Groove Location Research Articles

NUMERICAL STUDY OF GRADUAL CHANGE IN SHAFT DIAMETER AND RELIEF GROOVE RADIUS ON STRESS CONCENTRATION FACTOR

The purpose of this work is to investigate the effect of relief groove radius and the taper in gradual diameter change of shaft on stress concentration factors. Finite element analysis was used to conduct theoretical research in order to reduce the maximum value of stress in stepped shafts. In comparison based on a straight shaft without relief groove, the results show the decrease of taper angle has a significant effect in decrease the values of stress concentration factors. On the other hand, the increase of location of relief grooves from shaft shoulder tends to increase the stress concentration factors values, especially at high taper angle.

Numerical study on effect of design parameters of the single-circumferential groove on tip leakage flow reduction in a transonic turbine

In order to investigate the impact of design parameters (depth, width, and location) of the single-circumferential groove (SCG) on tip leakage flow (TLF) reduction in a transonic turbine stage, a systematic investigation was conducted by high-precision numerical simulation method. The numerical results show that the introduction of SCG could improve the stage efficiency (η) of turbine significantly. The optimal design parameters of depth coefficient (ζ), width (W), and location (L) were ζ = 3, W = W3, and L = 20%Cax (where Cax denotes the axial chord of the blade), which could reduce tip clearance leakage rate (m*) by 28.9% and improve the η by 0.56%. The implementation of flow field display methods reveals that the introduction of SCG influences the formation and development of the vortex system at the rotor tip region. The circumferential groove vortex (CGV), induced by SCG, divided the tip leakage vortex (TLV) into two segments TLV_1 and TLV_2 due to its blocking effect. TLV_1 interacted with the passage vortex (PV) and depress the strength of PV. Meantime, TLV_2 would regenerate from the trailing edge of SCG, due to its limited development range and insufficient growth, the strength and scale of TLV_2 were weakened. Given that the TLF passing through SCG flows in an opposite direction to the original TLF, the SCG at appropriate location could lead to a fact that the net flow rate of the leakage flow reached the minimum value, thereby considerably reducing the m* and flow loss caused by TLF.

Numerical simulation of the effect of interface morphology on the fracture behavior of bi-material Brazilian disks

As the most fragile component in a bi-material structures, the performance of rock-concrete interface will greatly affect the stability and durability of the whole structure. To investigate the influence of interface morphology on the interface bearing capacity and fracture characteristics of bi-material Brazilian disks, the sandstone-concrete bi-material Brazilian disk is taken as the research object, a series of sandstone-concrete bi-material Brazilian disks with interfaces of different groove widths, depths and spacings are simulated based on the cohesive zone model (CZM) method in this paper, and the effects of loading angle and location of groove interfaces on the fracture behavior are also investigated, the loading rate of all models is 0.1 mm/min. The loading angle is the main factor affecting the fracture patterns of the bi-material Brazilian disks. The loading angle increases from 0° to 90°, and the failure patterns can be divided into sawtooth fracture along the groove, mixed mode of sawtooth fracture along the groove and tensile fracture of the matrix, and tensile fracture of the matrix. The interface is the main bearing part at small loading angles, and when the loading angle exceeds 30°, the matrix is the main bearing part, and at this time, the morphology of the interface has little influence on the failure patterns and bearing performances of the specimens. The groove interface significantly improves the bearing capacity of the interface, in which the groove width has the greatest influence on the bearing capacity of the interface, and the groove spacing affects the location of crack propagation along the sawtooth (rock sawtooth or concrete sawtooth). The location of the groove interface affects the crack propagation mode at the interface, and this study mainly presents three cracking modes: failure along the rock sawtooth, failure along the concrete sawtooth and the combined failure of the rock sawtooth and the concrete sawtooth.

Reducing the condensing flow effects on the steam turbine blades through modified design geometry

Nowadays, a large part of energy is provided by steam turbines; thus, increasing the efficiency and improving the steam turbines performance are of special importance. The presence of the liquid phase in the low-pressure stage of the steam turbine can cause energy loss, efficiency drop, and erosion/corrosion problems; therefore, one of the essential issues is to identify wet steam flow and try to reduce condensation loss. In order to decrease the liquid fraction, the drainage groove technique can be applied. The drainage groove sucks the water droplets from the turbine blade surface and drains them into the condenser. In this study, the effect of the drainage groove location on the surface of steam turbine blades has been investigated on the condensation, droplet radius, inlet mass flow, erosion rate, liquid drainage ratio, condensation losses, and total drainage ratio. For modeling the condensing flow, the Eulerian–Eulerian approach has been applied. The results show that the location of the drainage groove affects the groove performance and flow pattern in the turbine blade. In the selected drainage, the liquid drainage ratio, condensation losses, and erosion rate are reduced by 7.6%, 12%, and 88%, respectively, compared with the no-drainage groove case. Also, the total drainage ratio is 7.2% in the selected drainage. The outcomes of the present work have been a major step forward in the techniques having a great influence on the lifetime, repair and maintenance, and the output power of steam power generation facilities.

