title: A study of the utility of measuring mandibular mobility by means of the interincisal dimension.
abstract: The purpose of this investigation was to determine the reliability of using the interincisal dimension as a measure of mandibular range of motion. Thirty patients who underwent mandibular advancement and 15 patients who underwent mandibular setback were included in this study. Preoperatively, a lateral cephalogram in centric relation and a second cephalogram with the mandible at maximum voluntary gape were obtained. Immediately following surgery, another centric relation cephalogram was obtained. A composite tracing of the two preoperative tracings was made to show how the mandible changed in position from the closed-mouth to the open-mouth radiographs. The proximal segment (ramus) of the postoperative cephalogram was then superimposed on the open-mouth mandibular ramus, and the distal segment of the postoperative mandible was drawn. This composite produced a tracing of what the postoperative maximal gape cephalogram would be if the same amount of condylar rotation and translation as in the preoperative tracing had occurred. The preoperative interincisal dimension was recorded on the composite tracings (factoring in any overbite or openbite) as was the would-be postoperative interincisal dimension. These measures were compared using the paired t test and Pearson's correlations to determine if there were any significant differences between them. The results showed that the interincisal dimension is a fairly reliable measure of mandibular mobility even when the length of the mandible is altered with surgery.
authors.affiliation: Department of Oral and Maxillofacial Surgery, University of Michigan, School of Dentistry.
authors.forename: E
authors.initials: E
authors.lastname: Ellis
authors.forename: R J
authors.initials: RJ
authors.lastname: Fonseca
authors.forename: L G
authors.initials: LG
authors.lastname: Upton
authors.forename: R F
authors.initials: RF
authors.lastname: Scott
mesh_terms: D002508:Cephalometry; D003768:Dental Occlusion, Centric; D006801:Humans; D007180:Incisor; D008334:Mandible / Q000033:anatomy & histology / Q000502:physiology*; D009055:Mouth / Q000033:anatomy & histology*; D009068:Movement