In vitro comparison of the force degradation of orthodontic intramural elastic from different compositions

Introduction and Objective: The synthetic intermaxillary elastic emerged as an alternative for clinical use in patients with latex sensitivity. However, there are disagreements about this elastic protocol use according to the force degradation. The aim of this study was to evaluate, in vitro, the forces generated by latex and synthetic elastics over time. Material and methods: Sample size of 840 elastics were used (420 latex and 420 synthetic), delivering medium strength (Dental Morelli®) with internal diameter of 1/8”, 3/16”, 1/4” and 5/16”. The elastics were randomly divided into 7 groups according to the time of the force measuring and immersed into distilled water at 37°C. To measure the force in each group, the elastics were stretched in six progressive increases of 100% of its internal diameter with the aid of a testing machine Emic and measured up to 72 hours. Data were analyzed with SPSS 16.0, using one-way analysis of variance (ANOVA). Results: Immediate force level of synthetic elastics was statistically higher than latex elastics in all strains, for the same size. However, the latex elastics mean force slightly decreased over time, while the synthetic elastics presented an abrupt decrease. Conclusion: The synthetic elastic presented severe force degradation, jeopardizing the cost-benefit ratio, which indicates a higher replacement frequency. The latex elastic showed better mechanical performance in comparison to synthetic ones.

Parâmetros de força ideal aplicada aos principais movimenetos ortodônticos

The orthodontic movement is a result of the system of forces application and it depends on the response of periodontal tissues to this system. The forces must have a magnitude considered ideal, to has maximum response of tissue without pain or root resorption, and keep the health of the periodontal ligament, during all the tooth movement. Therefore, it seems adequate by means of an available literature to estimate parameters of ideal force, for different types of movements; with intention of assisting the orthodontists in optimum control of the tooth movement and thus to diminish the possibility to generate deleterious effects.

Ground reaction forces during level ground walking with body weight unloading

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The influence of handrim design on the contact forces on hands'surface: a preliminary study

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Improving the Effectiveness of Independent Practice with Corrective Feedback

In this action research study of my 8th grade Algebra class, I investigated the effects of teacher-to-student written corrective feedback on student performance and attitude toward mathematics. The corrective feedback was given on solutions for selected independent practice problems assigned as homework. Each problem being assessed was given a score based on a 3- point rubric and additional comments were written. I discovered that providing teacher-to-student written corrective feedback for independent practice problems was beneficial for both students and teachers. The feedback positively affected the attitudes of students and teacher toward independent practice work resulting in an improved quality of solutions produced by students. I plan to extend my research to explore ways to provide corrective feedback to students in all of my mathematics classes.

The influence of "C-factor" and light activation technique on polymerization contraction forces of resin composite

Objectives: This study evaluated the influence of the cavity configuration factor ("C-Factor") and light activation technique on polymerization contraction forces of a Bis-GMA-based composite resin (Charisma, Heraeus Kulzer). Material and Methods: Three different pairs of steel moving bases were connected to a universal testing machine (Emic DL 500): groups A and B - 2x2 mm (CF=0.33), groups C and D - 3x2 mm (CF=0.66), groups E and F - 6x2 mm (CF=1.5). After adjustment of the height between the pair of bases so that the resin had a volume of 12 mm(3) in all groups, the material was inserted and polymerized by two different methods: pulse delay (100 mW/cm(2) for 5 s, 40 s interval, 600 mW/cm(2) for 20 s) and continuous pulse (600 mW/cm(2) for 20 s). Each configuration was light cured with both techniques. Tensions generated during polymerization were recorded by 120 s. The values were expressed in curves (Force(N) x Time(s)) and averages compared by statistical analysis (ANOVA and Tukey's test, p<0.05). Results: For the 2x2 and 3x2 bases, with a reduced C-Factor, significant differences were found between the light curing methods. For 6x2 base, with high C-Factor, the light curing method did not influence the contraction forces of the composite resin. Conclusions: Pulse delay technique can determine less stress on tooth/restoration interface of adhesive restorations only when a reduced C-Factor is present.

Effects of replica running shoes upon external forces and muscle activity during running

Twelve participants ran (9 km . h(-1)) to test two types of running shoes: replica and original shoes. Ground reaction force, plantar pressure and electromyographic activity were recorded. The shoes were tested randomly and on different days. Comparisons between the two experimental conditions were made by analysis of variance (ANOVA) test (P <= 0.05). The time to first peak, loading rate of the first peak and impulse of the first 75 ms of stance were significantly different between the shoes (P <= 0.05), revealing an increase of impact forces for the replica shoes. The peak plantar pressure values were significantly higher (P <= 0.05) when wearing replica shoes. During running, the contact area was significantly smaller (P <= 0.05) for the replica shoe. The electromyographic activity of the analysed muscles did not show changes between the two shoes in running. These findings suggest that the use of replica running shoes can increase the external load applied to the human body, but may not change the muscle activity pattern during locomotion. This new mechanical situation may increase the risk of injuries in these movements.

