Tooth Interference Research Articles

Effect of an Ayurvedic Compound and Hypnotherapy on Sleep Bruxism: A Case Report

Bruxism is defined as “diurnal or nocturnal parafunctional activity including clenching, bracing, gnashing, and grinding of the teeth.” The etiology of bruxism is unclear, but the condition has been associated with stress, occlusal disorders, allergies, and sleep positioning. The aetio-pathophysiology is still unclear. SB (Sleep Bruxism) has been associated with tooth interference, psychosocial and environmental factors, brain transmitters, and basal ganglia dysfunction. It is been reported that Sleep bruxism during all sleep stages, others observed the majority of bruxe episodes during light sleep and REM and are often associated with arousal transients. There is no specific treatment for sleep bruxism but each subject has to be individually evaluated and treated. Three management alternatives are used: dental, pharmacological, and psycho behavioural. A 69-year-old man came to OPD of VPSV Ayurveda College Hospital, complaining that he has been grinding his teeth and making sounds while sleeping for the last 15 years. The noise he created caused his wife's sleep to be disturbed as well. So she constantly gave him the blame. They noted that the patient's tendency to grind his teeth worsened whenever he became upset or overworked. The patient had been given Aswagandha Churna (3gm), Jatamansi Churna (2gm), Aparajita churna (2gm) 2 times after food with warm water and Mahapaishacika ghrta 10ml at night for 3 weeks and also by considering the stress factor hypnotherapy was given 4 sittings on every 3rd day. The patient had good improvement in the Perceived Stress Scale, it reduced from 20 to 11. After three weeks of treatment, sleep bruxism was completely cured and the patient was asymptomatic during the follow-up period also.

A novel method for testing accuracy of bite registration using intraoral scanners.

The evidence on the accuracy of bite registration using intraoral scanners is sparse. This study aimed to develop a new method for evaluating bite registration accuracy using intraoral scanners. Two different types of models were used; 10 stone models and 10 with acrylic resin teeth. A triangular frame with cylindrical posts at each apex (one anterior and two posteriors) was digitally designed and manufactured using three-dimensional (3D) printing. Such a structure was fitted in the lingual space of each maxillary and mandibular model so that, in occlusion, the posts would contact their opposing counterparts, enforcing a small interocclusal gap between the two arches. This ensured no tooth interference and full contact between opposing posts. Bite registration accuracy was evaluated by measuring the distance between opposing posts, with small values indicating high-accuracy. Three intraoral scanners were used: Medit i500, Primescan, and Trios 4. Viewbox software was used to measure the distance between opposing posts and compute roll and pitch. The average maximum error in interocclusal registration exceeded 50 μm. Roll and pitch orientation errors ranged above 0.1 degrees, implying an additional interocclusal error of around 40 μm or more. The models with acrylic teeth exhibited higher errors. A method that avoids the need for reference hardware and the imprecision of locating reference points on tooth surfaces, and offers simplicity in the assessment of bite registration with an intraoral scanner, was developed. These results suggest that intraoral scanners may exhibit clinically significant errors in reproducing the interocclusal relationships.

Study on nonlinear dynamic characteristics of power six-branch herringbone gear transmission system with 3D modification

The power six-branch herringbone gear transmission system has the advantages of large power transmission and transmission ratio. Because of its multi-way transmission and over-constraint structure, to prevent loaded tooth interference, there are large backlashes between teeth. The system shows complex nonlinear dynamic characteristics under the influence of backlashes, which seriously affects meshing performance. The modification technology can effectively improve gear meshing performance. Hence, on the basis of optimizing meshing performance of the active pair of the six-branch herringbone gear transmission system, this article will combine 3D modification with system nonlinear vibration characteristics and propose an analysis method of the system nonlinear vibration characteristics under 3D modification to reduce vibration and noise. First, the 3D modified tooth surface equation is determined by forming grinding, the loaded transmission error (LTE) of the system's active pair is obtained by tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) technology, and the optimal modification parameters are obtained by Ant Lion Optimizer (ALO) with the minimum error amplitude as optimization objective. Then, the time-varying meshing stiffness of system under the optimal modification is calculated, and the pure torsional nonlinear dynamic model with backlashes, meshing stiffness, and static transmission error (STE) is established. Finally, the global vibration characteristics in parameter field are studied through time domain and bifurcation diagram of system. Results show that the 3D modification can eliminate edge contact of tooth and improve tooth contact performance. With the increase of input power, the root mean square (RMS) values of acceleration increase and the RMS values and jump decrease after 3D modification. With the increase of input speed, the RMS curves appear multiple resonance peaks and jumps at low input speed. After 3D modification, the RMS, jump, and resonance peak values decrease. Compared with level І, the backlashes and STEs of level II and phase difference ϛsII have great influence on system dynamic characteristics and easily make system in chaotic motion, while the 3D modification reduces their influence and makes system motion periodic.

