Experimental analysis of the power losses induced by a high-speed lip seal under oil bath lubrication

Effect of active compensation on the performance of self-eccentric lip seals: Numerical and experimental investigation

Composite mandibulo-labial defects require restoration of mandibular continuity and oral competence. Stage 1 fibula free flap reconstruction restores bone and provides lining and cover, but oral competence depends on reestablishing orbicularis oris continuity. After stage 1, patients may continue to experience drooling, poor lip seal, and an obliterated gingivolabial sulcus due to scar tethering and muscle discontinuity. We describe a stage 2 salvage procedure, which includes release of vestibular scar bands, limited mobilization of the healed fibula free flap skin paddle for sulcus lining, and direct reapproximation of orbicularis oris stumps (figure-of-eight 3-0 poly-p-dioxanone). In a pediatric ballistic injury, lip seal improved; after rehabilitation, no visible drooling was observed during conversation, although active excursion remained limited.

The "equilibrium theory" posits that the tongue and perioral muscles, including the orbicularis oris (OO) muscle, function synergistically to maintain balanced tooth positioning. Surface electromyography (sEMG) is a valuable, nonivasive method for assessing muscle activity. However, previous electromyographic (EMG) studies comparing lip muscle activity in children with and without lip competence (LC) have yielded inconsistent results. Therefore, further research is needed to clarify OO muscle activity patterns in this population. The aim of the study was to evaluate the EMG activity of the superior (SOO) and inferior orbicularis oris (IOO) muscles in children with and without LC. The sample comprised 30 children with lip incompetence (LI) (mean age 9.46 ± 1.76 years) and 30 children with LC (mean age 8.85 ± 1.52 years). Electromyographic recordings of the SOO and IOO muscles were obtained using a DAB Bluetooth Instrument (Zebris Medical GmbH, Isny im Allgäu, Germany) at clinical rest, during saliva swallowing, lip protrusion ("kissing" position), lip compression, and while articulating the syllables /pa/, /ba/, and /ma/. Statistical analyses were performed using Stata v. 11.0 (StataCorp, College Station, USA). The level of significance was set at p < 0.05. Electromyographic activity of the SOO and IOO muscles during saliva swallowing (p < 0.001, adjusted p (padj) = 0.002) and lip compression (p = 0.001, padj = 0.013 for SOO; p < 0.001, padj = 0.005 for IOO) was significantly greater in children with LI compared to those with LC. Similar EMG activity at rest and during speech production was observed in children with and without LC. Children with LI demonstrate increased SOO and IOO muscle activity during saliva swallowing and lip compression, suggesting greater muscular effort is required to achieve lip seal. This increased activity may disturb the muscular force balance essential for proper maxillofacial growth and could contribute to the development of malocclusion.

Study on wear-aging coupled performance degradation of eccentric lip seals based on multi-physics coupling

The European Union’s regulatory mandate requirements for vehicular components include the integrity of sealing performance, mitigating leaks from fuel tanks and transmission systems in order to guard against environmental pollution. Non-compliance can result in significant costs for the OEM and their supplier base. The majority of the reported research regarding leakage from radial lip seals focuses on static analysis of leakage under a given set of laboratory conditions. However, in practice, seal conjunctions are often subjected to significant excitations due to vehicular vibration. In the current study, the case of a front-wheel drive vehicle, equipped with three-axle accelerometers and subjected to a comprehensive road test, is used as the basis for the development of a realistic representative test rig. The test rig is developed using bespoke components from the vehicle under investigation to assess the impact of the encountered natural frequencies on sealing performance in controlled laboratory conditions, when the system is subjected to controlled excitation. Experiments are conducted to evaluate leakage at the transmission interface, focusing specifically on the sealing system’s performance. The influence of driveshaft manufacturing processes using corundum grinding and subsequent surface topography upon leakage performance are also considered. Identified modal response frequencies are imposed upon the test rig using a shaker, whilst the seal leakage is measured. The importance of shaft roughness characteristics, such as topographical skewness upon seal leakage rate under various resonant conditions, are ascertained. The results indicate potentially significant leakage rates under excitation conditions, with a non-optimised shaft roughness profile.

