Evaluation of Changes in the Vertical Dimension following mesialization of mandibular molars between Average and Hyperdivergent Facial Type: A Retrospective Cephalometric Study

Abstract

Introduction: Orthodontists believe that extraction of mandibular first premolars produces more incisor retraction, whereas second mandibular premolars extractions result in more mesial mandibular first molar movement. However, these notions are based largely on clinical observations. In addition, according to the wedge effect concept, even small changes in mesial movement of molars result in a pronounced effect on the mandibular plane angle and FVD in this group. In spite of compelling evidence, premolar extractions continue to be implicated as a cause for decreased vertical dimensions

Aim: The aim of the study was to evaluate and compare the effects on the facial vertical dimensions after mesial movement of the mandibular molars following orthodontic treatment with mandibular bilateral premolar extraction in Average and Vertical growth pattern of face.

Methodology: Vertical parameters was recorded in the form of 3 angles (basal plane, mandibular plane, Sn-Go-Gn) and 4 linear dimensions (TAFH, LAFH,PFH,PFH/TAFH; for both pre and post cephalometric radiographs. The mesialisation which was obtained by measuring the parameters (L6o, L6m) pre and post treatment will be compared with each vertical parameter i.e (Angular and linear) which will show the relation of mesialisation with change in vertical dimension in different parameters.

Results: Both groups had increases in linear vertical dimensions (P _0.05), but the change was comparatively greater in the extraction group (P _0.05). Mesial movement of the maxillary and mandibular posterior teeth was coincidental with the extrusion to such an extent that it increased the vertical dimension, although the mandibular plane angle remained unchanged during treatment.

Conclusion: Linear vertical dimensions increased in both the extraction and the nonextraction groups. The changes in vertical dimension were comparatively greater in the extraction group.