Contribution of masticatory muscle pattern to craniofacial morphology in normal adults: A cross-sectional MRI study

ABSTRACT

Purpose:

The study aimed to determine the muscle pattern of medial pterygoid, lateral pterygoid, and masseter (length, cross-section, and angulation) in adult non-orthodontic patients and its effect on craniofacial structures.

Methods:

The study was conducted from January 14, 2019 to January 14, 2020. Ethical clearance of this study was obtained from the ethical committee Ethical Clearance was obtained from Faculty of Dental Sciences, IMS, BHU, Institutional Ethical Committee with Ref no. Dean/2019/EC/1824 dated 23.04.2019 of the university. The sample size was estimated using the G-power statistical program. Power analysis indicated a minimum sample size of 27. Inclusion and exclusion criteria were set. Consent was taken from participants. Seventy-seven subjects who were willing to participate and have given written consent were enrolled for the study. Participants were sent for lateral cephalometry (Dolphin Cephalometric software) Dolphin Imaging and management solution, for 6 angular and 11 linear measurements. Nineteen subjects did not turn up for the scan. Twenty-eight participants underwent MRI (magnetic resonance imaging) to evaluate muscle patterns (masseter, medial, and lateral pterygoid). The intra-class correlation coefficient (ICC), Kolmogorov–Smirnov (KS) test, descriptive statistics, and multiple regression analysis were computed. The P value was set as ≤0.001(highly statistically significant) and ≤0.05 (significant relation).

Results:

There was a highly statistically significant (p ≤ 0.001) association between masseter length to upper facial height (N-Ans) and ramal length (Cd-Go). Length of medial pterygoid was significantly related (p ≤ 0.05) with SNB and length of body of mandible (Pog-Go). The cross-section of this muscle showed significant relation with upper facial height (N-Ans) and ramal length (Cd-Go). The correlation of the length of lateral pterygoid with upper facial height (N-Ans) and maxillary length (A-Ptm) was highly significant.

Conclusion:

The muscle pattern has a significant correlation with maxillofacial morphology. The masseter muscle is the longest and thickest (cross-section) and is angulated vertically than the other two muscles (medial pterygoid and lateral pterygoid). Of the three muscles, the medial pterygoid influences more common craniofacial parameters suggestive of its symbiotic activity. Lateral pterygoid affects the maxillary length and facial height.

INTRODUCTION

The functions of the jaw muscles are considered to determine craniofacial growth and development. Muscles are attached to the basal bone and their activity causes bone remodeling. A similar effect occurs in the maxillofacial region due to the continuous movement of the muscles of mastication. The pattern of muscle, i.e. its length, cross-section, and angulation are a few important parameters that define facial morphology. The cross-section of a muscle is considered to be directly proportional to the maximum bite forces that the muscle can deliver.[1] A decrease in function will cause disuse atrophy of a muscle and also decreases the muscle mass. It is important to know the muscle pattern in a normal individual and in an individual who has altered maxillofacial morphology to determine the effect of form and function.

Masseter, temporalis, medial pterygoid, and lateral pterygoid are the masticatory muscles that correlate with the morphologic features of the craniomandibular apparatus. Beecher et al.[2] have shown that poor functional stimulus through mastication can lead to underdevelopment of the mandibular condyle. Kiliaridis et al.[3] proved that the density of the trabecular pattern and the thickness of cortical bone show poor development due to the low level of stimulation from the masticatory apparatus. Hence, the influence of weak muscles on morphology is not pronounced. Woods[4] stated that masseter and medial pterygoid muscles have large cross-sections in people with short-anterior face heights and small gonial angles. However, according to Spronsen et al.,[5] no significant correlations were seen between either anterior facial height or posterior facial height and cross-sectional areas of jaw elevators.

There are various methods for evaluating the cross-section of the facial muscle or defining their patterns, such as magnetic resonance imaging (MRI), computed tomography, and ultrasonography. MRI is a non-invasive method that uses a strong magnetic field and high-frequency radio waves for high-quality soft tissue imaging without causing any adverse effects such as high doses of radiation. A series of frontal, horizontal, sagittal, and angulated MRI images can be obtained without modification of the patient’s position and thus patients’ compliance is also minimized. Weijs et al.[6] have shown that, one can obtain the scanning plane by orienting the muscle in 30° from the Frankfort horizontal plane (especially masseter and medial pterygoid) without altering the patient’s position.

