Evaluation of Masseter Muscle Thickness and Its Relation with Mandibular Growth /jp-journals An Ultrasonographic Study JIOS

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Evaluation of Masseter Muscle Thickness and Its Relation with Mandibular Growth 10.

Raj Kumar Singh, 2 Sanjeev Kumar Verma, 3 Sandhya Maheshwari, 4 Gurkeerat Singh, 5 Juhi Ansar 6 Prabhat Kumar Choudhary, 7 Sridhar Kanan ABSTRACT Objective: Aims of the study were to measure the

Materials and methods: This was a double-blind study conducted on 40 subjects in the age range of 15 to 24 years consisting of twenty females and twenty males selected for the study based on clinical

1 Evaluation of Masseter Muscle Thickness and Its Relation with Mandibular Growth /jp-journals Pattern: An Ultrasonographic Study ORIGINAL RESEARCH Evaluation of Masseter Muscle Thickness and Its Relation with Mandibular Growth Pattern: An Ultrasonographic Study 1 Raj Kumar Singh, 2 Sanjeev Kumar Verma, 3 Sandhya Maheshwari, 4 Gurkeerat Singh, 5 Juhi Ansar 6 Prabhat Kumar Choudhary, 7 Sridhar Kanan ABSTRACT Objective: Aims of the study were to measure the thickness of masseter muscle in both males and females of different growth pattern and then to evaluate the relation of thickness of masseter muscle with different growth pattern in both genders. Materials and methods: This was a double-blind study conducted on 40 subjects in the age range of 15 to 24 years consisting of twenty females and twenty males selected for the study based on clinical examination. However four subjects which included four male subjects refused to undergo ultrasonography. Therefore, only thirty-six subjects were undergone ultrasonography. Their ultrasonography was done to measure the masseter muscle thickness. Lateral cephalograms taken to assess their growth pattern. Based on the growth pattern, the subjects were divided into three groups hypodivergents, normodivergents and hyperdivergents and their relation to muscle thickness was evaluated. A null hypothesis was formulated after beginning of study and it was assumed that masseter muscle thickness have no correlation with growth pattern. Results: The results showed significantly (<0.05) thicker muscle mass in hypodivergent subjects as compared to normodivergents (<0.01) and hyperdivergents (<0.001) but not between normodivergents and hyperdivergents (>0.05) in both normal and clenched position. Thicker muscle mass was found on the right side as compared to the left side in both males and females whereas gender wise thicker muscle mass was found in males as compared to females. Females showed more variation in muscle thickness values. Conclusion: It can be concluded that hypodivergent subjects have thickest masseter muscle thickness whereas hyperdivergents have thinnest muscle mass. Males have thicker muscle mass as compared to females. Hence, masseter muscle 1,5 Senior Lecturer, 2-4,7 Professor, 6 Assistant Professor 1,4,7 Department of Orthodontics, Sudha Rustagi College of Dental Sciences and Research, Faridabad, Haryana, India 2,3 Department of Orthodontics, Dr ZA Dental College, Aligarh Uttar Pradesh, India 5 Department of Orthodontics, Institute of Dental Sciences Rohilkhand, Uttar Pradesh, India 6 Department of Orthodontics, RIMS, Imphal, Manipur, India Corresponding Author: Raj Kumar Singh, Senior Lecturer Department of Orthodontics, Sudha Rustagi College of Dental Sciences and Research, Faridabad, Haryana, India, Phone: , rajortho2010@gmail.com thickness can be an important predictor of growth pattern and ultrasonography a noninvasive means for assessing muscle thickness. Thus, the null hypothesis assumed in the beginning, of study was rejected. Keywords: Masseter muscle thickness, Growth pattern, Ultrasonography. How to cite this article: Singh RK, Verma SK, Maheshwari S, Singh G, Ansar J, Choudhary PK, Kanan S. Evaluation of Masseter Muscle Thickness and Its Relation with Mandibular Growth Pattern: An Ultrasonographic Study. J Ind Orthod Soc 2014;48(4): Source of support: Nil Conflict of interest: None Received on: 26/6/14 Accepted after revision: 4/8/14 INTRODUCTION The effects of muscle thickness on bone morphology can be explained by well known theory which is recognized in the field of biodynamics as Wolff s law. 1 This law points out that the internal structure and the shape of the bone is closely related to function, and defines a relationship between bone shape and muscle function. 2 In order to describe facial morphology, the structure of the facial muscles should be investigated thoroughly to determine the pattern of interaction of the skeleton and muscles. The association between masseter muscle thickness (MMT) and vertical craniofacial morphology seems to here a negative relationship but, in contrast, the association between MMT and craniofacial width appears to be positive. 3-6 Masseter muscle thickness has been measured by various imaging techniques including ultrasound scanning, computed tomography (CT) 7 and magnetic resonance imaging (MRI). 4 Computed tomography was used by Weijs and Hillen 7 to measure masticatory muscle thickness in adults. However, CT has massive radiation exposure and MRI is much costlier. Ultrasonography has been used in recent years in different areas of medicine. It has several advantages over CT and MRI, which makes it suitable for large scale studies. 8 In contrast to CT, ultrasonography has no known cumulative The Journal of Indian Orthodontic Society, October-December 2014;48(4):

