Torsional Resistance Research Articles

Vascularized Periosteal Flaps Accelerate Osteointegration and Revascularization of Allografts in Rats.

Surgical reconstruction of large bone defects with structural bone allografts can restore bone stock but is associated with complications such as nonunion, fracture, and infection. Vascularized reconstructive techniques may provide an alternative in the repair of critical bone defects; however, no studies specifically addressing the role of vascularized periosteal flaps in stimulating bone allograft revascularization and osseointegration have been reported. (1) Does a vascularized periosteal flap increase the likelihood of union at the allograft-host junction in a critical-size defect femoral model in rats? (2) Does a vascularized periosteal flap promote revascularization of a critical-size defect structural bone allograft in a rat model? (3) What type of ossification occurs in connection with a vascularized periosteal flap? Sixty-four rats were assigned to two equal groups. In both the control and experimental groups, a 5-cm critical size femoral defect was created in the left femur and then reconstructed with a cryopreserved structural bone allograft and intramedullary nail. In the experimental group, a vascularized periosteal flap from the medial femoral condyle, with a pedicle based on the descending genicular vessels, was associated with the allograft. The 32 rats of each group were divided into subgroups of 4-week (eight rats), 6-week (eight rats), and 10-week (16 rats) followup. At the end of their assigned followup periods, the animals were euthanized and their femurs were harvested for semiquantitative and quantitative analysis using micro-CT (all followup groups), quantitative biomechanical evaluation (eight rats from each 10-week followup group), qualitative confocal microscopic, backscattered electron microscopic, and histology analysis (4-week and 6-week groups and eight rats from each 10-week followup group). When making their analyses, all the examiners were blinded to the treatment groups from which the samples came. There was an improvement in allograft-host bone union in the 10-week experimental group (odds ratio [OR], 19.29 [3.63-184.50], p < 0.05). In contrast to control specimens, greater bone neoformation in the allograft segment was observed in the experimental group (OR [4-week] 63.3 [39.6-87.0], p < 0.05; OR [6-week] 43.4 [20.5-66.3], p < 0.05; OR [10-week] 62.9 [40.1-85.7], p < 0.05). In our biomechanical testing, control samples were not evaluable as a result of premature breakage during the embedding and assembly processes. Therefore, experimental samples were compared with untreated contralateral femurs. No difference in torsion resistance pattern was observed between both groups. Both backscattered electron microscopy and histology showed newly formed bone tissue and osteoclast lacunae, indicating a regulated process of bone regeneration of the initial allograft in evaluated samples from the experimental group. They also showed intramembranous ossification produced by the vascularized periosteal flap in evaluated samples from the experimental group, whereas samples from the control group showed an attempted endochondral ossification in the allograft-host bone junctions. A vascularized periosteal flap promotes and accelerates allograft-host bone union and revascularization of cryopreserved structural bone allografts through intramembranous ossification in a preclinical rat model. If large-animal models substantiate the findings made here, this approach might be used in allograft reconstructions for critical defects using fibular or tibial periosteal flaps as previously described.

Torsional Behavior of WaveOne Gold Endodontic File with the Dedicated Motor of the Original WaveOne File.

This study compares the safety limits and torsional resistances of WaveOne Gold (WOG) and WaveOne (WO) endodontic files while using the original motor. The safety limits for reciprocating angles were tested by measuring the torsional limit before plastic deformation (TLP) after repetitive torsional loading at gradually increasing load, and after single continuous rotation. Statistical analysis was performed by independent t-test at 95% confidence level. The tested specimens were observed under a scanning electron microscope (SEM). Regardless of the test mode, the distortion angle at the TLP was higher for WOG than WO (p < 0.05), and all were greater than the 150-degree rotation of the original motor. The mean values of the distortion angle and torque from the single continuous rotation loading were significantly lower than those with repetitive loading movements. Comparing the two systems under SEM, WO showed a catastrophic change in comparison with WOG. Evaluation of the lateral aspects showed longitudinal micro-cracks after 270-degree repetitive movements. After 150-degree repetitive movements, no distorted machining grooves were found in either group, but WO showed evidence of longitudinal micro-cracks. Under the conditions of this study, the torsional loading from the pre-set mode of the dedicated motor for WO was safe for WOG as well.

