Variations and thicknesses of anterior belly of the digastric muscle: an ultrasonographic study.

PURPOSE: This study aims to evaluate the anatomy and anatomical variations of the anterior belly of the digastric muscle. METHODS: Hundred and fifty one ultrasonographic images of the digastric muscle pairs were evaluated in Near East University Faculty of Dentistry Department of Dentomaxillofacial Radiology. Morphological variations were recorded using the classification of the digastric muscle into 12 types by Kim et al. For the analysis, the Mann-Whitney U test and Chi-square test were used, and for the correlational analysis, Spearman's rho test was applied. P < 0.05 was considered statistically significant in all tests. RESULTS: Seventy female and 81 male patients aged 19-60 years were evaluated. Type 1 digastric muscle was observed in 145 of 151 patients, Type 2 in 3 patients, and Type 7 in 3 patients. The thicknesses of the right and left digastric muscles were measured, and a statistically significant difference was observed between the groups when the genders were compared. It was observed that both right and left digastric muscle thicknesses were higher in males than females. There was a statistically significant positive high correlation between right and left digastric muscle thicknesses (p = 0.000; r = 0.736). No statistically significant difference was found between genders (p = 0.596) in terms of anatomical variations. CONCLUSION: Considering that the variations of the digastric muscle may have a clinical significance role, the normal anatomy and variations of this muscle should be well known by maxillofacial surgeons and radiologists.

Comparison between botulinum toxin type A injection on masseter muscle only and additional injection on anterior belly of digastric muscle in sleep bruxism patients: A clinical trial.

OBJECTIVE: This study aims to evaluate the effects on bite force and muscle thickness of the botulinum toxin (BoNT) injection for patients with sleep bruxism (SB) by comparing injections into the masseter muscle only and both the masseter and the anterior belly of the digastric muscle (ABDM) in a clinical trial. METHODS: Twelve SB patients received BoNT-A injections using US-guided techniques into the masseter muscle only (Group A), while the remaining 12 SB patients received injections into both the masseter and ABDM (Group B). Bite force and muscle thickness were measured before injection, as well as 1 and 2 months after injection. RESULTS: The bite force and masseter muscle thickness decreased in both Group A and Group B before injection, and at 1 and 2 months after injection. However, there was no significant difference (p > .05, repeated measures analysis of variance) between the two groups, and there was also no significant difference in ABDM thickness (p > .05, repeated measures analysis of variance). CONCLUSION: This study is the first to assess the short-term effects of BoNT injected into ABDM for SB control. Results show no influence on SB reduction, suggesting the need for further research on BoNT's effectiveness in controlling intense ABDM contractions during sleep and assessing suprahyoid muscle potential impact on rhythmic masticatory muscle activity occurrence.

Double Chin Concerns after En Bloc Mandibular U-Shaped Osteotomy: Submental-Cervical Soft Tissue Changes and Anterior Belly of Digastric Muscle Assessment.

OBJECTIVE: To assess submental-cervical soft tissue changes after en bloc mandibular U-shaped osteotomy and examine alterations in the anterior belly of digastric muscle (ABDM). METHODS: A retrospective study analyzed 20 patients who underwent en bloc mandibular U-shaped osteotomy from 2018 to 2023. Preoperative (Tp) and long-term follow-up (Tf) CT data were collected for analysis, measuring mandibular volume, soft tissue thickness at menton (Mes) and cervicale (C), and ABDM parameters (length, cross-sectional area (CSA), volume, distance from centroid point to the mandibular margin). Correlation analyses were performed to investigate the connection between soft tissue thickness changes, ABDM changes, and mandibular osteotomy volume. RESULTS: Long-term follow-up revealed a significant increase in soft tissue thickness at the Mes and C points after U-shaped mandibular osteotomy, especially at the C point. The adaptive length of ABDM decreased, CSA increased, and volume decreased, but the ABDM centroid point shifted downward relative to the mandibular margin, indicating drooping protrusion. The increment of soft tissue thickness was moderately positively correlated with the amount of osteotomy, and the decrement of ABDM length and volume were slightly positively correlated with the amount of osteotomy. CONCLUSION: The degree of soft tissue relaxation after U-shaped osteotomy is related to the extent of osteotomy. Notably, the protrusion of ABDM relative to the mandibular margin affects submental-cervical contour aesthetics. Prior to U-shaped osteotomy, it is crucial to assess the soft tissue condition of the patient's lower face, and the individualized design of the osteotomy volume should be carried out cautiously and safely. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Sihler's staining of the anterior belly of digastric muscle for botulinum toxin injection.

