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At least 703 records · Page 39Linked to original sources
PubMed2003

ProTaper rotary root canal preparation: assessment of torque and force in relation to canal anatomy.

AIM: To investigate physical parameters for ProTaper nickel-titanium (NiTi) rotary instruments whilst preparing curved canals in maxillary molars in vitro. METHODOLOGY: A novel torque-testing platform was used to prepare root canals in 15 extracted human maxillary molars with ProTaper rotary instruments. Peak torque and force was registered along with numbers of rotations required to shape the canals. Canals were divided into 'wide' and 'constricted' groups depending on canal volumes assessed by micro computed tomography. Mean scores for each instrument type were calculated and statistically compared using anova and Scheffé posthoc tests. RESULTS: Mean torque varied between 0.8 +/- 0.5 and 2.2 +/- 1.4 N cm whilst mean force ranged from 4.6 +/- 2.6 to 6.2 +/- 2.7 N. Mean numbers of rotations totalled up to 21. All three variables registered were significantly correlated to preoperative canal volumes (P < 0.001) and differed significantly between 'wide' and 'constricted' canals (P < 0.001). CONCLUSIONS: Whilst high forces were used in some cases, no ProTaper instrument fractured when a patent glide path was present. There were significant positive correlations between canal geometry and physical parameters during shaping.

Analysis of Variance↗
PubMed2004

[Peak torque and proprioception at the ankle of dancers in professional training].

The ankle is a frequent site of injury for dancers. The aim of the controlled study was to examine the proprioceptive and sensorimotor control of the ankle in a group of dancers in professional training and to compare it with persons unused to physical training. The purpose was to investigate whether dance training influences the torque ratio of plantar flexion to dorsiflexion (PF/DF) and the proprioceptive performance compared to controls. 42 dancers (31 f, 11 m) in professional training and 40 sex- and age-matched controls performed a isokinetic peak torque test, a passive angle-reproduction test (Biodex System 3), and a single-limb-standing test. The female dancers showed a significantly higher peak torque ratio PF/DF at 30 degrees/s. The difference between male dancers and the controls did not reach a significant level. The dancers did not demonstrate lower absolute errors in passive angle-reproduction (5 degrees and 25 degrees PF) than controls. In the single-limb-standing test, the dancers achieved significantly better results than controls. Dancers could profit from special training of the dorsiflexors. In view of the balance deficits, coordinative exercises should be integrated into school and recreational sports more frequently.

Adolescent↗
PubMed2005

Torque and power-velocity relationships in cycling: relevance to track sprint performance in world-class cyclists.

The aims of the present study were both to describe anthropometrics and cycling power-velocity characteristics in top-level track sprinters, and to test the hypothesis that these variables would represent interesting predictors of the 200 m track sprint cycling performance. Twelve elite cyclists volunteered to perform a torque-velocity test on a calibrated cycle ergometer, after the measurement of their lean leg volume (LLV) and frontal surface area (A(p)), in order to draw torque- and power-velocity relationships, and to evaluate the maximal power (P(max)), and both the optimal pedalling rate (f(opt)) and torque (T(opt)) at which P (max) is reached. The 200 m performances--i.e. velocity (V200) and pedalling rate (f 200)--were measured during international events (REC) and in the 2002 French Track Cycling Championships (NAT). P(max), f(opt), and T(opt) were respectively 1600 +/- 116 W, 129.8 +/- 4.7 rpm and 118.5 +/- 9.8 N . m. P(max) was strongly correlated with T(opt) (p < 0.001), which was correlated with LLV (p < 0.01). V200 was related to P(max) normalized by A(p) (p < or = 0.05) and also to f(opt) (p < 0.01) for REC and NAT. f 200 (155.2 +/- 3, REC; 149 +/- 4.3, NAT) were significantly higher than f(opt) (p < 0.001). These findings demonstrated that, in this population of world-class track cyclists, the optimization of the ratio between P(max) and A(p) represents a key factor of 200 m performance. Concerning the major role also played by f(opt), it is assumed that, considering high values of f 200, sprinters with a high value of optimal pedalling rate (i.e. lower f200-f(opt) difference) could be theoretically in better conditions to maximize their power output during the race and hence performance.

Adult↗
PubMedDate not supplied

[Changes in muscle torque in patients after total knee arthroplasty].