Comparative Analysis of Torsion Resistance Performance between Traditional Support Structure System and Structure with Diagonal Brace

Traditional support structure system of air-cooled condense adopts hybrid structure system of steel truss and reinforced concrete pipe column, and this type of structure has a remarkable torsion effect because that the quality and rigidity is badly non-uniform at the vertical direction. In order to study the natural vibration period, vibration type and dynamic response under multidimensional ground motions, this paper chooses the support structure system with diagonal brace to analysis the dynamic characteristic and lateral-torsional coupled seismic response of the structure, and compares the results with the traditional structures to study the reasons of these changes so as to make recommendations on the designing of structure. The results show that this new-type structure could reduce the torsional effect, lateral displacement and strengthen overall seismic capacity.

Behavior of partially encased composite members under various load conditions: Experimental and analytical models

This study addresses the experimental behavior of octagonal partially encased composite column under axial and bending load conditions. The complementary study on axial and combined axial–torsional behavior is done through finite element analysis. The main parameters for the experiment part are reinforcement details and failure modes. The six parameters of this analytical analysis include width-to-thickness ratio of flange, transverse links spacing and diameter, welding line arrangements, and different types of retrofit of cross-shaped steel (concrete encasement, use of stiffener plates and transverse links). To verify accuracy of the proposed three-dimensional finite element model, the axial behavior of the numerical models was compared with test specimens. Experimental results of the axial study show that concrete crushing phenomena and local buckling behavior occurred for all specimens under ultimate stage of loading. It should be noted that local buckling behavior occurred after crushing phenomena. The analysis of bending assessment demonstrated that the use of stirrups has no remarkable effect on increasing the effective bending moment strength of octagonal partially encased composite columns. Meanwhile, an equation was developed based on comprehensive parametric study of octagonal partially encased composite column using detailed finite element analyses. Under axial–torsional load conditions, one could conclude that steel shear plates should be placed at the end zones of column to heighten torsional resistance of member. Meanwhile, transverse links were found to exert marginal effect on torsional behavior of octagonal partially encased composite column.

Development of Improved Frequency Expressions for Composite Horizontally Curved Bridges with High-Performance Steel Girders

Composite curved I-girder bridges are often used in modern highway systems, but the open sections of I-girders mean that these structures suffer from low torsional resistance. The curvature also results in quite complex behaviors due to the coupled bending and torsional responses of curved I-girder bridges. High-performance steel, which adds strength, enhances durability and improves weldability, addresses both the economic and structural problems associated with curved bridges. However, as yet, there are no simplified design methods in the form of practical equations with which to optimize the design parameters of curved bridges and their dynamic behavior remains controversial. This study evaluated the effects of various design parameters on the free vibration responses of curved HPS I-girder bridges. A sensitivity analysis of 278 prototype simple-span and continuous bridges was conducted using CSIbridge software to create a set of simple, practical expressions for the fundamental frequencies of these structures.

Torsional Fatigue Resistance of Blue-treated Reciprocating Instruments

IntroductionThe aim of the present study was to evaluate the influence of blue thermal treatment on the torsional resistance behavior of M-Wire Reciproc files (VDW, Munich, Germany). MethodsTen M-Wire Reciproc R25 (25/0.08v) and 10 Reciproc Blue R25 (25/0.08v, VDW) instruments were used. The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. Three millimeters of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. The fracture surface of all fragments was examined with a scanning electron microscope. Results were statistically analyzed using the Student t test at a significance level of P < .05. ResultsThe maximum torsional strength of M-Wire Reciproc was higher than Reciproc Blue instruments (P < .05). Reciproc Blue instruments showed significantly higher angular rotation to fracture than M-Wire Reciproc instruments (P < .05). Scanning electron microscopy of the fracture surface showed similar and typical features of torsional failure for the 2 types of instruments, including concentric abrasion marks and the fibrous dimple marks at the center of rotation. ConclusionsReciproc Blue instruments showed a higher angle of rotation to fracture but a lower torque to failure than M-Wire Reciproc instruments.

