Vertical anterior relapse

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1. 1. The purpose of this study was to show that changes in vertical jaw relation produced by mandibular rotation resulting from growth after orthodontic treatment contribute in part to vertical anterior relapse. Twenty-six patients were selected on the basis of return to deep-overbite or open-bite following orthodontic treatment as observed directly from dental casts. Dental casts and corresponding sagittal roentgen head films before orthodontic treatment, at the beginning of retention, and at a subsequent date sometime after the end of retention were analyzed to evaluate the return toward the original overbite or open-bite relationship. 2. 2. Two sets of measurements for each patient were obtained to determine the changes in tooth-to-bone relationship and bone-to-bone relationship occurring during the time interval studied. The first set of measurements was based on constructed lines and planes of reference, the second on structural landmarks. 3. 3. A method was described for superimposition of the head films using structural (anatomic and bony) landmarks to eliminate or reduce the error in measuring from lines and planes constructed through changing landmarks. A method described by Skieller 40 40 Skieller V.: Cephalometric growth analysis in the treatment of overbite, Trans. Eur. Orthod. Soc. 43: 147–157 1967. was used to determine mandibular growth rotation. 4. 4. Changes in maxillary and mandibular incisor axial inclination and root apex vertical position producing tooth-to-bone relationship changes were analyzed with respect to their contribution to vertical anterior relapse. 5. 5. Changes in maxillary and mandibular molar vertical position in relation to posterior facial height changes producing bone-to-bone relationship changes were also analyzed and discussed with respect to their contribution to vertical anterior relapse. 6. 6. Those patients who exhibited anterior deep-overbite relapse showed greater posterior facial height increase than combined sutural and alveolar growth of the maxilla and alveolar growth of the mandible. In contrast, those patients who exhibited anterior open-bite relapse showed greater combined sutural and alveolar growth of the maxilla and alveolar growth of the mandible than posterior facial height increase. 7. 7. The patients showing deep-overbite relapse exhibited forward mandibular growth rotation, whereas those showing anterior open-bite relapse exhibited backward mandibular growth rotation. 8. 8. Depression of elongated posterior teeth was not found to contribute to anterior deep-overbite relapse. 9. 9. Possible sources of error in this study and the time to begin orthodontic treatment were discussed briefly. Type of retention, based on the original vertical anterior relation and on the type of mandibular growth rotation, was also discussed. Finally, the length of retention based on the age when growth of the jaws is complete was suggested.