Classification of Malocclusion

The system used in orthodontics to classify how teeth bite (i.e. occlusion) was first proposed by the "father of orthodontics" Edward Angle. By studying the human skull, Angle defined the occlusion into three major groups: Class I, Class II, and Class III based upon the relationship of upper and lower 1st molars when jaws close.

Class I is defined when upper 1st molar occludes behind the lower 1st molar, Class II is defined when upper 1st molar occludes ahead of lower 1st molar, and Class III is defined as upper 1st molar occludes far behind the lower 1st molar.

Besides simplicity, Angle's classification offers a convenient way to assess jaws' relationship by checking the molar's occlusion. In general, Class I refers to a neutral upper and lower jaw relationship; Class II refers to either a protrusive upper jaw or retrusive lower jaw; and Class III refers to a retrusive upper jaw or protrusive lower jaw. These assessments can help orthodontist identify the problem to be corrected and formulate an achievable treatment plan.