2 Raj Kumar Singh et al biological effects. It is proven to be a reproducible, simple and inexpensive method for accurately measuring muscle thickness, provided the operator adheres to a strict imaging protocol. 5,9,10 Studies regarding thickness of masseter muscle and its association with growth pattern in all the three facial types in both males and females included in one study are few in literature. 11 Therefore, the aim of this study was to first measure the MMT bilaterally in subjects of both gender randomly based on clinical examination and then assess the growth pattern cephalometrically followed by evaluation of any association between MMT and growth pattern in subjects of both genders. MATERIALS AND METHODS Ethical approval was obtained for the study from the university ethical committee and all subjects were properly explained about the study and written informed consent for the study was taken. The participants in the study were those subjects who were already enrolled for orthodontic treatment. Masseter muscles thickness was measured bilaterally in all the thirty six subjects (20 females and 16 males) of different growth pattern in both normal and clenched condition on both right and left side after their clinical assessment. All the subjects were also underwent cephalometric assessment for their growth pattern and then were divided into three groups hypodivergents, normodivergents and hyperdivergent. The age of subjects under study were ranging from 15 to 24 years with mean (±SD) ± 2.80 years, ± 2.89 years and ± 1.59 years, in hypodivergents, normodivergents and hyperdivergents respectively (Table 1). Subjects with any visible facial asymmetry, history of orthodontic or dentofacial orthopedic treatment in past, any congenital defect in dentofacial or in head and neck region, history of trauma or surgery in orofacial region, history of any neuromuscular disorder, history of pain in masticatory muscle and temporomandibular joint, cases having functional problem like crossbite or bruxism, were excluded from the study. Ultrasound Procedures All scans were carried out in the department of radiology of the University. Each subject was examined by the same operator, using ultrasonography machine (Toshiba istyleaplio XG) and high frequency linear (7-12 MHz) probe. A water-based gel was applied to the probe before the imaging procedure. Copious gel being applied during measurement of MMT to avoid tissue irritation. During imaging procedure, the transducer was held perpendicular to the surface of the skin and special care was taken to avoid excessive pressure. The MMT measurement site was chosen at the thickest part of the masseter, close to the level of the occlusal plane, approximately in the middle of the mediolateral distance of the ramus. The imaging 5 and measurements were performed bilaterally with the subjects seated in upright position (Fig. 1) under two different conditions (Figs 2 and 3), when the teeth were occluding gently with the muscle in a relaxed position and during maximal clenching, with the masseter muscle contracted. The ultrasonographic measurements were made directly from the image at the time of scanning. The imaging and muscle thickness measurements were performed two times on each side with an interval of 5 minutes between each measurement. Fig. 1: Position of the patient during ultrasonography Table 1: Distribution of subjects into groups according to vertical facial pattern Characteristics Hypodivergent (n = 10) Normodivergent (n = 14) Hyperdivergent (n = 12) p-value Age (years) Mean ± SD ± ± ± Range Gender Males 5 (50.0%) 6 (43.0%) 5 (42.0%) Females 5 (50.0%) 8 (57.0%) 7 (58.0%) 526