PURPOSE: The anterior belly of the digastric muscle (ABDM) is the target of botulinum toxin injection; however, anatomical considerations related to the injection point are absent. This study used Sihler's staining to analyze the intramuscular nerve distribution of ABDM to identify the most effective botulinum toxin injection points. METHODS: We used 12 specimens from 6 embalmed cadavers in this study. The specimens were manually dissected to preserve the mylohyoid nerve and subjected to Sihler's staining. From the gnathion to and hyoid bone, the ABDM was divided into three equal parts, distinguishing the anterior, middle, and posterior thirds. RESULTS: Only a branch of the mylohyoid nerve entered the ABDM, and its entry point was located in the middle-third region in all cases. The nerve endings were concentrated in the middle third (100%), followed by the anterior third (58.3%) and were not observed in the posterior third. CONCLUSION: The landmarks used in this study (gnathion and hyoid bone) are easily palpable on the skin surface, allowing clinicians to target the most effective injection site (middle third of ABDM). These results provide scientific and anatomic evidence for injection points, and will aid in the management of ABDM injection procedures in clinical practice.

Effect of local administration of eicosapentaenoic acid on the jaw-opening reflex in rats.

Although eicosapentaenoic acid (EPA) application in vitro inhibits voltage-gated Na+ (Nav) channels in excitable tissues, the acute local effect of EPA on the jaw-opening reflex in vivo remains unknown. The aim of the present study was to determine whether local administration of EPA to adult male Wistar rats could attenuate the excitability of the jaw-opening reflex in vivo, including nociception. The jaw-opening reflex evoked by electrical stimulation of the tongue was recorded by a digastric muscle electromyogram (dEMG) in pentobarbital-anesthetized rats. The amplitude of the dEMG response was significantly increased in proportion to the electrical stimulation intensity (1×-5× threshold). At 3×, local administration of EPA dose-dependently inhibited the dEMG response, lasting 60 min, with maximum inhibition observed within approximately 10 min. The mean magnitude of dEMG signal inhibition by EPA was almost equal to that observed with a local anesthetic, 1% lidocaine, and with a half dose of lidocaine plus a half dose of EPA. These findings suggest that EPA attenuates the jaw-opening reflex, possibly by blocking Nav channels of primary nerve terminals, and strongly support the idea that EPA is a potential therapeutic agent and complementary alternative medicine for the prevention of acute trigeminal nociception.

Modulation of reflex responses of the anterior and posterior bellies of the digastric muscle in freely moving rats.

BACKGROUND: Chewing and licking are primarily activated by central pattern generator (CPG) neuronal circuits in the brainstem and when activated trigger repetitive rhythmic orofacial movements such as chewing, licking and swallowing. These CPGs are reported to modulate orofacial reflex responses in functions such as chewing. OBJECTIVE: This study explored the modulation of reflex responses in the anterior and posterior bellies (ant-Dig and post-Dig, respectively) of the digastric muscle evoked by low-intensity trigeminal stimulation in conscious rats. METHODS: The ant-Dig and post-Dig reflexes were evoked by using low-intensity electrical stimulation applied to either the right or left inferior alveolar nerve. Peak-to-peak amplitudes and onset latencies were measured. RESULTS: No difference was observed between threshold and onset latency for evoking ant-Dig and post-Dig reflexes, suggesting that the latter was also evoked disynaptically. The peak-to-peak amplitude of both reflexes was significantly reduced during chewing, licking and swallowing as compared to resting period and was lowest during the jaw-closing phase of chewing and licking. Onset latency was significantly largest during the jaw-closing phase. Inhibitory level was similar between the ant-Dig and post-Dig reflex responses and between the ipsilateral and contralateral sides. CONCLUSION: These results suggest that both the ant-Dig and post-Dig reflex responses were significantly inhibited, probably due to CPG activation during feeding behaviours to maintain coordination of jaw and hyoid movements and hence ensure smooth feeding mechanics.

More than two - A cadaveric study on the morphometry and classification of the digastric muscle in a selected kenyan population.

