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Article Category: Case Report
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Online Publication Date: 28 Aug 2024

A skeletal Class III young adult with severe maxillary transverse deficiency treated with maxillary skeletal expander

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Page Range: 332 – 346
DOI: 10.2319/012724-71.1
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ABSTRACT

This case report describes correction of maxillary constriction using a maxillary skeletal expander (MSE) in a 15-year-old female with a skeletal Class III pattern and asymmetry. The maxillary expansion device with four mini-implants was used to correct the constricted maxilla, bilateral crossbite of the posterior teeth, and crowding of the dentition. Comparison of cone-beam computed tomography scans before and after treatment showed that the majority of maxillary expansion was orthopedic, with minimal alveolar bone bending and tooth tipping. Fixed appliances were used to correct the crowding and malocclusion. Stable and satisfactory maxillary expansion was obtained by using MSE non-urgically.

Keywords: Maxillary skeletal expander (MSE); Maxillary transverse deficiency; Young adult; Micro-screw

INTRODUCTION

Maxillary transverse deficiency is a common problem in orthodontics, with the prevalence indicated between 8% in mixed dentition, 23% in primary dentition, and less than 10% in adults.1 To achieve a stable occlusion, it is very important to resolve the transverse deficiency between the maxilla and mandible.

The etiology of arch and jaw constriction may be genetic or environmental or a combination of both.2 It often develops during growth and has a low probability of spontaneous correction, which may affect the permanent dentition and craniofacial growth.3 Patient treatment goals are not just to improve esthetic issues, as several problems may be associated with posterior crossbite, such as occlusal disharmony, impaired masticatory function, skeletal asymmetry, and obstructive sleep apnea syndrome (OSAS).4

Rapid maxillary expansion (RME) is a traditional appliance used to correct transverse discrepancies in patients whose midpalatal sutures are not fully closed.5 The main purpose of RME is to separate a narrowed maxilla mechanically, widen a deep palatal vault, correct posterior crossbite, and increase width of the maxillary arch.6 However, it becomes less effective with age due to increasing resistance to the opening of the midpalatal and circummaxillary sutures. A number of side effects can occur, such as buccal tipping of the alveolar bone and teeth, root resorption, reduction of buccal bone thickness, and marginal bone height, which may lead to buccal dehiscence.7 Surgically assisted rapid maxillary expansion (SARME) may reduce these side effects and potential limitations.8 However, patients often tend to refuse surgery because of the high risk and cost.

Considering these problems, some experts recommend the use of micro-implant-supported anchorage devices with rapid maxillary palatal expansion (MARPE) to avoid the potential side effects of RME in more mature patients without the need for surgery.9,10

Maxillary skeletal expansion (MSE) is a special MARPE that uses four micro-implant supports to achieve bicortical engagement (palatal and nasal cortical bone layers),11 positioned parallel to the midsagittal plane (MP) and nasal septum, posterior to the hard palate and just anterior to the soft palate, providing a greater skeletal effect and more parallel expansion pattern for the posterior and superior aspects of the nasal cavity.12

This case report describes a young adult patient who underwent MSE in combination with fixed orthodontic treatment, with a good outcome.

CASE REPORT

Diagnosis and Etiology

The patient was a 15-year-old female who complained of malocclusion. She had no history of orthodontic treatment, no bad habits, or family history, but had chronic rhinitis since childhood.

Extraoral examination revealed an asymmetry in the frontal view, a deviation of the chin to the left and a long lower third of the face. When smiling, the maxillary and mandibular midlines were not coincident, with the maxillary midline deviating to the right and the mandibular midline deviating to the left relative to the facial midline. In the lateral view, the profile appeared straight (Figure 1).

Figure 1.Figure 1.Figure 1.
Figure 1.Initial facial photographs.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Intraoral examination showed that the right molar relationship was cusp to cusp Class III and the left full-step Class II. The patient exhibited normal overbite and overjet. The maxillary and mandibular dental arches were narrow, with the posterior teeth in crossbite bilaterally (Figure 2). The intermolar width on study models showed that the upper arch was 38 mm and the lower arch was 48 mm (Figure 3). The arch length discrepancy was 6 mm in the upper arch and 5 mm in the lower arch. The patient was in good periodontal condition (Figure 2).

