A New Methodology for the Digital Planning of Micro-Implant-Supported Maxillary Skeletal Expansion

Abstract

Introduction

Miniscrew-assisted rapid palatal expansion (MARPE) appliances utilize the skeletal anchorage to expand the maxilla. One type of MARPE device is the Maxillary Skeletal Expander (MSE), which presents four micro-implants with bicortical engagement of the palatal vault and nasal floor. MSE positioning is traditionally planned using dental stone models and 2D headfilms. This approach presents some critical issues, such as the inability to identify the MSE position relative to skeletal structures, and the potential risk of damaging anatomical structures.

Methods

A novel methodology has been developed to plan MSE position using the digital model of dental arches and cone-beam computed tomography (CBCT). A virtual model of MSE appliance with the four micro-implants was created. After virtual planning, a positioning guide is virtually designed, 3D printed, and utilized to model and weld the MSE supporting arms to the molar bands. The expansion device is then cemented in the patient oral cavity and micro-implants inserted. A clinical case of a 12.9-year-old female patient presenting a Class III malocclusion with transverse and sagittal maxillary deficiency is reported.

Results

The midpalatal suture was opened with a split of 3.06 mm and 2.8 mm at the anterior and posterior nasal spine, respectively. After facemask therapy, the sagittal skeletal relationship was improved, as shown by the increase in ANB, A-Na perpendicular and Wits cephalometric parameters, and the mandibular plane rotated 1.6° clockwise.

Conclusion

The proposed digital methodology represents an advancement in the planning of MSE positioning, compared to the traditional approach. By evaluating the bone morphology of the palate and midface on patient CBCT, the placement of MSE is improved regarding the biomechanics of maxillary expansion and the bone thickness at micro-implants insertion sites. In the present case report, the digital planning was associated with a positive outcome of maxillary expansion and protraction in safety conditions.

Keywords:

• miniscrew-assisted rapid palatal expansion
• MARPE
• CBCT
• MSE
• virtual planning
• cephalometrics-based digital planning
• CBDP
• workflow
• TAD

Abbreviations

MARPE, Miniscrew-assisted rapid palatal expansion; MSE, maxillary skeletal expander; CBCT, cone-beam computed tomography; FOV, field of view; DICOM, digital imaging and communications in medicine; STL, standard tessellation language; MP, midsagittal plane; MS5, midpalatal suture 5; MS7, midpalatal suture 7; VP, vomer posterior; HPP, horizontal palatal plane; BZL, bi-zygomatic line; ZR, most lateral point of zygomatic process on right maxillary half; ZL, the most lateral position of the zygomatic process on left maxillary half; CM, center of the maxilla; MI, micro-implant; CA, center of MSE appliance; BT, bone thickness; DM, appliance distance from the mucosa; ML, micro-implant length; GBI, guiding bar interference; CBDP, cephalometrics-based digital planning.

Author Contributions

DC, GS, PZ, MDF, and WM participated in the study conception, elaborated the study methodology, contributed towards data analysis, and drafting and revising the paper. LG, CB, ALG, and GI contributed towards data analysis and drafting and revising the paper. All authors gave final approval of the version to be published, and agreed to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.