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Classes of Occlusion

Occlusion is the way that the upper and lower rows of teeth line up in the human mouth. There are three classes of occlusion, meaning that there are three different ways that teeth line up in the mouth. There are degrees of variation in each class, but only one is considered to be "normal" or healthy.

  1. Class I

    • Class I occlusion is the standard for normalcy in teeth alignment. A person with a Class I occlusion has teeth that line up properly, creating balance between the upper and lower jaws. When this type of occlusion occurs, the person's first molars on top and bottom touch each other when the mouth closes. The top front teeth protrude just slightly in front of the bottom front teeth.

    Class II

    • Class II occlusion is the most common deformity, according to drspiller.com. In Class II occlusion, the bottom jaw sits slightly behind where it should. This gives the person a "weak chin" or receded chin in their profile. Some people actually find this type of profile attractive in women, because it often leads the viewer to focus his attention on the woman's eyes. However, Class II occlusion is sometimes a functional problem. It can lead to having the front teeth overlap too far and can create a gummy appearance when a person smiles.

    Class III

    • A Class III occlusion creates the opposite problem to a Class II occlusion. In this case, the top jaw is further back than it should be. This leads to a profile with a protruding chin. Traditionally, some people associate this type of profile with a stereotypical masculine appearance. This can cause the lower teeth to show too much when a person smiles. Functionally, a person with a severe Class III occlusion might have difficulty biting. While a person with a Class I occlusion can bring his or her lower jaw forward to bite with the front teeth, a person with a Class III occlusion cannot bring the lower jaw backward to do the same. A person with a Class III occlusion that is severe enough might not be able to use his front incisors to bite through foods.

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