Figure 2.Figure 2.Figure 2.
Figure 2.Initial intraoral photographs.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 3.Figure 3.Figure 3.
Figure 3.Pretreatment digital models.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Panoramic and cephalometric radiographs were taken using computed tomography (CBCT; Figures 4 and 5). Cephalometric analysis showed a skeletal Class III relationship (ANB = −2.3, Wits = −5.6 mm) with a normodivergent facial pattern (FAM = 24.0). The upper incisors were labially inclined (U1-SN = 105.1) and the lower were lingually inclined (IMPA = 76) (Table 1). Normal root morphology, healthy alveolar bone, and four developing third molars were revealed in the panoramic image (Figure 4). Visualization of the palate before treatment showed that the midpalatal suture was closed (Figure 6).

Figure 4.Figure 4.Figure 4.
Figure 4.Initial panoramic radiograph.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 5.Figure 5.Figure 5.
Figure 5.Initial cephalometric radiograph and tracing.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 6.Figure 6.Figure 6.
Figure 6.Screenshot of pretreatment palate, occlusal view.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Table 1.Cephalometric Assessment
Table 1.

Coronal slices of the CBCT at the maxillary and mandibular first molars showed bony narrowing of the maxilla (Figure 7). The width measurements recommended by the University of Pennsylvania transverse analysis were used to determine the required expansion values of the maxilla on CBCT cross-sectional views.13 This revealed that the ideal maxillary width should be 5 mm greater than that of the mandible. The width of the maxilla was at the depth of the concavity of the lateral maxillary contours and the junction of the maxilla and zygomatic buttress. The width of the mandible was between the buccal surface of the cortical bone opposite the furcation of the mandibular first molar. Based on the CBCT measurements, the pretreatment widths of the maxilla and mandible were 49 mm and 52 mm, respectively. To achieve the optimal transverse skeletal relationship, the maxillary required 8 mm of expansion (Figure 8).

Figure 7.Figure 7.Figure 7.
Figure 7.Coronal CBCT slice at the level of maxillary first molars show palatal inclination of maxillary molars; bony narrowing of the maxilla; low position of the tongue. CBCT indicates cone beam computed tomography.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 8.Figure 8.Figure 8.
Figure 8.CBCT transverse analysis.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Based on the findings, the patient’s diagnosis was skeletal Class III malocclusion with moderate crowding of the upper and lower arches, bilateral posterior crossbite, midline deviation, maxillary constriction, labial inclination of the maxillary anterior teeth, and lingual inclination of the mandibular anterior teeth.

Treatment Objectives

The objectives of treatment were skeletal expansion of the upper arch to match the width of the lower arch, correction of the bilateral posterior crossbite, alignment of the teeth, adjustment of the maxillary and mandibular midlines to be coincident with the facial midline, establishing Class I molar and canine relationships, achieving normal overjet and overbite, maintaining the profile, improving the wide buccal corridor on smile, and obtaining a stable treatment outcome.

Treatment Alternatives

Based on the treatment objectives, three treatment options were available for this patient.

Option 1.

Combined orthodontic and orthopedic treatment in adulthood to treat the constricted maxilla surgically and improve the incongruous profile.

Option 2.

Orthopedic expansion of the maxilla to correct the transverse skeletal discrepancy and maintain the profile. Since the midpalatal suture was closed on the CBCT and the magnitude of maxillary expansion required was too great for dental compensation, MSE was preferred for achieving maxillary expansion. Fixed appliances would then be used to idealize the occlusal relationship.

Option 3.

Compensatory treatment by extracting the maxillary second and mandibular first premolars to eliminate crowding, retract incisors, and establish Class I molar and canine relationships. However, there would be no improvement of the posterior crossbite or of the discrepancy between the maxilla and mandible.

Advantages and disadvantages of the options were explained to the patient and her parents. Eventually they chose option 2 for reducing the risks and costs of the surgery.

