Statement of problem

Asymmetries in mandibular movements (MMs) can be found in patients with some temporomandibular joint disorders, condylar fracture, or after orthognathic or orthodontic surgery. Quality and symmetry of the MMs should be recorded and analyzed. However, methods for this purpose are limited.

Purpose

The purpose of this clinical study was to determine the symmetry of MMs on asymptomatic participants by applying an innovative technique based on 3D electromagnetic articulography.

Material and methods

The symmetry of MMs was studied in 16 fully dentate participants (8 men and 8 women). A 3D electromagnetic articulograph was used to register MM by placing a sensor on the interincisal midline of the mandible. The border movements related to the frontal (FP), sagittal (SP), and horizontal (HP) polygons of the Posselt envelope of motion were recorded, as well as masticatory movements. Digital data processing was applied to calculate the trajectory and ranges of mandible displacement, area of the right and left sectors of FP and HP, similarity index between the right and left sectors of FP and HP, and orientation of the individualized masticatory cycles. The Shapiro-Wilk statistical test was used to determine the normality of the sample. To compare the characteristics of the right and left sectors of the polygons, a paired-samples t test (normal distributions) and Wilcoxon test for paired samples (non-normal distributions) were applied (α=.05).

Results

No statistically significant differences were found between the right and left sectors of the frontal and horizontal polygons in terms of trajectory (FP, P=.408; HP, P=.417), ranges of movement (FP, P=.736; HP, P=.650), areas (FP, P=.736; HP, P=.233), or orientation of the cycles (P=.506). The similarity index between the morphology of the right and left sectors of the polygons was 68 ±12% for the FP and 67 ±11% for the HP. The areas, trajectories, and ranges had similar values, but they had a different morphology on each side of the polygons. Regarding masticatory cycles, a balanced distribution was observed in terms of their orientation.

Conclusions

The technique used allowed the assessment of symmetry of MM on asymptomatic participants. The evaluated parameters maintain similar values at both left and right sides; however, a different morphology of the trajectories and areas was observed.

中文翻译：

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下颌运动的对称性：应用于无症状参与者的3D电磁关节造影技术

问题陈述

在患有一些颞下颌关节疾病，con突骨折或正颌或正畸手术后的患者中，可以发现下颌运动（MMs）不对称。MM的质量和对称性应予以记录和分析。但是，用于此目的的方法是有限的。

目的

这项临床研究的目的是通过应用基于3D电磁关节造影的创新技术来确定无症状参与者的MM的对称性。

材料与方法

MM的对称性在16个完全齿状的参与者（8名男性和8名女性）中进行了研究。通过将传感器放置在下颌骨的内切中线上，使用3D电磁关节描记器对MM进行定位。记录了与波塞特运动包络线的正面（FP），矢状（SP）和水平（HP）多边形有关的边界运动以及咀嚼运动。应用数字数据处理来计算下颌骨位移的轨迹和范围，FP和HP左，右扇形区域的面积，FP和HP左，右扇形之间的相似性指数，以及各个咀嚼周期的方向。Shapiro-Wilk统计检验用于确定样品的正态性。为了比较多边形的左右扇形的特征，使用成对样本对配对样本进行了t检验（正态分布）和Wilcoxon检验（非正态分布）（α= .05）。

结果

在轨迹（FP，P = .408； HP，P = .417），运动范围（FP，P = .736 ； HP ）方面，在正面和水平多边形的左右扇形之间没有发现统计学上的显着差异，P = .650），面积（FP，P = .736 ； HP，P = .233）或循环的方向（P = .506）。多边形的左右扇形的形态之间的相似度指数对于FP为68±12％，对于HP为67±11％。面积，轨迹和范围具有相似的值，但是它们在多边形的每一侧具有不同的形态。关于咀嚼周期，在它们的定向方面观察到平衡的分布。

结论

使用的技术可以评估无症状参与者的MM对称性。评估的参数在左侧和右侧都保持相似的值；但是，观察到了不同的轨迹和区域形态。