Numerical study of location and depth of rectangular grooves on the turbulent heat transfer performance and characteristics of CuO-water nanofluid flow

This current work expresses numerical simulation of forced turbulent flow convection in a grooved cylinder. Rectangular grooves with a spacing of A = 1, A = 1.1, and A = 1.3, and groove depth to cylinder diameter of e/D = 0.1 and 0.2 were considered. This research concentrates on the effect of groove depth, location of the grooves and CuO nanoparticles on the heat transfer for Reynolds numbers 10000, 12,500, 15,000 and 17,500 in volume fractions of 0, 1, 2, 3 and 4% of nanoparticles. Results show that grooves improve heat transfer. This behavior at a lower A ratio results in a significant Nu number increase so that the highest Nu number occurs for A ratio of 1, 1.1 and 1.3. Increasing e/D ratio, due to increasing the channel section in this area, results in loss of velocity and dissipation of flow momentum, resulting in lower convective heat transfer and lower Nu number. Changing the pitch for e/D = 0.1 results in a 1.1 to 1.6 times increase of Nu number compared with the smooth channel, and for e/D = 0.2 this value is 1.1–1.5 times the smooth channel for similar Re, φ and geometry. Changing groove pitch at e/D = 0.1 results in a 2.1–2.9 times increase in friction factor compared with the smooth channel in similar conditions. For e/D = 0.2, this increase is 1.8–2.8 times the smooth channel. In low Re, the thermal performance is higher than in higher velocities. This is because the grooved channel acts as a smooth channel at high Re, and the average Nu does not have significant growth.

Numerical investigation of flow past a circular cylinder modified with a single groove at low Reynolds number

Flow past a circular cylinder modified by grooves is one of the passive control techniques to control the drag and lift forces. The presence of grooves tends to reduce the hydrodynamic drag and lift. The aim of this work was to numerically investigate the influence of a single groove modification on a circular cylinder and how it was impacting the hydrodynamic coefficients based on its position and shape at low Reynolds numbers. Three types of grooves were considered, namely, dimple, square, and triangular, with identical width and depth which is 0.1 times the diameter. The Reynolds numbers considered were 100, 150, and 200. The computational domain was set to a blockage ratio of 0.01 after carrying out a detailed domain independence test. It was observed that the drag and lift reduction was maximum at groove location 90° with the decrements being more for the square groove shape. The viscous drag showed a decrease in its values for all the groove positions located on the flow-facing side of the cylinder; however, the pressure drag showed an increment in its values for these groove locations, and these increments were relative of larger magnitudes, thus influencing a net increase in the total mean drag when compared to the smooth case; this was evident at groove locations 120° and 150°. The vorticity patterns for the grooves located on the front side showed large irregularities in magnitude between the anticlockwise and the clockwise vortices with the groove side vortices being of larger magnitudes, and for the wake side, the irregularities were negligible. The coefficient of pressure and separation angles were also investigated. The CP vs θ plots showed discontinuity at groove locations with abrupt variations at the front face of the cylinder; for the wake side grooves, these discontinuities were low and almost coincided with the CP vs θ plots of the smooth cylinder. The grooves located at 90° showed a delay in separation and at 60° the boundary layer tends to detach earlier.

Multi-objective optimization of supercooled vapor suction for decreasing the nano-water droplets in the steam turbine blade

Nowadays, decreasing the losses in industrial equipment as well as increasing their lifetime are of special importance. A steam turbine is one of the essential equipment in power plants. Due to the high prices of steam turbines, the issues of loss decrease and maintenance are crucial. One of the remarkable problems in the last stage of the steam turbine is the two-phase flow which leads to efficiency reduction and mechanical damage to the turbine blades. One of the techniques for decreasing the liquid phase in the steam turbines is the drainage groove. The innovation of the present paper is utilizing the drainage groove for supercooled vapor suction. Then, through optimization of the drainage groove, attempts are made to decrease the condensation losses, erosion rate, and the entropy generated in the steam turbine blade. To do this, the multi-objective optimization method of TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) is used. The optimization is done on the variables of the drainage groove (location, angle, width, and the pressure of drainage grooves). Based on the results, the optimized status is as follows: location 3, angle 90, width 0.06, and drainage pressure 80 kPa. In this status, condensation loss and erosion rate decreased by 5% and 62%, respectively, the entropy generated increases up to 1.03%, and the liquid drainage ratio and total drainage ratio are 3.22% and 3.8%.

