Oblique Teeth Research Articles

Investigation on the cavitation characteristic of a novel cylindrical rotational hydrodynamic cavitation reactor

Hydrodynamic cavitation reactors are of great promise for the applications of chemical process intensification and water treatment. In this work, a novel cylindrical rotational hydrodynamic cavitation reactor (CRHCR) with rectangular grooves and oblique tooth protrusions on the rotor surface was studied. The three-dimensional characterization of cavitation within the CRHCR was observed from the front and left views by the high-speed camera experiments. Interestingly, a new phenomenon of simultaneous formation of the attached cavitation and shear cavitation was found in the CRHCR. The synergistic effect of attached cavitation and shear cavitation contributes to the enhancement of the cavitation performance of CRHCR. In addition, the evolution of attached cavitation is explored. It is found that attached cavitation forms a trapezoidal-shaped cavitation cloud in the groove, which undergoes three various stages: incipient, development, and collapse. Finally, the pulsation frequency and cavitation intensity of shear cavitation in the chamber were investigated. The results show that the cavitation pulsation frequency is the same at the same rotational speed in the chamber near diverse oblique teeth. As the rotational speed increases, the cavitation pulsation frequency increases linearly. These findings in this paper are of great benefit to understanding the mechanism of the cavitation effect of CRHCR.

Healing of oblique tooth root fracture concomitant with coronal fragment extrusion in permanent dentition: A case report

Healing of oblique tooth root fracture concomitant with coronal fragment extrusion in permanent dentition: A case report

Improvements of tooth movement efficiency and torque control in expanding the arch with clear aligners: a finite element analysis.

Objectives: The purpose of this study was to analyze the effect of different movement strategies, embossment structures, and torque compensation of the aligner on tooth movement during arch expansion using clear aligners by finite element analysis. Methods: Models comprising the maxilla, dentition, periodontal ligament, and aligners were created and imported into a finite element analysis software. The tests were performed using the following: three orders of tooth movement (including alternating movement with the first premolar and first molar, whole movement with second premolar and first molar or premolars and first molar), four different shapes of embossment structures (ball, double ball, cuboid, cylinder, with 0.05, 0.1, 0.15-mm interference) and torque compensation (0°, 1°, 2°, 3°, 4°, and 5°). Results: The expansion of clear aligners caused the target tooth to move obliquely. Alternating movement resulted in higher movement efficiency with lower anchorage loss as compared with whole movement. Embossment increased the efficiency of crown movement but did not contribute positively to torque control. As the angle of compensation increased, the tendency of oblique tooth movement was gradually controlled; however, the movement efficiency decreased concurrently, and stress distribution on the periodontal ligament became more even. For each 1° increase in compensation, the torque per millimeter of the first premolar would decrease by 0.26°/mm, and the crown movement efficiency eliminate decreased by 4.32%. Conclusion: Alternating movement increases the efficiency of the arch expansion by the aligner and reduces anchorage loss. Torque compensation should be designed to enhance torque control in arch expansion using an aligner.

Sealing Behavior Research on the Radial Ferrofluid Seal Structure with Oblique Teeth

Considering various unstable factors when the large-diameter spindle operates at a high speed, such as eccentricity, centrifugal force, etc., the ordinary ferrofluid seal structures will show poor sealing performance. This paper proposes an axial-radial bidirectional ferrofluid seal structure with radial oblique teeth to improve the sealing performance. The pressure resistance of the radial ferrofluid seal structure in the magnetic circuit is theoretically analyzed. The magnetic flux distribution characteristic in the gap of the oblique teeth is studied by magnetic field simulation. According to the analysis results of the magnetic induction intensity, to obtain the larger theoretical pressure resistance, the optimal angle of oblique teeth is 77.87°, 64.28° and 62.81° under the radial seal structure with different gaps of 0.1 mm, 0.15 mm and 0.2 mm, respectively. In addition, simulation analysis is carried out to obtain the fluid pressure and velocity distribution of the radial ferrofluid seal structure with different oblique teeth angles. When the oblique teeth angle is small, the pressure drops and gas flow speeds in the ferrofluid area are all lower, and the pressure resistance is higher.

