Lip Force Research Articles

Prediction of the dynamic oscillation threshold in a clarinet model with a linearly increasing blowing pressure

Reed instruments are modeled as self-sustained oscillators driven by the pressure inside the mouth of the musician. A set of nonlinear equations connects the control parameters (mouth pressure, lip force) to the system output, hereby considered as the mouthpiece pressure. Clarinets can then be studied as dynamical systems; their steady behavior being dictated uniquely by the values of the control parameters. Considering the resonator as a lossless straight cylinder is a dramatic yet common simplification that allows for simulations using nonlinear iterative maps.

Mathematical Modeling of Cutting Forces in Microdrilling

In drilling, the primary and secondary cutting lips of the drill shear the material while the central portion of the chisel edge indents the workpiece, making the cutting process complex to understand. As we go for microdrilling, it exhibits an added complexity to the cutting mechanism as the edge radius gets comparable to chip thickness at low feeds. The presented work models the forces by the primary cutting lip of a microdrill analytically using slip-line field that includes the changes in the effective rake angle and dead metal cap during cutting for cases of shearing as well as ploughing. To study the variation of forces experimentally, the primary cutting lip and chisel edge forces are separated out by drilling through pilot holes of diameter slightly above the drill-web thickness. Finally, the analytical and experimental results are compared and the model is calibrated.

Facial palsy in individuals with thalidomide embryopathy: frequency and characteristics

Earlier studies have shown that individuals with thalidomide embryopathy can have skeletal deformities, ear and eye aberrations, and facial palsy. This study aimed to survey the frequency and characteristics of facial palsy in this group of individuals. Thirty-one individuals with thalidomide embryopathy (age range, 45-47 years) and 25 healthy adults (age range, 41-56 years; mean age ± standard deviation, 49 ± 4.2 years). Voluntary facial movements, lip force and three-dimensional lip motion analysis. Four of the thalidomide embryopathy individuals (13 per cent) had congenital facial palsy. All four had eye aberrations, three had ear anomalies and one had a limb anomaly. Individuals with thalidomide embryopathy without a clinical diagnosis of facial impairment had significantly weaker lips and more restricted lip mobility than healthy controls. This study contributes to the overall knowledge of thalidomide embryopathy by adding a description of how facial expression can be affected in this condition.

Changes in oro-facial function and hand-grip strength during a 2-year observation period after stroke

Recovery from stroke-related oro-facial impairment has rarely been investigated. In this longitudinal study chewing efficiency, maximum lip and bite force as well as masseter muscle thickness were evaluated and compared with hand-grip force. Thirty-one hospitalized stroke patients and 24 controls were recruited for this cohort study with 2-year follow-up. Chewing efficiency was evaluated with a color mixing ability test, lip forces with a traction dynamometer, bite force with a digital gauge, masseter muscle thickness using ultrasound measurements and grip strength with a hand dynamometer. During the 2-year observation period, patients were evaluated four times. A total of 21 patients dropped out of the study. Stroke patients showed significantly impaired chewing efficiency and lower lip forces than controls with no significant improvement over time. Bite forces were not different between ipsi- and contralesional sides, in contrast to contralesional hand-grip strength which was significantly impaired and did not improve during the observation period. On the first examination with a median of 40days after stroke, masseter thickness was reduced contralesional, but did not continue to show significant side-differences during follow-up. Stroke affects the upper limb and the masseter muscles differently on a functional and morphological level. Further research is needed to evaluate the predictive value of oro-facial parameters on functional outcome after stroke. Impaired chewing efficiency and reduced lip force are quantifiable symptoms in stroke patients which seem not to improve in absence of oro-facial rehabilitation procedures.

Force Control under Auditory Feedback: Effector Differences and Audiomotor Memory

Audiomotor integration is a basic form of sensorimotor control for regulating vocal pitch and vocal loudness, but its contribution to general motor control has only been studied minimally. In this paper, auditory feedback for prolonged force control was investigated by comparing manual and oral force generation and testing short-term audiomotor memory for these effectors. Ten healthy volunteers between the ages of 20 and 30 years old were recruited. The participants produced continuous force for 30 sec. with the lip or finger to match auditory targets. In the feedback condition, when auditory feedback was provided for 30 sec., lip force was more variable than finger force. In the memory condition, the force output of both effectors remained stable for approximately 4 sec. after feedback removal, followed by significant decay. A longer short-term memory capacity could facilitate encoding of motor memories for tasks having acoustic goals. The results demonstrate that "audiomotor" integration was effective for sustaining forces, and that audiomotor force memory is comparable to reports of visuomotor force memory.

