Zygomatic miniplates for skeletal anchorage in orthopedic correction of Class III malocclusion: A controlled clinical trial

Abstract

Objective: To evaluate the effects of facemask therapy, which was anchored from the zygomatic buttresses of the maxilla by using two miniplates, in skeletal Class III patients with maxillary deficiency.

Methods: Eighteen skeletal Class III patients (10 girls and 8 boys; mean age, 11.4 ± 1.28 years) with maxillary deficiency were treated using miniplate-anchored facemasks, and their outcomes were compared with those of a Class III control group (9 girls and 9 boys; mean age, 10.6 ± 1.12 years). Two I-shaped miniplates were placed on the right and left zygomatic buttresses of the maxilla, and a facemask was applied with a 400 g force per side. Intragroup comparisons were made using the Wilcoxon test, and intergroup comparisons were made using the Mann-Whitney U-test (p < 0.05).

Results: In the treatment group, the maxilla moved 3.3 mm forward, the mandible showed posterior rotation by 1.5°, and the lower incisors were retroclined after treatment. These results were significantly different from those in the control group (p < 0.05). No significant anterior rotation of the palatal plane was observed after treatment. Moreover, changes in the sagittal positions of the maxillary incisors and molars were similar between the treatment and control groups.

Conclusions: Skeletally anchored facemask therapy is an effective method for correcting Class III malocclusions, which also minimizes the undesired dental side effects of conventional methods in the maxilla.

Keywords: Class III; Facemask; Miniplate; Skeletal anchorage.

Figure 1. A and B, Miniplates and screws used for fixation. C, Design of a miniplate.

Figure 2. A, Elevated mucoperiosteal flap between the maxillary canine and the distal border of the first molar. B and C, Miniplates shaped to match the anatomic structure of the zygomatic buttresses and fixation with two self-drilling miniscrews. D, Closed flap with the C-shaped head of the miniplates exposed at the level of the soft tissue between the maxillary canine and first premolar.

Figure 3. A and B, Facial and profile views of a patient wearing the Petit-type facemask. C, Elastics from the miniplates to the facemask (blue-colored line) extend in downward direction at an angle of 30° with reference to the occlusal plane (black-colored line).

Figure 4. Cephalometric angular measurements evaluated in the present study.

2, SNA; 7, SN/ANSPNS; 8, SNB; 9, SN/GoGn; 10, ArGoMe; 18, ANB; 19, ANSPNS/GoGn; 20, SN/OP; 25, U1/NA; 26, U1/ANSPNS; 27, L1/NB; 28, L1/GoMe; 29, U1/L1; 42, nasolabial angle.

Figure 5. Cephalometric linear skeletal measurements evaluated in the present study.

x, The tuberculum sella-wing (T-W) plane; y, the perpendicular plane to the T-W plane at the T point; 1, S-N; 3, Co-A; 4, A-x; 5, A-y; 6, ANS-PNS; 11, Co-Gn; 12, Go-Me; 13, Ar-Go; 14, B-x; 15, B-y; 16, Co-x; 17, Coy; 21, Wits; 22, N-ANS; 23, ANS-Me; 24, S-Go; 40, UL-S line; 41, LL-S line.

Figure 6. Cephalometric linear dental measurements evaluated in the present study.

x1, The ANS-PNS plane; y1, the perpendicular plane to the ANS-PNS plane at the PNS point; x2, the Go-Gn plane; y2, the perpendicular plane to the Go-Gn plane at the Go point; 30, U1-NA; 31, U1-x1; 32, U1-y1; 33, U6-x1; 34, U6-y1; 35, L1-NB; 36, L1-x2; 37, L1-y2; 38, overjet; 39, overbite.

Figure 7. Pretreatment facial and dental images of patient. A–C, Frontal, oblique and profile view in occlusion; D–F, frontal, oblique and profile view in smiling. G, Intraoral frontal view; H, intraoral lateral view (right); I, intraoral lateral view (left); J, maxillary occlusal view; K, overjet; L, mandibular occlusal view.

Figure 8. Posttreatment facial and dental images of the same patient. A–C, Frontal, oblique and profile view in occlusion; D–F, frontal, oblique and profile view in smiling. G, Intraoral frontal view; H, intraoral lateral view (right); I, intraoral lateral view (left); J, maxillary occlusal view; K, overjet; L, mandibular occlusal view.