Treatment approach to patients with distal malocclusion complicated by temporomandibular joint pain-dysfunction syndrome

Research is effective sequencing of measures for orthodontic treatment active period and unfavorable course of retention period predictors in patients with distal malocclusion, complicated by temporomandibular joint pain-dysfunction syndrome. The retrospective study consists of 102 case reports of patients from 18 to 37 (average age is 26.75±3.25 years) with distal malocclusion (Angle Class II division 2 subdivision) associated with temporomandibular joint pain-dysfunction syndrome. Cases of successful treatment were 30.4% (n=31), semi-successful - 42.2% (n=43), semi-unsuccessful - 18.6% (n=19), unsuccessful - 8.8% (n=9). ANOVA analysis of orthodontic treatment stages reveals main risk factors for pain syndrome recurrence in retention period. The ineffective morphofunctional compensation and unsuccessful orthodontic treatment predictors are: incomplete pain syndrome elimination, persistent masticatory muscles dysfunction, distal malocclusion recurrence, condylar process distal position recurrence, deep overbite, upper incisors retroinclination for more than 15°, single posterior tooth interference. Thus, pain syndrome recurrence prevention in retention orthodontic treatment period includes pain and masticatory muscles dysfunction elimination in pre-treatment period, physiological dental occlusion and condylar process central position in active period.

Performance analysis of asymmetric toothed strain wave gear

Strain Wave Gear (SWG) or Harmonic Drive (HD) shows moderate performance under symmetrical involute teeth. Teeth interference, excessive teeth meshing, vibration due to improper teeth engagement are the major drawbacks of strain wave gear under symmetrical involute teeth. In the present paper, an attempt has been made to improve the performance of strain wave gear by replacing the symmetrical involute teeth with asymmetrical involute teeth. Present investigation finds that under ‘asymmetric toothed strain wave gear’, aspects such as teeth interference, teeth engagement and teeth contact stress of strain wave gear are improving clearly and as a consequence some other aspects such as individual teeth strength, load carrying capacity, tooth endurance are also improving inherently. In the present analysis for symmetrical teeth 20°–20° pressure angle and for asymmetrical teeth, three different combinations of pressure angles such as 25°–20°, 30°–20° and 35°–20° are taken.

Teeth interference in harmonic drives intended for heavy engineering

Based on geometric studies and force analysis of a heavy harmonic gearing and through application of the elasticity theory methods, motions of the deformed gearing from the theoretically preset positioning have been ascertained. A fundamental design feature of the heavy harmonic drive consists in a disk wave generator which permits to provide additional deformations of the flexible gear due to incomplete contact between the disks and the flexible wheel. The scale factor along with the small tooth module between 1.5 and 2 mm of the wave-type reducers and heavy loads imposed on the flexible gear increase its deformations and intensify formation of interference between the teeth. The above circumstances drastically reduce load-carrying capacities of the harmonic drives and actually restrict them due to the carrying capacity of a flexible bearing. The results obtained provide both qualitative and quantitative characteristics of the teeth interference depending on the wave generator swivel angle φ at various values of the transmitted torque between 0 and 5·105 kNm.

