Oct. 9 (Tue.), 2001

1. Introduction

The importance of chewing and its relationship to systemic health have been emphasized in "Healthy Japan 21" and "8020 Movement". Not only is chewing a means of nutritional intake, but it has effects on higher levels such as brain function according to recent data. There are various pieces of evidence from many studies indicating an association between occlusal function and systemic health. Occlusion is central to chewing function. During the period of growth and development, which is associated with an increasing incidence of malocclusions, the primary teeth exfoliate and are replaced with permanent teeth, and skeletal growth and neuromuscular development are also very active. It has been shown that the restoration and maintenance of harmony between form and function during this important period of occlusal development allows normal functional and morphological development of the maxillo-facial structures including the temporomandibular joints. It is therefore important to establish a concept and a system of treatment that will help normalize occlusal relationship at the earliest possible stage of growth and development. Discussion in this symposium will focus on characteristics and differential diagnosis of Class III malocclusions from the viewpoint of early treatment.

There are three possible situations in which early Class III treatment is not successful in day-to-day clinical practice. 1) Early treatment starting in the primary dentition does not result in adequate improvement of anterior crossbite. 2) A correct relationship of permanent incisors is achieved with early treatment but relapses back to a crossbite in the mixed dentition. 3) Excessive growth of the mandible occurs in the permanent dentition, necessitating orthognathic surgery.

I would like to present three sets of opposing views based on my clinical experience with interceptive or early treatment. Pros and cons of each view will be discussed.

First, there is a view that even a skeletal Class III malocclusion is correctable with active early treatment. The opposing view is that a true skeletal Class III problem is prone to relapse with growth after early treatment and therefore difficult to treat with orthodontics alone.

Second, a dentoalveolar or functional crossbite may progress to skeletal mandibular prognathism if left untreated. Another view is that this is due to the failure of correctly diagnosing skeletal mandibular prognathism, which is genetically determined and uncorrectable with orthodontics.@

Third, some people say that cross-sectional records taken at the time of the initial examination in the primary or mixed dentition allow precise orthodontic diagnosis and prediction of treatment outcome. Others say that in addition to these initial records, longitudinal studies of changes over time in similar cases are needed to obtain indices for prediction of patient response to Class III treatment.

These issues will be discussed and hopefully clarified in this symposium with an emphasis on the third point, the question of whether it is possible to derive indices for differential diagnosis from longitudinal observations of early treatment effects.