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

Soft-tissue modification in Class III non-growing patients treated with clear aligners: a prospective clinical trial

Introduction

The aim of the present prospective study was to assess the soft tissue modifications induced by camouflage treatment with clear aligners in adult patients with mild Class III malocclusion.

Methods

Patients were consecutively enrolled in the study sample according to the following inclusion criteria: adult age (≥19 years), permanent dentition including second permanent molars, skeletal Class I or slight Class III (-2° < difference between sella-nasion^ point A and sella-nasion^ point B < +2°), normal skeletal divergence pattern (SN^GoGn, 27°-37°), Class III canine and molar relationship at baseline (T0) with moderate lower arch crowding (≤+4 mm), and good compliance with aligners and elastics (≥20 h/day). All the participants underwent the lower distalization protocol, which included extraction of the lower third molars before starting treatment and a 50% sequential lower distalization, and Class III intermaxillary elastics (1/4 in., 6.5 oz) from buttons on the upper first molars to precision cuts at the level of the lower canines to reinforce the anchorage. Lateral cephalograms were taken at T0 (before treatment) and at the end of the clear aligner treatment (T1) with an average time interval of 24 ± 6 months. A customized digitization regimen and cephalometric analysis were created to assess the esthetic outcomes at T1. The significance level was set at P < 0.05.

Results

The lower distalization supported by Class III elastics resulted in a slight improvement of the facial esthetic profile with no significant changes in the lower third of the face. A mildly better projection of the upper lip was detected at the end of treatment, mainly due to the extensive use of Class III elastics.

Discussion

The lower distalization supported by Class III elastics determined slight improvement of the facial aesthetic profile with no significant changes in the lower third of the face. A mild better projection of the upper lip was detected at the end of treatment, mainly due to the extensive use of Class III elastics.

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.

Comparative Analysis of Early Class III Malocclusion Treatments-A Systematic Review and Meta-Analysis

Several therapeutic methods have been proposed for early class III malocclusion treatment; however, the existing literature does not provide evidence on the most recommended techniques or materials. The aim of the present systematic review and meta-analysis was to summarize the clinical evidence on the efficacy of each method. The PRISMA recommendations were followed. Four databases were searched for articles published up to February 2024. Controlled trials, randomized or non-randomized clinical trials, and prospective or retrospective studies with a control group and a minimum follow-up of 6 months were included. The risk of bias was assessed using the Cochrane collaboration tool. Inconsistency was assessed using the Q test, with a significance level of p < 0.05 and a forest plot. A total of 61 articles were identified, and eight were included in the meta-analysis, which examined three parameters: Sella-Nasion-A (SNA), Sella-Nasion-B (SNB), and A Point-Nasion-B (ANB) values. The meta-analysis was carried out using the random effects model and the inverse variance method. The effect size was determined as the difference between the means of the SNA, SNB, and ANB values in the initial and final intervention groups or between the intervention group and control group. Statistical significance was assessed using the z-test and was declared when p-value < 0.05. The heterogeneity of the meta-analysis was analyzed using the Q test and the I2 statistical index. Publication bias was analyzed using the trim-and-fill method to adjust the skewness of the funnel plot. The risk of bias in the selected studies was assessed using the Cochrane collaboration tool to analyze the methodological quality assessment of the clinical trials. There were statistically significant differences between traditional maxillary disjunction and traction and the different types of Alt-RAMEC protocols, with the latter allowing greater skeletal corrections.

Post-pubertal effects of the Face Mask Protocol with and without Bite Block appliance in the orthopedic treatment of Class III malocclusion: a comparative evaluation

OBJECTIVES

The purpose of this retrospective study was to compare the dento-skeletal changes observed in growing Class III patients treated with the Face Mask Protocol (FMP) with and without Bite Block (BB).

MATERIALS

Thirty subjects (12 f, 18 m) who underwent FM/BB therapy were compared to a matched group (FM) of 29 patients (15 f, 14 m) treated without BB. All patients were evaluated before treatment (T0), at the end of active treatment (T1), and at a post-pubertal follow-up observation (T2). A control group (CG) of 20 subjects (10 f, 10 m) with untreated Class III disharmony was used for the comparison of post-pubertal changes. Intergroup statistical comparisons were performed with the independent samples t-test (P < .05).

RESULTS

The comparison between treated samples showed a significant improvement of SN^GoGn (FM/BB vs FM, -2.1°), Overbite (FM/BB vs FM, +1.2 mm), and vertical position of lower molars FM/BB vs FM, -3 mm). When compared with the controls, both treated groups revealed a significant improvement of SNA (FM/BB, +1.8°; FM +2.1°), ANB (FM/BB +1.6°, FM +2.4°), gonial angle (FM/BB -4.9°; FM -4°), incisor inclination (Upper, FM/BB +1.7°, FM +2.3°; Lower, FM/BB -2.5°, FM -2.7°), and Overjet (FM/BB +3.2 mm; FM +4 mm). Improvement of SN^GoGn (-2.1°), Overbite (+1.8 mm), and vertical position of lower molars (-3.8 mm) were observed when FM/BB was compared with CG.

