Bone availability for mandibular molar distalization in adults with mandibular prognathism

Abstract

Objectives: To investigate the retromolar space available for molar distalization in patients with mandibular prognathism.

Materials and methods: Using cone-beam computed tomography, the posterior mandibular dimensions in 110 consecutive patients with Class I or Class III malocclusion were measured (mean age, 27.0 ± 7.1 years). The shortest linear distances from the distal root of the right mandibular second molar to the inner border of the mandibular cortex were measured at the level of root furcation and 2, 4, and 6 mm apical to the furcation along the sagittal line and the posterior line of occlusion. The retromolar distances were compared between the Class I and Class III malocclusion groups using general linear mixed models.

Results: The retromolar space measured through the sagittal line showed no significant intergroup difference. Among the distances measured through the posterior line of occlusion, the space measured at depths 0 and 2 mm to the furcation were significantly greater in the Class III group than in the Class I group.

Conclusions: Patients with Class III malocclusion have greater retromolar space for mandibular molar distalization along the posterior line of occlusion only at the level of the second molar furcation.

Keywords: Camouflage treatment; Mandibular prognathism; Molar distalization; Retromolar space.

Figure 1

The planes used to measure the retromolar distances to the inner cortex of the posterior mandible. (A) The 0-plane, which is parallel to the lower occlusal plane that passes the furcation of the mandibular second molar root. (B) The 2-plane, (C) 4-plane, and (D) 6-plane, which are parallel to the 0-plane and located 2, 4, and 6 mm, respectively, below the 0-plane.

Figure 2

Reference lines used in this study. (A) The sagittal line that is parallel to the midsagittal reference plane (a plane that passes through the crista galli, anterior nasal spine, and opisthion) and (B) the cuspal line connecting the buccal cusps of the first and second molars.

Figure 3

Definition of the retromolar space measured in this study. Distance from the most lingual point of the distal root of the right second molar to the (A) inner border of the mandibular cortex of the lingual bone along the sagittal line (B) the inner border of the mandibular cortex of the lingual bone along the cuspal line.