Oral myofunctional and electromyographic evaluation of the anterior suprahyoid muscles and tongue thrust in patients with Class II/1 malocclusion submitted to first premolar extraction

Denize Ramirez De Souza,Tatiana Adamov Semechini,Lucio Benedito Kröll,Fausto Berzin

doi:10.1590/s1678-77572007000100006

Abstract

Objective:The aim of this study was to assess the existence of myofunctional alterations before and after first premolar extraction in Class II/1 malocclusion patients that could endanger the long-term dental arch stability.Materials and Methods:The study was performed by means of morphological, functional and electromyographic analyses in 17 Class II/1 malocclusion patients (group T) and 17 Class I malocclusion patients (group C), both groups with 12-30-year age range (mean age: 20.93 ± 4.94 years).Results:Data analyzed statistically by Student’s t-test showed a significant decrease in the maxillary and mandibular dental arch perimeters after orthodontic treatment (p<0.05). The Kruskal-Wallis test analyzed data from tongue posture at rest and during swallowing, not showing significant differences after treatment (groups Tb and Ta) (p>0.05). However, group T differed significantly from group C (p<0.05). The electromyographic data showed that the anterior right and left suprahyoid muscles acted synergistically in both groups, while having a lower myoelectric activity in group T during swallowing.Conclusions:Myofunctional alterations observed after the orthodontic treatment in Class II/1 malocclusion seemed to jeopardize the long-term orthodontic stability, making recurrence possible. Further research should be conducted to compare electromyographic data before and after orthodontic treatment in order to corroborate the results of the present investigation.

Highlights

The pressures exerted by the orofacial muscles were first mentioned as etiologic factors of malocclusions early back in the 19th century[8]
The findings of the present study show that the tongue posture was forwarded both at rest and during swallowing. These results demonstrate that the long-term stability after completion of the orthodontic treatment, aimed by all orthodontists[2,8], can be jeopardized if myofunctional alterations, when present, are not treated after removal of the orthodontic appliance due to possibility of recurrence[2]
Based on the outcomes of the present study, it may be concluded that the orthodontic treatment in Class II/1 malocclusion patients decreased dental arch perimeter

Summary

Introduction

The pressures exerted by the orofacial muscles were first mentioned as etiologic factors of malocclusions early back in the 19th century[8]. The pressure on the premolar region during swallowing in Class II/1 patients is twice stronger than in individuals with normal dental occlusion[19]. This is region acts as redistributor of strength and can be strongly affected by differences between size and shape and/or skeletal unbalances[27]

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Methods

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Discussion

Conclusion