Comparative evaluation of molar distalization therapy with erupted second molar: Segmented versus Quad Pendulum appliance

Abstract

Background: There are controversial opinions about the effect of erupted second molars on distalization of the first molars. Most of the distalizing devices are anchored on the first molars, without including second molars; so, differences between sequentially distalize maxillary molars (second molar followed by the first molar) or distalize second and first molars together are not clear. The aim of the study was to compare sequential versus simultaneous molar distalization therapy with erupted second molar using two different modified Pendulum appliances followed by fixed appliances.

Methods: The treatment sample consisted of 35 class II malocclusion subjects, divided in two groups: group 1 consisted of 24 patients (13 males and 11 females) with a mean pre-treatment age of 12.9 years, treated with the Segmented Pendulum (SP) and fixed appliances; group 2 consisted of 11 patients (6 males and 5 females) with a mean pre-treatment age of 13.2 years, treated with the Quad Pendulum (QP) and fixed appliances. Lateral cephalograms were obtained before treatment (T1), at the end of distalization (T2), and at the end of orthodontic fixed appliance therapy (T3). A Student t test was used to identify significant between-group differences between T1 to T2, T2 to T3, and T1 to T3.

Results: QP and SP were equally effective in distalizing maxillary molars (3.5 and 4 mm, respectively) between T1 and T2; however, the maxillary first molar showed less distal tipping (4.6° vs. 9.6°) and more extrusion (1.1 vs. 0.2 mm) in the QP group than in the SP group, as well as the vertical facial dimension, which increased more in the QP group (1.2°) than in the SP group (0.7°). At T3, the QP group maintained greater increase in lower anterior facial height and molar extrusion and decrease in overbite than the SP group.

Conclusion: Quad Pendulum seems to have greater increase in vertical dimension and molar extrusion than the Segmented Pendulum.

Keywords: Class II malocclusion; Intraoral distalizing devices; Molar distalization; Non-compliance; Second molar.

Figure 1

Segmented Pendulum appliance. (a) Before distalization and (b) first molar distalization.

Figure 2

Quad Pendulum appliance. (a) Before distalization and (b) after distalization.

Figure 3

Cephalometric landmarks and measurements (a, b, c). (1) SNA, (2) SNPg, (3) ANPg, (4) SN/ANS-PNS, (5) ANS-PNS/Go-Gn, (6) SN/Go-Gn, (7) 1: ANS-PNS, (8) 1: Go-Gn, (9) 1/A-Pg, (10) overjet, (11) overbite, (12) interincisal angle, (13) molar relationship, (14) U1 horizontal, (15) U1 vertical (perpendicular to a line passing through the maxillary fiducial markers), (16) U4 horizontal, (17) U4 vertical, (18) U6 horizontal, (19) U7 horizontal, (20) U6 vertical, (21) U1 to FH, (22) U4 to FH, (23) U6 to FH, (24) U7 to FH, (25) L1 horizontal, (26) L1 vertical (perpendicular to a line passing through the mandibular fiducial markers), (27) L6 horizontal, and (28) L6 vertical.

Figure 4

Average craniofacial forms for Segmented Pendulum group at T1, T2, and T3. Cranial base (left), maxillary (top right), and mandibular (lower right) superimpositions.

Figure 5

Average craniofacial forms for Quad Pendulum group at T1, T2, and T3. Cranial base (left), maxillary (top right), and mandibular (lower right) superimpositions.