BACKGROUND: This study aims to elucidate anatomical variations of the digastric muscle in the Kenyan population. METHODS: A total of 41 bilateral neck dissections were performed whereby morphologic observations and morphometric measurements were carried out to characterize and classify the various presentations of the muscle. RESULTS: All cadavers presented with bilateral anterior (ABDM) and posterior (PBDM) bellies of the digastric muscle. Accessory ABDM was observed in 68.3% of cadavers with De-Ary-Pires et al.'s Type II (one accessory belly; 48.8%) and Type III (two accessory bellies; 34.1%) being the most common variations. Unilateral accessory ABDM (43.9%) was more common than bilateral accessory ABDM (24.4%). Two cadavers presented with a mentohyoid muscle. In addition, variations that have not been previously reported, namely fusion of ABDM to the midline and insertion of accessory ABDM into the hyoid bone were observed in one case each. Variation of the PBDM was less prominent, observed at 12.2% of sides dissected. Duplication of PBDM was observed on 4 sides with origin at the mastoid process. The PBDM was longer than the ABDM, but narrower in width. The mean length and width of the ABDM were 4.29±0.72cm and 1.52±1.07cm. The mean length and width of the PBDM were 5.64±1.31cm and 1.07±0.28cm, with the right side being statistically larger than the contralateral side. CONCLUSION: Variations of the digastric muscle are a common finding, with a high incidence at the ABDM. Two new variants were discovered.

Characterization of stimulus response curves obtained with transcranial magnetic stimulation from bilateral anterior digastric muscles in healthy subjects.

PURPOSE: The purpose of the study was to describe measurements of stimulus-response curves in the anterior digastric muscle (ADM) bilaterally following transcranial magnetic stimulation (TMS) to the right and left hemispheres. The first dorsal interosseous muscle (FDI) was the control muscle. MATERIALS AND METHODS: The subjects were 20 healthy young adults. Test sessions determined motor thresholds (MT) and stimulus-response curves (1.0, 1.2, 1.4, 1.6 × MT) from either the FDI or ADM following TMS to left and right hemispheres using the double cone coil. Bilateral recordings of MEPs in the left and right ADM allowed us to generate stimulus response curves following ipsilateral and contralateral TMS. RESULTS: Intraclass correlation coefficients (ICC) for MEP amplitudes from ipsilateral and contralateral ADMs were >0.60 at motor threshold (MT) and >0.90 at stimulus intensities above MT. There was a linear increase in MEP amplitudes across stimulus intensities for the FDI following contralateral TMS, while MEP amplitudes from the ADM following contralateral and ipsilateral TMS increased linearly across stimulus intensities [F(3, 57) [Muscle × Recording Site × Stim Intensity] = 33.57; p < 0.05]; (ηp2 = 0.64). The slopes of the stimulus-response curve of the contralateral FDI was greater than the slopes of the stimulus response curves of the ipsilateral and contralateral ADM (p < 0.05). CONCLUSIONS: The current study provided insights on the methodology for recording stimulus response curves in the ADM with TMS. These findings may translate into a valid, reliable, and relevant clinical outcome to study the pathophysiology of the corticobulbar motor system.

Changes in cortical, cardiac, and respiratory activities in relation to spontaneous rhythmic jaw movements in ketamine-anesthetized guinea pigs.

It has been reported that rhythmic jaw movements (RJMs) spontaneously occur in ketamine-anesthetized animals. The present study investigated the physiological processes that occur during the cortical, cardiac, and respiratory events which contribute to the genesis of RJMs in animals after supplemental ketamine injections. Fourteen guinea pigs were prepared to allow electroencephalographic, electrocardiographic, and electromyographic activities to be recorded from the digastric muscle, measurement of jaw movements, and nasal expiratory airflow under ketamine-xylazine anesthesia. Rhythmic jaw movements spontaneously occurred with rhythmic digastric muscle contractions, 23-29 minutes after injection of supplemental ketamine (12.5 and 25.0 mg kg-1 , intravenously). The cycle length of RJMs did not differ significantly between the two doses of ketamine (mean±SD: 12.5 mg kg-1 , 326.5 ± 60.0 ms; 25 mg kg-1 , 278.5 ± 45.1 ms). Following injection of ketamine, digastric muscle activity, heart and respiratory rates, and cortical beta power significantly decreased, while cortical delta and theta power significantly increased. These changes were significantly larger in animals given 25.0 mg kg-1 of ketamine than in those given 12.5 mg kg-1 . With the onset of RJMs, the levels of these variables returned to pre-injection levels, regardless of the dose of ketamine administered. These results suggest that, following supplemental ketamine injections, spontaneous RJMs occur during a specific period when the pharmacological effects of ketamine wear off, and that these RJMs are characterized by stereotypical changes in cardiac, respiratory, and cortical activities.

