Tomoo Kaneko

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

Abstract Purpose Lip-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 methods Eighteen 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″. Results Sealed 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. Conclusion Lip-endurance training improves lip-competence and could be useful for improving QOL of patients with lip-incompetence.

Differences in dento-facial morphology in lip competence and lip incompetence

Abstract Clinicians have hypothesized that lip competence is related to dental inclination, overjet, and overbite. Though some studies have been made to clarify this interrelation, a distinctive conclusion has not been reached. Studies have further shown that some subjects with normal occlusion show lip incompetence. Considering this, it could be hypothesized that dento-facial morphology plays a role in the causes of lip incompetence. To establish this it is necessary to distinguish dento-facial morphology factors from occlusal conditions such as overjet or overbite. A number of methods evaluate lip sealing: visual examination, cephalometric radiographs, and others; however these methods make determinations for short periods, and none evaluate the lip competence directly. The purpose of this study is to elucidate a correlation between lip competence and dento-facial morphology using subjects with normal occlusion, excluding overbite and overjet factors, with a sufficiently reproducible and reliable method to evaluate lip sealing. The study shows that individuals with normal occlusion (n = 30) can be divided into 3 groups based on lip sealing ability: a competent, a partially competent, and an incompetent group. Statistical evaluations showed morphologically significant differences between these groups on SNA, ANB, NA-Pog, NPog-A, ANS-Me, N-ANS/ANS-Me, ANS-Me/N-Me, Wits appraisal, L1-MP, NPog-U1, NPog-L1, and FMIA measurements. According to the results, more skeletal class II relationships, longer anterior lower facial height, and a backward positioned Pogonion were observed, in the group with lip incompetence.

Study of training for improving lip incompetence

Abstract Purpose We have been using myofunctional therapy in orthodontic treatment to improve orofacial disorders. Our previous study showed that lip training increased orbicularis oris muscle strength and endurance. The aim of this study was to determine the effectiveness of hypoxic lip training for improving lip incompetence. Subjects and methods: Twenty healthy subjects (10 males and 10 females, 23.6 ± 2.3 years old) with lip incompetence participated in this study. We recorded the sealed lip ratio calculated by using the formula “(lip-sealing time/total recorded time) × 100″ during relaxation (listening to soothing music) and during concentration (performing a mathematical calculation). Then the subjects performed a standardized hypoxic lip training (5 repetitive contractions with 80% of maximum tensile strength of the orbicularis oris muscle) with a traction plate. Training was repeated daily for 4 weeks. To estimate training effects, the sealed lip ratios during relaxation and concentration were recorded before training (T1), at 2 weeks (T2) and 4 weeks (T3) after the start of training, and at 4 weeks (T4) and 8 weeks (T5) after the end of training. Results The sealed lip ratios in both the relaxation and concentration conditions significantly (p < 0.003 after Bonferroni correction) increased during the training period. Although the sealed lip ratios slightly decreased during the post-training period, they were not significantly different from those at T3. Conclusions Hypoxic lip training increases the sealed lip ratio and is thus effective for improving lip incompetence. Sealed lip ratios were maintained after 8 weeks of training.

Biological Response in Orthodontics

This study was conducted to provide a biomechanical description of periodontal tissue changes caused by orthodontic forces. The maxillary canine of a cat was moved distally in the alveolar bone with an initial force of 100 g. First, the tissue accommodation process on the pressure side was observed by means of three-dimensionally reconstructed images of microscopic images. The degenerated tissue in the compressed periodontium was reduced as the tissue accommodation process continued. During the process, bone resorption occurred in the alveolar bone area adjacent to the degenerated tissue. This enlarged the periodontal space, loosening the compressed periodontium and releasing the internal stress. The process of accommodation to orthodontic force appeared to have a cycle of almost 4 weeks. A second experiment was designed to investigate the process of formation of degenerated tissue using light and electron microscopy. The intradegeneration zone (IZ) was observed in the compressed periodontium at 12h after the initial force was applied. At 4 days, a cell-free zone (CFZ), free of pyknotic cells or debris, had appeared at the peripheral area of the degenerated tissue. The results suggest that the CFZ is formed where cells and debris are carried away by the tissue fluid flow through interfiber gaps remaining under conditions less compressed than in the IZ.