Effect of Spanwise Semicircular Groove on NACA 0012 Airfoil

The efficiency of an airfoil can be improved by adjusting its surface. CFD software was used to investigate a 2D airfoil with and without a spanwise semicircular groove on the upper surface. NACA0012 airfoils with and without grooves were analyzed using the k-ω turbulence model. The lift and drag coefficients were used to compared. To investigate the effect of groove location on airfoil efficiency, a groove was added in various locations and compared to a smooth airfoil. The flow velocity remained constant at 20 m/s at all angles of attack (AOA). According to this study, which used ANSYS software to simulate it numerically, the presence of a semicircular groove affects the aerodynamics of the airfoil, resulting in an improved efficiency coefficient of lift, which has risen by 2.25 percent, while the drag coefficient has decreased by 4.32 percent.

Stress release mechanism of deep bottom hole rock by ultra-high-pressure water jet slotting

To solve the problems of rock strength increase caused by high in-situ stress, the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed. The stress conditions of bottom hole rock, before and after slotting are analyzed and the stress release mechanism of slotting is clarified. The results show that the stress release by slotting is due to the coupling of three factors: the relief of horizontal stress, the stress concentration zone distancing away from the cutting face, and the increase of pore pressure caused by rock mass expansion; The stress concentration increases the effective stress of rock along the radial distance from 0.6R to 1R (R is the radius of the well), and the presence of groove completely releases the stress, it also allows the stress concentration zone to be pushed away from the cutting face, while significantly lowering the value of stresses in the area the drilling bit acting, the maximum stress release efficiency can reach 80%. The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall. With the increase of groove depth, the stress release efficiency is significantly increased, and the release range of effective stress is enlarged along the axial direction. Therefore, the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.

Prevalence and correlation of C-shaped root canals of mandibular premolars and molars in Eastern Chinese individuals

The aim of this study was to investigate the prevalence, correlation, and differences of C-shaped root canals (CSRCs) morphology in permanent mandibular premolars and molars in Eastern Chinese individuals using cone-beam computed tomography (CBCT). A total of 8000 mandibular first premolars (MFPs), mandibular second premolars (MSPs), mandibular first molars (MFMs), and mandibular second molars (MSMs) CBCT images from 1000 patients (692 females and 308 males) were collected. The prevalence, correlation, bilateral/unilateral presence, the morphology of CSRCs, level of canal bifurcation, gender differences, and location of radicular grooves (RGs) were evaluated. The prevalence of CSRCs in MFPs, MSPs, MFMs and MSMs were 10.25%, 0.25%, 0.55% and 47.05%, respectively. The prevalence of CSRCs in MFPs of males was higher than that in females, while the prevalence of CSRCs in MSMs of females was higher than that in males (P < 0.05). The bilateral symmetry presence of CSRCs in MSMs was significant but not in MFPs, MSPs, and MFMs. RGs were predominantly found on the mesiolingual (ML) surface of premolars and the lingual surface of molars. There was a high prevalence of CSRCs in MFPs and MSMs in the Eastern Chinese population, but there was no correlation. The prevalence of CSRCs in MFPs and MSMs differ significantly by gender (P < 0.05).

Impact of grooved cylinder on heat transfer by natural convection in cylindrical geometry

The current study reports a numerical analysis of a two-dimensional steady-state natural convection heat transfer from grooved heated cylinder for laminar flow regime. Two groove shapes are investigated in this work: circular and triangular groove. Simulations were carried out by varying the groove location, radius ratio f from 0.1 to 1, and the Rayleigh number over the range [103–106]. The thermal and dynamic behaviors are carefully analyzed and compared to the case of non-grooved cylinder (model 0). It is found that the heat transfer rate rises up with the increase of Rayleigh number. In addition, the groove locations φ = −90, and 80° provide the lowest heat transfer rate. A decrease of 9.4% in the heat transfer rate is detected for the case of triangular groove with f = 0.7 and Ra = 105. On the other hand, the highest heat transfer rate is provided at a position φ = −45° and 45° for f &gt; 0.65. For these last groove locations, lower f present optimal configurations to accumulate heat on the cylinder. In fact, circular grooved cylinder with f = 0.1 decreases the heat loss by 9.3% and 12.4% for the locations φ = −45° and 45°, respectively compared to model 0. These results would be useful for engineering applications that are interested in the accumulation or transfer of heat through cylindrical ducts.