Treatment Progress

Fixed appliances were used to align the upper teeth to improve the upper arch shape before placing the expander. Six months later, an 8 mm expander with four 11 mm·1.8 mm micro-implants was placed close to the palatal mucosa (Figure 9). Based on CBCT combined with a digital model of the dental arches, an appropriate implant placement position was selected to ensure bilateral cortical perforation of the palatal vault and nasal floor (Figure 10). Then the patient was asked to activate the expander once a day. The maxillary archwire was cut between 11–21 during expansion to avoid affecting widening of the arch. Five weeks later, the posterior crossbite was improved and a gap of approximately 5 mm had appeared in the maxillary anterior region (Figure 11). The postexpansion CBCT showed that the maxilla had widened significantly (Figure 12). Coincidence between the maxillary and mandibular midlines had also significantly improved, with the molar relationship improving from Class II to Class I on the left side (Figure 11). The MSE was retained for 1 year to ensure bone remodeling of the widened palatal suture was completed to maintain the expansion. Fixed appliances were used for tooth alignment and space closure. After 13 months of treatment, multiloop edgewise arch-wire (MEAW) was used on the lower right side to correct the midline deviation (Figure 13). Thirty-nine months later, the patient completed orthodontic treatment.

Figure 9.Figure 9.Figure 9.
Figure 9.Expander in place after alignment.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 10.Figure 10.Figure 10.
Figure 10.CBCT combined with the digital model of dental arches to ensure bilateral cortical contact with palatal vault and nasal floor.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 11.Figure 11.Figure 11.
Figure 11.Intraoral views after active expansion phase, 5-mm gap appeared between 11–21; midline deflection improved.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 12.Figure 12.Figure 12.
Figure 12.CBCT slices after expansion show midpalatal suture opening.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 13.Figure 13.Figure 13.
Figure 13.Photographs of MEAW to adjust the deviation of the mandibular midline. MEAW indicates multiloop edgewise arch-wire.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Treatment Results

Intraoral photographs showed that the molar relationship was Class I bilaterally, with coincident midlines and normal overbite and overjet. The maxillary transverse constriction was correct, along with the bilateral crossbite of the posterior teeth (Figure 14). The facial smile revealed that the dental midlines were consistent with the facial midline. The buccal corridor width was reduced during treatment so the patient displayed a nice, broad smile after treatment (Figure 15).

Figure 14.Figure 14.Figure 14.
Figure 14.Final intraoral photographs.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 15.Figure 15.Figure 15.
Figure 15.Final facial photographs.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

The panoramic radiograph showed good root parallelism and no obvious root resorption. A low-density image appeared at the apex of UR2, possibly related to secondary caries (Figure 16). A recommendation was given for the patient to visit an endodontist for examination and treatment.

Figure 16.Figure 16.Figure 16.
Figure 16.Posttreatment panoramic radiograph.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Posttreatment cephalometric analysis showed that the upper anterior teeth were retracted (U1-SN from 105.1° to 96.4°) and the lower incisors were protracted (IMPA from 76° to 82.8°). The ANB angle increased by 2.6° (from −2.3° to 0.3°) because SNA increased by 1.5° (from 73.7° to 75.2°) and SNB decreased by 1.1° (from 76° to 74.9°), indicating an improvement of the skeletal Class III relationship. Additionally, a slight clockwise rotation of the mandible occurred (MP-SN increased from 42.9° to 43.6°; SGn-SN increased from 73.4 to74.4), which facilitated the improvement of the Class III profile (Table 1, Figures 17 and 18). The posttreatment frontal images showed that the mandibular deviation had improved (Figure 19). The patient had a significant increase in nasal airway volume (Figure 20), improved nasal breathing and reported self-healing of rhinitis after expansion.

Figure 17.Figure 17.Figure 17.
Figure 17.Posttreatment cephalometric radiograph and tracing.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 18.Figure 18.Figure 18.
Figure 18.Overall superimposition, maxillary superimposition, and mandibular superimposition.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 19.Figure 19.Figure 19.
Figure 19.Pretreatment (A) and posttreatment (B) frontal images.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 20.Figure 20.Figure 20.
Figure 20.Comparison of nasal airway pretreatment (A) and posttreatment (B).