Investigation on meshing and dynamic characteristics of spur gears with tip relief under wear fault

Combining the loaded tooth contact analysis (LTCA) method and the gear dynamic model, a wear prediction model for spur gears with tip relief is established. The simulated wear depth is verified by the experimental results in a published reference. Based on the wear profile, the mesh stiffness and the tooth root stress obtained from the proposed model are compared with those obtained from the finite element model. Relative to the finite element method, the proposed method can greatly reduce the computation time. The effects of the tip relief and surface wear on the meshing and the dynamic characteristics are discussed. The tip relief can greatly decelerate the surface wear. Appropriate tip relief and slight wear can decrease the tooth interference and reduce the system vibration. Furthermore, the effects of the rotational speed on the wear depth are also studied and it is found that the quasi-static model is applicable to wear prediction when the rotational speed is away from the harmonic resonance peak.

Some New Gears Aspects

In today's mechanical transmissions most widely used, the gears, are spread across all industries. For this reason, their importance has become overwhelming, which is why we want to recall in this paper some important aspects regarding toothed wheels. It is the geometry, cinematic, the forces and the yields of these mechanisms, which will be presented in the work in the form of newly synthesized relations on modern bases. Another important aspect in toothed wheels is their synthesis by modern methods that avoid tooth interference during operation. To avoid the interference between teeth, we must know the minimum number of teeth of the driving wheel, in function of the pressure angle (normal on the pitch circle, alpha0), in function of the tooth inclination angle (beta) and in function of the transmission ratio (i). In optimal and high-efficiency gearing, gears require a modern design with increased coverage. These achievements can only be achieved today in the context of lowering the value of the alpha engagement angle. Through all the aspects presented, which relate to the dynamics of gears, the work can be considered among those of the optimal dynamic synthesis of the gears.

Characterization in children 6 years of age with tooth interference of primary schools

Characterize children from 6 years of age in primary schools belonging to the health area of the Policlinico Docente 30 November. Methods: He was an observational study descriptive and cross-sectional aiming to. The universe was composed of 83 children whose dental care is carried out in the Department of Stomatology of the Policlinico teacher 30 de Noviembre, in the period between June of 2017 and 2018 April. The data was an interview structured to parents or guardians, in order to obtain data accurate and verified, using as a summary measure the percentage and reflecting the data in contingency tables. He was the oral test to children using the tongue depressor and natural or artificial light. Results: The study dominated the female sex. The most practiced disfiguring habits were postural habits and digital suction. Conclusions: Most found anomaly was one-sided after reversed occlusion. Taking into account this recommended expanding research in other schools, since these results alert us to the need to intercept the tooth interference from an early age.

Some New Gears Aspects

In today's mechanical transmissions most widely used, the gears, are spread across all industries. For this reason, their importance has become overwhelming, which is why we want to recall in this paper some important aspects regarding toothed wheels. It is the geometry, cinematic, the forces and the yields of these mechanisms, which will be presented in the work in the form of newly synthesized relations on modern bases. Another important aspect in toothed wheels is their synthesis by modern methods that avoid tooth interference during operation. To avoid the interference between teeth, we must know the minimum number of teeth of the driving wheel, in function of the pressure angle (normal on the pitch circle, alpha0), in function of the tooth inclination angle (beta) and in function of the transmission ratio (i). In optimal and high-efficiency gearing, gears require a modern design with increased coverage. These achievements can only be achieved today in the context of lowering the value of the alpha engagement angle. Through all the aspects presented, which relate to the dynamics of gears, the work can be considered among those of the optimal dynamic synthesis of the gears.

Determining of actual profile clearances and screw compressor rotor positions depending on working conditions

In general, screw compressor characteristics depend on their working chamber clearances. One of the main of clearances in the working chamber of screw compressors are the clearances between rotors’ profiles, which are produced due to a reducing of theoretical rotor profiles. This reducing is made to compensate thermal deformation, manufacturing errors and other negative factors, which occur during the screw compressor working cycles and may cause a rotors’ teeth interference. This also may result in a transmission error, which increases the rotor profile clearance on one side of rotor tooth and reduces on other. A screw compressor rotor gearing mathematical model which can predict the actual rotor position and value of the transmission error was developed. An analysis of compressor working conditions influence on the transmission error value is done. Results of the presented work are used for working process mathematical models for improving their accuracy. They also may be used as basis for development of reducing theoretical profiles methods with the aim to reducing of the rotor profiles’ clearances and improve screw compressor characteristics.