Mechanical Properties of Glide Path Preparation Instruments with Different Pitch Lengths

IntroductionThis study compared the effects of pitch length on the torsional resistance and cyclic fatigue resistance of glide path preparation instruments. MethodsG-File (G1 and G2; Micro-Mega, Besançon, France) and new generation G-File (NG1 and NG2, Micro-Mega) instruments were compared to evaluate the effects of the shorter pitch of the latter (25% shorter than G-File). G1 and NG1 have a #12 tip size, whereas G2 and NG2 have a #17 tip size. All the files have the same taper of 3%. For comparing the torsional resistances (n = 15), the file was fixed at 4 mm from the tip, and the clockwise rotation at a constant rotational speed of 2 rpm was adjusted until the file fractured. The maximum torsional load and distortion angle at fracture were recorded. For comparing the cyclic fatigue resistances (n = 15), the files were freely rotated in a simulated canal (radius, 3 mm; curvature, 90°) at a speed of 300 rpm in a dynamic mode. When the file fractured, the time elapsed was recorded using a chronometer. The number of cycles to failure was calculated by multiplying the total time to failure by the rotation rate. Fractured fragments were examined under the scanning electron microscope. ResultsThe NG2 instruments had significantly higher fatigue resistance and torsional strength than the G2 instruments (P < .05) and showed approximately the same fatigue resistance as the G1. Scanning electron microscopic examinations revealed the typical appearances of 2 failure modes. ConclusionsA shorter pitch design increased cyclic fatigue resistance and torsional strength of the glide path instruments.

Cyclic fatigue using severely curved canals and torsional resistance of thermally treated reciprocating instruments.

To evaluate the cyclic fatigue using severely curved canals and torsional resistance of ProDesign R (Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil), Reciproc Blue (VDW, Munich, Germany), and WaveOne Gold (Dentsply Maillefer, Ballaigues, Switzerland) reciprocating instruments MATERIALS AND METHODS: Twenty instruments of the ProDesign R (25/0.06) system, 20 instruments of the Reciproc Blue (25/0.08v) system, and 20 instrument of the WaveOne Gold (25/0.07v) system were used. Cyclic fatigue resistance was tested measuring the time to fracture and the number of cycles to fracture in an artificial stainless steel severely curved canal with 80° angle and a 3-mm radius of curvature (n = 10). Torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. The fracture surfaces of all fragments were examined with a scanning electron microscope. Results were statistically analyzed using one-way ANOVA and Tukey's test at a significance level of p < 0.05. ProDesign R instruments showed a significantly longer cyclic fatigue life than the other tested instruments (p < 0.05). Reciproc Blue showed longer cyclic life than WaveOne Gold (p < 0.05). Reciproc Blue showed the higher torsional strength, followed by WaveOne Gold and ProDesign R instruments (p < 0.05). Moreover, Reciproc Blue showed significantly higher angular rotation to fracture than ProDesign R (p < 0.05). WaveOne Gold showed intermediary results regarding angular rotation to fracture with no differences when compared to Reciproc Blue or ProDesign R instruments (p < 0.05). ProDesign R presented the highest cyclic fatigue resistance in severely curved canals when compared with Reciproc Blue and WaveOne Gold. However, Reciproc Blue showed the higher torsional strength overall and higher angular rotation to fracture when compared to ProDesign R. Despite the numerous advantages of reciprocating instruments, these instruments still have some risk of fracture during its use, especially in severely curved canals. The present study evaluated the cyclic fatigue and torsional resistance of thermally treated reciprocating instruments.

Evaluation of dynamic and static torsional resistances of nickel-titanium rotary instruments

Background/purposeThis study evaluated the torsional resistances of nickel-titanium rotary instruments by two methods: i) dynamic resistance: repetitive torsional loading (RTL) and ii) static resistance: single torsional loading (STL) based on the International Organization for Standardization. Materials and methodsIn RTL method, a pre-set rotational loading (0.5 N cm) was applied after fixing the 3-mm tip of the file, and this clockwise loading to the pre-set torque and counter-clockwise unloading to original position was repeated at 50 rpm until the file fractured. The number of repetition cycles until fracture was counted. In STL method, the torsional strength was determined by continuous clockwise rotation (2 rpm) until fracture. Results from both methods were compared after testing the torsional resistances of four instrument systems (n = 15): Hyflex CM, HyFlex EDM, V-Taper2, and V-Taper2H. A scanning electron microscope (SEM) was used to examine the topographic features of the fractured surfaces and longitudinal aspects (n = 5) from both methods. ResultsThe RTL and STL methods had similar results: V-Taper2 had the highest resistance and the Hyflex CM had the lowest (P < 0.05). Spearman correlation test showed the results from two methods were strongly correlated (coefficient = 1). Under the SEM, specimens from the RTL showed ruptured aspects on cross-sections with multiple areas of crack propagation, while the STL showed the typical features of torsional failure such as circular abrasion marks and fatigue dimples. ConclusionsThis study suggests the clinically relevant torsional test (RTL) method yield similar results with the STL method, but they have different topographic findings.