Effect of a rocker non-heeled shoe on EMG and ground reaction forces during gait without previous training

Unstable shoes have been designed to promote "natural instability" and during walking they should simulate barefoot gait, enhancing muscle activity and, thus, attributing an advantage over regular tennis shoes. Recent studies showed that, after special training on the appropriate walking pattern, the use of the Masai Barefoot Technology (MBT) shoe increases muscle activation during walking. Our study presents a comparison of muscle activity as well as horizontal and vertical forces during gait with the MBT, a standard tennis shoe and barefoot walking of healthy individuals without previous training. These variables were compared in 25 female subjects and gait conditions were compared using ANOVA repeated measures (effect size:0.25). Walking with the MBT shoe in this non-instructed condition produced higher vertical forces (first vertical peak and weight acceptance rate) than walking with a standard shoe or walking barefoot, which suggests an increase in the loads received by the musculoskeletal system, especially at heel strike. Walking with the MBT shoe did not increase muscle activity when compared to walking with the standard shoe. The barefoot condition was more effective than the MBT shoe at enhancing muscle activation. Therefore, in healthy individuals, no advantage was found in using the MBT over a standard tennis shoe without a special training period. Further studies using the MBT without any instruction over a longer period are needed to evaluate if the higher loads observed in the present study would return to their baseline values after a period of adaptation, and if the muscle activity would increase over time. (C) 2012 Elsevier B.V. All rights reserved.

New Isomers in the Full Seniority Scheme of Neutron-Rich Lead Isotopes: The Role of Effective Three-Body Forces

The neutron-rich lead isotopes, up to Pb-216, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond Pb-208.

Analog of the susceptibility spectrum for levitation forces between a superconductor and a permanent magnet

We report on the measurements of both vertical and lateral levitation forces between a permanent magnet NdFeB and a polycrystalline YBa4Cu6O7-delta superconductor. The analysis of the obtained results revealed an interesting correlation between the behavior of the forces in the field-cooled and zero-field-cooled regimes, resembling the structure of the so-called susceptibility spectrum chi ''(chi'). Such force-force diagrams can be useful for identifying flux distribution structure inside a superconducting material. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4743006]

Comparison of active and passive forces of the pelvic floor muscles in women with and without stress urinary incontinence

Background: The reduction of the pelvic floor muscles (PFM) strength is a major cause of stress urinary incontinence (SUI). Objective: To compare active and passive forces, and vaginal cavity aperture in continent and stress urinary incontinent women. Method: The study included a total of thirty-two women, sixteen continent women (group 1 - G1) and sixteen women with SUI (group 2 - G2). To evaluate PFM passive and active forces in anteroposterior (sagittal plane) and left-right directions (frontal plane) a stainless steel specular dynamometer was used. Results: The anteroposterior active strength for the continent women (mean +/- standard deviation) (0.3 +/- 0.2 N) was greater compared to the values found in the evaluation of incontinent women (0.1 +/- 0.1 N). The left-right active strength (G1=0.43 +/- 0.1 N; G2=0.40 +/- 0.1 N), the passive force (G1=1.1 +/- 0.2 N; G2=1.1 +/- 0.3 N) and the vaginal cavity aperture (G1=21 +/- 3 mm; G2=24 +/- 4 mm) did not differ between groups 1 and 2. Conclusion: The function evaluation of PFM showed that women with SUI had a lower anteroposterior active strength compared to continent women.

Integrating on-line process control and imperfect corrective maintenance: An economical design

Existing studies of on-line process control are concerned with economic aspects, and the parameters of the processes are optimized with respect to the average cost per item produced. However, an equally important dimension is the adoption of an efficient maintenance policy. In most cases, only the frequency of the corrective adjustment is evaluated because it is assumed that the equipment becomes "as good as new" after corrective maintenance. For this condition to be met, a sophisticated and detailed corrective adjustment system needs to be employed. The aim of this paper is to propose an integrated economic model incorporating the following two dimensions: on-line process control and a corrective maintenance program. Both performances are objects of an average cost per item minimization. Adjustments are based on the location of the measurement of a quality characteristic of interest in a three decision zone. Numerical examples are illustrated in the proposal. (c) 2012 Elsevier B.V. All rights reserved.

Non-mean-field effects in systems with long-range forces in competition

We investigate the canonical equilibrium of systems with long-range forces in competition. These forces create a modulation in the interaction potential and modulated phases appear at the system scale. The structure of these phases differentiate this system from monotonic potentials, where only the mean-field and disordered phases exist. With increasing temperature, the system switches from one ordered phase to another through a first-order phase transition. Both mean-field and modulated phases may be stable, even at zero temperature, and the long-range nature of the interaction will lead to metastability characterized by extremely long time scales.

Isokinetic analysis of ankle and ground reaction forces in runners and triathletes

OBJECTIVE: To analyze and compare the vertical component of ground reaction forces and isokinetic muscle parameters for plantar flexion and dorsiflexion of the ankle between long-distance runners, triathletes, and nonathletes. METHODS: Seventy-five males with a mean age of 30.26 (±6.5) years were divided into three groups: a triathlete group (n=26), a long-distance runner group (n = 23), and a non-athlete control group. The kinetic parameters were measured during running using a force platform, and the isokinetic parameters were measured using an isokinetic dynamometer. RESULTS: The non-athlete control group and the triathlete group exhibited smaller vertical forces, a greater ground contact time, and a greater application of force during maximum vertical acceleration than the long-distance runner group. The total work (180º/s) was greater in eccentric dorsiflexion and concentric plantar flexion for the non-athlete control group and the triathlete group than the long-distance runner group. The peak torque (60º/s) was greater in eccentric plantar flexion and concentric dorsiflexion for the control group than the athlete groups. CONCLUSIONS: The athlete groups exhibited less muscle strength and resistance than the control group, and the triathletes exhibited less impact and better endurance performance than the runners.

Induced tooth movement: standardization of terms to describe the effects of forces on the periodontal ligament: compression/Traction instead of Pressure/Tension

There is no reason for Dentistry to use different terms for phenomena defined in Physics, the specific field in which concepts associated with forces are established and adapted. In place of pressure/tension, the compression/traction pair should be used. This study defines each one of these terms and justifies their use. Our contemporary world demands standardized criteria, methods, measures, concepts and terms to ensure that study protocols, results and applications are used in the same way in any country or area of human action.