Mouth breathing (MB) and incompetent lip seal (ILS) are common oral dysfunctions with potential repercussions for dentofacial development, systemic health, and psychological well-being. Although related, MB and ILS represent distinct conditions: ILS denotes difficulty maintaining lip closure at rest, whereas MB concerns the route of respiration. Despite growing recognition of their physical impacts, few studies have examined how MB and ILS are related to psychological stress in young adults. A cross-sectional study was conducted among 567 Japanese university students aged 18–27 years using a self-administered questionnaire. The survey included 53 items on oral conditions, lifestyle habits, and nasal symptoms, and 29 items from Section B of the Brief Job Stress Questionnaire to assess psychological stress. Exploratory factor analysis (EFA) was used to identify latent constructs. Extreme Gradient Boosting (XGBoost) was applied to classify high-stress individuals and highlight important predictors, while direct and indirect associations among ILS, MB, nasal disease, and stress were examined using structural equation modeling (SEM). EFA extracted five latent factors: nasal disease, ILS and MB, oral hygiene and bad breath, condition of the teeth and gums, and lip dryness. XGBoost achieved moderate predictive performance (accuracy = 0.69, F1 = 0.74), with top predictors corresponding to ILS- and MB-related items (“Do you sleep with your mouth open?” and “Is your mouth often open during the day?”). SEM indicated that nasal disease had a direct association with stress, whereas ILS and MB indirectly influenced stress through oral symptoms such as lip dryness and bad breath. Lip dryness also showed a direct path to stress, suggesting its dual role as both a symptom and a potential stressor. ILS and MB are associated with higher stress levels in young adults primarily through indirect pathways involving oral discomfort. Lip dryness may mediate this relationship. Their partial independence from nasal disease supports the view that ILS and MB are distinct but interrelated conditions. These findings highlight the need for early screening and integrated management of oral and nasal function to promote psychological well-being.

Performance evaluation and failure analysis of eccentric rotary lip seals: Numerical and experimental investigation

In high-load, highly contaminated, and maintenance-challenging harsh environments, rotary lip seals typically rely on grease lubrication. However, there is currently no suitable model for predicting the lifespan of grease-lubricated sealing systems. This study establishes a numerical simulation model to evaluate the lifespan of rotary lip seals under grease lubrication, considering rubber aging during storage and use, as well as wear. Based on experimental results from thermal aging and standardized wear testing, the evolution of reverse pumping rate and friction torque over aging and wear durations is analyzed. A performance evolution model is developed to predict the storage and service life of grease-lubricated lip seals, enabling leakage failure warnings and providing guidance for seal replacement cycles.

Abstract A numerical analysis investigates the feasibility of low-power-loss seals using alternative materials in a standard lip seal form factor for railcar bearing seal applications. This form factor is a common topology that finds use in other applications including air compressors, turbine engines, aircraft landing systems, and chemical equipment. The form factor, along with hyperelastic materials, most commonly nitrile butadiene rubber (NBR) for railcar bearing seals, is known for its reliability. The alternative materials of interest are polytetrafluoroethylene (PTFE) and filled PTFE with 15% glass and 5% MoS2 (PTFE-GM). In addition to a low friction coefficient, these materials exhibit dry-running capability and chemical compatibility. The impact of material choice, wear, and variations in seal design parameters on the contact zone and contact pressure distribution is presented. An axisymmetric, multiscale finite element model (FEM) with Archard wear of the flexible seal and rigid shaft is developed such that the materials operate at a stress state below the yield strength such that no plastic flow occurs during assembly, installation, and operation. Results are presented showing the contact pressure distributions of varying scraper angles, barrel angles, garter spring tensions, R-values, and interference fit. Results show PTFE-GM to be feasible for railcar bearing applications with a 49.6% reduction in power as compared to NBR. Pure PTFE shows a reduction of 87.6%, which represents an upper limit on power reduction but is not feasible in this form factor due to its high wear-rate.

Introduction: Freeway space is described as the space between the maxillary and mandibular teeth when the mandible is in the natural or physiological rest position. The incorrect measurement of freeway space can lead to bruxism of teeth, difficulties in creating the lip seal, artificial appearance, cheek biting, angular cheilitis, temporomandibular joint pain etc. The physiological rest position of themandible is widely used in clinical practice as a functional method for the determination of freeway space. However, the mandibular position is considered to be affected by various factors such as head and body postures. Thus, the purpose of this study is to determine and compare the average freeway space in dentate subjects with and without head stabilization. Methods: The total sample of 81 adult patients with the age range of 18-35 years were taken. Vertical dimension at rest and Vertical dimension at occlusion were measured with and without head stabilization and freeway space value was calculated. Paired sample t-test was used to compare the freeway space with head stabilization and without head stabilization. Results: The mean freeway space with head stabilization and without head stabilization was 2.7 + 1.25 mm and 2.52 + 1.32 mm respectively. There was no statistically significant difference in the freeway space with and without head stabilization. Conclusion: The freeway space in dentate adults range from 1-6 mm. There is no evidence to support that FWS values obtained after head stabilization is close to the recommended range of FWS compared to the values obtained without stabilizing head.