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Posttreatment transverse analysis showed well-matched upper and lower dental arches (Figure 21). The CBCT coronal slice showed that the maxillary width had significantly increased (from 49 mm to 57 mm) (Figure 22) and the discrepancy between the maxilla and mandible had improved (from −8 mm to 0 mm). In addition, the bilateral posterior crossbite was resolved (Figure 14).

Figure 21.Figure 21.Figure 21.
Figure 21.Posttreatment digital models.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 22.Figure 22.Figure 22.
Figure 22.Comparison of the maxillary width pretreatment (A), after maxillary expansion (B), posttreatment (C), and post-2-year retention (D).

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Cranial base 3D superimposition showed significant improvements in maxillary constriction and mandibular deviation (Figure 23).

Follow-up results after 2 years showed good stability. For the first 6 months, removable thermoplastic retainers were used during the day and Hawley retainers were used at night. Then, the patient switched to Hawley retainers at night. There was slight relapse of the mandibular midline deviation to the left, but still within acceptable limits (Figures 24 and 25).

Figure 23.Figure 23.Figure 23.
Figure 23.Superimposition of CBCTs.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 24.Figure 24.Figure 24.
Figure 24.2-year postretention intraoral photographs.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

Figure 25.Figure 25.Figure 25.
Figure 25.2-year postretention extraoral photographs.

Citation: The Angle Orthodontist 95, 3; 10.2319/012724-71.1

DISCUSSION

This patient was a young adult who complained of malocclusion with skeletal Class III, a constricted maxilla, and a deviated mandible. Due to the transverse and sagittal deficits of the maxilla and asymmetry of the mandible, orthognathic surgery was the first treatment option. However, the patient and her parents refused the surgical option because they did not want to change the existing facial profile and were afraid of the trauma and risks associated with surgery. Therefore, the difficulty of this case was how to resolve the skeletal deformity and maintain her existing facial profile without performing surgery.

Previous studies have shown that maxillary transverse deficiency is a pervasive skeletal problem that can cause many clinical problems, such as crowding, crossbite, wide buccal corridors, restricted nasal airflow, and mandibular deviation or developmental restriction. These symptoms often occur together and are termed “maxillary deficiency syndrome.”14,15 Additionally, maxillary transverse deficiency is often accompanied by sagittal malocclusion.14 Once the maxillary constriction is corrected, many sagittal imbalances between the maxilla and mandible are resolved.

Once the decision to avoid surgery was made, maxillary expansion become the first choice of nonsurgical treatment for this patient. RME is a traditional orthodontic technique for patients with transverse maxillary constriction, but it is more suitable for adolescents. The mature midpalatal suture and adjacent articular tissues make it difficult to achieve success with conventional RME in older individuals.16 When conventional RME is used to widen an arch in patients with completely closed midpalatal sutures, it is more likely to tip the teeth, which is extremely dangerous for patients whose teeth are already buccally inclined before orthodontic treatment to compensate for constricted maxilla. Further tipping of teeth would compromise occlusal function and periodontal tissue integrity, resulting in loss of buccal cortical bone, gingival recession, and fenestration.17 Lin et al. recently reported that bone-borne expanders demonstrated more orthopedic changes and fewer dentoalveolar side effects.18 The pretreatment CBCT cross-sectional image showed that the midpalatal suture of the patient was closed (Figure 6), so MSE was used to expand the constricted maxilla, as described previously,12 with many advantages: direct application of expansion force on the midpalatal suture,19 low risk of gingival recession and root resorption,10 suitable for young adults and adults,9 avoidance of orthognathic surgery, stable expansion results and reduced relapse,10 and opening of the airway.11

After maxillary expansion, the maxillary width on the CBCT slice changed from 49 mm to 57 mm (Figure 22). This indicated that the maxilla was significantly widened. Space was obtained to level the teeth and upright the upper incisors to normalize inclination and reduce the compensation of the incisors (Figure 17). Skeletal advancement of the maxilla (SNA increased by 1.5°) and clockwise rotation of the mandible (SNB decreased by 1.1°, MP-SN increased by 0.7°) improved the skeletal Class III relationship (ANB increased by 2.6°). This result was consistent with previous literature showing that SNA increased significantly after maxillary expansion.20 In addition, Keren et al.15 reported that, with the elimination of a posterior crossbite, the molar relationship may become more symmetric and a midline shift may be reduced consequently after maxillary expansion. For this patient, the left molar relationship changed from Class II to Class I and the mandibular midline improved after expansion. Considering that the narrow maxilla may affect the position of the mandible, there may be functional factors contributing to mandibular deviation. Additionally, studies21 have shown that maxillary expansion increases volume and width of the nasal cavity, lowers the palatal vault, straightens the nasal septum, and reduces nasal airflow resistance, thereby improving nasal breathing, which may be related to the resolution of self-reported rhinitis and the significant increase in nasal airway volume after treatment (Figure 20).

