Quantitative analysis of masseter muscle hardness with shear-wave elastography: Preliminary study on comparison between during rest and contraction in young adults

Yoshiyuki Minami; Ichiro Ogura

doi:10.4103/jomr.jomr_3_22

ORIGINAL ARTICLE

Year : 2022 | Volume : 10 | Issue : 1 | Page : 8-12

Quantitative analysis of masseter muscle hardness with shear-wave elastography: Preliminary study on comparison between during rest and contraction in young adults

Yoshiyuki Minami¹, Ichiro Ogura²
¹ Quantitative Diagnostic Imaging, Field of Oral and Maxillofacial Imaging and Histopathological Diagnostics, Course of Applied Science, The Nippon Dental University Graduate School of Life Dentistry At Niigata, Chuo-Ku, Niigata, Japan
² Quantitative Diagnostic Imaging, Field of Oral and Maxillofacial Imaging and Histopathological Diagnostics, Course of Applied Science; Department of Oral and Maxillofacial Radiology, The Nippon Dental University School of Life Dentistry At Niigata, Chuo-Ku, Niigata, Japan

Date of Submission	14-Feb-2022
Date of Decision	21-Mar-2022
Date of Acceptance	23-Mar-2022
Date of Web Publication	21-Apr-2022

Correspondence Address:
Yoshiyuki Minami
Quantitative Diagnostic Imaging, Field of Oral and Maxillofacial Imaging and AHistopathological Diagnostics, Course of Applied Science, The Nippon Dental University Graduate School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-Ku, Niigata, Niigata 951-8580
Japan

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jomr.jomr_3_22

Abstract

Background: Ultrasound examination is one of the widespread diagnostic imaging methods and still a developing method, which underwent an intense development for biomechanical evaluation of muscles important in temporomandibular disorders, muscle injuries, and training. Aims: This study aims to analyze masseter muscle hardness with shear-wave elastography, especially comparison between during rest and contraction in young adults. Materials and Methods: Thirty-seven volunteers (20 men and 17 women; mean age 25.0 years [age 22–43 years]) were examined by shear-wave elastography with a 14-MHz linear transducer. The shear elastic modulus and thickness of masseter muscles with ultrasonography were compared between during rest and contraction, and between men and women using Mann–Whitney U-test. The statistical analysis of the relationships between contraction and during rest was compared using Wilcoxon signed-rank sum test. P < 0.05 indicates significant differences. Results: Shear elastic modulus data of masseter muscles at contraction were significantly higher than those at during rest (P < 0.001). The thickness of masseter muscles at contraction was significantly higher than those at during rest (P < 0.001). Shear elastic modulus data of masseter muscles at during rest were not a significant difference between men and women (P = 0.402). Similarly, shear elastic modulus data of masseter muscles at contraction were not a significant difference between men and women (P = 0.223). Conclusions: Shear-wave elastography could be an effective tool for the quantitative analysis of masseter muscle hardness.

Keywords: Elastic modulus, masseter muscle, shear-wave elastography, ultrasonography

How to cite this article:
Minami Y, Ogura I. Quantitative analysis of masseter muscle hardness with shear-wave elastography: Preliminary study on comparison between during rest and contraction in young adults. J Oral Maxillofac Radiol 2022;10:8-12

How to cite this URL:
Minami Y, Ogura I. Quantitative analysis of masseter muscle hardness with shear-wave elastography: Preliminary study on comparison between during rest and contraction in young adults. J Oral Maxillofac Radiol [serial online] 2022 [cited 2023 Mar 28];10:8-12. Available from: https://www.joomr.org/text.asp?2022/10/1/8/343692

Introduction

In recent years, ultrasound examination is one of the widespread diagnostic imaging methods and still a developing method, which underwent an intense development for biomechanical evaluation of muscles important in temporomandibular disorders, muscle injuries, and training. When muscle fibers are damaged, muscles show shortening and hardening.^{[1],[2],[3],[4]} Exercise changes muscle hardness and thickness.^[1],[2] The hardness of the masticatory muscles can aid in the diagnosis and treatment of myalgia in patients with temporomandibular disorders.^{[5],[6],[7],[8]}

The types of sonoelastography include strain-type sonoelastography and shear-wave sonoelastography.^[9] Strain-type sonoelastography is an operator dependency and a low reproducibility evaluation.^{[10],[11],[12],[13],[14],[15]} Shear-wave elastography uses push pulses to stress tissues and an ultrafast ultrasound imaging technique to detect the induced shear waves.^{[16],[17],[18]} It is easier to perform than elastography requiring manual compression, and the results of the examination are more repeatable. Shear-wave sonoelastography is expected to lead to a reduction in operator dependency, high reproducibility, and quantitative evaluation.^{[19],[20],[21],[22],[23],[24],[25],[26],[27]} However, the current evidence in normal masticatory muscles is weak, and the clinical usefulness of such information is still unclear. The aim of this study was to analyze masseter muscle hardness with shear-wave elastography, especially comparison between during rest and contraction in young adults.

Materials And Methods

Subjects

This study was approved by the ethics committee of our institution (ECNG-R-400). All volunteers provided written informed consent. Thirty-seven volunteers (20 men and 17 women; mean age 25.0 years [age 22–43 years]) were examined by shear-wave elastography with a 14-MHz linear transducer at our university hospital from November 2020 to February 2021. The volunteers were our student doctor with healthy and had no missing teeth without wisdom tooth and had no severe medical history or symptoms.