Cross-sectional images of the muscle were previously obtained by using occlusal planes as the reference plane. But images obtained by this method showed an exaggerated cross-section of the muscles as the muscle was not oriented in its own longitudinal plane. With the help of MRI, we can reorient the muscle section through reconstructed images in its accurate anatomical landmarks, which is the best way to define the cross-section and length of the muscle. Most of the studies had stressed on the masseter muscle,[7] a few have studied about masseter and medial pterygoid[8] but little was known about lateral pterygoid. This study was critically designed to fulfill these lacunae and will highlight the pattern (length, angulation, and cross-section) of these three muscles (masseter, medial, and lateral pterygoid) and their possible effect on defining maxillofacial morphology.

METHODS

Data acquisition

The study was conducted at the Department of Orthodontics and Dento-facial Orthopedics and Department of Radiology, from January 14, 2019 to January 14, 2020. Ethical approval was taken from the ethical committee of the University (Dean/2019/EC/1824). The sample size was estimated to have an effect size of 0.973, which was determined by using the G-power statistical program (version 3.1; Heinrich Heine Universitat Dusseldorf Experiment elle Psycologie, Dusseldorf, Germany). Power analysis indicated that the required minimum sample size was 27 subjects to determine this effect size with 80% power and a significance level of 5%. Inclusion criteria (no history of orthodontic treatment; subjects with average or horizontal growth pattern based on Steiner’s mandibular plane angle; no missing teeth in the anterior segment, not more than two missing teeth in the posterior segment, apart from the third molars; no facial asymmetry observed from the clinical examination; no symptoms of temporomandibular joint (TMJ) disorders) are selected. The exclusion criteria (age ≤18 years and not >30 years; patient undergone orthodontic treatment; presence of crossbite, crowding, rotation, and subdivisions; individuals with congenital craniofacial deformity; patient with developmental disorders; and vertical growth pattern) were clearly defined. One hundred and twenty-four randomly selected patients were screened in the department of oral medicine and radiology. The study was described to them, 77 patients did not agree to undergo MRI. Consent was taken from the remaining (47) for their willingness to participate in the study. Then they were sent for lateral cephalometry (Epsilon EP-Dento OPG Machine, Carestream. kV = 90, mAs = 10). The cephalograms were analyzed by an investigator “A” who was unaware of the study design. Dolphin imaging software was used (Version 11.5, Chatsworth, Calif) to determine desired cephalometric parameters (6 angular and 11 linear measurements) [Table 1]. On the day of the MRI scan, 19 participants did not turn up. Finally, 28 (11 females, 17 males) aged 18–30 years (25.2 years ± 4.4) subjects underwent MRI (GE 0.5T VMX2 Magnet and Cryogen system with E-film Software) to measure various muscle patterns of the masseter, medial, and lateral pterygoid.

Table 1.

Six angular measurements and 11 linear measurements

Angular measurement	Linear measurement
SNA	N-Me (Anterior facial height)
SNB	N-ANS (Upper anterior facial height)
ANB	ANS - Me (Lower anterior facial height
Mandibular plane angle	A-Ptm (Maxillary length)
Ramus inclination	Gn - Cd (Length of mandible)
Gonial angle	Pog- Go (length of body of mandible)
	Cd-Go (length of ramus)
	Thickness of mandibular process
	Thickness of mandibular symphysis
	Thickness of condylar neck
	Height of the condyle

MRI (Measurement of muscle pattern)

The muscle pattern of the masseter, medial pterygoid, and lateral pterygoid of all the subjects in the study was evaluated using MRI (0.5 tesla). The subjects were asked to maintain occlusion in the centric occlusion when teeth are occluding gently with muscles in a relaxed position.

The MRI images were acquired in three sections, i.e. axial, coronal, and sagittal. The sagittal images [Figure 1] were taken to define the field in the study. In this field, all three muscles under study could be imaged and viewed. The superior limit was taken as the Frankfort horizontal plane and the distal limit was taken as distal to the pituitary fosse. The MRI images in the coronal section [Figure 1] defined the medio-lateral inclination of two muscles, i.e. masseter and medial pterygoid. A total of 80 image slices were taken in the coronal section. The depth of each slice was maintained at 1.5 mm. The clearest image in each section was chosen (on two consecutive days), by the method of repeated superimposition by a radiologist “R,” who had an experience of more than 10 years. These images showed the origin, insertion, length, and angulation (with respect to the Frankfort horizontal plane) of that particular muscle in this study.