Anterior open bite is a malocclusion characterized by a negative vertical overlap between the anterior teeth when the posterior teeth are in occlusion. Its etiology is multifactorial, potentially resulting from genetic disorders, normal inheritance, and anomalous craniofacial developmental conditions, primarily related to deleterious habits and environmental etiological factors associated with psycho-emotional behavior. In this sense, the main risk factor for the development of anterior dentoalveolar open bite is thumb sucking. Etiological factors can lead to changes in occlusal development, altered dental and lingual positioning, and lack of lip seal. Therefore, this study aimed to conduct a literature review on the relationship between the deleterious habit of thumb sucking and anterior open bite. For this study, the Pubmed, Bireme, Scielo, and Google Scholar databases were used, in addition to consultations with the bibliographic collection available at the Unicesumar – Curitiba Campus library, using the keywords: Open bite, Deleterious habits, and Digital sucking. Diagnosis should be made through a detailed medical history, clinical examination, and complementary tests; treatment should be conducted by mitigating the harmful habit. It should be carried out by a multidisciplinary team to verify and treat any possible damage caused. The earlier the diagnosis, the better the prognosis for treatment tends to be.

Objective: To evaluate differences in craniofacial skeletal pattern among subjects with competent and incompetent lip seal (ILS). Methodology: Sample of 261 subjects (177 females and 84 males) was constituted by random selection from patients who visited Orthodontic OPD. Lip seal was assessed by clinical examination on the basis of visual inspection of muscular tension in the mental region at mandibular rest position and subjects were divided into competent lip seal and incompetent lip seal group. Skeletal measurements were performed on lateral cephalograms to assess differences in vertical and sagittal skeletal pattern among subjects in both groups. Results: Competent lip seal was found in 64.4 % of the subjects and 35.6% of subjects had incompetent lips. ILS group had greater values of SNA and ANB whereas SNB value was reduced. The inclination of maxilla (SNPP) was larger in competent lip group and inclination of mandible (SNMP) was larger in incompetent lip group. Statistically significant differences were found between the two groups in the interbasal relationship (PPMP), Y-axis angle and anterior lower facial height ratio, with increased values of these measurements in incompetent lip group. Posterior facial height ratio was comparatively reduced in subjects with ILS. Conclusion: Patients with ILS have higher tendency to develop class II skeletal pattern with mandibular retrognathia, increased inclination of mandibular plane and tendency for clockwise rotation of mandible. Lip incompetence also leads to vertical growth pattern resulting in increased anterior lower face height and decreased posterior facial height

Texture optimizing method for rotating shaft with lip seal considering processing errors

Abstract Lip seals are crucial for preventing lubricating media leakage and intrusion of abrasive particles into rotating shaft oil tanks. While numerical simulations have advanced the understanding of oil-lubricated lip seals, grease's rheological complexities hinder accurate modeling. To address this limitation, this study proposes a novel fluid–solid coupling model tailored specifically for lip seals operating under grease lubrication conditions. By integrating deterministic surface topography, thermal characteristics of the seal working area, and the flow separation method, the model achieves precise solutions for seal performance parameters. Experiments validate this model, elucidating the effect of grease and operating parameters on characteristics such as friction torque and leakage rate. This research advances lip seal analysis, offering insights for optimizing grease-lubricated lip seal systems.

Background: Mouth breathing, commonly resulting from nasal obstructions, significantly affects craniofacial development by disrupting the balance of oral and facial muscles. This leads to altered posture, narrower maxillary arches, and increased vertical facial dimensions. Aims and Objectives: The present study aimed to compare maxillary arch widths and cephalometric characteristics between mouth breathers and nasal breathers. Methods and Materials: A total of 152 participants aged 15–45 years were examined at the College of Dentistry, Hawler Medical University. Breathing tests (lip seal, mirror, water retention), 3D intraoral scans, cephalometric radiographs, and digital arch measurements using Meshlab software. Results: showed that mouth breathers had significantly reduced arch widths (in first and second premolars, first molars area) and higher mandibular plane angles, anterior facial heights, and gonial angles compared to nasal breathers. Arch ratios were also lower among mouth breathers, indicating maxillary constriction. These craniofacial alterations were generally consistent across age groups, although anterior facial height increased slightly with age. Gender differences were minimal, with some variations observed in males. The study highlights the importance of early identification and intervention for mouth breathers to prevent long-term orthodontic and skeletal complications. Dental professionals should be aware of the structural implications of mouth breathing to guide timely diagnosis and treatment planning. Conclusion: In conclusion, the mouth breathing is accompanied with high risk of malocclusion. Mouth breathing is a significant risk factor for reducing maxillary arch width and increasing cephalometric measures. These maxillary and cephalometric changes are not affected by age, while somewhat affected by gender.

