[Tooth formation and eruption in skeletal Class II and Class III malocclusions]

The purpose of this study was to investigate the timing of the formation and eruption of the permanent teeth between Skeletal Class II and Class III malocclusions right before pubertal growth period. Samples consisted of twenty five Japanese girls of Class II and Class III malocclusions, respectively, with Class I girls as a control. Materials used in this study were panoramic X-rays, dental X-rays and intraoral photographs of each sample, all taken at age of 8 years. Lateral cephalometric X-rays, wrist bone X-rays and records of standing height were used to study the craniofacial characteristics and the stage of bone maturation. Results were as follows: 1. Lower teeth formation of Class III group tended to be advanced when compared with Class II group, especially at molars. 2. There was no significant difference between the two groups with regard to the timing of eruption except lower lateral incisors, but eruption of the upper second molar of Class III group tended to be delayed. Results suggested that the skeletal disharmony may be associated with different timing of formation and eruption of the permanent teeth.