Palatinal Oluk, Sırt ve Köprü Formasyonlarının Morfolojik ve Morfometrik Analizi: Bir Konik Işınlı Bilgisayarlı Tomografi Çalışması

Background: The study aims to provide information on the location and morphology of the greater palatine groove, crest, and bridge in the hard palate and to improve awareness of these structures. Methods: Two hundred cone beam computed tomography (CBCT) images were randomly selected and the existence of the groove/crest/bridge structures was evaluated in the upper first and second molar regions, regardless of dental situations (dentate or edentulous). The grooves were classified as flat (&amp;lt;1.5 mm), shallow (from 1.5 to 3 mm), and deep (&amp;gt; 3 mm). The presence and types of groove were recorded. All data were assessed according to different age groups and sex. Results: Of the 200 images evaluated, 163 individuals (81.5%) had at least one groove and only 37 (18.5%) had no groove. A total of 737 grooves were detected and the mean depth of the grooves was 2.19±1 mm. The frequency of grooves was significantly higher in dentate regions (p&amp;lt;0.05). In the first and second molar regions, 185 sites (46.25%) and 231 sites (57.75%) had at least one groove, respectively. The most common type was shallow groove (53.18%, 392/737). The higher mean values of groove depth were in the 61-70 and 71-86 years’ age groups. Conclusion: Palatal groove is not a rare anatomic condition. Physicians should be aware of this structure to prevent damage to the neurovascular structures contained in grooves during surgical procedures in related areas.

TOPOGRAPHY-ANATOMICAL VARIABILITY OF THE MYLO-HYOID NERVE IN THE SIDE OF THE LOWER JAW

The article is devoted to the study of individual- anatomical features of the location of the mylohyoid groove, where the mylohyoid nerve lies, in the lateral part of the lower jaws of people with diff erent face shapes. For this purpose, craniometric studies were performed on 32 natural human skulls from the anatomical museum fund and on 60 CT images of patients’ skulls in 3-D reconstruction. The types of structure of the facial department of the skull were determined. The location features of the mylohyoid groove were determined in them on the lateral parts of the lower jaws, and bone holes were searched on their lingual side. Craniometric studies have shown that at the level of the dental alveoli of the second and third molars of the mylohyoid groove is located 20.7±0.4 mm below the upper edge of the lower jaw on mesoprosopic skulls. In leptoprosopic skulls this distance was greater – 23.6±0.8 mm, and in hameprozops, respectively, less – 18.3±0.6 mm. Bone holes on the inner (lingual) surface of the lateral parts of the lower jaws were found in 20 skulls (21.7%). Their number varied from one to three. They were most often found on skulls with a leptoprosopic form of the facial skeleton – in 11 cases. Samples of the lower jaws predominated (13 cases) in which one hole was observed at the level of the top of the roots of the fi rst lower molars.

An experimental study on flexural performance of RC beams strengthened by NSM technique using GFRP strips for a resilient infrastructure system

Near surface mounted method (NSM) is an emerging technique with wider scope in repair and rehabilitation. In this method as lesser repair material is used and as FRP is placed inside grooves it offers higher serviceability, resistance to corrosion, higher impact damage resistance and fire resistance there by providing higher long-term economy. This method of strengthening avoids adverse environmental impacts, interruptions to service therefore considerable savings in time and cost. Hence, NSM technique helps in building resilience into infrastructure system. This paper is to present the experimental work on enhancing flexural performance of reinforced concrete beams by implementing NSM method. The side near-surface mounted (S-NSM) is an alternative method used for applying fibre reinforced polymer (FRP) flexural strengthening on reinforced concrete (RC) beams as in practical case the bottom face of the beam may be some times inaccessible. The S-NSM method places the FRP grooves at the sides of the beam on either side, rather than at the bottom in the normal near surface mounted (NSM) method. The present study is carried out on the use of NSM for strengthening of RC deficient beam designed for 30kN with NSM composite material namely glass fibre reinforced polymer (GFRP) strips as reinforcement. The experimental work included control specimen and strengthened beams at different locations and orientations of GFRP that is both bottom NSM and side NSM method (both horizontal and vertical orientation of strips) are studied and these beams are subjected to two point bending flexural test. The effect of groove location, crack pattern, deflection at midspan and quarter span and also different modes of failure are the characteristics studied based on results obtained.

