Thread Pitch Research Articles

An automatic measuring method and system using laser triangulation scanning for the parameters of a screw thread

An automatic non-contact measuring system for extracting the parameters of a screw thread was developed. It was integrated with a laser-based measuring unit for the longitudinal section of the thread profile and the dual-axis moving stage position system for the movement of the undetected object. Firstly, data points from the thread profile were collected by the measuring system, the non-uniform rational B-spline curve (NURBS) method with the minimal error constraints was used to carry out the fitting of the measured data and data partitioning was performed. Secondly, according to the processed data, the parameters, such as thread pitch, pitch diameter and half of thread angle, can be calculated. Thirdly, the errors were analyzed for the proposed system. Finally, the proposed system and method were verified for their good performance with acceptable accuracy and reliability. Compared with existing measurement methods, the designed non-contact optical measuring system was capable of measuring the parameters of the internal thread which is no less than the M4 and external thread with required accuracy.

Influence of thread pitch, helix angle, and compactness on micromotion of immediately loaded implants in three types of bone quality: a three-dimensional finite element analysis.

This study investigated the influence of thread pitch, helix angle, and compactness on micromotion in immediately loaded implants in bone of varying density (D2, D3, and D4). Five models of the three-dimensional finite element (0.8 mm pitch, 1.6 mm pitch, 2.4 mm pitch, double-threaded, and triple-threaded implants) in three types of bone were created using Pro/E, Hypermesh, and ABAQUS software. The study had three groups: Group 1, different pitches (Pitch Group); Group 2, same compactness but different helix angles (Angle Group); and Group 3, same helix angle but different compactness (Compact Group). Implant micromotion was assessed as the comprehensive relative displacement. We found that vertical relative displacement was affected by thread pitch, helix angle, and compactness. Under vertical loading, displacement was positively correlated with thread pitch and helix angle but negatively with compactness. Under horizontal loading in D2, the influence of pitch, helix angle, and compactness on implant stability was limited; however, in D3 and D4, the influence of pitch, helix angle, and compactness on implant stability is increased. The additional evidence was provided that trabecular bone density has less effect on implant micromotion than cortical bone thickness. Bone type amplifies the influence of thread pattern on displacement.

Effect of Tool Pin Thread Forms on Friction Stir Weldability of Different Aluminum Alloys

The primary objective of this study is to investigate parametric effects of pin features on material flow and friction stir weldability of two different aluminum alloys. A series of bead on plate friction stir welds were made on two different aluminum alloys (AA 7050 and AA6061) with cylindrical tool pin having four thread pitches (1.02mm, 1.41mm, 2.12mm & 3.18mm) including smooth/unthreaded pin attached to an unvarying single scrolled shoulder geometry. Welds were performed under a range of process parameters (welding & rotational speed). It was observed that thread forms are obviously beneficial for improving tool performance and reducing in-plane reactions (X & Y forces) forces on tool. Wormhole defects in the weld nugget were eliminated or minimized by employing threaded pins as a consequence of effective material transportation near the weld root. Tool pins having intermediate thread pitches (1.41mm and 2.12mm) perform better than either extreme over the range of attempted parameters. Defects are far more prevalent in 7050 welds than in 6061. In-plane reaction forces on pin are significantly larger in AA7050 welds than in AA 6061 and torque- peak temperature values are of similar order in both welded materials.

The influence of thread geometry on implant osseointegration under immediate loading: a literature review.

Implant success is achieved by the synergistic combination of numerous biomechanical factors. This report examines the mechanical aspect of implants. In particular, it is focused on macrodesign such as thread shape, pitch, width and depth, and crestal module of implants. This study reviews the literature regarding the effect of implant thread geometry on primary stability and osseointegration under immediate loading. The search strategy included both in vitro and in vivo studies published in the MEDLINE database from January 2000 to June 2014. Various geometrical parameters are analyzed to evaluate their significance for optimal stress distribution, implant surface area, and bone remodeling responses during the process of osseointegration.