Effect of Torsional and Fatigue Preloading on HyFlex EDM Files

IntroductionThe purpose of this study was to evaluate the effect of a low amount of torsional preloading on the fatigue life and different degrees of cyclic fatigue on torsional failure of HyFlex EDM (EDM; Coltene-Whaledent, Allstetten, Switzerland) and HyFlex CM (CM; Coltene-Whaledent) instruments. MethodsEDM and CM files were used. The fatigue resistance was examined in a 5-mm radius and 60° single curve, and the mean number of cycles to failure (Nf) was recorded. The torque and rotation angles at failure of the instruments were measured according to ISO 3630-1. New files were precycled to 0%, 50%, and 75% of the Nf, and torsional tests were then performed. Other new files were preloaded at 5%, 15%, 25%, and 50% of the mean rotation angles before the fatigue test. The fracture surfaces of the fragments were examined under a scanning electron microscope. ResultsThe fatigue resistance of EDM instruments was higher than that of CM instruments (P < .05). The torque and angle of rotation at fracture of the files were similar. Torsional preloading lowered the Nf of EDM at 15% preloading (P < .05) and the Nf of CM at 50% preloading (P < .05). However, the Nf of EDM files even with 50% torsional preloading was significantly higher than unused CM files (P < .05). Fatigue prestressing even at 75% had no negative effect on the torque and rotation angle of the EDM files. Moderate precycling (50%) of EDM files increased their torsional resistance. The fractographic patterns corresponded to the pattern defined by the last stage test. ConclusionsA low amount (15%) of torsional preloading reduced the fatigue resistance of EDM files, whereas even extensive (75%) precyclic fatigue was not detrimental to their torsional resistance.

Cyclic fatigue resistance, torsional resistance, and metallurgical characteristics of M3 Rotary and M3 Pro Gold NiTi files.

ObjectivesTo evaluate the mechanical properties and metallurgical characteristics of the M3 Rotary and M3 Pro Gold files (United Dental).Materials and MethodsOne hundred and sixty new M3 Rotary and M3 Pro Gold files (sizes 20/0.04 and 25/0.04) were used. Torque and angle of rotation at failure (n = 20) were measured according to ISO 3630-1. Cyclic fatigue resistance was tested by measuring the number of cycles to failure in an artificial stainless steel canal (60° angle of curvature and a 5-mm radius). The metallurgical characteristics were investigated by differential scanning calorimetry. Data were analyzed using analysis of variance and the Student-Newman-Keuls test.ResultsComparing the same size of the 2 different instruments, cyclic fatigue resistance was significantly higher in the M3 Pro Gold files than in the M3 Rotary files (p < 0.001). No significant difference was observed between the files in the maximum torque load, while a significantly higher angular rotation to fracture was observed for M3 Pro Gold (p < 0.05). In the DSC analysis, the M3 Pro Gold files showed one prominent peak on the heating curve and 2 prominent peaks on the cooling curve. In contrast, the M3 Rotary files showed 1 small peak on the heating curve and 1 small peak on the cooling curve.ConclusionsThe M3 Pro Gold files showed greater flexibility and angular rotation than the M3 Rotary files, without decrement of their torque resistance. The superior flexibility of M3 Pro Gold files can be attributed to their martensite phase.

Torsional fatigue resistance of pathfinding instruments manufactured from several nickel-titanium alloys.

