Although malocclusion was originally described as the primary cause of TMJ, in more recent years there has been controversy about the role of malocclusion in causing TMJ. And not everyone agrees on which types of malocclusion are most significant. A recent review compiled a list of seven different occlusal factors that have been linked to TMJ:
- Posterior crossbite
- Large overbite
- No overbite
- Large disparity between centric relation and maximum intercuspal position
- Open bite
- Missing teeth
Posterior crossbite occurs when your back teeth don’t meet properly because either the top or bottom teeth are closer to the tongue or cheeks.
An overbite has become the normal pattern of development for people since early history. Some have attributed this development to the appearance of eating utensils like forks or chopsticks, but it appears to be healthy as long as it isn’t too large. An overbite of larger than one fifth an inch seems to be associated with TMJ, as does the existence of no overbite or an underbite.
Centric relation is when your jaw is pushed as far back and up as possible. Closing your teeth together with your front teeth sliding past one another as much as they will go is the maximum intercuspal position (MIP). Most people can’t achieve MIP with their jaw in centric relation, but if the distance between these two positions is too great, it can lead to TMJ.
Ideally, your bite forces should be properly balanced, but if you have an open bite, where some teeth don’t come together, or if you have missing teeth, your bite forces get distributed unevenly.