• Journal of Dental Anesthesia and Pain Medicine
• /
• v.21 no.2
• /
• pp.139-153
• /
• 2021

Background: In anesthetic techniques, touching bones can cause needle bending. Theoretically, a needle should support such deflection without fracturing. However, it is possible that a needle may fracture depending on the quality and type of needle used. This study evaluated the physical, chemical, and micromorphological characteristics of long and short dental anesthetic needles, as well as the mechanical properties of flexural load and bending resistance when needles are subjected to different bending angles. Methods: Long and short needles (30G, Jets, Misawa, Selekto, Terumo, Unoject and 27G, Dencojet, Injex, Jets, Misawa, Procare, Setoject XL, Terumo) were evaluated. Scanning electron microscopy was used to evaluate the needle bevels and energy-dispersive X-ray spectroscopy was used for the chemical analysis of needle compositions. Flexural loading and bending strength assessments were performed using a universal testing machine by bending the needles (n = 5) to angles of 30°, 60°, or 90°, or until fracture occurred. Results: The Injex 27G, Jets 27G, and Septoject XL 27G needles were all less than 30 mm in length. There were small percentage variations in the chemical compositions of the needles. Superior smoothness was observed for the Unoject 30G needle, which exhibited the highest fracture resistance at 60°. The Jets 30G needle exhibited greater resistance to fractures at 90°. The Procare 27G needle exhibited the highest load resistance to bending, followed by the Septoject XL 27G needle, and both needles were tied for the lowest fracture resistance. No needle fractured when bent to 30° or at less than three bends to 60° or 90°. Conclusions: Greater needle resistance to bending increases the probability of early fracturing. Thinner and shorter needles are more resistant than longer and thicker needles. Performing a single bend does not result in any significant risk of fracture or obliterate the lumen, allowing for the continued passage of anesthetic liquid.

• Tribology and Lubricants
• /
• v.36 no.1
• /
• pp.34-38
• /
• 2020

The powertrain of the waterjet system of a special-purpose vehicle makes use of the cardan shaft, which is composed of universal joints and shafts. These universal joints, composed of spiders and needle roller bearings, have to be designed with consideration for the bending and compressive stresses of the spiders and needle roller bearings, and the rating lives of the bearings. The bending and compressive stresses of the spider and bearing of a universal joint have been studied by many researchers. However, to design a universal joint effectively, overall consideration of the different specifications of needle roller bearings is necessary. In this study, the bending stresses of spiders and compressive stresses of needle roller bearings are calculated to design universal joints for powertrain cardan shafts with different roller diameters of bearing. Furthermore, the rating lives of the needle roller bearings are predicted using the calculated basic dynamic load ratings of the bearings. As a result, roller diameters less than 𝜙2.5 mm are found suitable through an analysis of the bending stress of the spider. All compressive stresses between spider and bearing, regardless of roller diameter, satisfy the requirements. Moreover, roller diameters of more than 𝜙2 mm are found suitable for the required rating life.

• Journal of Dental Anesthesia and Pain Medicine
• /
• v.23 no.5
• /
• pp.281-285
• /
• 2023

Background: Dentists bend needles prior to certain injections; however, there are concerns regarding needle fracture, lumen occlusion, and sharps handling. A previous study found that a 30-gauge needle fractures after four to nine 90° bends. This fatigue life study evaluated how many 90° bends a 30-gauge dental needle will sustain before fracture when bent using a needle guide. Methods: Two operators at Element Materials Technology, an independent testing, inspection, and certification company tested 48 30-gauge needles. After applying the needle guide, the operators bent the needle to a 90° angle and expressed the anesthetic from the tip. The needle was then bent back to a 0° angle, and the functionality was tested again. This process was repeated until the anesthetic failed to pass through the end of the needle due to fracture or obstruction. Each operator tested 24 needles (12 needles from each lot), and the number of sustained bends before the needle fracture was recorded. Results: The average number of sustained bends before needle failure was 40.33 (95% confidence interval = 37.41-43.26), with a minimum of 20, median of 40, and a maximum of 54. In each trial, the lumen remained patent until the needle fractured. The difference between the operators was statistically significant (P < 0.001). No significant differences in performance between needle lots were observed (P = 0.504). Conclusion: Our results suggest that using a needle guide increases the number of sustained bends before needle fracture (P < 0.000001) than those reported in previous studies. Future studies should further evaluate the use of needle guides with other needle types across a variety of operators. Furthermore, additional opportunities lie in exploring workplace safety considerations and clinical applications of anesthetic delivery using a bent needle.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 1998.10a
• /
• pp.171-175
• /
• 1998

This study was to estimate the strength of pine needle ash concrete using cement, natural aggregates and pine needle ash(PNA). The highest strength was achieved by 5% pine needle ash filled PNA concrete respectively. It was increased 6% by compressive strength, 15% by tensile strength and 13% by bending strength than that of the normal cement concrete, respectively.