To evaluate the torsional properties of pathfinding nickel-titanium (NiTi) rotary instruments manufactured from several NiTi alloys, ProGlider (M-wire), Hyflex GPF (conventional NiTi Wire and controlled memory wire), Logic (conventional NiTi wire and controlled memory wire) and Mtwo (conventional NiTi wire). A total of 56 NiTi instruments from Glidepath rotary systems (n=8) were used: Logic (size 25, .01 taper), Logic CM (size 25, .01 taper), ProGlider (size 16, .02 taper), Hyflex GPF (size 15, .01 taper), Hyflex GPF CM (size 15, .02 taper; size 20, .02 taper) and Mtwo (size 10, .04 taper). The torsion tests were performed based on ISO 3630-1 (1992). Three millimetres of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. Data were analysed using a one-way analysis of variance (anova) and Tukey test with a significance level at a=5%. The Logic size 25, .01 taper had significantly higher torsional strength values (P<0.05). The ProGlider was significantly different when compared with Hyflex GPF size 15, .01 taper and size 15, .02 taper (P<0.05). The Logic CM size 25, .01 taper had significantly higher torsional strength than Hyflex GPF size 15, .01 taper and size 15, .02 taper (P<0.05). No difference was found amongst Mtwo size 10, .04 taper and Hyflex GPF groups (size 15, .01 taper; size 15, .02 taper; size 20, .02 taper). In relation to the angle of rotation, Logic CM size 25, .01 taper and Hyflex GPF size 15, .01 taper had the highest angle values (P<0.05). The ProGlider had the lowest angle values in comparison with all the groups (P<0.05) followed by Mtwo size 10, .04 taper. The Logic size 25, .01 taper had significantly higher angle of rotation values than ProGlider and Mtwo size 10, .04 taper (P<0.05). The Logic size 25, .01 taper instrument made of conventional NiTi alloy had the highest torsional strength of all instruments tested. In addition, the ProGlider instrument manufactured from M-Wire alloy had the lowest angle of rotation to fracture in comparison with the other instruments.

Industrialización del algodón nativo peruano de color

The objective of this study is to evaluate the technical feasibility to obtain high quality yarns from Peruvian native cotton. This cotton grows in the north coast of Peru and is characterized by being naturally pig-mented with colors such as cream, green, brown, purple, white and beige without being dyed. However, this cotton has some features such as short fiber and low torsional resistance which makes it impossible to spin it with conventional machinery; therefore, a machine specially adapted for the spinning process was used.

A Simplified Approach for Fire Resistance Design of High Strength Q460 Steel Beams Subjected to Non-uniform Temperature Distribution

Presented in this paper is an analytical investigation on fire resistance of high strength Q460 steel beam subjected to non-uniform temperature distribution. Based on the critical bending moment associated with overall flexural stability and results obtained from the previous experimental investigation on the mechanical properties of Q460 steel at elevated temperature, an equivalent stiffness method is established to evaluate the fire resistance of the beam with the consideration of the influence of temperature gradient across the section of the beam. Lateral torsional buckling resistance, critical temperature and overall stability coefficient are obtained for flexure of high strength Q460 steel beams at elevated temperature. A 3-D nonlinear finite element model, which is capable of accounting for temperature gradient and predicting critical bending moment of Q460 steel beam at elevated temperature, is developed. Results from the finite element simulations are compared with the results determined by the proposed equivalent stiffness method and there is a good agreement between the results of the two methods with the maximum difference of 6%. Using the equivalent stiffness method, parametric studies were carried out to investigate effects of steel grade and temperature distribution pattern on fire resistance of high strength Q460 steel beams. Accordingly, a simplified design approach was proposed to predict the critical temperature and overall stability coefficient of Q460 steel beams subjected to non-uniform temperature distribution. The simplified approach is applicable to high strength Q460 steel beams with cross section dimensions ranging from 175 mm to 350 mm and 250 mm to 500 mm for flange width and section height, respectively.

Cyclic fatigue and torsional strength of three different thermally treated reciprocating nickel-titanium instruments.

