This study aimed to quantify the directional specificity of multidirectional lip-closing force (LCF) and evaluate the reliability of multidirectional LCF measurements made using a novel system. In fourteen healthy subjects (seven females, seven males, median age = 28 years), LCFs in eight directions and electromyograms (EMGs) from four parts of the orbicularis oris muscles (OOM) were recorded during voluntary pursing-like lip closure tasks. The quantitative reliability was assessed from repeated measurements of the LCFs in the eight directions and from summed values for all eight directions [total lip-closing force (TLCF)]. The intra- and inter-investigator reliabilities for TLCF were assessed by the interclass correlation of the measurements by the same investigator and two investigators, respectively. Lip-closing forces showed directional specificity in vertical, horizontal and oblique directions but those in oblique and horizontal directions were symmetrical bilaterally. The quantitative reliability of measurements was between 0·735 and 0·948 in the eight directions and that of TLCF was 0·934. Interclass correlations of intra- and inter-investigator reliabilities were 0·96 [lower limit of 95% confidence interval (95% LL), 0·87] and 0·96 (95% LL, 0·91), respectively. The intra- and inter-investigator differences of measurements were randomly distributed in the whole range of measurements. The 95% confidence intervals of these differences were significantly narrower than those of the limits of agreement (mean ± 1·96 s.d.). In 13 subjects, Pearson's correlation coefficients between LCF and EMGs from OOM were above 0·95. We conclude that this system has a reasonable quality and reliability for quantitative measurements of multidirectional LCF for evaluating lip functions.

The objectives of this study were to quantitatively evaluate the gender differences in the lip-closing force (LCF) generated during pursing-like lip-closing movement using a multidirectional LCF measurement system in healthy young adults. In 40 healthy subjects (20 women, 20 men; median age = 26·5 years, range = 22-41 years), LCF was recorded in eight directions during the performance of a voluntary pursing-like lip-closing task in four measurement sessions. The correlations between the total sum of the forces generated in all eight directions [total LCF (TLCF)] and each directional LCF (DLCF) and those between opposing DLCF were statistically analysed. The TLCF obtained from the highly reproducible measurements acquired in the four different sessions was normally distributed in both genders. The TLCF in men was significantly greater than that in women. Among the eight pairs of opposing DLCF, seven pairs of opposing DLCF showed significant correlations in men, while five pairs were significantly correlated in women. In men, no significant difference was observed between opposing DLCF; however, three pairs of opposing DLCF were significantly different in women. The present results quantitatively indicate that there are gender differences in the magnitude and directional specificity of the LCF produced during pursing-like lip-closing movement in healthy young adults.

The objectives of this study were to identify the regulatory relationship between tactile sensation at the vermilion of the lips and the output of pursing-like lip-closing force (LCF), as measured by a multidirectional LCF measurement system. Thirty-six healthy subjects were divided into Anaesthesia and Vaseline groups. The tactile detection threshold (TDT) at six sites on the vermilion and the maximum voluntary LCFs in eight directions were recorded before and during partial or whole application of the agent and 6 h after whole application (Recovery). Five per cent lidocaine gel and Vaseline was applied to the vermilion in the Anaesthesia and Vaseline groups, respectively. These agents were applied to either the right part of the vermilion of the lower lip (Partial) or the whole vermilion (Whole). Partial application of 5% lidocaine gel significantly decreased the magnitudes of six of eight directional LCFs, while it only increased the TDT at one site. The subsequent whole application of 5% lidocaine gel did not affect the magnitude of the LCFs in five of these six directions although its application increased the TDTs at all sites. These reductions in LCF were reversed after recovery from surface anaesthesia. Vaseline application did not affect either TDT or LCF in any conditions. We concluded that tactile sensation at the vermilion of the lips is related to the output of LCF, without any particular directional specificity. The present results suggest the presence of a common synaptic drive ordering the pursing of the relevant muscles.

The objectives of this study were to estimate the effects of cleft lip and/or palate (CLP) repair on the multidirectional lip-closing forces (LCF) produced during maximum voluntary pursing-like lip-closing movement in children. Thirty Japanese children were divided into the control group and repaired unilateral CLP (RUCL) group, which was subdivided into the unilateral cleft lip and/or alveolus (UCLA) and the unilateral cleft lip and cleft palate (UCLP) groups. The maximum voluntary LCF were recorded in eight directions. No significant differences in any of the directional LCF (DLCF) or total LCF were observed between RUCL and control groups. Symmetrical DLCF were seen in the oblique directions on both sides of the upper lip in the control group, while the oblique DLCF on the non-cleft side was significantly greater than that on the cleft side in RUCL group. Furthermore, symmetrical vertical DLCF were observed in the upper and lower directions in control and UCLA groups, while the vertical DLCF obtained from the lower direction was significantly greater than that obtained from the upper direction in UCLP group. These results indicate that children with repaired CLP display impaired directional specificity, which may cause secondary deformities. These findings aid our understanding of the pathology of secondary deformities in CLP patients after primary surgery for cleft lip or palate. We propose that quantitative assessments of lip-closing function based on the directional specificity of the multidirectional LCF produced during maximum voluntary pursing-like lip-closing movement are useful for assessing the nature of lip-closing dysfunctions.

A simplified procedure of maxillary augmentation with a porous hydroxyapatite block graft in the anterior aspect of the maxillary parapiriformis area is described. This procedure is an alternative for maxillary advancement osteotomy and is simple to perform for maxillofacial deformity of cleft lip and palate and other deformities. It is effective for facial aesthetics in association with mandibular surgery, such as mandibular setback by sagittal splitting osteotomy, mandibular segmental osteotomy with premolar extraction, bimaxillary osteotomy, and/or genioplasty. We used this procedure on 21 patients (15 for cleft lip and palate jaw deformity and 6 for aesthetic reasons). Although postoperative infection requiring removal of the hydroxyapatite block occurred in one cleft deformity patient, satisfactory results were obtained in all patients.