The compensatory mechanism in high-angle malocclusions: a comparison of subjects in the mixed and permanent dentition

Dentoskeletal morphology was assessed in 191 untreated and unselected children with a hyperdivergent (high-angle) mandibular plane (ML/NSL > or =40 degrees) by analyzing lateral roentgenographic cephalograms. The subjects were divided into mixed dentition and permanent dentition groups, and further divided into subgroups based on the amount of overbite (OB) as a measure of dentoalveolar compensation of jaw base hyperdivergency: OB < 0 mm (openbite) = insufficient/no compensation; OB 0 to 4 mm (normal overbite) = acceptable compensation; OB > 4 mm (deepbite) = overcompensation. Openbite was observed in 20% of the children, normal overbite in 50%, and deepbite in 30%. Skeletally, the deepbite mixed dentition group was characterized by a relatively posterior inclination of the maxilla, while the deepbite permanent dentition group had a relatively anterior inclination of the mandible. Dentoalveolar compensation was accomplished by relative increases in maxillary and mandibular anterior dentoalveolar heights in the mixed dentition group and by relative decreases in maxillary and mandibular posterior dentoalveolar heights in the permanent dentition. Positive overbite was found in the majority (80%) of children with high-angle morphology. Thus, mandibular hyperdivergency is frequently compensated for. Skeletal characteristics and dentoalveolar compensatory mechanisms differ with dental maturity and seem to be influenced by mouth breathing and other oral habits.