Mandibular lip bumper for molar torque control

Treatment effects of lip bumpers alone include flaring of the mandibular incisors, distalization and uprighting of the mandibular first molars, and buccal expansion of the canines, premolars, and molar. Lip forces are transmitted through this appliance onto the molars. Moreover the lip bumper is able to derotate, expand or constrict, upright and reinforce the anchorage whereas torque control is lacking. Aim of this paper is the presentation of a new type of lip bumper that allows the molar torque control.

Oral health-related quality of life in hospitalised stroke patients

The aim of this study was to test the hypothesis that impairment of orofacial function following stroke affects the patients' oral health-related quality of life (OHRQoL). From the University Hospitals of Geneva, 31 stroke patients (18 men, 13 women, mean age 69.0 ± 12.7 years) with unilateral facial and limb palsy were recruited (patient group, PG). In the study, the Oral Health Impact Profile (OHIP)-EDENT was utilised to assess OHRQoL. Further examinations comprised a test of masticatory efficiency and lip force, stroke severity National Institute of Health Stroke Scale and dental state. The control group (CG) consisted of 24 subjects with similar age, gender and dental state. The PG mean OHIP-EDENT sum score was 18.8 ± 15.5 and proved higher than one of the CG, indicating a lower OHRQoL in the PG (p < 0.01). The score of the sub-domains 'functional limitation' and 'physical pain' were significantly higher in PG (p < 0.03 and p < 0.02, respectively). The masticatory efficiency was significantly lower in the PG (p < 0.0001) and was associated with the OHIP-EDENT sum score and its sub-domains, except for 'physical disability'. This effect was not present in the CG. The OHRQoL is significantly reduced in hospitalised stroke patients whereby functional impairment seems predominant when compared with psychological and psycho-social aspects.

Masticatory Function and Bite Force in Stroke Patients

Orofacial functions are frequently affected by stroke, but little is known on the nature and extent of the impairment of mastication, which is investigated in this observational study. Thirty-one stroke patients, aged 69.0 ± 12.7 yrs, presenting with a hemi-syndrome with facial palsy, were recruited. Chewing efficiency, maximum bite and restraining lip forces were tested. Stroke severity (National Institutes of Health Stroke Scale) and dental state were recorded. The control group was similar in age, gender, and dental state (n = 24). The chewing efficiency was significantly lower in the stroke group (p ≤ 0.0001) and was related to both the dental state and the lip forces measured with small and medium-sized labial plates. The maximum bite force proved to be not significantly different between sides or groups (n.s.), whereas lip force was significantly lower in the stroke group (p ≤ 0.05). Chewing efficiency is severely affected by stroke; thus, rehabilitation protocols should aim to restore the strength and co-ordination of the orofacial muscles.

Exploring quantitative methods for evaluation of lip function

The objective was to explore quantitative methods for the measurement of lip mobility and lip force and to relate these to qualitative assessments of lip function. Fifty healthy adults (mean age 45 years) and 23 adults with diagnoses affecting the facial muscles (mean age 37 years) participated in the study. Diagnoses were Möbius syndrome (n=5), Facioscapulohumeral muscular dystrophy (n=6) and Myotonic dystrophy type 1 (n=12). A system for computerised 3D analysis of lip mobility and a lip force meter were tested, and the results were related to results from qualitative assessments of lip mobility, speech (articulation), eating ability and saliva control. Facial expressions studied were open mouth smile and lip pucker. Normative data and cut-off values for adults on lip mobility and lip force were proposed, and the diagnostic value of these thresholds was tested. The proposed cut-off values could identify all inviduals with moderate or severe impairment of lip mobility but not always the milder cases. There were significant correlations between the results from quantitative measurements and qualitative assessments. The examined instruments for measuring lip function were found to be reliable with an acceptable measuring error. The combination of quantitative and qualitative ways to evaluate lip function made it possible to show the strong relation between lip contraction, lip force, eating ability and saliva control. The same combination of assessments can be used in the future to study if oral motor exercises aimed at improving lip mobility and strength could have a positive effect on lip function.