3: Ultrasonographic image of masseter muscle thickness measurements of patients left side under relaxed and clenched position Source of variation (SS) Table 2: ANOVA summary of masseter muscle

3 Evaluation of Masseter Muscle Thickness and Its Relation with Mandibular Growth Pattern: An Ultrasonographic Study Fig. 2: Ultrasonographic image of masseter muscle thickness measurements of patients right side under relaxed and clenched position Fig. 3: Ultrasonographic image of masseter muscle thickness measurements of patients left side under relaxed and clenched position Source of variation (SS) Table 2: ANOVA summary of masseter muscle thickness (mm) Mean sum of square (SS) Degree of freedom (DF) Mean square (MS) f-value p-value Site Position <0.001 Group <0.001 Site* position Site* group Position* group Site* position* group Error Total Site* position (f = 0.05, p = 0.817); Site* group (f = 0.29, p = 0.746); Position* group (f = 0.32, p = 0.725); Site* position* group (f = 0.12, p = 0.885) STATISTICAL METHOD Statistical analysis of the data obtained from the ultrasonography was undertaken using statistica statistical software (Windows version 6.0). Continuous data were summarized as Mean ± SD while discrete (categorical) in percentage. Continuous variables were compared by two (Group and Gender) and three (Site, Position and Group) factor analysis of variance (ANOVA) and the significance of mean difference within and between the groups was done by Tukey s post hoc test after ascertaining the normality (W = 0.98, p = 0.171) and homogeneity of variances (F = 0.91, p = 0.532) by Shapiro Wilk (W) test and Levene s (F) test, respectively. Categorical variables were compared by Chi-square (χ 2 ) test. A two-sided (α = 2) p < 0.05 was considered statistically significant. RESULTS When the three groups under study were compared for the thickness of masseter muscle (Table 2) significant association (p < 0.05) was observed between different groups with lower MMT in both normodivergent subjects (< 0.01) and hyperdivergent subjects (< 0.001) as compared to hypodivergent subjects at both sites (right and left) and both positions (normal and clenched). However, the mean MMT did not differed significantly (p > 0.05) between normodivergent subjects and hyperdivergent subjects at both sites and positions (Table 3). For each group when we compared the mean MMT between the sites (right vs left) (Table 4), revealed nonsignificant (p > 0.05) MMT in all the groups and positions. The MMT for each group during different position (normal vs clenched) showed significant difference (p < 0.05) in hypodivergent subjects and normodivergent subjects and revealed significantly different and higher MMT at clenched positions in both hypodivergents and normodivergent as compared to the respective normal positions (Table 5). However, MMT did not differ significantly (p > 0.05) between the two positions in hyperdivergent subjects. Further when we compared the mean MMT for each group between two genders revealed significant (p < 0.05) difference and higher MMT in males in all three groups as compared to respective females (Graph 1). Similarly, for The Journal of Indian Orthodontic Society, October-December 2014;48(4):

Raj Kumar Singh et al Table 3: For each site and position, significance (p-value) of mean difference of masseter muscle thickness between the groups by Tukey test Comparisons Right Left Normal