Research of the influence of axial displacement on the wear of hob milling tools

The need to increase productivity and cost-effectiveness of gear cutting of cylindrical gears with oblique teeth creates favorable conditions for the development of research in the field of tribology and the increasing application of tribological knowledge in industrial practice. Improving the gear cutting process by hob milling is important and useful for both gear manufacturers and hob milling tools manufacturers. Increasing productivity and increasing of the quality of serration are the basic directions of improving the process of gear cutting by hob milling. Technological parameters significantly affect the wear of cutters and taking into account the parameters for defining the economy of the process affect the achievement of optimal parameters of the cutting regimes. Based on experimental research, the paper presents an analysis of the influence of axial displacement, as one of the technological parameters, on the wear of hob milling tools in the gear cutting of cylindrical gears with oblique teeth.

Laminar flow heat transfer enhancement in square and rectangular channels having: (1) A wire-coil, axial and spiral corrugation combined with helical screw-tape with and without oblique teeth and a (2) spiral corrugation combined with twisted tapes with oblique teeth

Heat transfer enhancement is a vital area of research as it helps to design heat exchangers of reduced sizes and improved heat transfer rates. Thus, there is a pressing need for techniques which result in significantly increased heat transfer over and above increased pressure drop. In this paper, the benefits of different compound techniques using (1) wire-coil inserts and helical screw-tape inserts with oblique teeth, (2) wire-coil inserts and helical screw-tape inserts without oblique teeth, (3) spiral corrugation and helical screw-tape inserts without oblique teeth, (4) axial corrugation and helical screw-tape inserts without oblique teeth, and (5) spiral corrugation and twisted-tape inserts with oblique teeth were studied experimentally for laminar flow in a non-circular duct (aspect ratio = 1, 0.5 and 0.33). Servotherm medium oil with Prandtl number ranging from 430 to 530 was used as working fluid. The experiment was conducted for a uniform heat flux boundary condition. The effect of geometric parameters of the inserts such as wire-coil diameter, wire-coil helix angle, tooth angle and tooth horizontal length of the screw tape and the twisted tape, corrugation height and corrugation pitch, etc. on heat transfer and pressure drop characteristics was presented. The influence of duct geometry (aspect ratio) on Nusselt number and friction factor was also studied. Correlations for Nusselt number and friction factor were developed and a performance evaluation was done.

New combined heat transfer enhancement techniques used in laminar flow through non-circular ducts

The problem of heat transfer enhancement using different combinations of transverse ribs, transverse corrugations and twisted-tape insert with oblique teeth, twisted tape with centre clearance and helical screw-tape insert in square and rectangular channel was investigated. The study also involved the thermohydraulic performance of inserts in non-circular channels in the laminar regime. Non-circular channels having aspect ratios of 1, 0.5 and 0.33 were considered. The techniques used for heat transfer augmentation in the present study were and the problem was (1) transverse ribs with twisted tape with oblique teeth, (2) integral transverse corrugation and centre-cleared twisted-tape insert, (3) transverse rib and helical screw-tape insert, (4) axial ribs and centre-cleared twisted-tape insert and (5) integral transverse rib and centre-cleared twisted-tape insert. These combined fin geometry are supposedly important from possible heat transfer enhancement point of view. In the channels, the combined influence of insert geometry such as rib pitch, rib height, twist ratio of twisted tape, twisted tape tooth horizontal length and twisted tape tooth angle was studied. The experiment was carried out using Servotherm oil as the working fluid, which had a wide range of Prandtl number (430–530). Uniform heat flux boundary condition was used. The methods used in the experiment have been discussed in the text of the presentation. The important results of the experimental investigation showed that the thermohydraulic performance using a combination of inserts was better than that of bare ducts and that of the individual enhancement technique acting alone. Both the increase in pressure drop and heat transfer augmentation occurred due to the addition of inserts, but heat transfer enhancement dominated over the increase in pressure drop. Nusselt number and friction factor correlations have also been developed and are presented in this paper. The experimental program considered different fin arrangements with various parameters and therefore, it should be very helpful in designing heat exchangers of different shapes and sizes used for industrial purpose. It is concluded from the present investigation that 31–52 per cent increase in heat duty at constant pumping power and 25–36 per cent reduction in pumping power at constant heat duty are achievable. This is the novelty of the present work since no such study and the observations have been made earlier. These types of combined fin configurations have not been tried before. The findings are likely to have good impact in the industry.

