Torque

The purpose of this study was to analyze, in an animal model, the histologic and biomechanical phenomena at the bone-implant interface of implants inserted with high torque (HT) as compared to low torque (LT) during the first 6 weeks of healing. Forty tapered-screw-form implants were placed in five hybrid sheep. The implant sites were placed in the mandible, using an extraoral approach; four were placed with HT (test: mean 110 Ncm) on one side and four were placed with LT (control: mean 10 Ncm) on the contralateral side. After 1, 2, 3, 4, and 6 weeks of healing, removal torque testing and resonance frequency analysis were performed and the animals were sacrificed for histologic examination. Implants from the HT group showed significantly higher bone apposition than implants from the LT group at all examined healing times. Similarly, removal torque was consistently higher for the HT as compared to the LT group. A significant loss of primary stability in the HT group was evident 7 day...

The aeration of an oil film flowing between the faces of two closely spaced circular plates (one stationary, and one rotating) is examined experimentally, numerically, and with an improved lubrication model. The gap between the plates is small compared to their radii, making lubrication theory appropriate for modeling the flow. However, standard lubrication boundary conditions suggested by Reynolds (1886, "On the Theory of Lubrication and its Application to Mr. Beauchamp Tower’s Experiments, Including an Experimental Determination of the Viscosity of Olive Oil," Philos. Trans. R. Soc. London, 177, pp. 157-234) of p = 0 and pn = 0 (Dirichlet and Neumann conditions on pressure) at the gas-liquid interface do not allow for the inclusion of a contact line model, a phenomenon that is important in the inception of aeration. Hence, the standard theory does not adequately predict the experimentally observed onset of aeration. In the present work, we modify the Neumann boundary con...

The purpose of this study was to evaluate active knee flexion range of motion and hamstring strength following hamstring anterior cruciate ligament (ACL) reconstruction. Case control study, consecutive sample. Seventy-four consecutive patients who had undergone hamstring ACL reconstruction underwent isokinetic muscle strength testing at 2 years post surgery. Measurements of the maximum standing active knee flexion angle with the hip extended were also taken. During isokinetic testing, we evaluated flexion torque at 90 degrees of knee flexion, in addition to the peak flexion torque. We further compared these parameters of muscle strength around the knee for the patients in whom only semitendinosus tendon was harvested as a graft source (ST group), and those from whom the semitendinosus tendon and the gracilis tendon were harvested (ST/G group). Isokinetic testing showed that, in both the ST and ST/G groups, the knee flexor strength of the involved leg was less effectively restored at 90 degrees of knee flexion than at the angle at which the peak torque was generated. Conversely, no significant difference was seen in the side-to-side ratio in either the peak flexion torque or the 90 degrees flexion torque between the groups. The side-to-side ratio in mean maximum standing knee flexion angle was significantly lower in the ST/G group than in the ST group. This study suggests that the loss of knee flexor strength following the harvest of the hamstring tendons may be more significant than has been previously estimated. Furthermore, multiple tendon harvest may affect the range of active knee flexion.

ABSTRACT One of the most efficient ways to reduce the pollution and fuel consumption of an automotive engine is to downsize the engine, whilst maintaining a high level of power and torque. This is achieved by using turbochargers. In urban, and often in suburban, traffic conditions the engine power demand is weak in relation to the maximum power available, so the turbocharger runs at low speed. To appreciate and improve engine performance, it is necessary to know the characteristics of the turbomachinery in this functioning area, characteristics which are not given by turbocharger manufacturer. The reason for this lack of information will be explained and the experiments we are currently conducting at low turbocharger speed are presented. Experimentally, it has been demonstrated that the measured performances of the compressor are dependent on heat exchange (convection and conduction) and are also linked to the pressure and temperature of the lubricating oil. At the CNAM laboratory, the turbocharger test rig has been equipped with a special torquemeter, allowing rotation speeds of up to 120000 rpm, set up between the turbine and the compressor. The turbine is thus separated from the compressor and could be considered as a drive which provides mechanical power to the turbocharger (torquemeter + compressor + bearing unit). Temperature and pressure of the lubricating oil can be adjusted to an experiment’s requirements. The test bench lay out is described. To achieve accurate measurements and evaluate the influence of heat exchanges, tests have been carried out with the whole compressor thermally isolated and with preheated inlet air. The compressor can be assumed to be adiabatic, and the power given to the air flow can be calculated using the first law of thermodynamics. Mechanical bearing losses can be deduced from this calculation and torquemeter power, but also from measurements of lubricating oil flow, and oil temperature at inlet and outlet. The results of experiments for different lubricating oil temperatures and pressures and turbocharger speeds are presented. Real compressor characteristics curves are set up and a comparison of experimental mechanical power losses with a journal bearing CFD model is presented.