LIMITATIONS

Limitations are related to the difficulty to recruit a larger contemporary long-term control group due to ethical reasons.

CONCLUSION

Both FM protocols induced favorable changes in the treatment of Class III malocclusion with a good post-pubertal stability. The BB allows a more efficient control of the vertical skeletal relationship.

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.

Experimental validation of mechanical oscillating IPR system

BACKGROUND

Interproximal enamel reduction (IPR) is a clinical procedure which involves reduction and anatomic recontouring of interproximal surfaces of enamel as a method of gaining space. The biological effects related to this clinical procedure have long been discussed. Thus, the aim of this study was to evaluate the enamel reduction efficiency and the effects on enamel surfaces of the oscillating mechanical system for interproximal enamel reduction (IPR).

METHODS

Fifteen complete oscillating IPR sequences included one opener (0.1 mm), two metallic strips for active IPR phase (0.2 and 0.3 mm), three resin strips for active and initial polishing phases (0.4 and 0.5 mm), and one resin strip for polishing phase (0.15 mm). Sequences were selected and tested on fifteen freshly extracted teeth by means of tribological tests with alternative dry-sliding motion (Linear Reciprocating Tribometer; C.S.M. Instruments, Peseaux, Switzerland). A 3D analysis of treated surfaces was performed by using a TayMap software. Then, enamel surfaces were qualitatively evaluated before and after the tribological analysis, with a FEI Quanta 200 (FEI, Hillsboro, OR, USA) in high vacuum at 30.00 kV. Images were acquired at a 30×, 100× and 300× magnification.

RESULTS

Minimum surface irregularities were observed on all treated enamel surfaces when compared with untreated ones. The 3D analysis showed a uniform wear pattern after tribological tests. Meanwhile, the SEM analysis revealed smooth and regular wear lines on treated surfaces after the entire mechanical IPR sequence. The macroscopic irregularities illustrated can be considered similar to those of untreated surfaces.

CONCLUSIONS

The adoption of a standardized oscillating IPR sequence allows an efficient reduction of the interproximal enamel, leaving regular and harmonious surfaces. Adequate polishing procedures should always be performed at the end of active IPR phases in order to guarantee a good long-term prognosis and proper respect of biological structures.

Effects of aligner activation and power arm length and material on canine displacement and periodontal ligament stress: a finite element analysis

BACKGROUND

This study aimed to assess the impact of aligner activation and power arm length and material on canine and aligner displacement, von Mises stress in the power arm, and principal stress in the periodontal ligament (PDL) during canine tooth distalization using finite element analysis (FEA). The effects of aligner activation and power arm length were primary outcomes, while the effect of the power arm material was a secondary outcome.

METHODS

Aligner activation (0.1 mm or 0.2 mm) was applied without using a power arm in two models. The effects of aligner activation, power arm length (12, 13, or 14 mm) and power arm material (stainless steel [SS] or fiber-reinforced composite [FRC]) on canine distalization were investigated in 12 models by evaluating displacement and stress via ALTAIR OptiStruct analysis.

RESULTS

Greater canine displacement was observed in all models with 0.2 mm than 0.1 mm of aligner activation. When models with the same aligner activation were compared, reduced mesiodistal tipping, increased palatal tipping, and increased extrusion of the canine cusp were observed with increasing power arm length. Moreover, the von Mises stress increased as the power arm length increased. Increasing the aligner activation and power arm length increased the maximum principal stress in the PDL. Power arms of the same length in both materials showed the same results in terms of canine displacement, clear aligner displacement, and maximum principal stress in the PDL. However, under conditions of equal length and aligner activation, the von Mises stress of the SS power arm was higher than that of the FRC power arm.

CONCLUSION

Using a power arm in canine distalization reduced mesiodistal tipping but increased palatal tipping and extrusion of the canine cusp. Aligner activation and additional force increased tooth movement and principal stress in the canine PDL. FRC power arms exhibited less von Mises stress than SS power arms.

Clinical finite element analysis of mandibular displacement model treated with Twin-block appliance

INTRODUCTION

The mechanical distribution of the mandible is an important factor that affects functional orthosis during Twin-block (TB) appliance correction. Changes in the mandible before and after TB appliance correction are also key factors in maintaining the therapeutic effect. Finite element analysis, a powerful numerical, analytical tool, is widely used to predict the stress and strain distribution of the craniofacial bone that orthodontics generates.