A Finite Element Study of Short Dental Implants in the Posterior Maxilla

Elevated bite forces and reduced bone densities and dimensions associated with posterior regions of the maxilla cause relatively high failure rates when short dental implants are placed to substitute missing teeth. This study uses the finite element method to evaluate four distinctly different short implant designs (Bicon, Neodent, Nobel Biocare, and Straumann) for their influences on the von Mises stress characteristics within the posterior maxilla. Finite element models of the supporting bone and tooth crowns are developed based on computed tomography data, and implant geometries are obtained from manufacturers' catalogs. The finite element models are meshed using three-dimensional hexahedral and wedge-shaped brick elements. Assumptions made in the analyses are: linear elastic material properties for bone, 50% osseointegration between bone and implant, and crown height-implant length ratio of 2:1. Bicon's neck indentation produced reduced stress in the cortical bone when compared with the Nobel Biocare and Straumann systems. The increased taper of the Neodent design decreased the stress level in cancellous bone. Nobel Biocare's rounded thread crest and reduced thread pitch produced a smoother stress profile. Straumann's increased thread pitch produced elevated stress in the cancellous bone. Generally, stresses were concentrated in the crestal bone region around the implant neck, attributable to the inclined nature of the masticatory force. Nobel Biocare and Bicon systems are recommended for use in type 4 cancellous and cortical bone, respectively.

The Study of Thread Parameter Based on Machine Vision for Automatic Measurement

In order to improve the measurement accuracy of thread parameter and can realize the automatic measurement of parameter, this paper propose a non-contact measuring method which is based on machine vision, we use the industrial linear array CCD with high-precision scan the projection of the thread which in the field of parallel light, using the image recognition, image acquisition, image data processing technology enable your computer finish the pitch diameter, thread pitch, tooth type angle on a non-contact of real-time, on-line measurement. This article also provides detailed measuring method with the main parameters of thread.

Differential Thread Principle’s Application in Manual Drawing Device

The differential thread is composed of two threads, which generally both rotate in clockwise direction, but their screw pairs have distinct thread pitches. When they rotate a period, the movement distance is the screw distance of the screw pairs. Through the application of differential thread, the transmission, which includes distance and force transmission, can be increased or decreased [1]. Based on this principle, when it is applied to the manual drawing device, better effects can be received. So, the multifunction manual drawing device is designed by using the principle of differential thread and it can be strengthened effectively, over 75% stronger than ordinary drawing force. The new design acquires much stronger drawing force.

Investigation of graphite/carbon spiral nanoribbons using FeCl3–CuCl2–graphite intercalation compounds as precursors

FeCl3–CuCl2–graphite intercalation compounds (GICs) were applied to synthesize graphite/carbon spiral nanoribbons (G/CSNRs) by chemical vapor deposition (CVD) of acetylene and hydrogen. The G/CSNRs were characterized by XRD, SEM and Raman spectra. The XRD patterns confirmed the G/CSNRs did contain graphite. The as-grown CSNRs were thin and twisted, owning a width of ~92nm, a thread pitch of ~56nm and a length in micrometer scale. The Raman spectra showed the imperfect crystallinity of CSNRs. During this CVD process, FeCl3–CuCl2–GICs acted as providers of graphite substrates as well as catalyst carriers. The CVD method mediated by GICs also provided possibilities to design and prepare a variety of hybrid carbon structures.

