جستجوی مقالات مرتبط با کلیدواژه "torque" در نشریات گروه "پزشکی"

The aim of this study was to compare the mechanical properties of the polymer brackets with metal and ceramic brackets and verify if the polymer brackets could be used clinically.

A thorough search was conducted in four electronic databases, including Scopus, PubMed, Cochrane, Ovid, and Lilacs, with article selection based on Preferred Reporting Items for Systematic Reviews and Meta‑Analysis standards. A computerized search of the database was done from January 1990 to June 2024. Two independent reviewers were involved in study selection, data extraction, and synthesis. Disagreements were resolved by discussion with a third reviewer. The risk of bias was assessed by the quality assessment tool for in vitro studies (QUIN tool). The outcomes measured included permanent deformation, hardness, and torquing capacity.

Ten studies were selected after excluding duplicates, screening, and complete text reading to identify the articles that met the eligibility criteria. All ten studies showed medium risk based on the quality assessment tool for in vitro studies (QUIN Tool).

The following findings were obtained: Polymer brackets have lower mechanical properties in terms of torque loss, fracture resistance, hardness, and torsional creep compared to metal brackets. Among the polymers listed in the studies, it was found that polyamide exhibited low hardness and polyoxymethylene exhibited the highest torque loss. Torque deformation was highest with a ceramic‑reinforced polymer bracket, followed by pure polymer. Torque deformation was minimal with metal slot‑ and ceramic‑reinforced polymers, followed by metal slot‑reinforced polymers.

Previous studies have suggested that ankle position and hip position can influence hamstring strength, but none have considered the influence of both joint positions at the same time.

This study aimed to investigate the effect of ankle and hip position on peak torque (PT), normalized PT (NPT), angle of PT (APT), and surface electromyographic (SEMG) activity during isokinetic knee flexion.

In this within-subject study design, thirteen physically active men in a single session performed three maximal isokinetic unilateral knee flexion repetitions in four different ankle and hip positions: sitting with dorsal/plantar flexion and supine with dorsal/plantar flexion at two angular velocities of 60 and 180°/s on the isokinetic dynamometer. The individual SEMG activity of the gastrocnemius (GL), biceps femoris (BFl), and semitendinosus (ST) muscles was detected using a wireless SEMG system.

Ankle and hip positions had a significant impact on the PT, NPT, and APT (p < 0.05), but did not affect SEMG activity of BFl, ST, and GL muscles for both angular velocities (p > 0.109). Specifically, the flexed hip and dorsiflexed ankle provided the greatest torque production, while the extended hip and plantarflexed ankle led to a decrease in hamstring torque production. An increase in angular velocity also led to an increase in APT.

Both hip and ankle positions have a significant impact on the PT, NPT, and APT, but not on BFl, ST, and GL activation during maximal knee flexion, for both angular velocities, 60 and 180°/s.

Throwing movements are repetitive motions in overhead athletes that cause soft tissue adaptations and ultimately lead to shoulder joint damage. The current study purposed to determine the torque of internal and externalrotation of joint shoulder in overhead athletes with and without impingement syndrome in the ball throwing position.

This cross-sectional study was conducted on 63 male overhead athletes (33 with and 30 without shoulder impingement syndrome(. Simulated maximum functional torque was evaluated while the athlete threw a ball into a net from a sitting position. A 6-camera Vicon Motion Capture system incorporated markers on the upper limb and trunk. A kinematic model of the upper limb was used in OpenSim software with inverse dynamics to obtain maximum torque.

The internal and external rotation and elevation torques differed significantly in athletes with shoulder impingement syndrome compared to those without impingement syndrome (P<0.001, P=0.012, and P<0.001,respectively), while no significant difference was seen in shoulder depression (P=0.283) between the two groups.

The current findings suggest that there may be adaptations to shoulder strength and torque in response to throwing a ball that ultimately cause injury to the shoulder.

Statement of the Problem: 

Various factors have been introduced to achieve normal occlusion. One of them is anterior teeth torque that has a significant effect on orthodontic treatment outcomes.

The aim of this study was to investigate the effect of changes in anterior teeth torque on changes in the space occupied by six anterior teeth by using computer-aided three-dimensional interactive application (CATIA).

In this experimental finite element study, acrylic teeth with pre-adjusted MBT braces were aligned and three-dimensional (3D) scans were made by 3Dscaner. In the CATIA software program, upper incisors’ torque was changed to -2, -4, -6, +2, +4 and+6 degrees and in the lower incisors to -1, - 3, -5, +3 and+5 degrees; the space was measured at 3 heights of maxillary incisor crowns and at incisal edges of mandibular incisors. Then maxillary incisors were then tapered and the measurements were made again. To evaluate the effect of tooth size, these procedures were carried out on teeth with +17% and -17% magnifications

The results showed that by increasing anterior torque from 14.7 to 20.7 degrees in maxillary incisors, the space occupied by anterior teeth increased. Maximum changes were at cingulum height with 1.421mm. Reduction in anterior torque from 14.7 to 8.7 degrees resulted in a decrease in this space and maximum changes were observed in the cingulum height with 1.824mm. In the mandibular arch, a 10-degree change in anterior torque resulted in an -.752mm change in the space. Changes in the space occupied by anterior teeth was not significant in tapered and normal teeth in +6 and -6-degree torque (p Value= 0.78 and p Value=0.83).

By increasing or decreasing the incisors’ torque, the space occupied by anterior teeth increased and decreased, respectively. These changes were less in tapered teeth. Size variations had no significant effect on the results.