Figure 1.

Sagittal and coronal section to define the field under study

The long axis of the muscle [Figure 2] was defined by drawing a line from the superior most point of origin to the inferior most point of insertion. This image showed that the muscles’ origin and insertion are oriented according to the true anatomy. The images of the particular muscle were then reconstructed perpendicular to the coronal section so that a lateral oblique view can be obtained. This view clearly defines the maximum cross-section of the muscle. The images in the axial section were taken to define the orientation of the lateral pterygoid muscle where the head of the muscle adheres to the articular disc and also to the mandibular condyle. These images were then reconstructed in the same manner as stated above. The cross-section, i.e. the greatest bulge of the muscle was measured at an angle perpendicular to the reconstructed image of the muscle. To ensure that minimum error remains by the marginal tracing of the muscle, three readings were taken at the maximum bulge area on the selected MRI image by the radiologist, each at a 1 mm difference. The mean was then used to find out the actual cross-section of the muscle.

Figure 2.

The origin, insertion, length of the masseter, medial, and lateral pterygoid, angulations of medial pterygoid and masseter muscle

Statistical analysis

The distribution of various measurements was tested using the Kolmogorov–Smirnov (KS) test and all the variables were found to be normally distributed. Reproducibility (intra-observer) was assessed by repeating all the measurements on five randomly chosen cases which was calculated using intra-class correlation coefficient (ICC) [Table 2] and was found to be 0.912 (MRI readings). To examine the effect of the masseter, medial pterygoid, and lateral pterygoid on maxillofacial morphology, a multiple regression analysis (MRA) was performed where various skeletal parameters were independent variables and the muscle pattern was the dependent variable.

Table 2.

Intra-class correlation coefficient of MRI parameters

MRI parameters	Intra-class correlation coefficient
Muscle length M-RT	0.839
Muscle length M-LT	0.997
Muscle length MP-RT	0.939
Muscle length MP-LT	0.92
Muscle length LP-RT	0.901
Muscle length LP-LT	0.905
Cross-section -MRT	0.854
Cross-section -MLT	0.883
Cross-section -MPRT	0.822
Cross-section -MPLT	0.999
Cross-section -LPRT	0.878
Cross-section -LPLT	0.932
Angulation -MRT	0.913
Angulation -MLT	0.981
Angulation -MPRT	0.87
Angulation -MPLT	0.961

RESULTS

The study [Tables 3 and 4, Figures 3 and 4] showed a bilateral significant positive correlation between the muscle pattern and maxillofacial morphology. Statistically highly significant relation (p ≤ 0.001) exists between masseter length (Right = 7.46 ± 0.61 cm and left = 7.53 ± 0.634 cm) to upper facial height (N-Ans) and ramal length (Cd-Go). Significant relation (p ≤ 0.05) exists between masseter muscle length to ramus inclination, lower anterior facial height (Ans-Me), and length of the mandible (Gn-Cd). The cross-section (Right = 3.17 ± 0.45 cm and left = 3.28 ± 0.415 cm) of this muscle shows significant relation between anterior facial height (N-Me) and maxillary length (A-Ptm). The angulation (Right = 74.154 ± 3.17° and left = 77.846 ± 2.475°) of masseter muscle shows significant relation with the position of the mandible (SNB).

Table 3.

Mean and standard deviation of the variables of cephalograms and muscle pattern of masseter (M), medial pterygoid (MP), and lateral pterygoid (LP) (Length, cross-section, and angulations) (Right-R, Left-L)