Management of Sub-gingival Fracture of Tooth by Multi-disciplinary Approach

Dental trauma is commonly occur in children and may involve adult person also. In permanent dentition crown fracture is common and it may be uncomplicated or complicated. Complicated crown-root fractures require a multidisciplinary treatment modality for longterm success. Here we presented multidisciplinary treatment of a traumatized permanent maxillary incisor of a young male patient where oblique tooth fracture involved coronal pulp. As more than 50% of the crown and palatal coronal part of the root had been fractured and the tooth could not be properly isolated during endodontic procedure which is essential for success of root canal treatment. An intra-canal wire hook was cemented in the root canal and attached to another wire fixed to the adjacent teeth. With the help of elastic band attached with hook the fractured tooth fragment was extruded to create clinical crown. Finally, gingival re-contouring was performed to establish optimum biological width. At last, porcelain fused to metal crown was placed and the patient was comfortable both esthetically and functionally.International Journal of Human and Health Sciences Vol. 03 No. 03 July’19. Page: 165-168

Analysis of a dimensional tolerances’ series of 2PW-SE gear pumps using multi valued logical trees

Gear pumps of a prototype series 2PW-SEW belonging to II group were the research object. Wrocław University of Technology in co-operation with the company HYDROTOR S.A. designed the units. The experimental pump has been designed with taking into consideration technological possibilities of the company HYDROTOR S.A. The innovation of the prototype unit is based on using oblique gears with an involute tooth modified in the lower and upper part of the profile. The modification in the lower part was made using the so-called tooth root undercutting. Multivalent logic trees with designated rank of importance parameters structural/operational were used, considering the effect of tolerances construction. The area has been increased by cutting the oblique teeth. In order to determine the influence of the manufacturing technology on the level of the emitted noise, it has been decided to make gears using the shaving technology.

Diagnostic value of cone beam computed tomography for recognition of oblique root fractures: An in vitro study.

Diagnosis of tooth root fractures is based on radiographic examination, which is not reliable in the case of oblique root fractures. The aim of the study was to evaluate the efficacy of cone beam computed tomography (CBCT) imaging of oblique root fractures. Twenty-four bovine incisors were used in the study. They were randomly divided into 2 groups: an experimental group with artificially created oblique root fractures and a control group without fractures. The teeth underwent a CBCT evaluation with a CS 9300 cone-beam scanner (Carestream, Rochester, USA) using a 5 × 5 cm field of view with the resolution up to 90 μm, and a dental radiography. The specimens were examined by 2 observers with different job experience. In the CBCT scans, fracture lines were detected in 95.8% of cases (the 1st observer made a proper diagnosis in 100% of cases and the 2nd in 91.7%). Fracture lines were identified on radiographs in 33.3% of roots (the 1st observer was able to see the lines in 41.7% of cases and the 2nd in 25%). The inter-observer agreement was very high (the kappa coefficient for CBCT scans was 1.00 and 0.88 for radiographs). The best diagnostic value was recorded for contiguous slices. Cone beam computed tomography with a small field of view and high resolution significantly surpasses radiographs in effective imaging of oblique tooth root fractures and should be the method of choice in the diagnosis of these fractures.

