The ABO discrepancy index: a measure of case complexity.

A criterion for determining the acceptability of a case presented for the American Board of Orthodontics (ABO) Phase III clinical examination is case difficulty. Case difficulty can often be subjective; however, it is related to case complexity, which can be quantifiable. Over the past 5 years, the ABO has developed and field-tested a discrepancy index, made up of various clinical entities that are measurable and have generally accepted norms. These entities summarize the clinical features of a patient's condition with a quantifiable, objective list of target disorders that represent the common elements of an orthodontic diagnosis: overjet, overbite, anterior open bite, lateral open bite, crowding, occlusion, lingual posterior crossbite, buccal posterior crossbite, ANB angle, IMPA, and SN-GoGn angle. The greater the number of these conditions in a patient, the greater the complexity and the greater the challenge to the orthodontist. The ABO is considering several options for applying the discrepancy index to the Phase III clinical examination.