The aim of this study was to evaluate the cyclic and torsional fatigue resistance of the reciprocating single-file systems Reciproc Blue 25.08 (VDW GmbH, Munich, Germany), Prodesign R 25.06 (Easy Dental Equipment, Belo Horizonte, Brazil), and WaveOne Gold 25.07 (Dentsply/Tulsa Dental Specialties, Tulsa, OK, USA). Sixty reciprocating instruments of the systems Reciproc Blue R25 (RB #25 .08 taper), Prodesign R (PDR #25 .06 taper), and WaveOne Gold (WOG #25 .07 taper) (n = 20) were used. Cyclic fatigue resistance testing was performed by measuring the time to failure in an artificial stainless steel canal with a 60° angle of curvature and a 5-mm radius located 5mm from the tip (n = 10). The torsional test (ISO 3630-1) evaluated the torque and angle of rotation at failure of new instruments (n = 10) in the portion 3mm from the tip. The fractured surface of each fragment was also observed using scanning electron microscopy (SEM). In addition, a supplementary examination was performed to measure the cross-sectional area of each instrument 3 and 5mm from the tip. The data were analyzed using one-way ANOVA and Tukey's test, and the level of significance was set at 5%. The cyclic fatigue resistance values of PDR 25.06 were significantly higher (P < 0.05). RB 25.08 showed higher fatigue resistance than WOG 25.07 (P < 0.05). The torsional test showed that PDR 25.06 had lower torsional strength (P < 0.05). No differences were observed between RB 25.08 and WOG 25.07 (P > 0.05). PDR 25.06 showed higher angular rotation values than RB 25.08 and WOG 25.07 (P < 0.05). RB 25.08 presented higher angular rotation than WOG 25.07 (P < 0.05). The cross-sectional area analysis showed that PDR 25.06 presented the smallest cross-sectional areas at 3 and 5mm from the tip (P < 0.05). PDR 25.06 presented the highest cyclic fatigue resistance and angular rotation until fracture compared to RB 25.08 and WOG 25.07. In addition, RB 25.08 and WOG 25.07 had higher torsional strength than PDR 25.06. In endodontic practice, thermally treated reciprocating instruments have been used for the root canal preparation of curved and constricted canals; therefore, these instruments should present high flexibility and suitable torsional strength to minimize the risk of instrument fracture.

Prediction of Torsional Strength for Very High Early Strength Geopolymer

Very early high strength geopolymers are gaining acceptance as alternative repair materials for highways and other infrastructure. In this study, a very rapid geopolymer binder based on Metakaolin (MK) and Parawood ash (PWA), developed by the authors, was experimentally tested and a prediction model for its torsional strength is proposed. The geopolymer samples were subjected to uniaxial compression, flexural beam, and torsion tests. The modulus of rupture and torsional strength in terms of compression strength were found to be well approximated by 0.7(f’c)1/2 and 1/7(x2y) (f’c)1/2, respectively. Also an interaction relation to describe combined bending and torsion was developed in this study. In addition, the effects of aspect ratio (y/x) were studied on both torsional strength and combined bending and torsion. It was found that an aspect ratio of y/x = 3 significantly reduced the torsional resistance, to about 50 % of the torsional strength of a square section.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.17280

Cyclic and Torsional Fatigue Resistance of XP-endo Shaper and TRUShape Instruments

IntroductionThe purpose of this study was to evaluate the cyclic and torsional fatigue resistance of the XP-endo Shaper (FKG Dentaire, La Chaux-de-Fonds, Switzerland) and TRUShape (Dentsply Tulsa Dental Specialties, Tulsa, OK) instruments. MethodsTwenty XP-endo Shaper (30/0.01) instruments and 20 TRUShape (30/0.06v) instruments were used. Cyclic fatigue resistance was tested by measuring the number of cycles and time to fracture in an artificial stainless steel canal with a 60° angle and a 5-mm radius of curvature (n = 10). The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630-1. The fracture surface of all fragments was examined with a scanning electron microscope. Results were statistically analyzed using the Student t test at a significance level of P < .05. ResultsThe XP-endo Shaper instruments showed a significantly longer number of cycles to fracture and time to failure in seconds than the TRUShape instruments (P < .05). The XP-endo Shaper also presented a lower maximum torque load (P < .05) but a significantly higher angular rotation to fracture than TRUShape (P < .05). ConclusionsThe XP-endo Shaper instruments showed a higher cyclic fatigue resistance and angle of rotation to fracture but lower torque to failure than TRUShape instruments.

The 16-Year Evolution of Proximal Modular Stem Design – Eliminating Failure of Modular Junction