Variations of the digastric muscle and accessory bellies - A study of gross anatomic dissections.

OBJECTIVE: Variations of the bellies of the digastric muscle is reported for a long time and is not uncommon. However, there is still not a full consensus about the classifications and many different types of variations. The aim of this study was to examine the variations of the digastric muscle on cadaver dissections and to create a pictorial collection of variations related to present-day by combining with existing knowledge. METHOD: In the present study, a total of 40 formalin-fixed cadavers and head specimens' digastric muscles were analyzed bilaterally. RESULTS: Previous results were utilized for classification of the variations. Anterior belly, intermediate tendon, and posterior belly variations were evaluated according to unilateral, bilateral and unclassified types. 10 variations were identified in the digastric muscle of 40 cadavers. Thus, five of the variations were unilateral and rest of them were bilateral. Two of the variations were residing in the central area. One accessory muscle bundle was found obliquely residing between the left and right sides of the anterior bellies. Remaining variation was the crossing of the accessory anterior belly of digastric muscle fibers at the central line. Intermediate tendon variation as piercing the stylohyoid muscle was observed in only one case. Posterior belly exhibited no variation. CONCLUSION: Reporting the abnormalities and variations of the digastric muscle is very important in surgical attempts and evaluation of the lymphadenopathy of the submental area and in the floor of the mouth tumors, numerous clinically significant esthetic surgeries for head and neck surgeons, radiologists and plastic surgeons.

Anatomical assessment of the digastric branch of the facial nerve as a landmark to localize the extratemporal facial nerve trunk.

PURPOSE: Localization of the facial nerve trunk (FNT) [i.e., the portion of the facial nerve between the stylomastoid foramen (SMF) and pes anserinus] may be required during various surgical interventions such as parotidectomy and hypoglossal-facial anastomosis. Several landmarks have been proposed for efficient identification of the FNT. We sought to assess the anatomical features of the digastric branch of the facial nerve (DBFN) and its potential as a landmark to identify FNT. METHODS: Fifteen sides of eight cadaveric heads were dissected to find the DBFN. Anatomic features of DBFN including its point of origin relative to SMF, length, and important relationships, as well as the distance between the insertion point on the digastric muscle and mastoid tip were recorded. RESULTS: DBFN was found in all specimens originating from the FNT outside the SMF with an average length (± standard deviation) of 15.4 ± 3.4 mm. In all specimens, the DBFN inserted on the superomedial aspect of the posterior belly of the digastric muscle (PBD). In 8/15 specimens, DBFN was accompanied by the stylomastoid artery on its anteromedial side. Average distance (± standard deviation) between the mastoid tip and the nerve insertion point on PBD was 13.6 ± 2.0 mm (range 10-17). CONCLUSIONS: The DBFN is a reliable landmark for identifying the FNT. It could be consistently identified within 15-20 mm of the mastoid tip on the superomedial aspect of the PBD. The DBFN may be used as a supplementary landmark for efficient localization of the FNT. LEVEL OF EVIDENCE: Not applicable (anatomic study).

Simple laryngeal suspension procedure by suturing the digastric muscle to the periosteum of the mandible in neck dissection for tongue cancer.