Rotary lip seals serve as critical sealing components in industrial equipment, traditionally relying on the reverse pumping theory for their sealing mechanism. However, increasing operational demands characterized by high fluid pressure differentials, elevated speeds, and multi-physics coupling environments have revealed limitations in the applicability of the classical theory. This study aims to develop a comprehensive model to quantitatively characterize rotary lip seal performance, specifically frictional torque and reverse pumping rate, and to elucidate underlying mechanisms beyond classical theory. We developed a Mixed Thermo-Hydrodynamic Lubrication (MTHL) model that explicitly integrates fluid–solid–thermal coupling effects to simulate seal behavior under complex operating parameters. The simulations reveal that reverse pumping rate increases near-linearly with rotational speed from −8.54 mm3/s (0 m/s) to 122.82 mm3/s (3 m/s) and 220.27 mm3/s (6 m/s), validating classical theory, while under elevated fluid pressure differentials, a distinct non-monotonic trend emerges: rates evolve from 122.82 mm3/s (0.10 MPa) to 172.93 mm3/s (0.12 MPa), then decline to 52.67 mm3/s (0.18 MPa), and recover to 69.87 mm3/s (0.22 MPa), a phenomenon that cannot be explained by classical sealing mechanisms. Mechanistic analysis indicates that this anomaly stems from a competitive interaction between pressure-driven and shear-driven flow. This discovery not only enhances the reverse pumping theoretical system but also provides a theoretical foundation for optimizing sealing performance under diverse operational conditions.

Moebius syndrome represents a rare congenital disorder characterized by non-progressive unilateral or bilateral paralysis of the facial and abducens nerves. The aim of this study is to report the oral and dental manifestations of Moebius syndrome present in two Brazilian children. Clinical case 1: 9-year-old girl, diagnosed with Moebius-Poland syndrome, presented to the Baby Clinic of (omitted information) for preventive dental treatment. Clinical and radiographic examination revealed anterior open bite, unilateral crossbite, microstomia, lack of buccal elasticity, dry labial mucosa, dental fluorosis in upper and lower teeth associated with enamel hypoplasia, dental crowding, upper right canine ectopic eruption, palate ogival, micrognathism, lip sealing and adequate lingual tonus. Clinical case 2: 26-month-old girl, attended in the same service for preventive dental treatment. Clinical and radiographic examination revealed anterior open bite, microstomia, lack of buccal elasticity, high arched palate, hypotonic tongue, micrognathism, inadequate lip seal and dental caries. In both cases, episodes of dentoalveolar trauma were related by parents. Pediatric dentists play a fundamental role in the early diagnosis of oral and facial characteristics that may be present from birth and imply potential repercussions on the development of the stomatognathic system.

Effect of angle eccentricity on lip seal performance of helicopter gearbox

Robinow syndrome (RS) is a rare genetic disease that may involve cardiovascular, skeletal and urogenital systems and manifest through short limb dwarfism, defects in vertebral segmentation, hypoplastic genitalia and cranial and facial abnormalities. In this article, we hereby present a patient of a 10-year-old Brazilian boy with RS who presented with a remarkable number of classical general and dental features. Physical examination revealed disproportionate short stature with shortening limbs, syndromic face with normal hair appearance, low-set ears, macrocephaly, prominent forehead, hypertelorism and ocular prominence, nose anomalies, triangular mouth with long/short philtrum, incompetent lip seal, midface hypoplasia, retrognathia, deficient malar prominence, among others. Clinical examination revealed gingival hyperplasia, malocclusion, crowding dental, diastemas, microdontia, enamel hypoplasia, prolonged retention, dental caries, delay of dental eruption v-shaped palate, bifid tongue and ankyloglossia history. Radiographically, dental agenesis, hypertaurodontism and thick roof pulp chambers and delayed tooth eruption were observed. Preventive, restorative and rehabilitative dental procedures are being carried out. Robinow syndrome presents clinical and radiographic findings that may be present from birth and require pediatric dentistry follow-up. Furthermore, the pediatric dentist plays an essential role in developing effective planning and treatment in terms of health promotion, aesthetic rehabilitation and functional interventions in the stomatognathic system.