Descriptive statistics	Mean	Std. deviation
Muscle Length-M-R	7.462	0.611
Muscle Length-M-L	7.527	0.635
Muscle Length-MP-R	5.177	0.600
Muscle Length-MP-L	5.100	1.160
Muscle Length-LP-R	3.531	0.332
Muscle Length-LPL	3.481	0.332
Cross-section M-R	3.168	0.452
Cross-section M-L	3.278	0.415
Cross-section MP-R	1.955	0.236
Cross-section MP-L	1.923	0.242
Cross-section LP-R	2.270	0.221
Cross-section LP-L	2.266	0.228
ANGULATION M-R	74.154	3.170
ANGULATION M-L	77.846	2.475
ANGULATION MP-R	108.808	4.659
ANGULATION MP-L	113.385	5.306
SNA	83.482	3.391
ANB	-0,001	7.279
SNB	82.336	6.095
MANDIBULAR PLANEANGLE	24.311	6.284
GONIAL ANGLE	116.895	24.812
RAMUS INCLINATION	89.635	11.466
N-ME	112.742	31.947
N-ANS	53.962	6.787
ANS-ME	70.536	8.370
A-PTM	52.183	4.680
GN-CD	124.912	9.409
POG-GO	79.371	6.488
CD-GO	63.547	6.379
tHICKNESS OF MANDIBULAR PROCESS	9.044	1.812
tHICKNESS OF MANDIBULAR SYMPHYSIS	14.944	1.950
tHICKNESS OF CONDYLAR HEAD	12.409	1.179
HEIGHT OF CONDYLE	13.212	2.822

Table 4.

Pearson correlation value with level of significance of correlation coefficients *P≤0.05, **P≤0.001((masseter (M), medial pterygoid (MP), lateral pterygoid (LP), right (R), left (L))

Cephalometric parameters Muscle pattern	SNA	SNB	ANB	Mandibular plane angle	Gonial angle	Ramus inclination	N-Me	N-ANS	ANS-Me	A-Ptm
Muscle length
M-R	-0.046	-0.058	0.087	-0.079	0.015	0.358*	0.213	0.431**	0.365*	0.177
M-L	0.009	-0.109	0.145	0.023	0.052	0.382*	0.182	0.585**	0.394*	0.331*
MP-R	0.262	0.329*	-0.007	0.053	0.154	0.101	0.169	0.324*	0.212	0.275*
MP-L	0.191	0.437*	-0.202	-0.088	-0.025	-0.236	0.044	0.183	-0.090	0.312
LP-R	-0.069	-0.117	0.269	-0.193	-0.033	0.328*	0.170	0.524**	0.167	0.564**
LP-L	-0.118	-0.196	0.427*	-0.228	-0.223	0.292	0.150	0.565**	0.244	0.446**
Cross-section
M-R	0.132	0.004	0.077	-0.116	0.167	0.347*	0.362*	0.015	0.261	0.333*
M-L	0.279	0.316	-0.161	-0.357*	0.033	0.088	0.391*	0.296	0.121	0.354*
MP-R	0.061	-0.080	0.122	-0.101	-0.047	0.294	0.174	0.422*	0.212	0.362*
MP-L	0.054	0.036	-0.007	-0.165	-0.023	0.238	0.174	0.323*	0.182	0.286
LP-R	0.268	0.159	0.149	0.259	-0.121	0.163	0.336*	0.314*	0.328*	0.320*
LP-L	0.103	0.141	0.152	0.245	-0.030	0.140	0.296	0.357*	0.255	0.442**
Angulation
M-R	0.287	0.334*	-0.267	0.334*	0.253	-0.136	0.116	-0.273	0.054	0.033
M-L	0.523**	0.431*	-0.283	-0.282	-0.041	-0.310	0.146	-0.216	-0.064	0.017
MP-R	0.272	0.269	0.091	0.241	-0.030	0.035	-0.086	-0.020	-0.099	0.050
MP-L	0.189	0.351*	-0.229	-0.176	-0.058	-0.349*	-0.034	-0.259	-0.198	-0.068
Cephalometric parameters Muscle pattern	Gn-Cd	Pog-Go	Cd-Go	Thickness of mandibular process		Thickness of mandibular symphysis			Thickness of condylar head	Height of condyle
Muscle length
M-R	0.351*	0.306	0.544**	0.090		0.196			0.201	0.193
M-L	0.406*	0.361*	0.527**	0.139		0.263			0.164	0.315
MP-R	0.449**	0.405*	0.439*	-0.033		-0.117			-0.166	0.165
MP-L	0.300	0.360*	0.177	0.037		-0.103			-0.158	0.061
LP-R	0.297	0.370*	0.404*	0.207		0.331*			0.268	0.338*
LP-L	0.175	0.351*	0.242	0.171		0.377*			0.197	0.050
Cross-section
M-R	0.038	0.203	0.042	0.127		0.271			0.185	-0.032
M-L	0.232	0.427*	0.248	0.206		0.233			-0.122	0.048
MP-R	0.161	0.294	0.322*	0.256		0.302			0.167	-0.122
MP-L	0.166	0.227	0.310*	0.115		0.273			0.255	-0.004
LP-R	0.391*	0.451**	0.235	-0.205		-0.045			-0.092	-0.041
LP-L	0.447**	0.441**	0.309	-0.054		0.000			0.079	0.165
Angulation
M-R	0.289	0.214	-0.051	0.020		-0.024			-0.082	0.057
M-L	0.084	-0.010	0.000	-0.006		0.183			-0.166	0.116
MP-R	0.071	0.080	-0.089	-0.132		-0.201			-0.245	-0.143
MP-L	-0.155	-0.038	-0.341*	-0.026		-0.055			-0.357*	-0.240

