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Effects of upper lip closing force on craniofacial structures
Min-Ho Jung1, Won-Sik Yang, Dong-Seok Nahm
1Department of Orthodontics, Seoul National University, Korea.
Summary
The strength of the orbicularis oris muscle significantly impacts incisor angulation in Class I malocclusion. Weakening of this lip muscle may contribute to the development of malocclusion.
Area of Science:
- Dentistry
- Orthodontics
- Biomechanics
Background:
- Perioral muscle forces are recognized as critical in influencing tooth position and malocclusion.
- The orbicularis oris muscle plays a significant role in oral function and facial aesthetics.
Purpose of the Study:
- To investigate the correlation between the force exerted by the orbicularis oris muscle and incisor angulation.
- To determine the influence of upper lip closing force on craniofacial morphology in patients with Class I malocclusion.
Main Methods:
- Utilized a Y-meter with a load cell to measure maximum and average upper lip closing forces.
- Collected lateral cephalograms to analyze skeletal structures and incisor angulation.
- Performed correlation and stepwise regression analyses to assess relationships between lip force and morphology.
Main Results:
- The average upper lip closing force (AVE) was measured at 7.16 N.
- A significant relationship was found between upper incisor angulation and perioral muscle force.
- The maxillary incisor to Frankfort horizontal angle demonstrated strong negative correlations with both average (-0.681) and maximum (-0.652) lip closing forces.
Conclusions:
- Upper incisor angulation is demonstrably related to the force generated by the orbicularis oris muscle.
- Stepwise regression analysis confirmed the strong association between upper lip closing force and maxillary incisor angulation.
- Disuse atrophy of the orbicularis oris muscle is suggested as a potential contributing factor in malocclusion development.