Different metabolic responses during incremental exercise assessed by localized 31P MRS in sprint and endurance athletes and untrained individuals.

Until recently, assessment of muscle metabolism was only possible by invasive sampling. 31P magnetic resonance spectroscopy (31P MRS) offers a way to study muscle metabolism non-invasively. The aim of the present study was to use spatially-resolved 31P MRS to assess the metabolism of the quadriceps muscle in sprint-trained, endurance-trained and untrained individuals during exercise and recovery. 5 sprint-trained (STA), 5 endurance-trained (ETA) and 7 untrained individuals (UTI) completed one unlocalized 31P MRS session to measure phosphocreatine (PCr) recovery, and a second session in which spatially-resolved 31P MR spectra were obtained. PCr recovery time constant (τ) was significantly longer in STA (50±17 s) and UTI (41±9 s) than in ETA (30±4 s), (P<0.05). PCr changes during exercise differed between the groups, but were uniform across the different components of the quadriceps within each group. pH during recovery was higher for the ETA than for the UTI (P<0.05) and also higher than for the STA (P<0.01). Muscle volume was greater in STA than in UTI (P<0.05) but not different from ETA. Dynamic 31P MRS revealed considerable differences among endurance and sprint athletes and untrained people. This non-invasive method offers a way to quantify differences between individual muscles and muscle components in athletes compared to untrained individuals.

[Simulation of bone strain by orthodontic implants using the finite element method]. / Simulation der Knochenbelastung durch orthodontische Implantate mit Hilfe der Finite-Elemente-Methode.

Load direction of applied forces, implant geometry and other biomechanical parameters lead to varying reactions in the surrounding bone structure. Three types of endosseous implant measuring 9 mm in length and 3.3 mm in diameter with and without superperiosteal step, and a threaded surface were investigated with the aid of a finite element method using the COSMOS/M 2.5 program. The load on the implant was investigated under vertical, horizontal, and diagonal forces of between 0.01 N and 100 N. Vertical loading of simple implants caused bone deformation of more than 600 mu eps. The application of the superperiosteal step clearly reduced the deformation. The largest deformations under vertical loading were observed in the trabecular bone with all 3 implant geometries. On horizontal loading the deformation shifted from the trabecular to the cortical bone and was particularly marked at the transition between the two. The smallest deformations, less than 300 mu eps, were measured at implants with a superperiosteal step under diagonal loading. The thread did not improve loading capacity. Implants with a superperiosteal step are recommended since they contribute to more rapid healing and strengthening of the bone.

Three-dimensional analysis of endosseous palatal implants and bones after vertical, horizontal, and diagonal force application.

The effects of bite and orthodontic forces exerted on endosseous palatal implants are not completely understood. This applies especially to the biomechanical properties inherent in the different implant geometries and resulting bone remodelling reactions on the one hand, and to the influence on the direction and magnitude of the applied forces on the other. The results of this study should help in the selection of implants for clinical use. Three types of endosseous implants (all 9 mm in length and 3.3 mm in diameter, made of titanium) were used for this investigation. Type 1 was a simple, cylinder-shaped implant; type 2 a cylinder-shaped implant with a superperiosteal step; and type 3 a cylinder-shaped implant, subperiosteally threaded, with a superperiosteal step. The load on the implant was investigated under three conditions of bite and orthodontic forces from 0.01 to 100 N (vertically, horizontally, and diagonally). The study results were calculated by means of a finite element (FE) method. Vertical loading caused bone deformation of more than 600 microeps at the simple implant. The largest deformations at this load were found in the trabecular bone with all three implant geometries. However, trabecular bone deformation was reduced by a superperiosteal step. Horizontal loading of the implants shifted the deformation from the trabecular to the cortical bone. Furthermore, a large deformation was measured at the transition from cortical to trabecular bone. The smallest deformations (less than 300 microeps) were found for implants with a superperiosteal step and diagonal loading (type 2). The use of threads provided no improvement in loading capacity. All implant types investigated showed good biomechanical properties. However, endosseous implants with a superperiosteal step had the best biomechanical properties under low loads. Thus, the trend should be to optimize the design of implants by producing small implants with additional anchorage on the bone surface.

Hard palate deformation in an animal model following quasi-static loading to stimulate that of orthodontic anchorage implants.

The aim of the present investigation was to identify adequate implant treatment for young patients. In an animal model palate deformation was investigated by acute quasi-static loading. Three series of tests (with newborn, young and adult pigs) were performed, each with two groups (one or two-point stress) and 5-7 animals per group. Discs with a diameter of 3 and 5 mm were placed in group 1 in the suture area, and in group 2 at both the right and left sides of the suture. Deformation was analysed by a computerized three-dimensional (3D) photo-imaging evaluation system. In young animals the one-point load at a significantly lower force level led to fractures in comparison with the two-point load (P < 0.001). Similar results were measured by an increase in the size of one disc from 3 to 5 mm (P < 0.001). In contrast, adult pigs showed stable results with both methods. In general, a larger disc diameter led to less instability. The one-point load seems to be suitable for adult animals, whereas a two-point load might be favourable during ossification. The advantage of the two-point load is the generation of a higher stress and therefore improved control of dental fixation. However, further tests are necessary to investigate the long-term effects.