연결부 형태가 다른 두 가지 scallop 임플란트에서 경부 나사선 피치가 응력 분포에 미치는 영향 : 삼차원적유한요소분석

본 연구는 삼차원적 유한요소분석을 통하여 연결부 형태가 다른 두 가지 scallop 임플란트의 경부 나사선 피치가 응력 분포에 미치는 영향을 간접적으로 확인하고자 하였다. 4가지 경부 나사선 피치 (0.4mm, 0.5mm, 0.6mm, 0.7mm)를 갖는 scallop 임플란트를 두 가지 다른 연결부 형태 (platform matching connection, platform mismatching connection)로 지대주와 연결되는 유한요소모형을 설계하였다. 8개의 모든 모델에 100N의 하중을 수직 및 30도 경사 방향으로 인가하여, 임플란트, 지대주, 그리고 치조골에 가해지는 최대등가응력을 분석하였다. 유한요소분석결과 응력은 치밀골에 집중되었다. 작은 나사 피치가 설계된 platform mismatching connection 모델에서 수직 방향과 경사하중 시 최대등가응력이 가장 낮게 나타났다. 측정되었다. Platform matching connection 모델에서는 경사하중의 경우 0.6mm, 수직하중의 경우 0.4mm 나사 피치에서 가장 낮은 최대등가응력을 보였다. 따라서 scallop 임플란트에서 platform mismatching connection은 최대등가응력을 감소시키는 데 중요한 역할을 하며, 경부 나사 피치가 작을수록 최대등가응력이 감소되는 경향을 보임을 알 수 있었다. Purpose of present study is to investigate the effects of thread pitch in coronal portion in scalloped implant with 2 different connections on loading stress using 3 dimensional finite element analysis. Scalloped implant with 4 different thread pitches (0.4mm, 0.5mm, 0.6, and 0.7mm) in the coronal part was modeled with 2 different implant-abutment connections. Platform matching connection had the same implant and abutment diameter so that they were in flush contact at the periphery while platform mismatching connection had smaller abutment diameter than implant so that their connection was made away from periphery of implant-bone interface. Occlusal loading of 100N force was applied vertically and 30 degree obliquely to all 8 models and the maximum von Mises bone stress was identified. Loading stress as highly concentrated in cortical bone. Platform mismatching scalloped implant with small thread pitch (0.4mm) model had consistently lowest maximum von Mises bone stress in vertical and oblique loads. Platform matching model had lowest maximum von Mises bone stress with 0.6mm thread pitch in vertical load and with 0.4mm thread pitch in oblique load. Platform mismatching connection had important roles in reducing maximum von Mises bone stress. Scalloped implant with smaller coronal thread pitch showed trend of reducing maximum von Mises bone stress under load.

Investigation of the effects of thread pitch and water cooling action on the mechanical strength and microstructure of friction stir processed AZ31

Friction stir process (FSP), as a severe plastic deformation, has a considerable effect on the mechanical and microstructure properties of a material. Recently, in new industrial applications, magnesium alloys are used widely due to their low density and appropriate material properties. One of the widely used alloys in automobile and aerospace industries is, AZ31. In this research, friction stir process was conducted on the AZ31 and the effects of cooling action, thread pitch of the pin, and traverse speed during FSP on material properties such as tensile strength, ductility, hardness, and microstructure were investigated. The FSP process tested pitch levels of the pin thread at one and three millimeters; with and without water cooling action, and at three different traverse speeds of 28, 40, and 58mm/min. According to the results, the pin with one millimeter pitch thread improved mechanical properties and microstructure uniformity more than the pin with three millimeter pitch thread. So, it can be concluded that thread pitch had a special effect on material properties of tensile strength, micro-hardness, and size and uniformity of grain. But, its effect on ductility was low. Furthermore, cooling action decreased grain size and increased tensile strength, hardness, and ductility of the material.

Influence of the Ultimate Torsion on the Geometry of Dental Implants

This study evaluated the profile of implants subjected to torsion test. Four types of implants (Conexão®) were analyzed: Master Porous (MP - external hexagon, cylindrical, double-porous surface implants; 11.5 X 3.75 mm), Master Screw (MS - external hexagon, cylindrical, machined implants; 11.5 X 3.75 mm), Conect Conic (CC - external hexagon, cylindrical, machined implants; 11.5 X 3.5 mm) and Master Conect AR (CA - internal hexagon, cylindrical, double-porous surface implants; 11.5 X 3.75 mm). The Nikon® model C profile projector was used for the analysis before and after torsion test with a Mackena® model MK-20XX digital torque meter. The measures analyzed in the profile of implants were: diameter and height of the platform, diameter of the screw/platform connection, angle of the screw/platform connection, external diameter, internal diameter, thread pitch, height and length of the thread. Statistical analysis was performed using ANOVA and Tukey test at 5% significance level. The torsion test caused a visible deformity on the external implant profile. There was a statistical difference among the implants before and after torsion (p<0.05) for the variables: platform diameter, platform height, diameter of the screw/platform connection and length. Changes were observed in platform height of CC and CA, fracture of CA implants, fracture of the MP and MS assembler/connectors, and internal thread stripping of CC. Thus, it was concluded that excessive or some unadvised torque by the manufacturer can lead to changes in different geometric measurements of implants.

