The effects of micro-implant assisted rapid palatal expansion (MARPE) on the nasomaxillary complex--a finite element method (FEM) analysis.

Matt Macginnis,Andre Wilson Machado,George Youssef,Howard Chu,Kimberley W Wu,Won Moon

doi:10.1186/s40510-014-0052-y

Abstract

BackgroundOrthodontic palatal expansion appliances have been widely used with satisfactory and, most often, predictable clinical results. Recently, clinicians have successfully utilized micro-implants with palatal expander designs to work as anchors to the palate to achieve more efficient skeletal expansion and to decrease undesired dental effects. The purpose of the study was to use finite element method (FEM) to determine the stress distribution and displacement within the craniofacial complex when simulated conventional and micro-implant-assisted rapid palatal expansion (MARPE) expansion forces are applied to the maxilla. The simulated stress distribution produced within the palate and maxillary buttresses in addition to the displacement and rotation of the maxilla could then be analyzed to determine if micro-implants aid in skeletal expansion.MethodsA three-dimensional (3D) mesh model of the cranium with associated maxillary sutures was developed using computed tomography (CT) images and Mimics modeling software. To compare transverse expansion stresses in rapid palatal expansion (RPE) and MARPE, expansion forces were distributed to differing points on the maxilla and evaluated with ANSYS simulation software.ResultsThe stresses distributed from forces applied to the maxillary teeth are distributed mainly along the trajectories of the three maxillary buttresses. In comparison, the MARPE showed tension and compression directed to the palate, while showing less rotation, and tipping of the maxillary complex. In addition, the conventional hyrax displayed a rotation of the maxilla around the teeth as opposed to the midpalatal suture of the MARPE. This data suggests that the MARPE causes the maxilla to bend laterally, while preventing unwanted rotation of the complex.ConclusionsIn conclusion, the MARPE may be beneficial for hyperdivergent patients, or those that have already experienced closure of the midpalatal suture, who require palatal expansion and would worsen from buccal tipping of the teeth or maxillary complex.

Highlights

Orthodontic palatal expansion appliances have been widely used with satisfactory and, most often, predictable clinical results
In a non-invasive way, finite element method (FEM) makes it possible to compare the effects of conventional hyrax and micro-implant-assisted rapid palatal expansion (MARPE) expansion forces on the craniofacial complex
FEM is a valid method for comparing the effects of maxillary expansion appliances on the craniofacial complex

Summary

Introduction

Orthodontic palatal expansion appliances have been widely used with satisfactory and, most often, predictable clinical results. The purpose of the study was to use finite element method (FEM) to determine the stress distribution and displacement within the craniofacial complex when simulated conventional and micro-implant-assisted rapid palatal expansion (MARPE) expansion forces are applied to the maxilla. The simulated stress distribution produced within the palate and maxillary buttresses in addition to the displacement and rotation of the maxilla could be analyzed to determine if micro-implants aid in skeletal expansion. The force of the appliance counteracts the existing anatomical resistance from the dentoalveolus, midpalatal suture, zygomaxillary buttress, and circummaxillary sutures [9,10,11,12,13,14,15]. Other RPE studies have proposed that during the opening of the midpalatal suture, the maxilla moves downward and forward [17], supporting the theories of disarticulation and separation of maxillary segments. Conventional RPE provokes an orthodontic effect of buccal tipping and movement of the posterior teeth

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