperly fitted retainers or braces
  • Mouth or jaw tumors
  • A jaw that doesn’t heal properly after severe injury

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