Three-dimensional finite element analysis of the mechanical properties of helical thread connection

Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfied results. A parameterized 3D finite element model of bolted joints with real helical thread geometry is established and meshed with refined hexahedral elements. The Von Mises plasticity criterion, kinematic hardening rule of materials and interfacial contacts are employed to make it possible for the suggested model be able to approach real assembly conditions. Then, the mechanical properties of bolted joints with different thread pitches, thread numbers and modular ratios are investigated, including the contact pressure distribution at joint interfaces, the axial load distribution and stress concentration in screw threads during the loading and unloading process. Simulation results indicate that the load distribution in screw threads produced by the suggested model agrees well the results from CHEN’s photoelastic tests. In addition, an interesting phenomenon is found that tightening the bolt with a large preload first and then adjusting the clamping force by unloading can make the load distribution more uniform and reduce the maximum residual equivalent stress in thread roots by up to 40%. This research provides a simple and practical approach to constructing the 3D finite element model and predicting the mechanical properties of helical thread connection.

Biomechanical Investigation of Thread Designs and Interface Conditions of Zirconia and Titanium Dental Implants with Bone: Three-Dimensional Numeric Analysis

Bone stress and interfacial sliding at the bone-implant interface (BII) were analyzed in zirconia and titanium implants with various thread designs and interface conditions (bonded BII and contact BIIs with different frictional coefficients) for both conventional and immediately loaded treatments. A total of 18 finite element models comprising two implant materials (zirconia and titanium), three thread designs (different shapes and pitches), and three interface conditions (bonded and contact BIIs) were analyzed to assess the effects on bone stresses and on sliding at the BII. The material properties of the bone model were anisotropic, and a lateral force of 130 N was applied as the loading condition. In the immediately loaded implant, the stress was highly concentrated at one site of the peri-implant bone. The peak bone stress was more than 20% lower in zirconia implants than in titanium implants for a bonded BII and 14% to 20% lower for a contact BII. The bone stresses did not differ significantly between implants with V-shaped threads and square threads. However, sliding at the BII was more than 25% lower with square-thread implants than with V-shaped-thread implants for titanium implants and 36% lower for zirconia implants. Reducing the thread size and pitch in cortical bone (via two V-shaped threads with different pitches) decreased the bone stress by 13%. Increasing the frictional coefficient reduced sliding at the BII in both zirconia and titanium implants. As an implant material, zirconia can reduce the bone stress in the crestal cortical region. Bone stress and sliding at the BII are heavily dependent on the thread design and the frictional coefficient at the BII of immediately loaded implants.

Acrylic Customized X-Ray Positioning Stent for Prospective Bone Level Analysis in Long-Term Clinical Implant Studies

Objectives: This paper describes a technique to produce individualized X-ray positioning devices for intraoral digital imaging of dental implants with long-term stability. Materials and Methods: An X-ray positioning device was built for Gendex ® Visualix ® eHD sensor, using the Dentsply rinn XCP-DS ® system individualized by the incorporation of the bite piece within an acrylic stent to perform successive standardized radiographs to 16 patients. X-ray tube stabilization was achieved with polivinylsiloxane. Series of 3 radiographs were taken to each patient in different moments. Specific linear measurements as the implant diameter (mesio-distal width) and the height between consecutive threads (thread pitch) were made to all radiographs to determine the reproducibility and accuracy of the procedure. Results: The intraclass correlation coefficient for the mesio-distal width was 0.964 [(0.920 - 0.986) 95% CI] (p < 0.01) and 0.990 [(0.976 - 0.996) 95% CI] (p < 0.01) for the thread pitch. Bland-Altman plots comparing implant diameter showed mean bias of 0.01 ± 0.01975, 0.01 ± 0.02243 and 0.0006 ± 0.025 for groups 1 - 2, 1 - 3 and 2 - 3 respectively. Mean bias of 0.0024 ± 0.00552, 0.0027 ± 0.00552 and 0.0003 ± 0.0012 was found for the thread pitch analysis of groups 1 - 2, 1 - 3 and 2 - 3. One sample t-test for trueness of mesio-distal width, thread pitch and ratio showed mean difference of 0.00156 mm for the test value of 3.3 (p = 0.9), −0.00026 mm for 0.8 (p = 0.96) and 0.0124 for 4.125 (p = 0.72), respectively, after the application of a magnification correction factor. Conclusion: The device produced reproducible images in different moments and was suitable for comparative clinical examinations of marginal bone as it was convenient to perform reliable linear measurements.