Background: The complexity of hip reconstruction has been and continues to be a perplexing problem with restoring leg length, femoral offset, joint stability and overall hip implant fixation. These were contributing factors that lead to the development of a novel proximal femoral component design “Apex Modular Stem” (Omni, Raynham, MA). The basic stem geometry features a straight stem with a metaphyseal fit and fill cone, a medial triangle and a modular neck junction that allows for version and offset adjustment.In recent years, there has been great concern with the use of modularity in total hip arthroplasty. The goals of this study are (1) to identify complications with the use of a proximal modular design and (2) demonstrated factors that have eliminated those complications.Methods: This is a retrospective study of a single surgeon series (Design A and Design B) of using the same cementless stem and proximal modular neck body (Apex Modular Stem and Omni Mod Hip Stem) from 2000 to 2016 totaling 2,125 stems. 483 stems were the Design A and 1,642 stems, were of the Design B style.Results: Design A, 483 stems were implanted between 2000 and 2004. 31 alignment pins sheared resulting in a revision rate of 6.4%. Design B, 1,642 stems have been implanted between 2004 and 2016 all by the same surgeon, with no failures of the modular junction.Conclusion: All implant devices entail a multitude of risks and benefits. The Apex Modular Stem (Design A), provided excellent fixation, minimal risk of modular junction corrosion, and simple control of anteversion and femoral offset. The limitation was found to be the risk of the alignment pin shearing (6.4%). The pin was enlarged to make it 225% stronger in torsional resistance, and in a subsequent series of over 1,600 femoral stems in a single surgeon series, there were no pin failures over a 12 year duration.

Mechanical Properties of Various Heat-treated Nickel-titanium Rotary Instruments

AimThe purpose of this study was to compare the bending stiffness, cyclic fatigue, and torsional fracture resistances of heat-treated and conventional nickel-titanium rotary instruments. MethodsV-Taper 2 (VT2; #25/.08), V-Taper 2H (V2H; #25/.06), Hyflex CM (HCM; #25/.06), HyFlex EDM (HDM; #25/variable taper), and ProTaper Next X2 (PTN; #25/variable taper) were tested. The bending stiffness was measured with the customized device (AEndoS), and the files (n = 15) were fixed at 3 mm from the tip and bent at 45° with respect to their long axis. Cyclic fatigue resistance was tested by pecking and rotating instruments (n = 15) in artificial canal with a 7.8-mm radius and 35° angle of curvature until fracture. The ultimate torsional strength and toughness were estimated by using AEndoS. The file tip of 5 mm was fixed between resin blocks and driven clockwise at 20 rpm until fracture. The results were analyzed by using one-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of each group were examined under the scanning electron microscope. ResultsCM-wire instruments had lower bending stiffness than others. HDM showed the highest cyclic fatigue resistance, followed by VTH and HCM (P < .05). VT2 showed the highest ultimate strength, followed by HDM, VTH-PTN, and HCM. HDM and VT2 showed significantly higher toughness than VTH, HCM, and PTN (P < .05). Scanning electron microscope analysis showed typical fractographic features of cyclic fatigue and torsional fractures. ConclusionsCM-wire instruments showed higher flexibility and cyclic fatigue resistance than M-wire and conventional nickel-titanium instruments. Large cross-sectional area and conventional nickel-titanium showed high torsional resistance.

Suitability of jetted and grouted precast pile for supporting mast arm structures

Jetted and grouted precast piles (JGPPs) are prefabricated piles installed utilizing jetting and pressure grouting. These piles are well-suited for urban environments as they overcome the inherent drawbacks of currently chosen deep foundations (e.g., noise and vibration disturbances due to pile driving, quality control issue with cast-in-place construction). Past studies in a large test chamber facility have shown that JGPPs can support very high axial and torsional loads owing to their improved skin and tip resistances subsequent to the side- and tip-grouting. However, this new pile has not yet been implemented in practice due to the lack of field verification of its constructability as well as load resistance. This paper presents the full-scale field construction of two JGPPs and the load test program performed to investigate the applicability of the new pile as a foundation for miscellaneous structures. As such structures are subjected to high torsion and lateral load during severe wind-loading (e.g., hurricanes), the test program included combined torsion and lateral loading as well as simple lateral loading. An actual pole – mast arm assembly was used in the coupled torsion and lateral load test to simulate the typical field-loading scenario. The load was applied using a crane and the pile’s rotations and translations were monitored using the novel instrumentation systems. The field tests showed that JGPPs possess high torsion and lateral resistances compared to identically sized drilled shafts, which is a common foundation type used for such structures. The two methods available for predicting axial resistance of the new pile are found to be suitable for the estimation of torsional resistance as well. It was also found that the concurrent application of torsion significantly reduces lateral resistance of the new pile foundation as observed for drilled shafts. In general, the study reveals that the JGPPs are well-suited foundations for miscellaneous structures.