Multi-parametric investigation of interference in non-standard spur gear teeth

Tooth interference, normally avoided altogether by adhering to standard design guidelines, becomes a concern when non-standard tooth forms with reduced radial clearance are employed, such as large-fillet short-dedendum gears. These tooth forms have shorter involute working flanks and excess material at the root, which can lead to non-conjugate corner contact and penetration at the tooth root. Existing models for interference are unable to predict this, or rely on calculation-intensive simulations, which make them impractical for design.This work proposes a general and fast mathematical model for calculating corner penetration at the tooth root, which is applicable to both analytically expressed and discretised tooth geometries. Based thereupon a non-dimensional multi-parametric investigation is carried out to quantify the effect of addendum and dedendum length, cutter tip radius, number of teeth and contact ratio on the interference risk. On this basis generalised guidelines are produced for the design of compact non-standard large fillet short dedendum 20° involute gears, including a method using standard cutters with indexing offsets. Prior analytical and numerical interference models in the literature are shown to be limited subcases of this model.

2.5MW 풍력발전기 기어박스 치형수정

This paper reports a method to modify the gear tooth profile of a wind turbine gearbox to reduce the noise caused by the impact of the gear teeth. The major causes of tooth impact are the elastic deformation of the gear teeth, shafts, and case of the gearbox under loading, and the fabrication tolerances in gear manufacturing. In this study, the tooth profile was modified considering the elastic deformation of the gear tooth and the tooth lead modification to compensate for tooth interference in the lead direction as a result of shaft deformations. The method was applied to the gearbox of a 2.5MW wind turbine, and the transmission error was characterized before and after modifying the gear teeth. For the modified gear teeth, the transmission error (67.6%) was lower by 17.8%. Additionally, the gear contact stress was reduced by 6.3%, to 22.3%.

ZK 웜과 인볼류트 헬리컬기어로 결합된 CVVL용 웜기어 설계

The worm gear is used in the motor drive system of automotive CVVL because of its compactness and self-locking ability. A ZK worm and an involute helical gear can be meshed in order to reduce production cost. However, the gearing is not suitable for the reliability and the NVH problem. To improve the dynamic performances, an optimal design process is considered. The transmission error is calculated theoretically and minimized with the several gear design parameters. An inequality condition such as the teeth interference elimination is added.

Theoretical flowrate characteristics of the conjugated involute internal gear pump

The aim of this article is to study the theoretical flowrate characteristics of the conjugated involute internal gear pump. The conjugated involute internal gear pump has a different internal gear, the profile of which is completely conjugated to that of pinion, from the conventional involute internal gear pump. To describe briefly, the former pump is called ‘conjugated pump’ while the latter pump ‘conventional pump’. This structure makes the conjugated pump have smaller volumes of trapped fluid than the conventional pump, which indicates the conjugated pump has a better flowrate performance. Although there have been numerous investigations into gear pumps, none of them have dealt with the conjugated pumps yet. This article presents a systematic study on the theoretical flowrate characteristics of the conjugated pumps. It is expected to obtain some generalized conclusions to guide the design of internal gear pumps. Firstly, a double envelope concept is applied to derive the mathematical models of the conjugated involute internal gear couple. Next, mesh characteristics of the gear couple, which mainly decide the fluid delivery performance of the pumps, are analyzed. Finally, using a control volume approach, the theoretical flowrate characteristics of the pump under different design parameters of gears are investigated. Results show the conjugated pump has a better performance than the conventional one. To design a conjugated pump with good flowrate characteristics, it’s feasible to choose a proper shifting coefficient, a larger tooth number of the pinion, a smaller tooth number of the internal gear, a larger pressure angle and a larger fillet radius, under the condition that no tooth interference occurs.