Influence of crosshead speed on failure load and failure mode of restored maxillary premolars.

We analyzed the effect of the crosshead speed of an applied load on failure load and failure mode of restored human premolars. Fifty intact, noncarious human premolars were selected. Class II mesio-occlusodistal preparations were made with a water-cooled high-speed preparation machine, and the teeth were restored with composite resin. The specimens were divided into five groups (n = 10 each) and tested individually in a mechanical testing machine, in which a 6.0-mm-diameter steel cylinder was mounted to vary the crosshead speed: v0.5: 0.5 mm/min; v1: 1.0 mm/min; v2.5: 2.5 mm/min; v5: 5.0 mm/min; and v10: 10.0 mm/min. The cylinder contacted the facial and lingual ridges beyond the margins of the restorations. Peak load to fracture was measured for each specimen (N). The means were calculated and analyzed with one-way analysis of variance followed by Tukey's test (a = 0.05). The mean load at failure values were (N) as follows: v0.5, 769.4 ± 174.8; v1, 645.2 ± 115.7; v5, 614.3 ± 126.0; v2.5, 609.2 ± 208.1; and v10, 432.5 ± 136.9. The fracture modes were recorded on the basis of the degree of the tooth structural and restorative damage: (I) fracture of the restoration involving a small portion of the tooth; (II) fractures involving the coronal portion of the tooth with cohesive failure of the composite resin; (III) oblique tooth and restoration fracture with periodontal involvement; and (IV) vertical root and coronal fracture. Varying crosshead speeds of 0.5-5.0 mm/min did not influence the failure load of restored maxillary premolars; however, increasing the crosshead speed to 10 mm/min decreased the failure load values and the degree of tooth structural damage.

Laminar Flow Through a Circular Tube Having Transverse Ribs and Twisted Tapes

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral transverse rib roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral transverse rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Thermal and friction characteristics of laminar flow through a circular duct having helical screw-tape with oblique teeth inserts and wire coil inserts

Helical screw-tape inserts and wire coil inserts both individually are enhancement techniques. Naturally, therefore, it is worthwhile to try their combinations as a potential enhancement technique. The experimental friction factor and Nusselt number data for laminar flow through a circular duct having helical screw-tape and wire coil inserts have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the helical screw-tape inserts in combination with wire coil inserts perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of the fin parameter.

CBCT is valuable for diagnosis of tooth fracture.

PubMed, Embase, Web of Science, ProQuest Dissertations & Theses, CNKI and SIGLE databases. Two reviewers independently selected studies. Studies examining the diagnostic accuracy of CBCT for tooth fractures in vivo were considered. Only studies with a minimum of ten participants using a reference test of surgical exploration or extractions to establish the diagnosis of tooth fractures were included. Data abstraction was carried out independently by two reviewers and study quality assessed using the Quality Assessment of Studies of Diagnostic Accuracy-2 (QUADAS-2) tool. The main study outcomes were sensitivity, specificity, positive likelihood ratio (LR), negative LR and summary receiver operating characteristic (SROC). Twelve studies were included in a meta-analysis. The pooled sensitivity was 0.92 (95% CI=0.89-0.94) and pooled specificity 0.85 (95% CI=0.75-0.92). The pooled positive and negative likelihood ratios were 5.68 (95% CI=3.42-9.45) and 0.13 (95% CI=0.09-0.18) respectively. The summary receiver operating characteristic was 0.94 (95% CI=0.90-0.98). The pooled prevalence of tooth fractures in patients with clinically suspected but periapical-radiography-undetected tooth fractures was 91% (95% CI = 83%-97%). Positive and negative predictive values were 0.98 and 0.43 (subgroup analysis: 0.98 and 0.28 for endodontically treated teeth; 0.99 and 0.77 for non endodontically treated teeth). We suggest that CBCT has a high diagnostic accuracy for tooth fractures and could be used in clinical settings. We can be very confident with positive test results but should be very cautious with negative test results. For patients with negative results, close follow-ups are recommended. The diagnostic accuracy of CBCT is similar among different types of tooth fractures, which should be interpreted with caution due to unavailability of data for subgroup analysis on horizontal and oblique tooth fractures.