AIM: The purpose of this study was to compare muscle torque during isokinetic knee movements of patients after total knee arthroplasty (TKA) with a similar healthy group. METHOD: 43 patients were examined 3 years after primary total knee arthroplasty with an isokinetic dynamometer (Cybex 340). Torque measurements were evaluated for extension and flexion with 4 different velocities. The results were compared with a group of 43 people without knee disease. Bouth groups consist of 29 women and 14 men. The mean age was also comparable (66.4 vs. 65.8 years). RESULTS: A mean peak torque of 65.9 Nm was measured during extension with low velocity (60 degrees /s) in the group of patients with TKA -- 84.3 % of the control group (p = 0.079). At the highest velocity the patients produced 30.2 Nm. This was 72.8 % of the control group (difference statistically significant, p = 0.006). No differences were found in the Extension/Flexion ratio between the two groups. CONCLUSION: The deficites of knee strength in patients after TKA are more distinct in high velocities of motion.

Aged↗
PubMed1999

The influence of age on isokinetic torque of the upper and lower leg musculature in sedentary men.

While strength patterns in aging for the knee joint have been well investigated in the concentric mode, few data are available about the behaviour in the eccentric mode and for either modus in the ankle. The purpose of this study was to compile reference data for the lower extremities in untrained men between 20 and 60 years of age to determine the influence of age, especially in the eccentric work mode. Sixty-four male subjects between 20 and 60 years were divided into four age groups. Using a LIDO ACTIVE dynamometer, maximum torque was tested for the knee between 90 degrees to 0 degrees and for the ankle between 30 degrees to -10 degrees at velocities 60, 180, 240, 300 degrees/s concentric, 60 and 120 degrees/s eccentric and isometric with angles 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees for the knee and 30 degrees, 20 degrees, 10 degrees, 0 degrees , -10 degrees for the ankle. Individual parameters for age-dependence were checked using linear correlation calculation with p < 0.01 set as significant. The peak torque (PT) of the knee extensors and flexors showed a typical course with the highest values in the eccentric and isometric mode and a decrease in the concentric mode with increasing angular velocity. In the concentric mode there was a significant negative correlation between PT and age at all angular velocities, but none for isometric and eccentric mode. The greatest maximum torque in the ankle was attained in the eccentric mode at 60 degrees/s. The difference to the knee was smallest in this mode compared to isometric and concentric. The plantar flexion showed age-dependence at all concentric velocities, less in eccentric and none in isometric mode. There was no correlation in dorsiflexion. The influence of loss of muscle fiber and degeneration in the course of aging has thus less influence in eccentric measurements than in the concentric mode. On the contrary, it must be assumed that the high eccentric tensions which are possible due to the quasi-elastic structures in the muscle, are maintained by the increase in stiffness of the connective tissue.

Adult↗
PubMed2002

The effect of repeated torque and salivary contamination on the preload of slotted gold implant prosthetic screws.

STATEMENT OF PROBLEM: Screw loosening and/or fracture is common and has been attributed to many factors, including improper torque and preload. Purpose. This study evaluated the effect of repeated preload torque and salivary contamination on the preload of the slotted gold implant prosthetic screw. MATERIAL AND METHODS: Fifteen slotted gold prosthetic screws were tested in an unused stack of components consisting of an implant, an abutment cylinder, and a screw and gold cylinder. A custom load frame and load cell and associated electronics were used. The component stack was lubricated with human saliva. Each screw was tightened to 10 Ncm with a hand-held torque wrench fitted with strain gauge electronics and then removed 10 times. Preload values at the first (Group 1X), fifth (Group 5X), and tenth (Group 10X) repetition were measured. Repeated-measures 1-way analysis of variance (P<.05) and paired comparisons were used to analyze the data. RESULTS: The mean preload value increased from Group 1X (184.3 N +/- 28.9) to Group 5X (202.5 N +/- 27.7) to Group 10X (220.2 N +/- 29.0). The differences among these groups were significant (P=.004). CONCLUSION: Within the limitations of this study, higher preload was achieved after the repeated use of a saliva-lubricated gold prosthetic retaining screw.

Analysis of Variance↗
PubMed2006

Torque-speed relationship of the bacterial flagellar motor.

Many swimming bacteria are propelled by flagellar filaments driven by a rotary motor. Each of these tiny motors can generate an impressive torque. The motor torque vs. speed relationship is considered one of the most important measurable characteristics of the motor and therefore is a major criterion for judging models proposed for the working mechanism. Here we give an explicit explanation for this torque-speed curve. The same physics also can explain certain puzzling properties of other motors.

