According to the American Association of Orthodontists, occlusion is the relation between the upper (maxillary) and lower (mandibular) teeth as they perform their practical purpose of biting and chewing, or when the jaws are shut. When you bring the chewing surfaces of your teeth together, this affects the other teeth, as well as your gums, the muscles of the jaw, the jaw joint, and your neck and head.

Occlusion is concerned with your chewing forces, or what happens when your teeth come together. Chewing, clenching, or grinding the teeth can cause a wearing down of the teeth, gums, muscles and joints. Your dentist can determine if there are any problems associated with chewing force and the necessary steps to correct them.

Occlusion Theories

There are five different ways that dentists can think about and view occlusion. Each of these theories has its value, and treatments that stem from each have been successful. The theories all share the same view of normal occlusion, in that the upper and lower teeth should fit together in an even way. There should not be a tooth that comes together higher than another. Furthermore, only the front teeth should make contact when the upper and lower jaws move from side to side; the back teeth should not touch. These theories of occlusion differ in the consideration of where the jaw or temporomandibular joint should be positioned during treatment.

  • Intercuspal theory: Tooth contact determines occlusion.
  • Musculoskeletal/centric relation theory: The balance of the jaw muscles, rather than the way the teeth come together, determines the occlusion.
  • Most posterior retruded position theory: The manner in which the ligaments brace the components of the jaw joint determines occlusion, in particular around the rearmost hinge axis.
  • Anterior protrusive position theory: The manner in which the muscles brace the components of the jaw joint determines occlusion.
  • Neuromuscular theory: Gravity determines the occlusion, determined by the point in the jaw muscles that is most relaxed.

Your dentist may decide to follow one theory or another depending on several factors, such as patient characteristics and the type of treatment that is proposed for the patient. The dentist’s education, training, and various other factors also come into play.

Classifying Occlusion

Occlusion is considered normal when the upper and lower teeth fit properly and evenly together with the smallest amount of harmful interference. Malocclusion is defined as abnormal occlusion, or when the upper and lower teeth do not fit evenly together.

There are three classes of occlusion that describe how the teeth come together:

Class I occlusion: Usually considered the “ideal” and least destructive. Simply stated, a Class I occlusal relationship is frequently recognized by the lower anterior incisors sitting just behind the upper anterior incisors when biting down.

Class II malocclusion: Also referred to as an overbite, it is identified by the lower anterior incisors positioned significantly behind the upper anterior incisors when biting down. It is typical that the lower front teeth sit close to or on the gum tissue behind the upper teeth. A Class II malocclusion may cause discomfort, excessive wear of the front teeth, damage to the bone, and if not treated in time, the eventual loss of the upper anterior incisors.

Class III malocclusion: Also referred to as a crossbite, it is recognized by the lower anterior incisors situated edge to edge with, or just in front of, the upper anterior incisors when biting down.

While these classifications aid in understanding the types of occlusion or malocclusion, be aware that just because teeth might not seem to have normal occlusion, if there are no signs or symptoms of pathology, then occlusion is most likely “normal” for that person. Likewise, it is possible that a person with a “normal” occlusion may experience dental problems and need to adjust his or her occlusion.

Understanding Malocclusion

There are five main muscles in the head that control your capacity to open and close your mouth. When you chew, clench or grind your teeth, these muscles combine to produce great forces. If your teeth are misaligned, these forces can be destructive to the ligaments and bone that hold the teeth in place, as well as to the muscles of the head, neck, and jaw joint. This destruction is manifested in symptoms including chronic headaches, muscle pain, and temporomandibular joint disorder (TMD). It could also be harmful to the teeth, resulting in tooth wear and sensitivity, tooth injuries, or tooth loss.

Causes of Malocclusion

Malocclusion may be caused by one or more biological or habitual factors:

  • A small mouth can restrict teeth from growing because of reduced space. Teeth will undergo crowding especially when the permanent teeth erupt.
  • If extra teeth develop, or not enough teeth grow and surface, malocclusion can result. The loss of baby teeth or teeth harmed by traumatic injury to the face or jaw can also affect the bite. Additionally, teeth that protrude in certain ways contribute to malocclusion.
  • If the jaw or supporting bone structure is misaligned, the bite may be affected, resulting in difficulty with chewing, speaking, or performing other functions of the teeth. Moreover, malocclusion may be a factor in other oral health problems like TMD and teeth grinding.
  • Thrusting the tongue forward and pressing it strongly against the lips may result in the protrusion of teeth or “open bite,” especially for children.
  • Poor habits such as thumb sucking during and beyond infancy may result in protrusion of teeth. Adults who persist in sucking their fingers or thumb are in danger of forming poorly developed dental and facial features.

Identifying Malocclusion

Malocclusion may be identified by one or a few of these common signs. Your dentist will help to evaluate if you experience these signs and have a problem with your occlusion.

  • Tooth sensitivity
  • Tooth wear and tear
  • Tooth breakage
  • Tooth loss
  • Previous root canals
  • Jaw joint pain
  • Joint noises
  • Head and neck muscle pain
  • Headaches