Finite element analysis of the effect of novel Lock Screw system preventing abutment screw loosening

PURPOSE: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. MATERIALS AND METHODS: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. RESULTS: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. CONCLUSION: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

Effect of axial load test in assisting Taylor spatial frame for tibia and fibula fractures / 中华创伤杂志

Objective To investigate the effect of axial load test in Taylor spatial frame treatment of external fixation for tibia and fibula fractures.Methods A retrospective case-control study was conducted to analyze the clinical data of 36 patients with open fracture of tibia and fibula admitted to Tianjin Hospital from March 2015 to June 2017.There were 22 males and 14 females,aged 21-71 years[(46.1±14.2)years].All patients received Taylor spatial frame external fixation for tibia and fibula fracture within 1 week after injury.After operation,18 patients received axial load test(experiment group),and the other 18 did not(control group).When the value of axial load test was less than 5% in experiment group,the Taylor spatial frame was removed.The control group used traditional method to remove the Taylor spatial frame.Comparisons were made between the two groups in terms of treatment duration,total cost,re-fracture after Taylor spatial frame removal and incidence of stent-tract infection.Results All patients were followed up for 3-14 months with an average of 8.6 months.Compared with control group,the treatment duration[(36.17±11 .44)weeks vs.(44.50±9.16)weeks]and total cost[(93.7±7.9)thousand yuan vs.(120.1±10.6)thousand yuan]of experiment group were significantly lower(P＜0.05).In the experiment group,there was 0 patient with re-fracture and two patients with stent-tract infection,with the complication incidence of 11%,while there were two patients with re-fracture and three patients with stent-tract infection,with the complication incidence of 28% in the control group(P＞0.05).Conclusions After Taylor spatial frame external fixation for tibia and fibula fractures,regular axial load test can safely and timely guide the removal of Taylor spatial frame.It can reduce the treatment duration and cost compared with the traditional removal method,being safe and reliable.

Effect of Device Rigidity and Physiological Loading on Spinal Kinematics after Dynamic Stabilization : An In-Vitro Biomechanical Study

OBJECTIVE: To investigate the effects of posterior implant rigidity on spinal kinematics at adjacent levels by utilizing a cadaveric spine model with simulated physiological loading. METHODS: Five human lumbar spinal specimens (L3 to S1) were obtained and checked for abnormalities. The fresh specimens were stripped of muscle tissue, with care taken to preserve the spinal ligaments and facet joints. Pedicle screws were implanted in the L4 and L5 vertebrae of each specimen. Specimens were tested under 0 N and 400 N axial loading. Five different posterior rods of various elastic moduli (intact, rubber, low-density polyethylene, aluminum, and titanium) were tested. Segmental range of motion (ROM), center of rotation (COR) and intervertebral disc pressure were investigated. RESULTS: As the rigidity of the posterior rods increased, both the segmental ROM and disc pressure at L4-5 decreased, while those values increased at adjacent levels. Implant stiffness saturation was evident, as the ROM and disc pressure were only marginally increased beyond an implant stiffness of aluminum. Since the disc pressures of adjacent levels were increased by the axial loading, it was shown that the rigidity of the implants influenced the load sharing between the implant and the spinal column. The segmental CORs at the adjacent disc levels translated anteriorly and inferiorly as rigidity of the device increased. CONCLUSION: These biomechanical findings indicate that the rigidity of the dynamic stabilization implant and physiological loading play significant roles on spinal kinematics at adjacent disc levels, and will aid in further device development.

Effects of axial loading on the coupling vibration in bioliquid-filled microtubules / 医用生物力学

Objective To describe the effects of axial loading, small-scale parameter, bioliquid density in a microtubule (MT) and constrained stiffness of surrounding biomedium on the coupling vibration frequency in the bioliquid-filled MT, and to provide references for ultrasonic inspection on nano-MT under axial loading and the clinical application of biological medicine. Methods The non-local elastic theory was utilized to describe the nano-scale characteristics of the MT, and the analytic solutions to the coupling vibration frequency of the bioliquid-filled MT under axial loading were given. Results The axial loading exerted on the bioliquid-filled MT made the couple vibration frequency drop rapidly, and as the small-scale effect increased, the couple vibration frequency of the bioliquid-filled MT was gradually decreased. The effect of axial loading on the couple vibration frequency of the bioliquid-filled MT was larger than that of the small-scale parameter. Conclusions When the density of bioliquid in MT increases, the first order frequency of the bioliquid-filled MT embedded in biomedium is decreased; when the initial axial loading exerted on the bioliquid-filled MT increases, the effect of bioliquid density in MT on the first order frequency of bioliquid-filled MT is reduced gradually.

Extensometria: estudo das microdeformações ao redor de três implantes de conexão protética cone-morse, fundidos com coifas plásticas e usinadas, submetidos à carga vertical estática / A comparative study of microstrain around three-morse taper implants,casting with machined and plastic copings, under axial loading

Objetivo: Analisar, por meio da extensometria, as microdeformações ao redor de implantes cone-Morse com diferentes tipos de coifas-plásticas (n = 5) e usinadas (n = 5). Foram inseridos linearmente três implantes cone-Morse no bloco de poliuretano. Método: Quatro extensômetros (SG) foram colados na superfície do poliuretano e foram identificados pelo SG1, que foi colado adjacente e mesialmente ao implante A, pelos SG2 e SG3 colados adjacentes mesial e distalmente ao implante B, e o SG4, que foi colado distalmente ao implante C. Dez supraestruturas em CoCr foram parafusadas sobre pilares protéticos Microunit com torque de 10 N.cm, com o auxílio de um torquímetro manual. Cargas axiais de 30 kg foram aplicadas em pontos pré-determinados (A, B, C) sobre os respectivos parafusos de retenção das próteses. Os extensômetros foram capazes de analisar as microdeformações em um limitado segmento ao redor dos implantes. Os registros foram comparados utilizando-se ANOVA de medidas repetitivas e teste múltiplo de Tukey (a = 0,005). Resultado: Os registros não evidenciaram diferença estatística signficante para o tipo de coifa (p = 0,0838); contudo, evidenciou-se diferença estatística para os pontos de aplicação de carga (p = 0,0338). Conclusão: Não houve evidências de que as coifas usinadas reduziram as microdeformações ao redor dos implantes. O ponto de aplicação de carga determinou a quantidade de microdeformações.