PURPOSE: In this article, a simple, new laryngeal suspension procedure is described. The effect of hyoid bone suspension by suturing the digastric muscle to the periosteum of the mandible is analyzed. MATERIALS AND METHODS: To elucidate the effect of hyoid bone suspension, CT scans of 26 patients who underwent ipsilateral neck dissection with primary resection of tongue cancer were retrospectively reviewed, and the distance between the hyoid bone and the mandible was measured on the operated and unoperated sides of the neck. A total of 14 patients who underwent suturing of the digastric muscle to the mandible (digastric muscle-sutured group) and the 12 patients who did not (control group) were compared. RESULTS: In the digastric muscle-sutured group, the average distance between the hyoid bone and the mandible was significantly smaller on the operated side (17.8 ±â€¯0.57 mm) than on the unoperated side (19.8 ±â€¯0.93 mm; p < 0.05). In the control group, there was no significant difference between the operated side (21.0 ±â€¯1.42 mm) and the unoperated side (19.7 ±â€¯1.39 mm). The difference in the distance between the operated and unoperated sides was significantly larger in the digastric muscle-sutured group (1.97 ±â€¯0.79 mm) than in the control group (-1.32 ±â€¯0.61; p < 0.05). CONCLUSIONS: It was shown for the first time that suturing of the digastric muscle to the periosteum of the mandible in neck dissection with primary resection of tongue cancer resulted in hyoid bone suspension. This simple procedure can be useful for laryngeal suspension.

Unilateral asymmetrical anterior bellies of the digastric muscle in coexistence with accessory muscle bundles in the submental triangle: A rare case report.

A three-headed anterior belly of the digastric muscle (ABDM) on the right side of a 54-year old Greek male cadaver coexisted with two accessory muscle bundles (AMB) in the submental region. The left ABDM was typical. Typical ABDM was attached to the digastric fossa, while the accessory right anterior bellies to the lower border of the mandible. A muscle bundle arising from the attachment of the left ABDM to the hyoid bone was also observed fusing with the AMB of the ipsilateral side. It is of extreme importance to be aware of the submental region anatomical variations during surgery, imaging interpretation or differential diagnosis of neck masses.

Unilateral hypoplasia with contralateral hypertrophy of anterior belly of digastric muscle: a case report.

Anomalies of the anterior belly of the digastric muscle (DM) are uncommon. We present a case of hypoplasia of the anterior belly of the left DM with hypertrophy of the anterior belly of the contralateral DM. The importance of recognizing this finding is to differentiate hypoplasia of the anterior belly of the DM from denervation atrophy, and not to confuse contralateral hypertrophy with a submental mass or lymphadenopathy. In denervation atrophy of the anterior belly of the DM, associated atrophy of the ipsilateral mylohyoid muscle is present. Hypertrophy of the anterior belly of the contralateral DM can be differentiated from a submental mass or lymphadenopathy by recognizing its isodensity on computed tomography and isointensity on magnetic resonance imaging to other muscles, without abnormal contrast enhancement.

Symmetrical anatomical variant of the anterior belly of the digastric muscle: clinical implicat.

The digastric muscle is an important surgical landmark. Several anatomical variants of the digastric muscle are reported in literature and, in particular, the presence of accessory anterior bellies of the muscle is not uncommon. Here, an unreported symmetrical variant of the digastric muscle was found during a dissection of the suprahyoid region. The dissection showed digastric muscles with an accessory anterior belly, which originated from the anterior belly of muscles in proximity and anteriorly to the intermediate tendon. The accessory bellies were fused together on the midline and were attached with a unique tendon to the inner surface of the mental symphysis. These muscles completely filled the submental triangle. This unreported anatomical variant could be considered an additional contribution to description of the anatomical variants of the digastric muscle, with several implications in head and neck pathology, diagnosis and surgery.

Effect of ß-hydroxy-ß-methylbutyrate in masticatory muscles of rats.

The aim of this research was to examine the influence of ß-hydroxy-ß-methylbutyrate (HMB) on changes in the profile of muscle fibers, whether these alterations were similar between the elevator and depressor muscles of the jaw, and whether the effects would be similar in male and female animals. Fifty-eight rats aged 60 days (29 animals of each gender) were divided into four groups: the initial control group (ICG) was sacrificed at the beginning of the experiment; the placebo control group (PCG) received saline and was fed ad libitum; the experimental group (EG) received 0.3 g kg(-1) of HMB daily for 4 weeks by gavage as well as the same amount of food consumed by the PCG in the previous day; and the experimental ad libitum group (EAG) received the same dose of the supplement along with food ad libitum. Samples included the digastric and masseter muscles for the histoenzymological analysis. Data were subjected to statistical analysis with a significance level of P < 0.05. Use of HMB caused a decrease in the percentage of fast twitch glycolytic (FG) fibers and an increase in fast twitch oxidative glycolytic (FOG) fibers in males in both experimental groups (EG and EAG). However, it produced no increase in the muscle fiber area, in either gender, in the masseter muscle. In the digastric muscle, the HMB did not change the frequency or the area of any muscle fiber types in either gender. Our data suggest that the use of HMB caused small changes in the enzymological profile of fibers of the mastication muscles; the changes were different in the elevator and depressor muscles of the jaw and the results were different depending on gender.