Figure 3.

Scatter diagrams showing a significant correlation between muscle parameters and cephalometric variables

Figure 4.

Research design

Length of medial pterygoid (Right = 5.81 ± 0.6 cm and left = 5.1 ± 0.16 cm) is significantly related (p ≤ 0.05) with SNB and length of body of mandible (Pog-Go). The cross-section (Right = 1.955 ± 0.236 cm and left = 1.92 ± 0.242 cm) of this muscle shows significant relation with upper facial height (N-Ans) and ramal length (Cd-Go).

Length of lateral pterygoid (Right = 3.53 ± 0.32 cm and left = 3.46 ± 0.32 cm) is highly significant (p ≤ 0.001) with upper facial height (N-Ans) and maxillary length (A-Ptm). Length of body of mandible (Pog-Go) and thickness of mandibular symphysis is significantly related (p ≤ 0.05) to the length of lateral pterygoid. The cross-section (Right = 2.27 ± 0.0221 cm and left = 2.266 ± 0.228 cm) of this muscle shows significant relation with upper facial height (N-Ans), length of body of mandible (Pog-Go), length of mandible (Gn-Cd), and maxillary length (A-Ptm).

DISCUSSION

Equilibrium in force distribution between oral and perioral structures is important for the harmonious development of the facial skeleton and dentition. Based on the functional matrices theory developed by Moss,[9] any alterations in the craniofacial muscle activities that control the oral functions may influence the developing underlying structures. Various studies[10,11] have demonstrated and shown a distinct relationship between muscle morphology, i.e. length, cross-section, and angulation with the architectural pattern of the skeletal morphology of the face. This also gives an insight into the differences in craniofacial morphology in individuals and various skeletal malocclusions. It has been seen that musculature does have an influential effect on vertical parameters[12,13] and transverse[14-17] and sagittal dimensions[18] of facial morphology. To access the muscle pattern, there are various diagnostic methods available such as computed tomography, MRI, ultrasound, and electromyography (EMG) (for muscle activity). Of these, MRI images give a clear differential image of soft tissue as compared to conventional computed tomography. It also has the benefit of zero radiation during investigative procedures. This study shows a significant association between the pattern of muscle and its relationship with the underlying skeletal structure.

The length of the masseter muscle is positively correlated to ramus inclination, length of the mandible, ramal length, and upper and lower facial height. This is contrary to Azaroual et al.[11] where the relationship between masseter length and lower facial height is statistically insignificant. In this study, the length of the masseter muscle reveals a significant association between vertical parameters as compared to sagittal parameters. Based on statistically significant parameters, the cross-section of the muscle influences facial height (N-Me). This is contradictory to Van Spronsen et al.[19] that the masseter cross-sectional area is not significantly correlated with adult vertical craniofacial dimensions. The length of the masseter muscle (left side) is significantly negatively correlated with the mandibular plane angle, which is in accordance with the study done by Gionhaku et al.[20] This is also in consensus with Satiroglu et al.[21] who found a negative correlation between masseter thickness and divergence. The angulation of the muscle showed that it is significantly correlated with SNB and mandibular plane angle on the right side and with SNA and SNB on the left side. Based on the number of significant parameters, the left side seems to have more influence than the right. The difference between the influential effect of the right and left side of the masseter muscle could be because of the difference in bite forces and chewing pattern of the individual. In a study done by Hsu et al.,[18] angulation of the masseter muscle is compared with the medial pterygoid muscle, and it was concluded that the masseter is oriented more vertically than the medial pterygoid which is in accordance to our study with respect to the orientation of masseter muscle.