4 Raj Kumar Singh et al Table 3: For each site and position, significance (p-value) of mean difference of masseter muscle thickness between the groups by Tukey test Comparisons Right Left Normal Clinched Normal Clinched Hypodivergent vs normodivergent Hypodivergent vs hyperdivergent p < p < p < p < Hyperdivergent vs normodivergent Table 4: For each group and position, significance (p-value) of mean difference of masseter muscle thickness between the sites by Tukey test Groups Normal Clinched Hypodivergent Normodivergent Hyperdivergent Table 5: For each group and site, significance (p-value) of mean difference of masseter muscle thickness between the positions by Tukey test Groups Right Left Hypodivergent p < Normodivergent p < Hyperdivergent Table 6: For each gender, significance (p-value) of mean difference of masseter muscle thickness between the groups by Tukey test Groups Females Males Hypodivergent vs normodivergent Hypodivergent vs hyperdivergent Hyperdivergent vs normodivergent p < p < p < p < Graph 1: Comparative mean masseter muscle thickness of three groups between the genders each gender, comparing the mean MMT between the groups (Table 6), revealed significantly (p < 0.001) different and lower MMT in both females and males of normodivergents and hyperdivergents as compared to respective females and males of hypodivergents. However, the mean MMT did not differ significantly between both females and males in hyperdivergents compared to normodivergents (p > 0.05). DISCUSSION The objective of the study was to determine the relationship between the thickness of the masseter muscle and the vertical growth pattern in young adult in both genders. Various studies have investigated the association between MMT and vertical craniofacial pattern. The facial morphology of subjects participated in those studies were defined by several variables measured either on lateral cephalograms or standardized facial photographs. 5,12,13 In the present study, all subjects were classified into different growth pattern post ultrasonography to minimize 528 subject bias in the study, according to their vertical facial pattern based on their SN-MP angle 14 and then MMT compared according to the relevant group. In the literature, relaxed muscle thickness measurement has been considered less accurate, due to the higher susceptibility to the pressure with which the probe is placed on the cheek during muscle thickness measurement. 5,8 In the present study, during muscle relaxation, the participants were properly motivated and instructed to maintain light interocclusal contacts but do not clench and where as in other position, the subjects were asked to clench maximally in the intercuspal position. It is possible that this position does not always coincide with maximal muscle contraction, and therefore may not be indicative of the true contraction potential of the ultrasonographic muscles. 6 The relaxed and clenched conditions under which the ultrasonographic measurements were made were based on subjective criteria and were difficult to control hence twice measurements were done bilaterally with a gap of 5 minutes. The results of this study showed that there is a large variation in masseter muscle thickness among individuals, during both relaxation and contraction. Interindividual differences in the cross-section of the masseter muscle may be due to variable number of muscle fibers, variation in fiber size or both. 5

