Stresses in the midpalatal suture in the maxillary protraction therapy: a 3D finite element analysis.

Orlando M Tanaka,Matheus Melo Pithon,Marco Andre Argenta,Amando Yukio Saga

doi:10.1186/s40510-016-0121-5

Abstract

BackgroundThe aim of the present work was to evaluate the stress magnitudes and directions along the midpalatal suture in the maxillary protraction therapy.MethodsThe geometry of the maxilla and teeth were digitally reconstructed based on computer tomography images obtained from the skull of a girl in a mixed dentition stage with skeletal and dental class III malocclusion. An appliance commonly used for rapid palatal expansion (RPE) was also digitally modeled for anchorage of the protraction force and meshed for finite element analysis. The maxillary protraction was simulated applying 600 cN (300 cN for each side) directed 30° forward and downward to the maxillary occlusal plane.ResultsThe principal stresses, through the force application, exhibited similar distribution patterns. A higher stress area was observed in the region of the midpalatal suture located in front of the incisive canal. All the sections showed vectors of compressive nature.ConclusionsBecause of the compressive nature of the stresses distributed along the midpalatal suture in the maxillary protraction therapy simulation, which is opposite to the natural growth transversal tendency, maxillary expansion is advisable in clinical cases.

Highlights

The aim of the present work was to evaluate the stress magnitudes and directions along the midpalatal suture in the maxillary protraction therapy
The skeletal class III malocclusion is caused by sagittal growth disharmony of the jaws that could occur due to underdevelopment of the maxilla, overdevelopment of the mandible, or a combination of both [1]
A hyrax-type appliance commonly used for rapid palatal expansion (RPE) attached to the maxilla was digitally constructed with the sole objective of applying protractive force (Solidworks®, Dessault Systèmes Solidworks Corp., Concord, Ma) (Fig 1)

Summary

Introduction

The aim of the present work was to evaluate the stress magnitudes and directions along the midpalatal suture in the maxillary protraction therapy. Forward movement of the maxilla using an extraoral protraction force could correct the skeletal class III in children with retrognatic maxilla and apply tensile forces on the circum-maxillary sutures [2,3,4,5,6,7]. It was histologically demonstrated that maxillary protraction therapy outcomes depend on the direction and magnitude of traction force [8, 9]. Based on the maxillary growth and ossification patterns, bone deposition in the midpalatal suture plays an important role in the progressive widening of the palate and alveolar arch [10]. A possible side effect of maxillary protraction is the possibility of mechanical constriction of the anterior region, since compressive strains were observed in the palate [11, 12]

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