Management of Class III Malocclusion with Microimplant-Assisted Rapid Palatal Expansion (MARPE) and Mandible Backward Rotation (MBR): A Case Report

Abstract

Class III malocclusion prevalence varies significantly among racial groups, with the highest prevalence observed in southeast Asian populations at 15.80%. These malocclusions often involve maxillary retrognathism, mandibular prognathism, or both, accompanied by maxillary constriction and crossbites. Comprehensive treatment should address anteroposterior, transverse, and vertical imbalances. Microimplant-assisted rapid palatal expansion (MARPE) has shown high success rates for transverse maxillary expansion in late adolescents and adults, presenting a viable alternative to surgically-assisted rapid palatal expansion (SARPE). This case report aims to demonstrate the successful treatment of a young adult female with borderline Class III malocclusion using MARPE and mandibular backward rotation (MBR) techniques. A 21-year-old female presented with a Class III skeletal pattern, anterior/posterior crossbites, and mild dental crowding. Despite her concerns about a concave facial profile, the patient declined orthognathic surgery due to a negative experience reported by a friend. The treatment plan included MARPE to correct maxillary transverse deficiency and MBR to alleviate Class III malocclusion severity. Lower arch distalization was performed using temporary anchorage devices (TADs) on the buccal shelves, and Class II elastics were used to maintain MBR and prevent retroclination of the lower labial segment during anterior retraction. Significant transverse correction was achieved, and the severity of Class III malocclusion was reduced. The lower dentition was effectively retracted, and the application of Class II elastics helped maintain MBR. The patient's final facial profile was harmonious, with well-aligned dentition and a stable occlusal relationship. The treatment results were well-maintained after one year. The MARPE with MBR approach presents a promising alternative for treating borderline Class III cases, particularly for patients reluctant to undergo orthognathic surgery. This case report highlights the effectiveness of combining MARPE and MBR techniques in achieving stable and satisfactory outcomes in the treatment of Class III malocclusion.

Keywords: Class III malocclusion; mandibular backward rotation; microimplant-assisted rapid palatal expansion.

Figure 1

The initial facial portraits and intraoral photographs show the patient with a mildly concave profile, an average Frankfort-mandibular plane angle, and mandibular prognathism (a–d). Intraoral images reveal a Class III malocclusion with reverse overjet and anterior open bite (e–g). The maxilla appears relatively constricted in comparison to the mandible, with mild crowding observed in both arches (h,i).

Figure 2

Initial Orthopantomographic (OPG) and lateral cephalometric radiographs and tracing. Orthopantomographic (OPG) radiographic examination revealed no significant caries or pathological conditions, and the patient exhibited good periodontal status. The lower right second molar had undergone endodontic treatment with no apical lesion present (a). Cephalometric radiograph and tracing showed a skeletal Class III relationship with an average Frankfort-mandibular plane angle (b,c).

Figure 3

Treatment mechanics of Class II elastic (yellow ellipse) causing occlusal plane backward rotation. Class II elastics can simultaneously promote extrusion of the lower molars and upper incisors, resulting in occlusal plane backward rotation. This effect improves upper incisor display and helps maintain the backward rotation of the mandible.

Figure 4

Pretreatment cone beam computed tomography (CBCT) images and measures. Inter-furcation distance of upper first molars was 44.8 mm, and inter-furcation distance of lower first molars was 49.6 mm. According to Yonsei Transverse Index (YTI), about 5 mm of maxillary expansion was needed. (Red line: Sagittal plane; green line: Coronal plane; blue line: Axial plane).

Figure 5

Pre- and post-expansion CBCT images and measures. Molar inclinations were not worsened after MARPE. Expansion pattern was fairly parallel from anterior to posterior on the axial view. (Red line: Sagittal plane; green line: Coronal plane; blue line: Axial plane).

Figure 6

Post-MARPE facial portraits (a–d), intra-oral photos (e–i) and lateral cephalometric radiograph (j). A median diastema was present as a result of mid-palatal suture opening. The mandible underwent backward rotation due to changes in molar occlusion.

Figure 7

Intra-oral photos (a–e) of anterior retraction stage. During this period, a mild reverse curve of Spee was added to prevent further retroclination of the lower incisors during lower arch distalization.

Figure 8

Mandible backward rotation stage (MBR) facial portraits and intra-oral photos. Facial portraits show a reduction in chin prominence and a more harmonious facial profile (a–d). Intraoral photographs demonstrate lower arch distalization using NiTi coil springs anchored by TADs, assisted by Class II elastics from the mandibular molars to the maxillary anterior hooks on both sides (e–i). This approach aimed to enhance molar extrusion and maintain the mandible in a backward position.

Figure 9

Final facial portraits and intra-oral photos. Facial portraits show a Class I skeletal pattern with a harmonious facial profile (a–d). A full-crown smile with an ideal smile arc was achieved. Intraoral photographs demonstrate good dental alignment, solid interdigitation, and proper overjet and overbite (e–i).

Figure 10

Final orthopantomographic (OPG) and lateral cephalometric radiographs and tracing. Good root parallelism was achieved, with no significant root resorption observed (a). Lateral cephalometric radiographs and tracings demonstrate a skeletal Class I relationship with reduced chin projection. Both the upper and lower incisors show proper inclination (b,c).

Figure 11

One-year-review facial portraits and intra-oral photos. The Class I skeletal pattern and harmonious facial profile were maintained (a–d). Good dental alignment, solid interdigitation, and proper overjet and overbite were also preserved (e–i).

Figure 12

Cephalometric tracing comparisons and superimposition.