5 Evaluation of Masseter Muscle Thickness and Its Relation with Mandibular Growth Pattern: An Ultrasonographic Study Table 7: Masseter muscle thickness (mean ± SD mm) of three groups according to genders Groups Females (n = 20) Males (n = 16) p-value Hypodivergent ± 1.16 (20) ± 1.67 (20) Normodivergent ± 1.23 (32) ± 1.87 (24) Hyperdivergent ± 0.80 (28) ± 1.53 (20) A strong correlation was found between vertical facial pattern and MMT, indicating that individuals with a thin masseter have a relatively longer face (Tables 3 and 4). These results were found to be in agreement with previous studies which have shown that the masseter muscle is especially thick in shortface individuals. 5-7,15,16 Also, a significant difference was found in MMT between males and females in hypodivergents and normodivergents with male having higher measurements than females whereas in hyperdivergent subjects males have higher measurements than females but the MMT was not found to be significant (Tables 6 and 7). These results also were in accordance with the previous studies. 5,6,15 Thus, the present study strengthens the previous studies done on subjects assessing the relation of MMT with different mandibular growth pattern. CONCLUSION Ultrasonography of the masseter muscle was found to be a relatively simple, rapid and reproducible method of accurately measuring muscle thickness, as long as the operator adheres to a strict imaging protocol and avoids excessive pressure with the transducer. The results showed a significant association between vertical facial pattern and MMT. Thus, the null hypothesis assumed in the beginning of study was rejected. There is insufficient information detailing what influence do the masticatory muscles exert on the maxilla? Also, the effect of jaw and facial expression muscle thickness on the dimensional and structural characteristics of the posterior and anterior alveolar bone should be investigated in further studies. ACKNOWLEDGMENT We thank all the subjects who helped us directly or indirectly for this study. REFERENCES 1. Dibbets JMH. One century of Wolff s law. Bone biodynamics in orthodontic and orthopedic treatment. In: Carlson DS, Goldstein SA editors. Bone biodynamics in orthodontic and orthopedic treatment. Monograph No. 27, Craniofacial growth series, center for human growth and development, University of Michigan Ann Arbor p Wolff J. Uber die innare architectur der knochenundihre budeutung fur die Fragevorn Knochenvasthum. Virchow s Archive 1870;50: Weijs WA, Hillen B. Correlations between the cross-sectional area of the jaw muscles and craniofacial size and shape. Am J Physical Anthropology 1986;70(4): Hannam AG, Wood WW. Relationships between the size and spatial morphology of human masseter and medial pterygoid muscles, the craniofacial skeleton and jaw biomechanics. Am J Physical Anthropology 1989;80(4): Kiliaridis S, Kälebo P. Masseter muscle thickness measured by ultrasonography and its relation to facial morphology. J Dent Res 1991;70(9): Raadsheer MC, Kiliaridis S, Van Eijden TMGJ, Van Ginkel FC, Prahl-Andersen B. Masseter muscle thickness in growing individuals and its relation to facial morphology. Archives Oral Biol 1996;41(4): Weijs WA, Hillen B. Relationships between masticatory muscle cross-section and skull shape. J Dent Res 1984;63(9): Raadsheer MC, Van Eijden TMGJ, Van Spronsen PH, Van Ginkel FC, Kiliaridis S, Prahl-Andersen B. A comparison of human masseter muscle thickness measured by ultrasonography and magnetic resonance imaging. Archives Oral Biol 1994;39(12): Esformes JI, Narici MV, Maganaris CN. Measurement of human muscle volume using ultrasonography. European J Applied Physiology 2002;87(1): Emshoff R, Bertram S, Brandlmaier I, Scheiderbauer G, Rudisch A, Bodner G. Ultrasonographic assessment of local crosssectional dimensions of masseter muscle sites: a reproducible technique. J Oral Rehabilitation 2002;29(11): Satiroglu F, Arun T, Tsik F. Comparative data on facial morphology and muscle thickness using ultrasonography. Eur J Orthod 2005;27(6): Bakke M, Tuxen A, Vilmann P, Jensen BR, Vilmann A, Toft M. Ultrasound image of human masseter muscle related to bite force, electromyography, facial morphology and occlusal factors. Scan Dinavian J Den Res 1992;100(3): Kubota M, Nakano H, Sanjo I, Satoh K, Kamegari T, Ishikawa FM. Maxillofacial morphology and masseter muscle-thickness in adults. Eur J Orthod 1998;20(5): Isaacson JR, Isaacson RJ, Speidel TM, Worms FW. Extreme variation in vertical facial growth and associated variation in skeletal and dental relations. The Angle Orthod 1971;41(3): Benington PCM, Gardener JE, Hunt NP. Masseter muscle volume measured using ultrasonography and its relationship with facial morphology. European J Orthodont 1999;21(6): Sushma R, Ravi MS. Masseter muscle thickness in different skeletal morphology: an ultrasonographic study. Indian J Dent Res 2010;21(3): The Journal of Indian Orthodontic Society, October-December 2014;48(4):

Masseter muscle thickness and maxillary dental arch width

European Journal of Orthodontics 25 (2003) 259 263 2003 European Orthodontic Society Masseter muscle thickness and maxillary dental arch width Stavros Kiliaridis*, Ioanna Georgiakaki* and Christos Katsaros**,