• The Journal of the Korean dental association
• /
• v.44 no.2 s.441
• /
• pp.139-144
• /
• 2006

Local anesthesia is routine procedure in dental practices and has several complication. One of them, needle fracture is not uncommon in past, but rare in recent. The number of cases reported in the literature of broken needle in local anesthetic procedure has shown a marked decrease since the use of disposable spiral-constructed dental needle began. This complication results from lack of patient cooperation, inaccurate anesthetic technique, sudden movement of patient, error in the manufacturing procedure, use of short needle, and bending before use. Most common site is pterygomandibular space during inf. alveolar nerve block. In two patients, we removed broken needles under general anesthesia without complication. So we report cases with review of literatures.

• The Research Journal of the Costume Culture
• /
• v.21 no.6
• /
• pp.967-973
• /
• 2013

During high speed sewing, the needle thread is exposed to dynamic loading, short strike loading, inertia forces, friction, rubbing, force of check spring, bending, pressure, friction, impact, shock and thermal influence. The dynamic thread loading/tension alters throughout the stitch formation cycle and along its passage through the machine. The greatest tensile force occurs at the moment of stitch stretching, when the take up lever pulls for required thread length through the tension regulator. These stresses act on the thread repeatedly and the thread passes 50-80 times through the fabric, the needle eye and the bobbin case mechanism, before getting incorporated into the seam, which result in upto 40% loss in tensile strength of the sewing thread. This damage in the sewing thread adversely affects its processing and functional performance. In this paper, the contribution of dynamic loading, passage through needle and fabric, and bobbin thread interaction in the loss in tensile properties has been studied. It is observed that the loss in tensile properties occurs mainly due to the bobbin thread interaction. Dynamic loading due to the action of take up lever also causes substantial loss in tenacity and breaking elongation of cotton threads.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.42 no.1
• /
• pp.99-104
• /
• 2000

This study is performed to evaluate the physical and mechanical properties of pine needle ash (PNA) concrete. Materials used for this experiment are PNA, normal portland cement, natural fine and coarse aggregate. Test results show that the unit weights of PNA concrete are decreased 1 % ∼3% and the highest strength is achieved by 5% PNA filled PNA concrete. Compresive strength increased by 5% , tensile strength by 20% and bending strength by 15% as compared with those of the normla cement concrete , respectively. The highest ultrasonic pulse velicity and dynamic mudulus of elasticity are acheved by 5% PNA filled PNA concrete, which are similar to those of the normal cement concrete.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.34 no.1
• /
• pp.51-58
• /
• 2021

In this paper, a multi-scale finite element (FE) modeling methodology for three-dimensional (3D) needle-punched (NP) C/SiC with a complex microstructure is presented. The variations of the material properties induced by the needle-punching process and complex geometrical features could pose challenges when estimating the material behavior. For considering these features of composites, a 3D microscopic FE approach is introduced based on micro-CT technology to produce a 3D high fidelity FE model. The image processing techniques of micro-CT are utilized to generate discrete-gray images and reconstruct the high fidelity model. Furthermore, a subcell modeling technique is developed for the 3D NP C/SiC based on the high fidelity FE model to expand to the macro-scale structural problem. A numerical homogenization approach under periodic boundary conditions (PBCs) is employed to estimate the equivalent behavior of the high fidelity model and effective properties of subcell components, considering geometry continuity effects. For verification, proposed models compare excellently with experimental results for the mechanical behavior of tensile, shear, and bending under static loading conditions.

• Journal of Korea Foundry Society
• /
• v.22 no.6
• /
• pp.281-287
• /
• 2002

In order to investigate the variation of microstructure and property of the Electro-slag Remelted M2 steel, microstructure observation, hardness, and bending test were performed by using optical microscope. SEM/EDS, rockwell hardness tester, charpy impact tester and bending tester, respectively. It was revealed that the number of inclusions and content of gas elements(S, O, N) in M2 steel fabricated by ESR process decreased markedly compared to those of AIM. It seems to be due to refining effect of ESR process. The volume fraction of carbides in quenched and tempered specimens after austenitizing at 1150$^{\circ}C$ and 1240$^{\circ}C$ was measured. The volume fraction of grain boundary carbides were found to be similar for both specimens. However, The volume fraction of carbides in grain decreased with an increase of austenitizing temperature. When specimen was austenitized at 1150$^{\circ}C$, grain boundary carbides showed needle like morphology. But, the carbides were broken with an increase of austenitizing temperature. The specimen austenitized at 1240$^{\circ}C$ showed higher hardness and lower bending strength compared to that of 1150$^{\circ}C$. As expected, toughness increased with sub-zero quenching treatment.

• Journal of the Korean Ceramic Society
• /
• v.34 no.4
• /
• pp.380-386
• /
• 1997

The tribological properties of ceramics are very important in the application to engineering ceramic parts such as seal rings, pump parts, thread guides, and so on. In this study, the effects of graphite addition on the mechanical and tribological properties of alumina/graphite composites were investigated. The composites were prepared by the adding of graphite powder to the mixture of Al2O3, talc and calcium carbonate. Bending strength, water absorption, friction coefficient, the amount of worn out material at a certain time, and maximum surface roughness(Rmax) of the prepared composites were measured. Crystalline phases and microstructure were examined with XRD and SEM. The melt of Al2O3-CaO-MgO-SiO2 system was shown over 10 vol% graphite composition. As the amount of the graphite is increased, needle like crystals of mullite were formed and grown. We obtained the good properties of friction coefficients and wear resistance at the powder composition containing 15 vol% of graphite.