Association between muscle activity and overjet in class II malocclusion with surface electromyography

Symmetrical activity of the chewing muscles and its relationship with skeletal class and body posture

OBJECTIVE

To describe the role of body posture and skeletal class in the symmetrical activity of chewing muscles.

METHODS

Descriptive study with association. Skeletal class measured by the Steiner method. Postural analysis through APECS mobile application for forward head posture and shoulder discrepancy, and surface electromyography with Biopac® device.

RESULTS

The skeletal class, forward head posture, and shoulder discrepancy presented statistical association with the symmetrical electromyographic response of digastric muscles and masseter muscles during swallowing.

DISCUSSION

This study exhibited a positive relationship between digastric muscle symmetry and skeletal class during swallowing. The compensation of the hyoid system explains these results, showing that skeletal Class III has better electromyographic balance. In contrast, masseter muscle symmetry during swallowing presented a negative relationship with skeletal class. The stabilization role that this muscle plays during swallowing explains these findings, caused by the different lengths and direction of this muscle in skeletal Class III.

An assessment of masticatory efficiency and occlusal load distribution in adolescent patients undergoing orthodontic treatment with functional jaw orthopedics: A prospective cohort study

INTRODUCTION

Functional jaw orthopaedics, produces a radical change in the occlusal scheme and the masticatory apparatus, particularly in patients with Class II malocclusion. It remains to be seen how the changes brought about by a functional appliance alter the masticatory ability of a growing child, who needs the necessary nutrition to properly grow the craniofacial region.

MATERIALS AND METHODS

Pretreatment and Post-treatment values of masticatory efficiency and the distribution of the occlusal load at centric occlusion were evaluated and compared for 20 patients with Class II division 1 malocclusion undergoing functional jaw orthopaedics.

RESULTS

Significant increase in the masticatory efficiency was seen during and after treatment (p < 0.5) There was an increase in the anterior distribution of occlusal load associated with a concomitant decrease in the posterior region at centric occlusion.

CONCLUSION

Improvement in the masticatory efficiency was observed after treatment of a retrognathic mandible with functional jaw orthopaedics in the adolescent participants with Class II malocclusion. This highlights the importance of treatment with functional jaw orthopaedics, which apart from providing esthetic and functional improvement also improves the ability of a growing child to extract proper nutrition from his/her diet.

Electromyographic Assessment of the Masseter and Temporalis Muscles in Skeletal II Malocclusion Subjects With Varying Overjets: A Pilot Study

Introduction Class II malocclusions are commonly associated with some muscle disharmony and imbalance. Diagnosis of muscle imbalance helps in treating the malocclusion as well as preventing relapse of the treatment. The aim of this study is to compare the muscle activity of masseter and temporalis in patients with skeletal Class II division 1 malocclusion with varying overjet using surface electromyography (sEMG). Materials and methods Ten subjects in the age range 18-35 years with skeletal Class II malocclusion and varying overjets who required orthodontic treatment were included in this study. Out of these 10 patients, five of them had a 2-4mm overjet and the other five had an overjet >4mm. A four-channel sEMG system was used to conduct the sEMG of muscles. Muscle activity, synergy, and symmetry of masseter and temporalis muscles were assessed and compared between the two groups with an Independent t-test. Results There were no significant differences in the muscle activities of the temporalis and masseter muscles in both groups. Symmetry and synergy of these muscles in the two groups also showed no significant difference (p>0.05) at rest and clenching. However, during chewing, the masseter muscle showed poor balance and activity. Conclusion The overjet in Class II division 1 malocclusions did not seem to affect the muscle activity at rest and during clenching. In patients with increased overjet, during chewing, masseter activity in terms of intensity and balance was poor.

Correlation of masticatory muscle activity and occlusal function with craniofacial morphology: a prospective cohort study

OBJECTIVES

Masticatory function, including masticatory muscle activity and occlusal function, can be affected by craniofacial morphology. This study aimed to investigate the relationship between craniofacial morphology and masticatory function in participants who had completed orthodontic treatment at least two years before and had stable occlusion.

MATERIALS AND METHODS

Fourty-two healthy participants were prospectively enrolled and divided into three vertical cephalometric groups according to the mandibular plane angle. Masticatory muscle activity (MMA) in the masseter and anterior temporalis muscles was assessed using surface electromyography. The occlusal contact area (OCA) and occlusal force (OF), defined as occlusal function in this study, were evaluated using occlusal pressure mapping system. Masticatory muscle efficiency (MME) was calculated by dividing MMA by OF. The craniofacial morphology was analyzed using a lateral cephalogram. The masticatory function was compared using one-way analysis of variance. Pearson correlations were used to assess relationships between craniofacial morphology and masticatory function.

RESULTS

The hypodivergent group had the lowest MMAand the highest MME in the masseter (167.32 ± 74.92 µV and 0.14 ± 0.06 µV/N, respectively) and anterior temporalis muscles (0.18 ± 0.08 µV/N, p < 0.05). MMA in the masseter showed a positive relationship with mandibular plane angle (r = 0.358), whereas OCA (r = -0.422) and OF (r = -0.383) demonstrated a negative relationship (p < 0.05). The anterior temporalis muscle activity negatively correlated with ramus height (r = -0.364, p < 0.05).

CONCLUSIONS

Vertical craniofacial morphology was related to masticatory function. Hypodivergent individuals may have low MMA and high occlusal function, resulting in good masticatory muscle efficiency.

CLINICAL RELEVANCE

Hypodivergent individuals require careful consideration in orthodontic diagnosis and prosthetic treatment planning.

Correlation between lip print patterns and skeletal class I and II malocclusions - A tool to diagnose early

BACKGROUND

Cheiloscopic analysis has been shown to have close association with skeletal malocclusion. Hence, aim of the present study was to explore any association between lip prints patterns and skeletal class I and II malocclusions.

MATERIALS AND METHODS

A study sample of 90 subjects aged between 18 and 25 years was selected from individuals opting for orthodontic therapy. Skeletal malocclusion using ANB angle was assessed using lateral cephalograms while lip print patterns were analyzed using the cellophane-adhesive method. Statistical analysis: Mean ± SD was analyzed and significance was assessed using ANOVA.

RESULTS

Skeletal class I group showed more branched pattern (29%). Other patterns in decreasing order were intersected (25%), reticular (24%), and vertical lip patterns (22%), while the skeletal class II group showed branched pattern as most common (32%), followed in decreasing order by reticular (29%), intersected (25%), and vertical lip patterns (14%). No statistical significance was derived between lip pattern type and skeletal malocclusion.

CONCLUSION

Lip print patterns are important indicators of malocclusion and can help in predicting the same at an earlier stage.