Weave pattern of accessory heads to the anterior digastric muscle.

During routine anatomical dissection, we discovered bilateral superficial and deep heads of the anterior belly of the digastric muscle with concomitant accessory heads arranged in a weave pattern in the submental triangle. In addition, the left stylohyoid muscle coursed deep into the intermediate tendon of the digastric muscle bellies.

Utility of Digastric Muscle Flap in Reconstruction of Floor of Mouth Defects.

In the era of free flaps, we propose a simple yet effective local flap, the digastric muscle flap, to reconstruct floor of the mouth defects and to repair an orocervical fistula that is created during excision of tongue and/or floor of the mouth malignancies. The digastric muscle flap was used in 15 patients who were diagnosed with oral squamous cell carcinoma of the tongue and/or floor of the mouth. Partial glossectomy was performed in 4 cases, hemiglossectomy in 4 cases, and wide local excision in 7 cases. Adjuvant radiation was given in 9 patients. In all cases, the neck was addressed followed by the tumour excision. The floor of the mouth defect created while excising the tumour was repaired with the digastric muscle flap. Post-operative healing was satisfactory in all the cases. No flap failure was seen even in radiated cases. Patients were discharged by the 5th-7th day. Oral feeds were started by the 10th day. Patients were followed for 3 months to 5 years. The digastric muscle flap is an ideal flap for reconstructing small- to medium-sized floor of the mouth defects. The flap can withstand radiation. Due to the high success rate, we propose utilisation of this flap in reconstructing floor of the mouth defects and to seal orocervical fistulas.

Functional Reconstruction of a Hemiglossectomy Defect With an Innervated Musculocutaneous Submental Artery Island Flap.

This report presents the use of an innervated musculocutaneous submental artery island flap (MSAIF) for the functional reconstruction of a hemiglossectomy defect, with the aim of preserving the volume and mobility of the reconstructed tongue to facilitate swallowing and intelligible speech. A 30-year-old male patient diagnosed with T3N0 stage squamous-cell carcinoma of the tongue underwent hemiglossectomy and ipsilateral I-IV selective neck dissection. For reconstruction, an innervated MSAIF with a 9x4 cm skin paddle, including the left submental vessels, ipsilateral anterior belly of the digastric muscle, mylohyoid muscle, and mylohyoid nerve, was harvested and inserted into the tongue defect. Postoperative healing at both donor and recipient sites proceeded without complications. At a three-year follow-up, the MSAIF has maintained its volume, mobility, and contractility. The patient remains disease-free and reports satisfaction with his swallowing and speech capabilities. The innervated MSAIF represents a reliable and cost-effective reconstruction approach for hemiglossectomy defects, showing favorable results in both swallowing and speech.

A Comparison Between Skeletal Class II and Class III Malocclusion Patients in Terms of the Masticatory Muscles' Activity: A Cross-Sectional Study.

Background This study aimed to determine if individuals with skeletal Class II and skeletal Class III malocclusions had different levels of masticatory muscle activity. Materials and methods This cross-sectional study, conducted at the University of Damascus, investigated the myoelectric activity of perioral muscles in patients with Class II and III malocclusions. The sample size of 60 patients was determined according to a prior sample size calculation. Patients were selected based on specific inclusion and exclusion criteria and divided into Class II and III groups. Electromyography was used to monitor the activity of various muscles, including the temporalis, masseter, orbicularis oris, buccinator, mentalis, and digastric muscles. Results The study found similar muscle activity within the same group in the temporalis, masseter, buccinator, digastric, and orbicularis oris muscles. No significant differences were observed between the Class II and III groups for several oral and perioral muscles (P > 0.05). However, the mean activity of the digastric muscle was significantly greater in the Class II group (P < 0.05), whereas the mean activity of the mentalis muscle was smaller in the Class II group (P < 0.05). Conclusions Perioral muscles influence facial complex development and jaw relationship, affecting orthodontic treatment. Digastric muscle activity is greater in Class II patients, while mental muscle activity is smaller in Class III patients. Further studies are needed for older age groups and other skeletal malocclusion types.