Effects of a novel magnetic orthopedic appliance (MOA-III) on the dentofacial complex in mild to moderate skeletal class III children

Abstract

Introduction: The objective of this study was to evaluate the changes of skeletal and dental structures in mild to moderate skeletal Class III children following the use of a new magnetic orthopedic appliance (MOA-III).

Methods: A total of 36 patients (14 boys and 22 girls, mean age 9 years and 5 months) who presented with a mild to moderate skeletal Class III jaw discrepancy were treated with MOA-III. Another group of 20 untreated patients (9 boys and 11 girls, mean age 9 years and 2 months) with the same level of deformity served as the control group. The average treatment time was 6.6 months. Radiographs were taken at the same time intervals for both groups. A paired t test was used to determine the significant differences before and after treatment, and a two-sample t test was used to analyze the differences between the treatment and control groups.

Results: The anterior crossbite in all subjects was corrected after MOA-III therapy. The maxillomandibular relationship showed favorable changes (ANB, Wits, overjet increased significantly, P < 0.001). The maxilla was anteriorly positioned (SNA, ptm-A, ptm-S increased significantly, P < 0.001) with clockwise rotation (PP-FH increased, P < 0.001). The mandible showed a slight downward and backward rotation (SNB decreased, P < 0.05, MP-SN, Y-axis increased, P < 0.05). The length of the mandibular body showed no significant changes (Go-Pg, P > 0.05). Significant upper incisor proclination and lower incisor retroclination were observed (UI-NA increased, P < 0.001, LI-NB, FMIA decreased, P < 0.001). The upper lip moved forward, and the lower lip moved backward (UL-EP increased, P < 0.001, LL-EP decreased, P < 0.05). In the control group, most of the parameters showed normal growth, except for some unfavorable mandibular skeletal and soft tissue changes (Go-Pg, Go-Co, MP-SN, N'-SN-Pg' increased, P < 0.001). Significant positive changes were induced with the MOA-III appliance compared to the untreated group.

Conclusions: The MOA-III was effective for the early treatment of a mild to moderate Class III malocclusion in children.

Fig. 1

Upper and lower appliance of MOA (a), Attractive configuration of magnets extraorally (b), Schematic view of appliance of MOA (c)

Fig. 2

Attractive forces produced between two 7 × 5 × 4 mm³ Nd₂Fe₁₄B magnets

Fig. 3

Reference points and reference lines. Reference points: (1) Sella (S), (2) Nasion (N), (3) Basion (Ba), (4) Porion (P), (5) Orbitale (Or), (6) Pterygomaxillary fissure (Ptm), (7) Point A (A), (8) anterior nasal spine (ANS), (9) Posterior nasal spine (PNS), (10) Upper incisor (UI), (11) Upper first molar (U6), (12) Point B, (13) Pogonion (Pog), (14) Gnathion (Gn), (15) Menton (Me), (16) Gonion (Go), (17) Condylion (Co), (18) Articulare (Ar), (19) Lower incisor (LI), (20) Lower first molar (L6), (21) Nasion of soft tissue (N′), (22) Pronasale (Prn), (23) Subnasale (Sn), (24) Point A of soft tissue (A′), (25) Upper labrale (UL), (26) Lower labrale (LL), and (27) Pogonion of soft tissue (Pg′). Reference lines of hard the tissues: (A) Anterior cranial base plane (SN), (B) Cranial base plane (N-Ba), and (C) Frankfort horizontal plane (FH)

Fig 4

A case treated with MOA-III (comparison of pre- and post-treatment). Pretreatment: Extraoral photos (a, b), intraoral photos (e, f, g), overbite/overjet (l). Posttreatment: Extraoral photos (c, d), intraoral photos (h, i, j), overbite/overjet (m). Intreatment: intraoral photos (k)

Fig 5

Diagram of the force direction created by MOA-III using repelling/attractive magnetic forces when the patients were at maximal mouth closure and the opening position. a: Repelling force at maximal mouth closure. b: Attractive force at maximal mouth closure. c: Repelling force at the mouth opening position (1/3 offset for opposing magnets). d: Attractive force at the mouth opening position (1/3 offset for opposing magnets)