Vertical and horizontal components of functional appliance therapy.

Disocclusion of the teeth has been postulated to have a deregulating or promoting influence on mandibular growth. The clinical effects of disocclusion were evaluated with a prospective pilot study of 16 children with mixed dentition who wore either a maxillary Hawley biteplane or the functional regulator of Fränkel. The pilot study was used to assess individual variations to establish the feasibility of a larger, more statistically valid investigation. The biteplane was used to evaluate the effects of vertical mandibular displacement on craniofacial growth. The Fränkel regulator was used to evaluate the effects of both vertical and horizontal mandibular displacement. The relationships between patient cooperation, personality characteristic, and treatment effects were also evaluated. After 9 months of treatment, the biteplane group had an increase in the mandibular plane angle with little or no horizontal mandibular growth and tendency toward an interior open bite. This was deemed to be clinically detrimental and the biteplane therapy was discontinued. The results of this study are presented to aid the clinician in his or her decision to use biteplane therapy. In the biteplane group, the bite opening was associated with molar, and not incisor, extrusion. Though the biteplane group had primarily a vertical increase in the length of the lower third of the face, the Fränkel group had a combination of anterior and inferior mandibular growth. In both groups, the mandibular incisor usually moved anteriorly. The maxially incisor usually moved labially in the biteplane group and lingually in the Fränkel group, although exceptions were in both groups. Correlation coefficients between self-esteem, compliance, and cognitive level were not statistically significant. These findings suggest that a constant protracting force on the mandible, rather than bite opening only, may be necessary for increasing mandibular length. Thus the biteplane should only be used to increase the vertical dentoalveolar and facial heights in patients with normal anteroposterior maxillary-mandibular relationships.