The effect of lip strengthening exercises in children and adolescents with myotonic dystrophy type 1

Objective Myotonic dystrophy type 1 (DM1) is a slowly progressive neuromuscular disease. Most children and adolescents with DM1 have weak lips and impaired lip function. The primary aim of the present study was to investigate if regular training with an oral screen could strengthen the lip muscles in children and adolescents with DM1. If lip strength improved, a secondary aim would be to see if this could have an immediate effect on lip functions such as lip mobility, eating and drinking ability, saliva control, and lip articulation. Methods Eight school aged children and adolescents (7–19 years) with DM1 were enrolled in an intervention study with a single group counterbalanced design. After three baseline measurements four children (Subgroup A) were randomly chosen to start 16 weeks therapy while the others (Subgroup B) acted as controls without therapy. After 16 weeks the subgroups changed roles. During treatment the participants exercised lip strength with an oral screen for 16 min, 5 days/week. Lip force, grip force (control variable), and lip articulation were followed-up every fourth week. At baseline, after treatment, and after maintenance, the assessment protocol was completed with measurements of lip mobility using 3D motion analysis and parental reports concerning eating ability and saliva control. Results Seven of eight participants improved maximal lip strength and endurance but only four showed significant change. Increased lip strength did not automatically lead to improved function. There was a wide intra-individual variation concerning speech and eating ability within and between assessments. The treatment programme could be carried out without major problems but the frequency and the effect of training were affected by recurrent infections in some. Conclusions Maximal lip force and lip force endurance can improve in school aged children and adolescents with DM1. Improved lip strength alone cannot be expected to have an effect on lip articulation, saliva control, or eating and drinking ability in this population. Lip strengthening exercises can be a complement but not a replacement for speech therapy and dysphagia treatment. A prefabricated oral screen is an easy to use tool suitable for strengthening lip exercises.

Auditory Motor Integration in Oral and Manual Effectors

ABSTRACT Sensorimotor integration of auditory feedback for oral and manual force control was compared in 10 healthy participants. Based on the notion that auditory-to-motor integration is a more typical form of feedback for oral articulators given their role in speech and singing, it was predicted that oral force generation would be more accurate and less variable on an auditory-motor task compared to manual force generation. However, finger force production showed similar accuracy and lower variability than lip force production. The authors propose that auditory feedback can be used for fine force control of both oral and manual effectors. Differences in performance are considered to arise from physiological differences between the effectors that are reflected in their typical functions. This novel study of oral and manual force control under auditory feedback is an important step in understanding how auditory information can be associated with fine force control.

Non-Newtonian Effects on Film Formation in Grease-Lubricated Radial Lip Seals

In existing models, the only lubricant property used for predicting film thickness in radial lip seals is the (base) oil viscosity. Lubricating greases show non-Newtonian behavior, and additional normal stress components develop that may contribute to the load-carrying capacity. This study investigates the shear rheology of greases and determines whether this “normal stress effect” in grease can significantly contribute to film formation in radial lip seals. First, the rheological behavior of grease is studied in a rotary plate–plate rheometer at small gaps of 25–500 μ m up to shear rates of 5 · 10 4 s −1 . The rheology measurements are used for a rheology model that predicts the first normal stress difference in the grease. Second, a seal lip model was developed to predict the lift force generated by the normal stress effect that separates the seal from the shaft. The model results show that the load-carrying capacity depends very much on the operating conditions: lip geometry, speed, and temperature. The model predicts a lift force that is over 50% of the seal specific lip force for low-contact pressure-bearing seals. The model can easily be used in existing oil seal models and makes it possible to optimize seal design by utilizing the normal stress effect.

Maximum Closing Force of Mentolabial Muscles and Type of Malocclusion

To measure the closing force of the upper and lower lips and to ascertain the relationship between the maximum closing force of the mentolabial muscles and types of malocclusion. Of those who showed the full eruption of a second molar and no permanent tooth loss, 99 subjects were chosen who showed a positive overbite and ANB and no skeletal asymmetry. By using the Y-meter, which can measure the lip force in the vertical direction using a load cell, the closing forces of the upper and lower lips were measured separately. A one-way analysis of variance (ANOVA) test and the Pearson's correlation test were used to evaluate the interrelationship between lip force and dentofacial morphology. The lip closing force was greater in male and Class I subjects. Upper lip force was greater than that of the lower lip in all groups. The values of lip closing forces were related to the variables of upper incisor angulation. In Class II subjects, the values of lip closing forces were also related to the vertical skeletal pattern. The mentolabial muscle force was highly correlated with dentofacial structure and types of malocclusion.

