J Korean Acad Pediatr Dent.  2019 Nov;46(4):343-352. 10.5933/JKAPD.2019.46.4.343.

Lip Closing Force and the Related Factors in Elementary School Children

  • 1Department of Pediatric Dentistry and Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Korea. pedo1997@jbnu.ac.kr


Abnormal orofacial functions such as lip incompetency in the period of growth and development can cause morphological anomalies of the craniofacial complex. Therefore, it is crucial to make an early diagnosis based on the evaluation of the myofunctional conditions, and to make appropriate treatment plans. The objectives of this study were to quantitatively evaluate the standard lip closing force (LCF) of each age in the elementary school children, and to evaluate the relationships between LCF and affecting factors. The sample consisted of 765 children who were 7 - 12 years old in Jeonju city. Clinical examination about occlusal conditions and lip competency, and LCF measurement were performed by a single examiner. LCF was measured three times for each children with the LCF measuring device. The LCF was correlated positively with age in both sexes. The distribution of LCF groups was correlated significantly with Angle's classes and lip competency (p = 0.016, 0.004). The proportion of children with high LCFs was greater in the "competent lip" group, whereas the proportion of those with low LCFs was greater in the "incompetent lip" group.


Lip closing force; Lip competency; Orofacial myofunctional disorder; Orofacial myofunctional therapy
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