Lip and mentalis activity and its influence on incisor position--a quantitative electromyographic study

Area of Science:

• Dentistry and biomechanics
• Oral and maxillofacial surgery

Background:

• Perioral muscular activity is crucial in oral function.
• Understanding its influence on tooth position is key for orthodontic and surgical interventions.
• Existing research lacks comprehensive analysis of clinical indicators and the impact of lip competence.

Purpose of the Study:

• To investigate the relationship between perioral muscular activity and tooth position.
• To identify clinical indicators of perioral muscular activity.
• To explore the role of lip competence in this relationship.

Main Methods:

• Two quantitative electromyography (EMG) studies were conducted.
• EMG activity was recorded during speech, chewing, swallowing, resting, and lip-seal (for incompetent lips).
• Measurements included study models, lateral skull radiographs, and clinical lip heights.

Main Results:

• The method demonstrated sufficient reproducibility for experimental application.
• Perioral muscular activity's effect on tooth position is significantly influenced by lip competence.
• Resting activity impacted incisor position in subjects with competent lips, but not intermittent activities.
• No reliable clinical indicators for perioral activity levels were identified.

Conclusions:

• Lip competence is a critical factor modulating the influence of perioral muscular activity on tooth position.
• Current clinical measures do not adequately indicate the level of perioral muscular activity.
• Further research may refine understanding of muscular forces in malocclusion treatment.