Somatosensory Gating Is Dependent on the Rate of Force Recruitment in the Human Orofacial System

Functional orofacial behaviors vary in their force endpoint and rate of recruitment. This study assessed the gating of orofacial cutaneous somatosensation during different cyclic lip force recruitment rates. Understanding how differences in the rate of force recruitment influences trigeminal system function is an important step toward furthering the knowledge of orofacial sensorimotor control. Lower lip vibrotactile detection thresholds (LL-VDTs) were sampled in response to sinusoidal inputs delivered to the lip vermilion at 5, 10, 50, and 150 Hz while adult participants engaged in a baseline condition (no force), 2 low-level lip force recruitment tasks differing by rate (0.1 Hz or 2 Hz), and passive displacement of the lip as a control to approximate the mechanosensory consequences of voluntary movement. LL-VDTs increased significantly for test frequencies at or below 50 Hz during voluntary lip force recruitment. LL-VDT shifts were positively related to changes in the rate of lip force recruitment, whereas passively imposed displacements of the lip were ineffective in shifting LL-VDTs. These findings are considered in relation to published reports of force-related sensory gating in orofacial and limb systems and the potential role of somatosensory gating along the trigeminal system during orofacial behaviors.

Study of brass performer gestures

Brass instrument playing requires the musican to control his respiratory gesture and the elastic properties of his lips. This raises the question of musician gesture optimisation and strategy in order to complete a musical exercise. It also makes gesture characterization very hard to conduct in a non-invasive way. On the other hand, it is possible to measure some control parameters (linked to the respiratory and lip-adjustment gesture) like lip force applied on the mouthpiece and mouth air pressure. Theses parameters measurements and also the specific mouthpiece receiver developed to measure lip force with a minimum interference to the player are presented. Respiratory flows during live playing are also evaluated thanks to the calibration of respiratory belts used on the thoracial and abdominal regions of musicians. Details of the method for carrying out this type of measurement and preliminary results are reported. During this measurement sound recording and analysis are also conducted thanks to a set of audio descriptors. Links between control parameters measurements and sound characterisation are examined. Parallel development of a automated artificial mouth, used for experimental validations, is also outlined. [Work, within the CONSONNES project, is lead with the support of the French Research National Agency ANR].

Reliable Lip Force Measurement in Healthy Controls and in Patients with Stroke: A Methodologic Study

A prefabricated oral screen has shown promising results as a muscle self-training device to improve the lip function of stroke patients affected by oropharyngeal dysphagia. However, a technique for the measurement of lip muscle force, whether in healthy individuals or in stroke patients, is lacking. The present study was designed to (1) test the intra- and interreliability of lip force measurements by means of a newly devised Lip Force Meter, LF100, (2) determine a normal lower limit for lip force in newtons (N), and (3) ascertain the instrument's sensitivity and specificity. LF100 is a modified strain gauge for recording the ability of lips to withstand pressure from a predentally placed oral screen. Forty-two healthy controls and 22 stroke patients agreed to participate in the trial. The controls and patients were examined three times with the LF100, with 2-min rest intervals, twice by investigator MH and once by investigator MO. Intrainvestigator reliability with the LF100 proved excellent in both controls and patients: ICC was 0.83 and 0.90, respectively. Interinvestigator reliability was good or excellent in both groups: ICC was 0.71 and 0.91. There was a significant difference in lip force between controls and stroke patients (mean = 24.7 +/- 6.3 N and 9.5 +/- 5.5 N, p < 0.001). The sensitivity of LF100 was 91% and the specificity 95%. The cutoff level for normal lip force was 15 N. The LF100 showed itself to be a suitable and reliable instrument for measuring lip force.