X – Zero Gear Drive with Minor Teeth Difference

Planetary gear drive with minor teeth difference (zd≤8) is one of the advanced transmitting styles and could meet the requirement of larger ratio in a smaller size of dimension. Generally the gears with addenda modifications play a principal role in planetary gear drive of minor teeth difference to avoid teeth interference during the mesh, and this transmission implies cumbersome parameters calculations and brings up higher angle of engagement to affect the load capacity because of life weakening on carrier bearings involved. In fact, provided some certain promise, zero addenda modification (viz. X-zero) drive with minor teeth difference could also qualify for gearing conditions so as to reduce the complicacy of calculations and angle of engagement mentioned above. From investigating the relationships amongst the total teeth number of internal gear, difference of tooth number between internal and external gear, addendum coefficient and teeth profile interference criterion, the unique design characteristic about X–zero gear drive with minor teeth difference are outlined.

Parameterized Modeling and Virtual Prototype of Planetary Reducer

The three-dimensional parameterized model of the planetary reducer was established on the platform of Pro/E. Especially, the parameterized gear model was built through transforming the accurate equations of the involute and the tooth root transition curve into the expressions that can be identified by the Pro/E. Therefore, the accuracy of the model is relatively high and the method used in the paper can eliminate tooth interference effectively. Then, the three-dimensional assembly model for planetary reducer was obtained through the Virtual Assembly Technique and the Assembly Module in Pro/E. In brief, the method used in the paper has supplied a relatively accurate model for the dynamic analysis. At the same time, it can reduce dramatically research cycle and cost, and has supplied an effective development approach for the planetary reducer.

Calculating planetary gear transmission parameters for the reduction gears in worm centrifuges

Descriptions are given of the features and shortcomings of various geometrical calculations on evolvent gear transmissions for internal coupling, as used in worm centrifuge reduction gears. A scheme is proposed for calculating the tooth interference of the wheels by means of the Mathematica program.

Vertical bone volume in the paramedian palate of adolescents: A computed tomography study

The paramedian palate (PP) has been used as a host site for orthodontic implant anchorage. Available bone and interference of adjacent tooth roots must be considered in identifying the most appropriate locations for implantations in the PP. Cone-beam computed tomography (CBCT) scans (NewTom QR-DVT 9000; QR s.r.l., Verona, Italy) were acquired in 183 orthodontic patients (ages, 10-19 years). Views of the PP region were reconstructed at increments posterior from the incisive foramen, and measurements of bone height were made in each reconstruction laterally from the midline to describe the PP. At 4 mm posterior to the incisive foramen and 3 mm lateral to the midline, 93% of the male and 91% of the female subjects met the criterion for implantation. At 8 mm posterior to the incisive foramen and 3 mm lateral to the midline, 86% of the male and 58% of the female subjects met the criterion for implantation. The PP contains several valid implant host sites in adolescent patients. At 4 mm distal and 3 mm lateral to the incisive foreman, 93.2% of the boys and 91.9% of the girls had sufficient vertical bone depth to host a 3-mm implant with little practical tooth interference. CBCT allows accurate assessment of the entire volume of a proposed implant site.

A Novel Harmonic Drive With Pure Involute Tooth Gear Pair

Consider commercially available “harmonic drives” or “strain wave gearings” (all patented designs). The tooth profiles of the mating pairs of teeth of the noncircular (pitch curve) flex gear and circular (pitch circle) ring gears are nearly conjugate and noninvolute. Evidently none of them offers ideal gear kinematics. In this paper, we propose a new wave generator (or cam) to drive flex gears of harmonic drives with fully conjugate gear pairs of purely involute profiles. The cam profile is made of circular arcs at the two diametrically opposite contact zones and shifted elliptical curves for the other two zones. The geometric construction is done in such a way that tip interference is properly avoided for both engagement and disengagement with nominally stubbed or full depth tooth involute gears. We develop the theory of geometric and gearing conditions. We have also built a physical model in order to verify the geometry of tooth interference and other relevant gearing kinematics.