Canal configuration and root morphology of mandibular premolars using cone-beam computed tomography in a Korean population.

This study aimed to investigate the anatomy of mandibular premolars from two perspectives-the canal configuration and radicular grooves-using cone-beam computed tomography (CBCT) in a large Korean population. CBCT images of mandibles acquired from March 2018 to December 2019 for dental treatment were randomly selected. In each image, the root canal of premolars was classified into 8 types according to the canal merging or diverging pattern and the number of apical foramens. The presence and the location of radicular grooves were also assessed. Statistical analysis was performed. A total of 1463 first and 1448s premolars from 732 patients (390 males, 342 females, mean age of 36.1years) were evaluated. A single canal with one foramen predominated in both first (85.7%) and second (99.5%) premolars, while complete or partial multi-canals accounted for 14.3% and 0.5% of first and second premolars, respectively. The prevalence of radicular grooves was significantly higher in first premolars (13.2%) than in second premolars (0.5%) and in males (4.3%, n = 119) than in females (2.5%, n = 73). Although most premolars were complete single canals, the first premolars showed a relatively higher number of complex canals compared to the second premolar. In addition, radicular grooves in mandibular premolars were significantly more common in male patients. When planning the endodontic treatment of mandibular premolars, clinicians should be aware of their morphologic complexity, especially in the first premolar of male patients.

Effect of Circumferential Single Casing Groove Location on the Flow Stability under Tip-Clearance Effect in a Transonic Axial Flow Compressor Rotor

Numerical simulations have been performed to study the effect of the circumferential single-grooved casing treatment (CT) at multiple locations on the tip-flow stability and the corresponding control mechanism at three tip-clearance-size (TCS) schemes in a transonic axial flow compressor rotor. The results show that the CT is more efficient when its groove is located from 10% to 40% tip axial chord, and G2 (located at near 20% tip axial chord) is the best CT scheme in terms of stall-margin improvement for the three TCS schemes. For effective CTs, the tip-leakage-flow (TLF) intensity, entropy generation and tip-flow blockage are reduced, which makes the interface between TLF and mainstream move downstream. A quantitative analysis of the relative inlet flow angle indicates that the reduction of flow incidence angle is not necessary to improve the flow stability for this transonic rotor. The control mechanism may be different for different TCS schemes due to the distinction of the stall inception process. For a better application of CT, the blade tip profile should be further modified by using an optimization method to adjust the shock position and strength during the design of a more efficient CT.

Numerical investigation on transient and steady phase change heat transfer in the evaporator of a loop heat pipe

The dynamic evolution of vapor-liquid distribution in a porous wick coupled with the heat conduction in the evaporator casing of a loop heat pipe is numerically solved. The mathematical model is validated based on the experimental results issued from the literature. Both the transient and steady-state thermal behaviors of the evaporator are focused on, with the self-adjusting ability, evaporator temperature, thermal resistance, and parasitic heat leakage analysis as the evaluation indexes. The gradual invasion of the vapor region into the wick over time and the robust response of the evaporator temperature to varying heat loads are tracked. Additionally, the steady-state performance is explored to optimize the structural parameters, namely, the location of grooves, wick material and porosity, casing material, and fin ratio, through which the specific influences of each parameter are figured out. It is found that locating grooves in wick yields a 7.63°C lower evaporator temperature and a more uniform temperature distribution on the evaporator with a difference of 0.75°C than in casing at 140 W. Additionally, a 0.9 mm thick nickel layer with a porosity of 0.4 combined with a 4.1 mm nickel stainless steel layer with a porosity of 0.75 constitutes an optimized layered wick, which exhibits a 7.04°C lower evaporator temperature and a 0.05°C/W smaller thermal resistance than a single-structured stainless steel wick with a porosity of 0.75. Considering the heat transfer and flow pressure drop, the counterbalanced fin ratio range of 0.5~0.6 and the better thermal performance of copper casing are identified. The numerical results are expected to provide references for the evaporator structure optimization, laying a solid foundation for applying loop heat pipes to thermal control fields.