METHODS

The sample was a 14-year-old male patient with Class II malocclusion during growth. A cone-beam computed tomography scan was undertaken at pretreatment and posttreatment. In the Finite element analysis of the pretreatment model, the remote displacement model of the mandible was established with the sella point as the center. A mandibular model under TB appliance loading was established. Its mandibular displacement and von Mises stress were compared before and after loading. Three-dimensional registration was conducted on the pretreatment and posttreatment models to measure the sagittal displacement of the centrosome.

RESULTS

The force on the mandible occurred mainly in the condyle neck and medial mandible after the TB appliance moved the mandible. After displacement, the posterior upper margin of the condyle was farther away from the articular fossa. Three-dimensional registration results showed that new bone had formed behind and above the condyle after TB appliance treatment.

CONCLUSION

The TB appliance provides additional advantages in treating skeletal Class II malocclusions by helping to reduce the burden on the temporomandibular joint and promoting the adaptive reconstruction of the mandible.

Stress and displacement patterns during orthodontic intervention in the maxilla of patients with cleft palate analyzed by finite element analysis: a systematic review

OBJECTIVE

Rationale for the review in the context of what is already known about the evaluation of stress and displacement patterns using finite element analysis in the maxilla of patients with cleft palate after orthodontic intervention.

METHODS

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). The protocol for this systematic review was registered with PROSPERO (CRD42020177494). The following databases were screened: Medline (via PubMed), Scopus, Embase, and Web of Science.

RESULTS

The search identified 31 records. 15 articles were retrieved for full texts and 11 of them were considered eligible for inclusion by 2 authors. Eventually, 11 articles were included in the qualitative analysis.

CONCLUSIONS

Finite element analysis is an appropriate tool for studying and predicting force application points for better controlled expansion in patients with UCLP.

Effectiveness of the attachment position in molar intrusion with clear aligners: a finite element study

Objective

To evaluate the biomechanical effects of different attachments’ position for maxillary molar intrusion with clear aligner treatment by finite element analysis.

Methods

Cone-beam computed tomography images of a patient with supra-eruption of the maxillary second molars were selected to construct three-dimensional models of the maxilla, periodontal ligaments, dentition, and clear aligner. The models were divided into four groups depending on the attachment location on the first molar: (1) no attachment (NA), (2) buccal attachment (BA), (3) palatal attachment (PA), and (4) bucco-palatal attachment (BPA). After applying an intrusion of 0.2 mm on the second molar, displacements and stress distributions of the teeth, aligner, and periodontal ligament were analyzed with the finite element software.

Results

All groups displayed equivalent movement patterns of aligners. The NA and BA groups showed buccal tipping of the second molar, while the PA group showed palatal tipping. The BPA group had the highest intruding value and the lowest buccal/palatal tipping value. All groups showed mesial tipping of the second molar. Stress distribution in the periodontal ligament strongly correlated with the attachment position. The BPA group showed the best stress distribution.

Conclusion

Combined BA and PA could effectively prevent buccal and palatal tipping and showed the best efficiency in intruding the second molar. The second molar showed an unavoidable tendency to tip mesially, regardless of the attachment position.

Stress on facial skin of class III subjects during maxillary protraction: a finite element analysis

BACKGROUND

Maxillary protraction with facemask (FM) is an orthopedic approach for treatment of Class III growing patients. Aim of the present investigation was to analyze tension loads produced by two different facial mask (FM) designs on facial skin of subject with skeletal Class III.

METHODS

A three-dimensional (3D) geometry of Delaire and Petit FM models were reconstructed from the original Computer Aided Design (CAD) 3D prototype using software package (ANSYS 5.7). A traction load of 9.8 N inclined of 30° to the occlusal plane was applied combining analytical FM models with a 3D facial model. Resulting stresses and deformations on the skin layer were tested through the von Mises yield criterion.

RESULTS

Overall tensions were mostly developed on the chin area, while lower stresses were observed on forehead area for both FM designs. When Delaire FM model was tested, maximum stresses were observed on the upper border of the chin cup corresponding to the inferior lip and to marginal gingiva of lower incisors. After Petit FM application, maximum stresses were more extensively localized at the level of both upper border and central area of the chin. Stresses measured on the chin area were significantly higher with Petit FM when compared with Delaire FM (44 KPa versus 29 KPa, respectively).

CONCLUSIONS

Delaire FM determined lower stresses and tensile tensions than Petit FM model. Highest tensions were observed at the level of chin cup area for both Delaire and Petit FM. Stresses following Delaire FM application were mostly observed on the upper border of the chin cup, while Petit FM determined stresses more extensively distributed to the central area of the chin.