Bacterial Physiological Phenomena↗
PubMed2002

Changes in muscle torque following anterior cruciate ligament reconstruction: a comparison between hamstrings and patella tendon graft procedures on 45 patients.

We designed a prospective study to examine the influence of graft type (hamstring or patella tendon) on thigh muscle torque recovery after anterior cruciate ligament reconstruction. 60 patients undergoing ACL reconstruction, using a hamstring or patella tendon graft, were studied and 45 were followed up to 1 year. Concentric and eccentric quadriceps and hamstring torque were recorded, using an isokinetic dynamometer preoperatively, 6 and 12 months after ACL reconstruction. We found an improvement in all muscle functions in both the operated and unoperated legs during the recovery period. Graft type had no effect on recovery. During the first 6 months, torque was restored to preoperative levels and continued to improve in all muscles and actions between 6 months and 1 year.

Adult↗
PubMed2006

Effects of allometric scaling and isokinetic testing methods on the relationship between countermovement jump and quadriceps torque and power.

Determination of the strongest possible relationship between isokinetic quadriceps and functional performance measurements in healthy females would allow sports medicine practitioners to establish normative values when examining muscular performance in injured females. Previous attempts to correlate both measurements have, however, produced inconsistent results. The purpose of this study was to examine the effects of allometric scaling, isokinetic testing velocities, reciprocal and non-reciprocal isokinetic testing on the relationship between countermovement jump (CMJ) and isokinetic quadriceps torque and power in recreational females athletes. Seventeen females (age 21.0 +/- 2.0 years, body mass index 19.5 +/- 1.0 kg x m(-2)) performed isokinetic quadriceps and CMJ tests. Isokinetic peak torque and average power were obtained reciprocally and non-reciprocally at 1.05 and 3.14 rad x s(-1), and were corrected for body mass by allometric modelling. Pearson product-moment correlation (r) was used to assess the relationship between the isokinetic parameters and the CMJ measurements. Coefficients of determination (r(2)) were calculated to determine the magnitude of common variance. The r-values for all non-allometrically modelled non-reciprocal parameters were greater (r = 0.58-0.63) than isokinetic parameters obtained reciprocally (r = 0.28-0.47). Using allometric scaling, non-reciprocal isokinetic data accounted for an additional 2-9% of the CMJ height variance, and statistically significant correlations were obtained at both 1.05 and 3.14 rad x s(-1). Allometrically scaled, non-reciprocal isokinetic peak torque and average power at 1.05 rad x s(-1) had the highest correlation with CMJ (r(2) = 0.49). At both 1.05 and 3.14 rad x s(-1), non-reciprocal quadriceps parameters correlated more closely with CMJ measurements than do reciprocal contractions. Normalization for body size by allometrically scaling may further improve correlations with CMJ performance.

Adult↗
PubMedDate not supplied

Experimental method to reveal the effect of rotor magnet size and air gap on artificial heart driving motor torque and efficiency.

To investigate experimentally the effect of rotor magnet design on artificial heart driving motor performance, seven rotors with different magnet lengths or thicknesses, as well as different peripheral angles, were manufactured and tested in the same motor stator with different rotating speeds. The input power (voltage and current) and output torque were measured and the motor efficiency was computed. The results demonstrated that the reduction of rotor magnet size and the enlargement of the air gap between the rotor magnets and the stator coil core have no significant effect on motor efficiency, but will reduce the torque value on which the motor achieves the highest efficiency; it could be remedied however by increasing the rotating speed, because the torque at the high efficiency point will increase along with the rotating speed. These results may provide a basis for developing small rotor magnets, large air gap and high efficiency motors for driving an artificial heart pump.

Air↗
PubMed1997

Torque Production Using Handwheels of Different Size During a Simulated Valve Operation Task.

Opening and closing valves in industrial facilities often requires operators to use bars and wrenches as levers (cheaters) in order to overcome initial actuation forces. In order to determine more appropriate operational specifications, the maximum torque production capability was measured when 12 male participants used 4 different valve handwheels at 3 different heights and 2 different angles (in relationship to the coronal plane). The results indicate that the participants produced significantly greater torque when the largest of the 4 wheels (40.6 cm diameter) was used than when the medium (22.9 cm), small (20.3 cm), and handled (17.8 cm) handwheels were used. Although the main effect of heights was found to be statistically significant, post-hoc analyses between the heights found them to be, essentially, equal. In addition, the vertical and horizontal wheel orientations were not found to be different. The results are applicable to all industries where handwheels are used and applicable to valve manufacturers for designing operational torque specifications below the values found in this study.

handwheels↗
PubMed2002

The use of mixer torque rheometry to study the effect of formulation variables on the properties of wet granulations.