Influência do macheamento do orifício piloto nos parafusos cervicais anteriores

OBJETIVO: Analisar experimentalmente a influência do macheamento do orifício piloto nas propriedades mecânicas e na interface osso-implante do parafuso cervical anterior. MÉTODOS: Oito carneiros da raça Santa Inês deslanados foram utilizados no estudo. Nos segmentos vertebrais cervicais de C2-C7 foram realizados orifícios piloto de 2,5mm, de ambos os lados da vértebra. No lado direto da vértebra foi realizado o macheamento previamente a inserção do parafuso cortical de 3,5mm, e no lado esquerdo o implante foi colocado sem o macheamento do orifício piloto. Foram realizados ensaios mecânicos para avaliar a força de arrancamento dos implantes e estudo histomorfométrico da interface osso-implante na fase aguda e oito semanas após a colocação dos implantes. O torque de inserção foi mensurado durante a colocação dos implantes. RESULTADOS: O torque de inserção e a resistência ao arrancamento dos implantes foram maiores nos implantes colocados sem o macheamento do orifício piloto. A interface osso-implante apresentou maior área de contato ósseo e maior área óssea no interior da rosca do implante nos parafusos implantados sem o macheamento prévio. Não foi observado diferença na área óssea fora do passo de rosca do implante. CONCLUSÕES: O macheamento do orifício piloto reduz o torque de inserção e a resistência ao arrancamento do implante na fase aguda e crônica, e reduz a área de contato osso-implante e área de osso no interior do passo de rosca.

Design characteristics, primary stability and risk of fracture of orthodontic mini-Implants: Pilot scan electron microscope and mechanical studies

Objectives: Orthodontic mini-implants (OMIs) are increasingly used in orthodontics but can fail for various reasons. This study investigates the effects of OMI design characteristics on the mechanical properties in artificial bone. Material and Methods: Twelve self-drilling OMIs (2 small, 6 medium, 4 large) from 8 manufacturers were tested for their primary stability in simulated medium-high cancellous bone and the risk to fracture in high-density methacrylate blocks. For the assessments of the maximum insertion torque (IT) and torsional fracture (TF) 5 of each OMI were used and for the pull-out strength (POS) 10. The OMIs were inserted with a torque screwdriver (12 sec/360°) until the bottom at 8 mm depth was reached. OMI designs were analyzed with a scan electron microscope (SEM). Results: SEM images revealed a great variation in product refinement. In the whole sample, a cylindrical OMI shape was associated with higher POS (p<0.001) but lower IT (p=0.002) values. The outer and inner OMI diameters were design characteristics well correlated with POS, IT and TF values (ranging from 0.601 to 0.961). Greater thread depth was related to greater POS values (r= 0.628), although OMIs with similar POS values may have different IT values. Thread depth and pitch had some impact on POS. TF depended mainly on the OMI inner (r= 0.961) and outer diameters (r=0.892). A thread depth to outer diameter ratio close to 40% increased TF risk. Conclusions: Although at the same insertion depth the OMI outer and inner diameters are the most important factors for primary stability, other OMI design characteristics (cylindrical vs. conical, thread design) may significantly affect primary stability and torsional fracture. This needs to be considered when selecting the appropriate OMI for the desired orthodontic procedures. Key words:Orthodontic mini-implants, primary stability, insertion torque, pullout strength, torsional fracture.