This study investigated the effects of short-duration high-intensity simulation of soccer fatigue on the dynamic balance and isokinetic strength of the lower limbs in youth soccer players.

Thirty-nine youth soccer players completed a high-intensity fatigue simulation in 5-min. The participants performed tests on dynamic balance and isokinetic strength before the fatigue simulation (PRE), immediately after simulation (POST5), and 20 min (POST20) and 35 min (POST35) after simulation. Dynamic balance was measured using the Y-Balance test for both legs in the anterior, posteromedial (PM), and posterolateral (PL) directions. The muscle strength of the lower limb was measured using the maximal isokinetic contraction of the dominant leg only.

Dynamic balance was significantly reduced after stimulation in all directions for both legs (P<0.005). Significant reduction in the eccentric hamstring, concentric hamstring, and concentric quadriceps peak torques were also observed (P<0.05). However, no significant reductions were found in the functional hamstring/quadriceps ratio and conventional hamstring/quadriceps ratio (P>0.05).

Fatigue influences dynamic balance, hamstrings, and quadriceps strength which may have implications for higher risk of knee injury in youth players.

The torque of posterior teeth is of great importance in esthetics and occlusion. In the present article, we introduce a simple but useful device to measure intermolar torque. The device consists of two movable and adjustable arms that lie on the selected molar teeth bilaterally; the graduated plane at the body of the appliance then shows the intermolar torque. This device can measure intermolar torque easily and rapidly, with high validity and at a low cost.

 Implementing the post-activation potentiation phenomenon before a competition in the warm-up section may be better than performing the usual warm-up.

 Therefore, the purpose of this study was to determine the effects of type and intensity of muscle contraction with different recovery periods on anaerobic power and peak torque in young trained girls.

 Twelve female subjects (age: 22 ± 2.95 years; height: 165.42 ± 5.35 cm; weight: 57.33 ± 9.15 kg) who had at least two years of continuous training experience were randomly selected. The subjects performed the contraction protocols (isometric (3×70/7s), concentric (3 × 90/4), and eccentric (3 × 110/5)) or control conditions in eight sessions with at least 48 hours intervals between the sessions. In this study, the countermovement jump test and Biodex isokinetic device (60°.S-1) model (ISO-1) were used for measuring anaerobic power and maximum peak torque, respectively. Two-way repeated-measures ANOVA and one-way independent ANOVA were used for analyzing the data (P < 0.05).

 The between-group comparisons showed that the highest anaerobic power and peak torque values in immediate and three-minute recovery periods were seen in the concentric protocol, and the highest values in seven-minute recovery periods were seen in the eccentric protocol (P < 0.05). These variables were also significant in concentric and eccentric contractions in within-group comparisons (P < 0.05).

 Eccentric contraction, similar to other contractions, can produce PAP. It seems that eccentric contractions due to a higher intensity of contractions can maintain more consistency of PAP than do other contractions.

Titanium miniscrews are used at an ever‑increasing rate to provide orthodontic anchorage. The aim of this study was to evaluate the mechanical performance of miniscrews after dry and steam sterilization.

In this experimental study, a total of 72 miniscrews from two different manufacturers with a diameter of 1.6 mm and height of 8 mm were divided into six groups (n = 12). One group of screws from each manufacturer was considered as the control group; the second underwent steam sterilization; and the last group was subjected to dry sterilization. Insertion and fracture torques of each miniscrew were assessed by a torque tester. Data were analyzed using the Kruskal–Wallis and Mann–Whitney tests (P < 0.05).

For Jeil miniscrew, no statistically significant differences were detected between the steam‑sterilized and control groups in their insertion torques (P > 0.05). There was a statistically significant difference between the steam sterilized, dry sterilized and control groups with respect to their fracture torque (P < 0.001). For Hubit miniscrew, there were no significant differences between steam sterilized, dry sterilized and control groups in their insertion torque (P > 0.05) and between steam sterilized and control groups with respect to their fracture torque (P > 0.05). There were significant differences in the mean values of insertion and fracture torques between the two different manufacturers (P < 0.001).

Steam sterilization had no detrimental effects on torque values of miniscrews, but dry heat sterilization affected their mechanical properties.

Screw loosening is a common problem with both screw-retained and cemented implant restorations. It is assumed that the abutment diameter affects detorque value and screw loosening. We aimed to determine the effect of two different abutment diameters on detorque value using cyclic loading and thermocycling.

This in-vitro experimental study was conducted on sixteen Morse-taper implants (4×10 mm) with two different diameters (3.9 and 5.2 mm) installed with a 25-Ncm torque (n=8). Eight screws from each group (3.9- and 5.2-mm abutments) were maintained for a month in a stable state while the rest of the screws underwent cyclic loading for 10,000 cycles with the frequency of 1 Hz and force of 75 N/cm. Then, thermocycling was done at 5-55°C. Detorque value was determined using the torque meter used for screw tightening. Removal torque values were recorded. Maximum deformation force and fracture resistance were documented. Data were analyzed according to Student's t-test using SPSS 21.0 software.

Detorque values were 18.25±1.91 and 21.13±1.46 Ncm with 3.9- and 5.2-mm abutments, respectively. Detorque loss value was 15.50±5.83% with 5.2-mm abutment and 27±7.63% with 3.9-mm abutment. The mean difference between the two abutment diameters was 2.87±0.85 Ncm. Significant differences were observed on torque loss with 3.9-mm- compared to 5.2-mm-diameter abutments (P=0.004).

The results suggested that torque loss was lower with 5.2-mm abutment diameter.