Mixer torque rheometry was used to investigate the rheological behavior of wet granulations with different concentrations of drug, binder, and water. An experimental design was employed to systematically study the effects of the three formulation variables on the torque profiles of the wet masses over time. Under comparable conditions, increasing binder and water concentrations tended to produce higher wet mass consistencies. Friability of the dried granules was measured as an indication of the strength of the granules. A reduced quadratic model in terms of each of the three variables was found to satisfactorily predict granule friability. Granule friability decreased with increases in the binder level and increased slightly with increasing drug concentration. An inverse relationship was seen between granule friability and the amount of water added to the formulation, especially at lower drug concentrations. Mixer torque rheometry is a useful method for studying the properties of wet granulations when minimal amounts of drug are available for the development of a wet granulated formulation.

Chemistry, Pharmaceutical↗
PubMed2002

Chronic intrathecal baclofen treatment and withdrawal: I. Changes in ankle torque and hind limb posture in normal rats.

This study evaluated reflex excitability and locomotor changes during chronic intrathecal infusion of the GABAb agonist baclofen (ITB) and its withdrawal, in the rat. We observed sustained velocity dependent decreases in ankle torque during four weeks of ITB treatment. These changes were correlated with a significant reduction of the EMG burst magnitude time locked to the dynamic phase of ankle dorsiflexion during the first ITB treatment week. However, a considerable recovery of EMG magnitude was observed during the third and fourth weeks of treatment. During baclofen withdrawal, significantly increased velocity dependent ankle torque was observed for 4 weeks. These increases in ankle torque were correlated with increased magnitudes of EMG time locked to the dynamic phase of ankle rotation. Measures of hind limb axis and base of support were obtained using analysis of footprints on a treadmill during ITB treatment and withdrawal periods. During ITB treatment and for up to 7 weeks of withdrawal, hindlimb axis and base of support were significantly altered compared with vehicle controls. These studies were performed to provide a foundation for evaluation of treatment and withdrawal in the setting of experimental chronic contusion spinal cord injury.

Animals↗
PubMedDate not supplied

Assessment with the dermal torque meter of skin pliability after treatment of burns with cultured skin substitutes.

The assessment of visco-elastic (V-E) properties in cutaneous scars is critical to reduction of impairment and restoration of function after grafting of excised burns. Cultured skin substitutes (CSS) that consist of autologous keratinocytes and fibroblasts attached to biopolymer substrates are alternatives for permanent closure of excised, full-thickness burns, but assessment of scarring has been subjective. V-E properties of CSS were measured with a Dia-Stron Dermal Torque Meter (DTM 310, Dia-Stron, Ltd, Broomall, Pa), which applies a constant torque (10 mNm) for a fixed interval (10 seconds) and measures rotational deformation and recovery. Parameters of skin deformation were measured in patients (n = 10) after grafting of CSS or meshed skin autograft. Native human skin (NHS) of healthy volunteers (n = 13) served as the control. Skin healed after treatment with CSS or autograft was evaluated for 1 year or longer after grafting. Elastic stretch (Ue), viscous stretch (Uv), total extensibility (Uf), elastic recovery (Ur), total recovery (Ua), and residual plasticity (R) were measured as degrees of rotation, were tested for significance (P < .05) by Student t test comparisons between treatment groups and controls, and were subjected to regression analysis. Assessment of burn scar with the Dermal Torque Meter detected time-dependent increases of all individual parameters of V-E properties for both CSS and autograft during the first year after grafting. At 1 year or later, no statistical differences were found between CSS and autograft for individual parameters, but Ue and Ur for autograft were significantly lower than for NHS. At 1 year or longer, autograft was significantly different from CSS or NHS, with a greater ratio of Uv to Ue, and both graft types had a lower ratio of Ur to Uf than NHS had. These results suggest that instrumental measurement of scar pliability may increase objectivity in assessment of patient recovery and establish an absolute scale for quantitative analysis of V-E properties in skin after grafting of conventional or alternative skin substitutes.

Biocompatible Materials↗
PubMed2003

A comparison of torque required to fracture three different nickel-titanium rotary instruments around curves of the same angle but of different radius when bound at the tip.