Obtaining stable treatment results is also one of the goals of orthodontic treatment. Correct diagnostic analysis, treatment design, and good occlusal relationship after orthodontic treatment is crucial. Intraoral images 2 years posttreatment (Figure 24) showed a very stable occlusion, which meant that the orthodontic treatment outcome was very stable.

CONCLUSIONS

  • The MSE can obtain stable and satisfactory maxillary expansion nonsurgically for young adults with a closed midpalatal suture, providing patients with nonsurgical options for treatment success.

Copyright: © 2025 by The EH Angle Education and Research Foundation, Inc.
Figure 1.
Figure 1.

Initial facial photographs.

Figure 2.
Figure 2.

Initial intraoral photographs.

Figure 3.
Figure 3.

Pretreatment digital models.

Figure 4.
Figure 4.

Initial panoramic radiograph.

Figure 5.
Figure 5.

Initial cephalometric radiograph and tracing.

Figure 6.
Figure 6.

Screenshot of pretreatment palate, occlusal view.

Figure 7.
Figure 7.

Coronal CBCT slice at the level of maxillary first molars show palatal inclination of maxillary molars; bony narrowing of the maxilla; low position of the tongue. CBCT indicates cone beam computed tomography.

Figure 8.
Figure 8.

CBCT transverse analysis.

Figure 9.
Figure 9.

Expander in place after alignment.

Figure 10.
Figure 10.

CBCT combined with the digital model of dental arches to ensure bilateral cortical contact with palatal vault and nasal floor.

Figure 11.
Figure 11.

Intraoral views after active expansion phase, 5-mm gap appeared between 11–21; midline deflection improved.

Figure 12.
Figure 12.

CBCT slices after expansion show midpalatal suture opening.

Figure 13.
Figure 13.

Photographs of MEAW to adjust the deviation of the mandibular midline. MEAW indicates multiloop edgewise arch-wire.

Figure 14.
Figure 14.

Final intraoral photographs.

Figure 15.
Figure 15.

Final facial photographs.

Figure 16.
Figure 16.

Posttreatment panoramic radiograph.

Figure 17.
Figure 17.

Posttreatment cephalometric radiograph and tracing.

Figure 18.
Figure 18.

Overall superimposition, maxillary superimposition, and mandibular superimposition.

Figure 19.
Figure 19.

Pretreatment (A) and posttreatment (B) frontal images.

Figure 20.
Figure 20.

Comparison of nasal airway pretreatment (A) and posttreatment (B).

Figure 21.
Figure 21.

Posttreatment digital models.

Figure 22.
Figure 22.

Comparison of the maxillary width pretreatment (A), after maxillary expansion (B), posttreatment (C), and post-2-year retention (D).

Figure 23.
Figure 23.

Superimposition of CBCTs.

Figure 24.
Figure 24.

2-year postretention intraoral photographs.

Figure 25.
Figure 25.

2-year postretention extraoral photographs.

Contributor Notes

aLecturer, Department of Orthodontics, Jinan Stomatological Hospital, Jinan, China.
bAssociate Professor, Department of Orthodontics, Jinan Stomatological Hospital, Jinan, China.
cProfessor, Department of Stomatology, The Affiliated Qingdao Central Hospital of Qingdao University, Qingdao, Shandong, China.
Corresponding author: Ping Liu, Associate Professor, Department of Orthodontics, Jinan Stomatological Hospital, 101 Jingliu Road, Jinan, Shangdong 250000, China (e-mail: 59155854@qq.com)
Received: 24 Mar 2024
Accepted: 30 Jul 2024
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