Clinical Tip for Adjusting Reverse Pull Facemask/Headgear Assembly

Evaluation of Load and Stress Distribution for a Novel Design of Maxillary Protraction Facemask by Finite Element Analysis

Background/Objectives: Protraction facemasks are commonly used to treat Class III malocclusion in growing patients. Personalized facemasks designed using 3D modeling software and based on individual 3D face images are now available. This study aimed to assess the mechanical properties of three novel designs of Petit-type facemask appliances through three-dimensional Finite Element Analysis (FEA). Methods: Three novel designs of the facemask were modeled by Solidworks 3D CAD (2023): anatomic, V-shape, and arc-shape. FEA was performed by Ansys 2021 (R2) software. The elements' sizes, shapes, and numbers were identified, and the material property was set on Acrylonitrile butadiene styrene copolymer (ABS) plastic. The support and loading conditions of two different intensities of load, 7.8 and 9.8 N, respectively, were applied in three angulations to the occlusal plane: 0°, 30°, and 50°. Stress, strain, and total deformation results were obtained. Results: The minimum stress was reported with the anatomic design at a 30° angulation, whereas the maximum value was reported in the arc-shape design at 50°; however, there was no significant difference among the three designs. The von Mises yield criterion showed that the overall stresses were distributed on the larger areas of the facemask structure at 30° angulation for all designs. The stresses induced in all facemask appliance designs did not cause permanent deformation. Conclusions: Anatomic design has better mechanical behavour than the V-shape or arc shape design. Downward inclination of 30° to the occlusal plane induces less stress. These findings support the use of customized anatomic facemasks for the effective and efficient treatment of Class III malocclusions in growing patients, potentially improving clinical outcomes and patient comfort. Further research, particularly clinical trials, is needed to validate the results of the present study.

Efficacy of SAVE: A Novel Maxillary Protraction Device-A Finite Element Analysis

Introduction

This study describes a novel device known as "SAVE" to effectively protract the deficient maxilla in class III malocclusion by quantifying and evaluating the changes in the maxilla through a finite element analysis (FEA).

Materials and methods

The patented novel SAVE device was three-dimensionally modeled using Autodesk Fusion 360. An existing computed tomography (CT) scan of a patient exhibiting class III malocclusion was used to generate a finite element (FE) model. The total number of nodes was 8,49,682 and 5,30,716 elements. The material of choice for the appliance was medical-grade polyetheretherketone (PEEK) polymer. The loading was performed to simulate maxillary protraction (after assigning material properties). The loading forces of 3.5, 5.5, and 9 N were simulated on each side with 30° angulations to the occlusal plane. The color changes in terms of areas of maximum (red) and minimum (blue) deformation.

Results

The FEA results with protraction forces of 3.5, 5.5, and 9 N showed deformation of the maxilla in the forward and downward directions. Equivalent von Mises stress on the SAVE appliance showed stress on the superior surface of the main frame and on the area below the struts where the force module was attached. In relation to the implant, the stress concentration was on the posterior and superior area around the implant.

Conclusion

The FEM analysis force vectors showed a forward and downward deformation of the maxilla with counterclockwise rotation, supporting the fact that the novel appliance could bring about effective maxillary protraction in a shorter duration.

How to cite this article

Shetty S, T NB, Amin V, et al. Efficacy of SAVE: A Novel Maxillary Protraction Device-A Finite Element Analysis. Int J Clin Pediatr Dent 2024;17(12):1377-1382.

Treatment outcomes of various force applications in growing patients with skeletal Class III malocclusion

OBJECTIVES

To evaluate skeletal, dentoalveolar, and soft tissue changes between intraoral light force application and extraoral heavy force application in growing patients with skeletal Class III malocclusion.

MATERIALS AND

Methods: A retrospective study was conducted with pretreatment and posttreatment lateral cephalometric data from 50 subjects with skeletal Class III malocclusion. In the first group (15 boys, 10 girls; 8.67 ± 2.13 years old), each subject wore a biocreative horseshoe appliance (CHS) with two Class III elastics that exerted a force of 200 g. In the second group (13 boys, 12 girls; 8.96 ± 1.82 years old), each subject wore a Petit-type facemask and a lingual arch with hooks fixed to the maxillary arch with a total force of 700 g. Both groups of patients were instructed to wear the appliance approximately 14 hours a day, and 22 linear measurements and 8 angular measurements were evaluated. Changes of measurements from each group were compared by paired t-tests, considering a 5% significance level.

RESULTS

Forward growth of the maxilla, improvement of the maxilla-mandible relationship, and upper incisor flaring were achieved in both groups without any statistically significant difference between them. Lateral cephalometric analysis also showed that U1 exposure, IMPA (Angle between mandibular plane and mandibular incisor axis), FMIA (Angle between FH plan and mandibular incisor axis), and L1-APog (Angle formed by the intersection of tooth axis of lower incisor and A-Pog line, Distance from lower incisor edge to A-Pog line) showed statistically significant differences. Lower incisors were inclined lingually in the CHS group.

CONCLUSIONS

During treatment of skeletal Class III malocclusion, the CHS with light Class III intermaxillary elastics therapy exhibits similar orthopedic changes to the maxillary complex and more dental changes to the lower anterior teeth compared with facemask therapy.

Facemask performance during maxillary protraction: a finite element analysis (FEA) evaluation of load and stress distribution on Delaire facemask

BACKGROUND

To evaluate load and stress distribution on Delaire facemask (FM) during maxillary protraction in class III growing patients by means of finite element analysis (FEA). A three-dimensional geometry of a Delaire FM was reconstructed from the original CAD 3D prototype, using software package (ANSYS 5.7). FM presented forehead and chin supports and stainless steel framework characterized by two lateral vertical bars connected to a crossbar with two pawls for elastic attachment. Two traction intensities (7.8 and 9.8 N) were applied on the FM pawls along three different downward inclined directions with respect to the occlusal plane (0°, 30°, or 50°, respectively). Resulting stresses and deformations were then tested through the von Mises yield criterion in order to underline the FM wear performance.

RESULTS

The analysis showed that higher stresses and deformations are mostly related to axial forces of 9.8 N rather than 7.8 N. Stresses also progressively increased with increasing downward force inclinations (0°, 30°, and 50° with respect to the occlusal plane). The overall tensions were inferior to the limit of the elastic behavior (yield point) characterizing the material they are applied on. Thus, the FM structure absorbed the load applied with an elastic deformation of the lateral and horizontal bars.

CONCLUSIONS

Resulting stresses and deformations were directly proportional to protraction load amounts and to increasing downward inclination of forces. In all tested conditions, protraction forces were not able to determine plastic deformation on FM structure compromising its performance and efficiency.