Long-term development in the mandible and incisor crowding with and without an orthodontic stabilising appliance

In children with dentoalveolar Class II malocclusion with proclined upper incisors treated with extraction of the maxillary first premolars and appliance in the upper jaw only has been reported to increase the lower arch crowding when compared with children with untreated normal occlusion. Stabilising orthodontic appliances might therefore be useful in the lower jaw. A comparison was made of Class II: 1 malocclusion with extraction in the upper arch in 35 individuals in whom a fixed orthodontic appliance was used in the upper arch only and 26 individuals with fixed appliances in both jaws. The mean age at the start of treatment was 12.9 and 12.8 years, respectively. Treatment effects and post-retention changes up to 4 to 5 years out of retention at the age of 20 to 22 years were evaluated from lateral head films and plaster casts. During treatment the orthodontic appliance in the lower arch relieved crowding. The available lower anterior space increased from -0.6 to +0.2 mm, compared, to a decrease from -0.4 to -1.3 mm in the group without mandibular appliances. After 4 to 5 years out of retention the lower arch available space had decreased in both groups, to -1.4 mm in the group where orthodontic appliances had been used in both jaws and to -2.5 mm in the group without an orthodontic appliance in the lower jaw. This difference was significant. But the subjective ranking of the amount of crowding in the lower jaw models showed no significant difference between the 2 groups at the age of 20 to 22 years.