Lip muscle training in stroke patients with dysphagia

Conclusion. Training with an oral screen can improve lip force (LF) and swallowing capacity (SC) in stroke patients with oropharyngeal dysphagia, irrespective of the duration of pretreatment of dysphagia, and irrespective of the presence or absence of central facial paresis. It is more plausible that treatment results are attributable to sensory motor stimulation and the plasticity of the central nervous system than to the training of the lip muscles per se. Objectives. A close relationship has been demonstrated between LF and SC in stroke patients whether or not they are affected by facial paresis. It is not known how training of lip function can improve swallowing capacity. The present study was therefore designed to ascertain: (i) if training with an oral screen can improve the LF and SC of stroke patients with oropharyngeal dysphagia; to establish (ii) if improvement in LF and SC is connected with the presence or absence of central facial palsy, (iii) on the interval between stroke onset and initiation of treatment, (iv) on age, or (v) on sex. Subjects and methods. This was a retrospective study of 30 stroke patients, 49–88 years old, who were investigated with a Lip Force Meter, LF100 (LF100) and a swallowing capacity test (SCT) before and after a period of self-training lasting at least 5–8 weeks, using an oral screen. Initial central facial paresis was present in 24 patients. Results. The median LF was 7 Newtons (N) (range 0–27) before treatment and 18.5 N (range 7–44) after treatment (p<0.001). The median SC was 0 ml/s (range 0–9.1) before treatment and 12.1 ml/s (range 0–36.7) at follow-up (p<0.001). There was no significant difference in swallowing improvement between patients with versus those without facial paresis. The interval between stroke attack and start of treatment, ranging from a few days up to 10 years, had no significant influence on the treatment results, nor did age or sex. The facial paresis was improved or at least ameliorated in all patients after the lip training period.

Functional Outcomes of Cleft Lip Surgery. Part III: Measurement of Lip Forces

To investigate lip force dynamics among participants with a repaired cleft of the lip and noncleft control participants. A parallel, three-group, nonrandomized clinical trial. Forty-eight participants with cleft lip and 36 noncleft participants. Participants attended two separate visits. At each visit, they were instructed to produce fine motor control and maximum compression forces with each upper and lower lip in response to visual force targets. Measures of force were extracted, and the data were fit using regression techniques. The upper and lower lips of the participants with a cleft lip demonstrated less time on target, while the lower lips had shorter rise time but higher peak forces, a higher rate of force recruitment, and increased maxima of the first derivative of force compared with the noncleft participants. For all participants, there was a learning effect for certain force variables between the two visits and with increasing age. For participants with a cleft lip, force regulation of the circumoral region within the operating range presumed important for facial and speech animation is compromised because of impairments in force recruitment, gradation, fractionation, and stability. In the presence of a change in upper lip tissue mechanics due to scarring or neuromotor impairment, such as a cleft, the lower lip typically exhibits compensatory motor actions.

Modulation of the trigeminofacial pathway during syllabic speech

The human orofacial system is richly endowed with low-threshold, slowly adapting mechanoreceptors that respond to self-generated movements and external loads. The functional linkage between these afferents and the recruitment of motor units in the lower face during the dynamics of speech is unknown. Mechanically evoked activity in the orbicularis oris muscles was studied in young human female adults ( N = 10) during a lip force recruitment task associated with the repetition of the nonsense speech utterance “ah- wah.” This speech task involved the recruitment of perioral motor units against an elastic load. A skin contactor probe coupled to a servo-controlled linear motor delivered punctate ipsilateral mechanical inputs (25 ms duration, 1800 μm displacement) to the glabrous surface of the upper lip in order to index the modulation and specificity of the compound trigeminofacial response as a function of speech force recruitment threshold (Ft). Modulation of the early (Ft = 0.2 N) and later (Ft = 1.0 N) components of the evoked perioral response was found at the two force thresholds. Beginning at approximately 60 ms post-stimulus, a significant suppression response was found among lower lip EMG recording sites and its magnitude was greatest when the mechanical perturbation occurred during the early phase of lip force recruitment. Variation in the lip force trajectories was manifest by a greater difference in net interangle force associated with lip perturbations indexed to the early Ft. This was interpreted to reflect the operation of a feedforward mechanism which may play a more significant role during an evolving speech action. Thus, the application of servo-controlled mechanosensory inputs effectively indexed the excitability of the facial motor nucleus during production of a simple speech phrase. Future studies are needed to explore mechanisms of short-term adaptation and trigeminofacial modulation during propositional speech in health and disease.

Functional Outcomes of Cleft Lip Surgery. Part III: Measurement of Lip Forces

Functional Outcomes of Cleft Lip Surgery. Part III: Measurement of Lip Forces