Single and Multiple Circumferential Casing Groove for Stall Margin Improvement in a Transonic Axial Compressor

Abstract The stability limit of a tip-stalling axial compressor is sensitive to the magnitude of the near-casing blockage. In transonic compressors, the presence of the passage shock could be a major cause for the blockage. Identification and elimination of this blockage could be a key to improving the stability limit of the compressor. In this article, using numerical simulation, the near-casing blockage within the transonic rotor, NASA Rotor 37, is quantified using a blockage parameter. For a smooth casing, the blockage at conditions near stall is maximum at about 20% of the tip axial chord downstream of the tip leading edge. This maximum blockage location is found to be consistent with the location of the passage shock–tip leakage vortex interaction. A datum single casing groove design that minimizes the peak blockage is found through an optimization approach. The stall margin improvement of the datum casing groove is about 0.6% with a negligible efficiency penalty. Furthermore, the location of the casing groove is varied upstream and downstream of the datum location. It is shown that the stability limit of the compressor is best improved when the blockage is reduced upstream of the peak blockage location. This article also discusses the prospects of a multigroove casing configuration.

Analysis of the water flow inside tire grooves of a rolling car using refraction particle image velocimetry

In order to better understand the hydroplaning phenomenon, local velocity measurements of water flow are performed inside the tire grooves of a real car rolling through a water puddle. Velocity fields are obtained by combining refraction Particle Image Velocimetry (r-PIV) illumination, seeding fluorescent particles, and either the classical two dimensional two components or the two dimensional three components stereoscopic recording arrangements. The presence of some bubble columns inside the grooves is highlighted by separate visualization using the fluorescent contrast technique evidencing two phase flow characteristics. A simple predictive model is proposed supporting the r-PIV analysis. It provides useful information to adjust the focusing distance and to understand the effect of the bubble column presence on the recorded r-PIV images, especially for the seeding particles located in the upper part of the grooves, as fluorescent light is attenuated by the bubbles. Also, the predictions provided by the model are compatible with the measurements. The velocity fields inside the grooves are analyzed using ensemble averaging performed over a set of independent snapshots, recorded with the same operating parameters. The variability of the longitudinal velocity distribution measured in a groove for several independent runs is explained by different mechanisms, like the random position of fluorescent seeding particles at various heights of the groove, the hydrodynamic interactions between longitudinal and transverse grooves, and the random location of the transverse grooves from one run to another. Three velocity components in cross sections of the longitudinal grooves are obtained using the stereoscopic arrangement. They are compatible with the presence of some longitudinal vortices assumed in the literature. The number of vortices is shown to be dependent on the aspect ratio characterizing a groove's rectangular cross section. We demonstrate, from measurements performed for several car velocities, that the velocity distribution inside longitudinal grooves shows self-similarity when using specific dimensionless length and velocity scales. Hydrodynamic interactions between longitudinal and transverse grooves are discussed on the basis of a mass budget; a fluid/structure interaction mechanism is proposed in order to correlate the overall direction of the flow in a transverse groove with its location inside the contact zone. Finally, some physical mechanisms are suggested for the birth of longitudinal vortices.

Mandibular second molars' C-shaped canal frequency in the Pakistani subpopulation: A retrospective cone-beam computed tomography clinical study

Introduction: The adequate knowledge of the canal configuration can improve the quality and prognosis of endodontic treatment. The aim of the study was to determine the frequency of C-shaped root canal in the mandibular permanent second molars among a Pakistani subpopulation sample by utilizing cone-beam computed tomography images. Materials and Methods: Cone-beam computed tomographic images of 360 patients with 720 mandibular second molars were analyzed for the presence of C-shaped canal configuration. The root canal system was classified according to Fan's classification at three distinct levels. Unilateral or bilateral presence of C-shaped root canals and the location of the longitudinal groove were assessed. Moreover, the correlation of frequency of C-shaped canal with the gender was measured using the Chi-square test. The data were analyzed using SPSS version 23. Results: Of 720 mandibular second molars of 360 patients, 10% of teeth were found to have C-shaped canals in 48 patients. The most commonly noted C-shaped canal configurations in the coronal and middle third were C1 (41.7%) and C3 (37.5%), respectively, whereas C2 (33.3%) and C4 (33.3%) configurations were commonly found in the apical third. Twenty-four of 48 patients had bilateral C-shaped root canals. Overall, 37.5% of the teeth were right-sided teeth and 62.5% were left-sided teeth. The frequency of C-shaped canals was significantly higher in females as compared to males, 15.6% and 4.2%, respectively (P = 0.03). The longitudinal groove was most commonly located on the lingual surface (66.7%). Conclusions: The frequency of C-shaped canal configuration in the Pakistani subpopulation was 10% in the mandibular second molar teeth.