A cephalometric appraisal of changes in the mandibular plane during and following orthodontic treatment

Thesis (M.Sc.D.)--Boston University School of Graduate Dentistry, 1975. Orthodontics. NOTE: page 29 is missing.Bibliography included.The present study was undertaken to examine the behavior of the mandibular plane during and post-orthodontic treatment, as well as its relation to the stability of the incisor segment of the dentition. Forty-four cases were selected from the files of the Department of Orthodontics, Boston University School of Graduate Dentistry. Case selection was based solely on the availability of pre-treatment and post-treatment complete records. A new set of records was taken at least one year after band removal to represent the retention period. Three cephalograms were traced for each patient. Angular and linear measurements were taken, and the data were analyzed statistically. Clockwise rotation of the mandible after treatment was apparent in the majority of the patients. Downward and backward movement of pogonion was observed, associated with mandibular rotation. The recovery of the mandible during retention was not complete. No significant difference could be observed between the extraction and non-extraction groups. There was a tendency, nevertheless, for the mandibular plane to remain more stable in the extraction group. A weak association was found between overjet decrease and mandibular plane flattening during retention. A great variation in the behavior of the lower incisors was observed during treatment. A tendency for the lower incisors to return to their original position was found in those cases in which .its procumbency was increased during treatment. This tendency was not observed when the axial inclination of the incisors was decreased