Muscular strength imbalance is an important risk factor for ACL injury, but it is not clear the impact of menstrual cycle on muscular strength balance. Our aims were to verify whether muscular balance (hamstring-to-quadriceps peak torque strength balance ratio) during menstrual cycle (luteal and follicular phases) and compare gender differences relative to strength balance to observe possible fluctuations in strength balance ratio. Thirty-eight soccer athletes (26 women and 12 men) took part in this study. Athletes participated in two identical isokinetic strength evaluations for both knee (non-dominant: ND and dominant: D). Peak torque for quadriceps and hamstring muscles were measured in concentric mode and hamstring-to-quadriceps peak torque strength balance ratio calculated. Women had significantly lower hamstring-to-quadriceps peak torque strength balance ratio during the follicular compared to luteal phase, for the ND limb (p=0.011). However, no differences, between luteal and...

The experimentally determined torque-rotation curve of the lumbar spine is mathematically described with a proposed dual-inflection point Boltzmann equation. The result is a method for describing functional spinal unit motion data. The benefit of the model is that each of the coefficients has a specific meaning in relation to the torque-rotation curve: the points A and B identify the respective minimum and maximum rotations of the functional spinal unit, m1 and m2 indicate the inflection points of the curve where the stiffness changes markedly, and α1 and α2 are associated with the rates of change of the curve at m1 and m2, respectively. The dual-inflection point Boltzmann captures the full quality of motion of the spinal segment and can also be used to derive relevant parameters such as range of motion, midrange stiffness, and hysteresis.

Torque failure for endosseous implants has been used as a biomechanical measure of anchorage, though the significance of such data is not known. A practical understanding of the resistance to torque failure of implant-tissue interfaces at stage 2 surgery would help in assigning torque levels for implant abutment-screw fastening. The purpose of this study was to measure torque failure levels of commercially pure (CP) titanium, Ti-6Al-4V, hydroxyapatite-coated (HA-coated) screw-shaped implants placed into the maxillae and mandibles of baboons. Implants identical in size were placed into the edentulous posterior maxillae and mandibles of six female baboons (n = 37 each group) using a standardized surgical protocol. Reverse-torque data were collected at postinsertion time intervals ranging from 3 to 4 months using a counterclockwise torque driver and the data were analyzed (repeated measures ANOVA) for torque differences related to time, biomaterial, and jaw. The HA-coated implants exhi...

To compare the clinical outcome of single implants which underwent immediate nonocclusal loading with implants subjected to early non-occlusal loading at 3 weeks, and implants conventionally loaded at 4 months. One hundred and five patients in five private practices requiring a single implant-supported crown were randomised to immediate loading (35 patients), early loading (35 patients) and conventional loading (35 patients) groups. To be immediately or early loaded, implants had to be inserted with a torque superior to 45 Ncm. Immediately and early loaded implants received non-occluding temporary crows, whereas conventionally loaded implants were directly restored with definitive crowns. Temporary crowns were replaced by definitive ones after 4 months. Outcome measures were crown and implant failures, complications and peri-implant marginal bone level changes recorded by a blinded assessor. Two patients dropped out from the immediate loading group up to 1-year post-loading. Two imp...