Relationship of Lip Closure Force and Lip Form with Normal Adults and the Jaw Deformities Patients

  • Kastuhiko Saitoh, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan
  • Akino Nakanishi, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan
  • Jyunko Yamaguchi, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan
  • Ryoko Kawashima, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan
  • Shinchi Nagishi, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan
  • Rie Kasai, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan
  • Ryosuke Hayashi, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan
  • Kazutaka Kasai, Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Japan

The object of this study is to measure the lip closure force in normal adult humans and the jaw deformities patients as well as to examine the correlation between the lip closure force, the lip forms and the facial hard tissue forms.
The subjects consist of 163 normal adults, the jaw deformities patients in mandibular prognathism(14 cases), mandibular retrognathism(10 cases) and open bite(6 cases).
The lip closure force was measured LIP DE CUM(COSMO INSTRUMENT CO.,Tokyo), and the average of 3 measurements was taken as the mean value. Furthermore, lateral cephalogram were taken for analysis of the lip forms and facial hard tissue forms, the results regarding the correlation between the lip closure force, lip forms, and facial hard tissue forms were obtained as follows:
1. The lip closure force of normal adult humans was 9.7 N.
2. The lip closure force in mandibular retrognathism shown smaller compared with the others cases in jaw deformities and normal adult humans.
3. Lingual inclination may increase in the lower incisors in the case of greater lip closure force, and the labial inclination may increase in the lower incisors in the case of smaller lip closure force.
Accordingly, the lip closure force affects the facial hard tissue forms and dental axis in the lower incisors and it is therefore suggested to be important to fully examine and diagnosis the lip closure force as well as treatment plan.