Instrument fracture is an unfortunate but possible sequela of instrumentation of canals, especially when the instrument is bound at the tip. The purpose of this study was to compare the torque required to fracture three file sizes of three different rotary file types around two simulated canal curvatures, gradual or acute, when the tip of the working end of the file was bound. Profile Series 29 0.04 and 0.06 taper and Profile 0.06 ISO rotary files were placed passively into simulated canal curvatures of the same angle but of different radii. The file tips were bound 2 mm from the working end and a measurable torque was applied until fracture. ANOVA with Tamhane post-hoc comparison showed that the 0.06 Series 29 did not differ from the ISO 0.06 taper or the 0.04 Series 29 but there was statistical difference (p < 0.01) showing that the 0.04 Series 29 broke with less force than did the 0.06 ISO files. Statistical tests (p < 0.01) also showed smaller files failed with less torque, as did files in more acute canal curvatures.

Analysis of Variance↗
PubMed1996

The contribution of anulus fibers to torque resistance.

STUDY DESIGN: Anulus fibers of the intervertebral disc oriented in one direction were dissected, and oppositely directed fibers were left intact as a result of a newly developed dissection method. Motion segments were dissected by this way, and motion segments after bilateral facetectomy were loaded in torsion and compared with each other. OBJECTIVES: To assess the contribution of facets and anulus fibers to torque resistance. SUMMARY OF BACKGROUND DATA: Mathematical models predict that torsional stress is transmitted only to those collagene fibers of the anulus that are angled in the direction of the applied torque. Torsion and forward bending or torsion and compression are likely to cause anulus damage. No experimental study that we are aware of has confirmed that anulus fibers are the main structure to resist against torque. METHODS: Pure axial rotation moments were applied on 12 lumbar motion segments. The six components of motion were recorded. Six motion segments were investigated intact after dissection of anulus fibers directed in one direction and after additional bilateral facetectomy. In six motion segments, bilateral facetectomy was performed before anulus dissection. RESULTS: With the application of an axial rotation moment of 8.5 Nm to the left, axial rotation increased 2 degrees after dissection of disc fibers in one direction, and 1.2 degrees after bilateral facetectomy (P = 0.002). In the opposite direction, there were no differences. After both injuries, axial rotation was 7.6 degrees to the left (direction of fiber dissection) and -3.3 degrees to the right (P = 0.0005). CONCLUSION: In lumbar motion segments without degeneration, anulus fibers restrict axial rotation more than the facets.

Adult↗
PubMed2006

Knee isometric torque and electromyographic specificities after semitendinosus and gracilis hamstrings anterior cruciate ligament reconstruction.

OBJECTIVES: Because the co-contraction of the gastrocnemius and hamstring muscles strains the anterior cruciate ligament, the role of the gastrocnemius muscle is of particular importance after semitendinosus and gracilis tendon autografts for anterior cruciate ligament reconstruction. This study aimed to examine the neuromuscular mechanisms underlying postsurgical torque deficits during knee flexion by using surface electromyography. DESIGN: A total of 14 volunteer patients (eight men, six women; age, 32.5 +/- 9.3 yrs; height, 172.7 +/- 6 cm; weight, 69.6 +/- 10.2 kg) were enrolled in the study; all had undergone anterior cruciate ligament reconstruction performed by the same surgeon. The neuromuscular mechanisms were assessed using isometric tests and surface electromyographic recordings at 19 mos post-reconstruction. The torque deficits in the injured knee were compared with the uninjured knee, which served as control values. RESULTS: Significant differences in torque production were observed between the two limbs at specific angular positions during the extension and flexion tests (P < 0.05). The difference in the root mean square myoelectrical activity between the limbs was computed at each tested position, revealing that the gastrocnemius muscle had greater activity at 75 degrees than at 45 degrees (P < 0.05). CONCLUSIONS: In deep flexion (>70 degrees), the gastrocnemius muscle may compensate for the weakened hamstrings and thereby strain the anterior cruciate ligament graft after anterior cruciate ligament semitendinosus and gracilis tendon reconstruction.

Adult↗
PubMed2000

How Fo-ATPase generates rotary torque.

The F-ATPases synthesize ATP using a transmembrane ionmotive force (IMF) established by the electron transport chain. This transduction involves first converting the IMF to a rotary torque in the transmembrane Fo portion. This torque is communicated from Fo to the F1 portion where the energy is used to release the newly synthesized ATP from the catalytic sites according to Boyer's binding change mechanism. Here we explain the principle by which an IMF generates this rotary torque in the Fo ion engine.

Amino Acid Sequence↗