Effectiveness of training methods to improve orbicularis oris muscle endurance in patients with incompetent lips

Abstract

PurposeLip-incompetence has various negative effects including malocclusion such as maxillary protrusion and open bite. We previously defined a lip-incompetence as having a sealed lip ratio of less than 30.1% during relaxation and less than 13.2% during concentration. The aim of this study was to estimate the effectiveness of lip endurance training in lip-incompetence. Subjects and methodsEighteen healthy volunteers (12 males and 6 females, 25.0±2.5 years) with lip-incompetence participated. The sealed lip ratio was estimated at the start of the study (T1) during relaxation (subjects listened to soothing music with their eyes closed) and during concentration (subjects were given a calculation task) and again after 4 weeks (T2). A traction plate was inserted into the oral vestibules of each subjects, who then performed a standardized lip-endurance training (20 repetitive contractions with 50% of maximum tensile strength of the orbicularis oris), repeated daily for 4 weeks. Sealed lip ratio was re-estimated at 2 weeks (T3) and 4 weeks (T4) after the start of training and at 4 weeks (T5) and 8 weeks (T6) after the termination of lip-endurance training. The sealed lip ratio was calculated “sealed lip ratio=(lip-sealing time/total recorded time)×100″. ResultsSealed lip ratios during relaxation (9.0±7.7%) and concentration (4.4±5.1%) increased at T3 (64.2±17.3% and 53.7±18.3%; P<0.01) and T4 (92.2±9.1% and 90.7±12.8%; P<0.01). During post-training, there was no apparent difference between T4, T5 and T6. ConclusionLip-endurance training improves lip-competence and could be useful for improving QOL of patients with lip-incompetence.