Shear-wave elastography

A conventional ultrasonography examination (grayscale and power Doppler ultrasonography) and shear-wave elastography were performed using a 14-MHz loner transducer (Aplio300, Cannon Medicals Systems, Otawara, Japan) by two oral and maxillofacial radiologists, following our institutional protocol.^[28] We used scan gel (ELK; Canon Life Solutions, Tokyo, Japan). The integrated shear-wave elastography software allowed the operator to place region of interest (ROIs) within the elastography window and automatically displayed shear elastic modulus data (kPa) for each ROI at during rest and contraction, respectively [Figure 1] and [Figure 2]. The thickness of masseter muscles (mm) using ultrasonography was measured at masseter muscles and maximum diameter at during rest and maximum force contraction, respectively. The volunteer's set position is sitting position on dental unit. The location for measurements is center of vertical length and front-back width. Shear elastic modulus data and thickness were average of measurements three times.

Figure 1: Masseter muscles at during rest with shear-wave elastography

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Figure 2: Masseter muscle at contraction with shear-wave elastography

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Statistical analysis

The coefficient of determination (R²) from the analyses was calculated to evaluate the relationship between thickness contraction and during rest of masseter muscle. The shear elastic modulus and thickness of masseter muscles were compared between during rest and contraction and between men and women using the Mann–Whitney U-test. The statistical analysis of the relationships between contraction and during rest was compared using the Wilcoxon signed-rank sum test. All analyses were performed with IBM SPSS Statistics Statistical Package version 26 (IBM Japan, Tokyo, Japan). P < 0.05 represented statistical significance.

Results

[Table 1] shows the shear elastic modulus data and thickness of masseter muscles at during rest and contraction. Shear elastic modulus data of masseter muscles at contraction (147.6 ± 25.3 kPa) were significantly higher than those at during rest (27.2 ± 12.6 kPa, P < 0.001). The thickness of masseter muscles at contraction (13.1 ± 2.5 mm) was significantly higher than those at during rest (9.9 ± 2.7 mm, P < 0.001).

Table 1: The shear elastic modulus data and thickness of masseter muscles at during rest and contraction

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[Table 2] shows those at shear elastic modulus data and thickness of masseter muscles at during rest and contraction in men and women. Shear elastic modulus data of masseter muscles at during rest were not a significant difference between men and women (P = 0.402). Similarly, shear elastic modulus data of masseter muscles at contraction were not a significant difference between men and women (P = 0.223). However, the thickness of masseter muscles at during rest of men (11.2 ± 2.6 mm) was significantly higher than those of women (8.4 ± 2.0 mm, P = 0.001). Furthermore, the thickness of masseter muscles at contraction of men (14.5 ± 2.2 mm) was significantly higher than those of women (11.5 ± 1.8 mm, P < 0.001).

Table 2: Shear elastic modulus data and thickness of masseter muscles at during rest and contraction on comparison between men and women in young adults

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We plotted during rest (X) against contraction (Y) and observed no significant correlation at shear elastic modulus data (Y = ‒0.161X + 152.029 [R² = 0.007, P = 0.633]; [Figure 3]). Similarly, we plotted during rest (X) against contraction (Y) and observed a significant correlation at thickness of masseter muscles (Y = 0.781X + 5.403 [R² = 0.687, P < 0.001]; [Figure 4]).

Figure 3: Relationships between contraction and during rest at shear elastic modulus data of masseter muscles

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Figure 4: Relationships between contraction and during rest at thickness of masseter muscles

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Discussion

Shear-wave sonoelastography is inexpensive, easy to use, noninvasive, takes a short time, and has no adverse effects compared to other prominent methods of medical imaging. This study demonstrated the effectiveness of shear-wave elastography of the masseter muscles.

Ariji et al.^[9] showed significantly difference that the mean hardness on shear-wave sonoelastography was 42.82 ± 5.56 kPa at rest and 53.86 ± 8.26 kPa during jaw clenching. In this study, the mean hardness was 27.2 ± 12.6 kPa at rest and 147.6 ± 25.3 kPa at contraction (P < 0.001). Furthermore, shear elastic modulus data at during rest and contraction were no significant differences between men and women. Arda et al.^[29] showed hardness of the masseter muscle of healthy volunteers in the supine position, and the result was 10.4 kPa. In this study, the mean hardness of the masseter muscle of healthy volunteers using shear-wave sonography was 27.2 ± 12.6 kPa at rest and 147.6 ± 25.3 kPa at contraction in sitting position on dental unit. The discrepancy between the three studies would be due to the differences in sex distribution of the subject, race, device, software, and measurement methods and ROI.

Hara et al.^[30] showed that masseter muscle stiffness is effective to assess tooth loss as well as an index of masseter muscle strength when evaluating maximum bite force and that there was no difference between men and women, except for masseter muscle thickness during rest (P = 0.001) and masseter muscle thickness during forceful biting (P = 0.001). In this study, thickness at contraction (13.1 ± 2.5 mm) was significantly higher than during rest (9.9 ± 2.7 mm, P < 0.001). Our study was a significant difference in thickness of masseter muscles depend on sex, but no significant difference in shear elastic modulus data depends on sex. We infer that muscle function influences the thickness of masseter muscles and muscle mass influence shear elastic modulus data.

Conclusion

There are several limitations to our study. In future, it will be necessary to increase the number of cases and to examine the relationship masseter muscle thickness, shear-wave sonoelastography maximum bite force, masticatory function, and aging. In conclusion, we analyzed masseter muscle hardness with shear-wave elastography, especially a comparison between during rest and contraction in young adults. The results of the present study indicate that shear-wave elastography could be an effective tool for the quantitative analysis of masseter muscle hardness.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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