Hsu et al.[18] further concluded in his study that the medial pterygoid muscle is inclined towards the mid-sagittal plane; therefore, its influence is found to be more on sagittal parameters which are in agreement with our study. Length of medial pterygoid shows association with more sagittal parameters (SNB, Gn-Cd, Pog-Go) than vertical parameter (upper facial height). However, a study done by van Spronsen et al.[19] was contradictory, where facial height was significantly correlated with the orientation of the jaw opening muscles (lateral pterygoid, anterior digastric, and supra-hyoid group of muscles) in the sagittal plane but was not significantly correlated with the orientation of the mandibular elevator muscles (medial pterygoid, masseter, and temporalis). In our study, the cross-section of this muscle shows significant relation with upper facial height (N-Ans), A-Ptm (maxillary length of the right side), and ramal length (Cd-Go). The results are in concordance with the study done by Gionhaku et al.,[20] where there is a positive correlation of the muscle with ramal length. The angulation of the medial pterygoid muscle does not have any significant correlation when compared to the parameters bilaterally but it was found in the study that angulation of the medial pterygoid on the left side was negatively correlated to ramus inclination, ramal length, and thickness of condylar head. However, the study done by Kusumah et al.[22] showed a positive association with the shape of the ramus.

In this study, the length of the lateral pterygoid was highly significant with maxillary length and upper facial height. This is in co-ordinance to Van Spronsen et al.[19] where muscles that open the mandible (lateral pterygoid and anterior digastric muscles) were significantly correlated with facial height. This is contradictory to Azaroual et al.[11] where no correlations were found between the length and width of the lateral pterygoid muscle and facial height (vertical dimension). The study shows a positive statistical correlation between maxillary length (A-Ptm) and thickness of mandibular symphysis. The cross-section of this muscle shows bilateral significant relation with facial height, maxillary length, mandibular body, and length of mandible, whereas Weijs et al.[16,17] found no association between the cross-section area of lateral pterygoid and facial parameters.

In our study, we found significant and complex relationships between masseter, medial, and lateral pterygoid and maxillofacial morphology. The left and right sides of the muscles showed a difference in the correlation of various independent variables, which might lead us to think about possible asymmetry; however, this asymmetry was not evident clinically. Consideration was made and stress was laid on only those parameters, which showed a statistically significant relationship when considered bilaterally. It was evident in this study that masseter muscle had the greatest influence followed by medial pterygoid and lateral pterygoid muscle on bony structures. Further masseter was more vertically oriented with respect to Frankfort horizontal plane when compared to the medial pterygoid muscle. The influence of muscle orientation on sagittal parameters is profound. In our study, it was deciphered that influence of masseter muscle is larger on various craniofacial structures bilaterally and is statistically significant. Masseter, medial, and lateral pterygoid have a statistically significant common relationship with upper facial height (N Ans), ramal length and SNB with masseter and medial pterygoid and length of body of mandible with medial and lateral pterygoid are also significant respectively. Medial pterygoid affects more common craniofacial parameters among all the three muscles under consideration. Therefore, it is important for the orthodontist as well as maxillofacial surgeons to keep this information in mind before deciding the bite jumping therapy in both sagittal and vertical planes in young adults or surgical correction of various abnormalities involving skeletal parameters.

LIMITATIONS

• 1)The study requires participants to keep their jaws in centric relation when teeth are occluding gently with muscles in a relaxed position, which is difficult to assess.
• 2)The study could have been designed by allotting the participants to various skeletal malocclusions (Skeletal I, II, and III) to get a complete insight into morphology and muscle pattern.

CONCLUSION

The results of this study suggest the muscle pattern has a significant correlation with maxillofacial morphology. The masseter muscle is the longest and thickest (cross-section) and is angulated vertically than the other two muscles (medial pterygoid and lateral pterygoid); therefore, it has the greatest muscular activity and affects the maxillofacial morphology the most. Of the three muscles, the medial pterygoid has more influence on common craniofacial parameters, which might be suggestive of the symbiotic relationship of this muscle. Lateral pterygoid affects the maxillary length and facial height. Future researches are required especially in cases of orthognathic surgeries to assess the changes brought about in muscle parameters (muscles of mastication) pre- and post-surgery to correlate it with stability.

Declaration of Patient

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.