1020 有限要素法解析による圧力円筒ねじ端の荷重分布へ及ぼすピッチの影響(OS01-4 機械要素とトライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

1020 有限要素法解析による圧力円筒ねじ端の荷重分布へ及ぼすピッチの影響(OS01-4 機械要素とトライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

Evaluation of the Effects of Different Surface Configurations on Stability of Miniscrews

Introduction. The aim of this study was to analyze the effects of screw design and force application on the stability of miniscrews, using RTT, SEM, and histomorphometric analyses. Materials and Methods. Eighty cylindrical, self-drilling, and Ti6Al4V alloy miniscrews (1,6 × 6 mm) were used. Four mini-screws were inserted in fibulas of each rabbit, and 115 G of force was immediately applied. Four miniscrews were inserted in the other fibula, on which no force was applied. Eight weeks after insertion, osseointegration between miniscrew and the surrounding bone was evaluated by the histomorphometric analyses, SEM, and RTT. Kruskal-Wallis and the paired t-tests were used for statistical analysis. Results. Values obtained from Group I were significantly higher than those of the other loaded groups (P < .05). There were no differences in RTT scores among Groups II, III, and IV. Similar findings were also observed for unloaded mini-screws. There was no significant difference between Groups I and IC, while the differences between loaded and unloaded controls for each miniscrew were statistically significant. Conclusions. Immediate loading of miniscrews does not impair screw stability. Also, the diameter of miniscrew and more frequent thread pitches have a positive effect on stability; however, length of miniscrews does not have a significant effect on the stability.

Design and Fabrication of Twisted Potato Crisps Maker

The paper describes the design and fabrication of twisted potato crisps maker. A twisted potato crisps maker is described herein comprising a base support having a first end and a second end for providing guided linear longitudinal motion along the base, longitudinal stud connecting to handle to manually rotate the stud, having a thread pitch of 13 triangular threads per inch, cutting blade which was made perpendicular to potato rotational axis and had a hole through which guide pin extended to provide support for potato, clipper, guide pin, nuts, support legs and framework. The combination of rotary and longitudinal motion produced by handle resulted in slicing of potato. This manually operated machine was designed to cut whole raw potatoes into consistent twisted crisps of thickness 2.0 mm approximately, suitable for frying as potato chips. The capacity of machine was 9.6 kg of potato per hour, and product loss was around 4.1%. Locally and easily available materials like cast iron, mild steel and stainless steel were used for the fabrication. This machine allows in its simplicity of design and modest cost with the ability to generate thin uniform slices utilizing approximately 95% of the potatoes.

Evaluation of Three Miniplate Systems for Fracture Stabilization in Pigeons (Columba livia)

Bone plates are rarely used in avian fracture management for several reasons, and until recently, there was no plating system considered appropriate for use in birds with a body mass less than 500 g. To evaluate 3 different miniplate systems in avian fracture repair, 3 groups (A, B, and C) of 6 pigeons (Columba livia) each were used. The left ulna and radius of the pigeons were transected, and the ulna was stabilized. In group A, a 1.3-mm adaption plate was used. In group B, a limited contact system was created with washers that were placed between a 1.3-mm adaption plate and the bone. The intention was to reduce the compression of the periosteum and vascular damage to the bone. In group C, a 1.0-mm maxillofacial miniplate was used. Healing was evaluated with radiographs after 14 and 28 days. A flight test was conducted on day 28; the birds were then euthanatized, and the wing was dissected. Birds in group A with the adaptation plate achieved the best flight results (100%). In group B birds, no effect of the limited contact concept was visible at necropsy, and a high percentage of the screws had loosened, leading to failure (33%). The maxillofacial miniplates of group C birds were too weak and bent (100%). These results indicate that the adaption plate 1.3 met the desired requirements. To improve the system, further trials, with smaller drill bits and with screws having a smaller thread pitch, are recommended.