Experimental investigation of laminar flow of viscous oil through a circular tube having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral axial corrugation roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Laminar fluid flow and heat transfer through a circular tube having spiral ribs and twisted tapes

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral spiral rib roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral spiral rib roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Experimental investigation of laminar flow of viscous oil through a circular tube having integral spiral corrugation roughness and fitted with twisted tapes with oblique teeth

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral spiral corrugation roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral spiral corrugation roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Design Refinement of Rolling Drill bit With Oblique-Tooth Fitting

Results of design refinement of a rolling drill bit fitted with oblique teeth are presented. Geometries of oblique-tooth fittings for drill bits with central and bottom jet flushing are developed. The new alternative designs of rolling drill bits with oblique-tooth fittings, which are described in this paper, make it possible to increase the cutting and mechanical drilling rate owing to more rational geometry of the fitting for the rolling cutter in combination with an effective flushing scheme.

Taxonomical study on a sample of pulmonates from Santa Maria da Vitória, Bahia, Brazil, with description of a new genus and four new species (Mollusca: Orthalicidae and Megalobulimidae)

A sample of Pulmonata collected in Santa Maria da Vitória, interior of Bahia, Brazil, in Caatinga semi-arid environment, is studied taxonomically. From the five species, four are revealed as new, including a new genus. The new taxa are the Bulimulidae (1) Kora corallina gen. et sp. n. characterized by the elongated shell with aperture somewhat dislocated from the shell axis, and an oblique tooth in middle level of inner lip; (2) Spixia coltrorum, mainly characterized by an uneven spire, delicate sculpture and peristome with 4 equidistant teeth; (3) Anostoma tessa, mainly characterized by a broad spire and well-developed anal canal; and the Megalobulimidae (4) Megalobulimus amandus, mainly characterized by pointed protoconch sculptured by dense quantity of axial cords. Rhinus suturalis is the only previously known species, but its geographic distribution is expanded southwards to Bahia state. A discussion with respect to necessity for improving the study on the malacofauna from the interior region of the Brazilian Northeast and the importance for preservation of the Caatinga biome is also provided.

Thermohydraulics of Laminar Flow Through Rectangular and Square Ducts With Axial Corrugation Roughness and Twisted Tapes With Oblique Teeth

The heat transfer and the pressure drop characteristics of laminar flow of viscous oil (175<Pr<538) through rectangular and square ducts with combined internal axial corrugations on all the surfaces of the ducts and with twisted-tape inserts with and without oblique teeth have been studied experimentally. The axial corrugations in combination with both twisted tapes with and without oblique teeth have been found to perform better than either axial corrugations or twisted-tape inserts acting alone. The heat transfer and the pressure drop measurements have been taken in separate test sections. Heat transfer tests were carried out in electrically heated stainless steel ducts incorporating uniform wall heat flux boundary conditions. Pressure drop tests were carried out in acrylic ducts. The flow friction and thermal characteristics are governed by duct aspect ratio, corrugation angle, corrugation pitch, twist ratio, space ratio, length, tooth horizontal length and tooth angle of the twisted tapes, Reynolds number, and Prandtl number. Correlations developed for friction factor and Nusselt number have predicted the experimental data satisfactorily. The performance of the geometry under investigation has been evaluated. It has been found that based on constant pumping power, up to 45% heat duty increase occurs for the combined axial corrugation and twisted-tape insert case compared with the individual axial corrugation and twisted-tape insert cases in the measured experimental parameters space. On the constant heat duty basis, the pumping power has been reduced up to 30% for the combined enhancement geometry than the individual enhancement geometries.