Objective: The aim of this in vitro study was quantify the microstrain around Morse taper implants using plastic (n = 5) and machined (n = 5) copings under axial loading. Methods: Three implants of Morse taper junction were embedded in the center of the polyurethane block. Four Strain gauges (SG) were bonded on the surface of polyurethane and it was designated SG1 placed mesially adjacent to implant A, SG2 and SG3 were placed mesially and distally adjacent to the implant B and SG4 was placed distally adjacent to the implant C. The ten CoCr superstructure?s occlusal screws were tightened onto the Microunit abutments with a torque of 10 N.cm using the manufacture?s manual torque- controlling device. Axial load of 30 kg was applied at three predetermined points (A, B, C). The strain gauges were only capable of detecting strain in a limited segment around the implants. All of the data were compared using RM ANOVA and post hoc multiple range Tukey test (a = 0.005). Result. The results did not show a statistically significant difference for the copings (p = 0.0838), but showed a statistically significant difference for the loading points (p = 0.0338). Conclusion: There were not evidences that the machined copings in reducing the strain around implant. The loading point persuaded in the magnitude of micro strain.

Extensometria – cargas axiais e não axiais sobre coroa unitária implantossuportada / Strain gauge analysis – axial and non-axial loads on the single-tooth implant-supported crown

Este estudo avaliou, in vitro, por meio da extensometria, as diferentes deformações ao redor de um implante de hexágono externo após a aplicação de carga em três pontos distintos sobre coroas unitárias, fixado em um bloco de poliuretano. Quatro extensômetros foram colados, diametralmente opostos e tangentes ao implante, na superfície do bloco para quantificar a microdeformação peri-implantar no momento da aplicação da carga. Um pilar protético esteticone foi conectado ao implante com torque de 20 Ncm. Sobre o pilar foi parafusado, a cada sessão de teste, um padrão fundido em liga de Co-Cr (n = 10) com torque de 10 Ncm, que recebeu o carregamento. A carga de 30 kg foi aplicada sobre três pontos predeterminados e os dados de microdeformação registrados com auxílio de um condicionador de sinais elétricos e do software Strain-Smart. Os resultados obtidos foram submetidos à análise estatística utilizando a Análise de Variância (Anova) e o teste de comparação múltipla de Tukey (5%). Os valores médios da microdeformação para as cargas foram: ponto A = 307,6 ponto B = 302,3 e ponto C = 669,5. Pôde-se concluir que os fatores de deslocamento centrífugo do ponto de aplicação de carga interferem significativamente na microdeformação gerada ao redor do implante.

This in vitro study evaluated microstrain levels around a single-tooth, external hexagon dental implant crown. An Estheticone abutment was connected to the implant with 20 Ncm torque, and a single crown cast in Co-Cr alloy (n=10) delivered with 10Ncm. Four strain gauges were bonded, diametrically opposed and tangential to the implant, on the surface of the polyurethane block. After, a 30Kg-load was applied at three different points (A, B, and C). Microstrain (µε) values were recorded with the aid of an electric signal conditioner and the Strain-Smart software. Statistical analyses were performed with Anova and multiple comparison Tukey´s test (5% significance level). Mean deformation values were: point A = 307.6 µε, point B = 302.3 µε, and point C = 669.5 µε. It was concluded that centrifugal displacement of the loading application point interferes significantly with microstrain levels around the dental implant.

Effect of Axial loading on Lumbar spine MRI: Comparative Study of Effect between a Patient Group with Claudication and a Patient Group without Claudication

STUDY DESIGN: This study intended to find out differences of effects by axial loading in MRI examination in a patient group with neurologic claudication and a group without neurologic claudication. OBJECTIVES: It was intended to understand in which group the effects of axial loading can be expected when taking MRI on the lumbar spine. SUMMARY OF THE LITERATURE REVIEW: The study of Willen and Danielson found spinal canal stenosis, which cannot be found by existing methods comparing an MRI taken in bended posture of lumbar without axial loading implementation by MRI taken with axial loading implementation. Hiwatashi et al. also reported that there was a change of treatment direction by laminectomy after axial loading in patients who were intended to take a conservational treatment before the axial loading. MATERIALS AND METHODS: A total of 39 patients and 54 intervertebral discs were compared. The distances from a sagittal plane before and after intervertebral discs were compared by measuring a sectional area of dura mater in a horizontal plane image and two groups were compared by existence of patients' neurologic claudication. RESULTS: The AP diameter before and after a intervertebral discs increased into 41.98 mm from 41.1 mm on the average and the sectional area of dura mater showed 137.47mm2 before loading and 119.86mm2 after loading on the average. There was not a significant difference in the distances before and after axial loading implementation, but a significant difference was found in the sectional area of dura mater. CONCLUSION: Axial loading would contribute to diagnose spinal disease, and especially, spinal canal stenosis in a patient group with claudication.