STATEMENT OF PROBLEM: Fatigue failure of implant components is a common clinical problem. Plasma nitriding, an in situ surface-strengthening method, may improve fatigue properties of dental implants. PURPOSE: The purpose of this in vitro study was to evaluate the effect of plasma nitriding on the fatigue behavior of implant systems. MATERIAL AND METHODS: The preload and friction coefficient of plasma nitrided abutment screws, as well as settlement of the implant-abutment interface, were measured. Then, the reverse torque values and pullout force were evaluated after cyclic loading. Finally, the fatigue properties of the implant system were investigated with static fracture and dynamic fatigue life tests, and the morphology of the fracture on the surface of the implant system was observed. RESULTS: The plasma nitriding treatment reduced the friction coefficient; increased the preload, settlement value, reverse torque values, pullout force, and static fracture load; and prolonged fatigue life. Furthermore, abutment screws with plasma nitriding treatment showed a different fatigue fracture mode. CONCLUSIONS: Plasma nitriding improved mechanical performance and may be a suitable way to optimize the fatigue behavior of dental implants.
Aging is associated with neurodegeneration and a loss of muscle function, especially in lower-limb muscles. While caffeine may augment muscle force generation through multiple effects on the central nervous system, no studies have yet compared the effects of caffeine on force-generating capacity between younger and older men, who might respond differently due to age-related changes in the structures on which caffeine acts. In a double-blind, controlled trial, 22 younger (25 ± 5 years) and 21 older (68 ± 6 years) men were tested for isometric plantarflexor torque on two separate days (2-7 days apart) before and 60 min after ingesting 3 mg/kg (∼2 cups of coffee) of caffeine or placebo. No effects of caffeine ingestion on peak torque or rate of torque development were detected in either older or younger men. Therefore, 3 mg/kg of caffeine may not acutely counteract age-related decreases in force capacity of the functionally important plantarflexor muscles.
- MeSH
- dvojitá slepá metoda MeSH
- kofein * farmakologie MeSH
- kosterní svaly fyziologie MeSH
- lidé MeSH
- přijímání potravy MeSH
- senioři MeSH
- stimulanty centrálního nervového systému * farmakologie MeSH
- točivý moment MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- randomizované kontrolované studie MeSH
This study aimed to compare the angle-specific (AS) and non-angle-specific (NAS) hamstring to quadriceps conventional and functional ratios between healthy, hamstring- and ACL-injured elite soccer players. One hundred and eleven players (27.42 ± 8.01 years, 182.11 ± 6.79 cm, 75.93 ± 7.25 kg) completed a series of concentric knee flexor and extensor strength in addition to eccentric knee flexor strength was measured at an angular velocity of 60°.s-1. Normalized and raw peak torque values, and the torque-angle profiles were extracted for analysis. Conventional and functional NAS (peak values) and AS (waveform ratios) hamstring to quadriceps ratios were calculated and compared between the groups. Healthy players produced greater functional and conventional ratios compared to players with either ACL or hamstring injury. Players with hamstring injury produced a lower AS functional ratios between 46° and 54° of knee flexion. Players suffering from ACL injury depicted a lower value for the AS functional ratio between 33° and 56° of knee flexion. Although NAS can identify soccer players with previous hamstring or ACL injury, the range where there is a strength deficiency is eluded. With the use of AS the range where the deficiency is present can be identified, and clinicians can benefit from this analysis to design robust rehabilitation protocols.
OBJECTIVES: This study evaluates the effect of post-activation potentiation (PAP) after 5x5s maximal voluntary isometric contractions (activation stimulus, AS) on tensiomyography (TMG) and torque twitch contractile parameters of vastus lateralis (VL) and medialis (VM), respectively. Further, we validated the decomposition of TMG response to separate responses of three fiber types. METHODS: 15 healthy individuals participated in this study (40% women; age 19±2.3 years). A decomposition of VL TMG response was done after optimal fitting of three exponential curves. RESULTS: We found main effects in contraction time (Tc) for muscle, method and time. Furthermore, we found interactions between muscle*method, method*time and muscle*method*time. Compared to PRE AS, we found shorter TMG Tc in VL and VM during the first two minutes after AS. Torque Tc remained unchanged in VL, while it increased in VM within 30 seconds after AS. A decomposition of VL TMG response confirmed PAP effects being present only in decomposed type IIb muscle fibers. CONCLUSION: The TMG is a sensitive method to detect PAP effects with a sensor mounted directly above the muscle belly. After the decomposition of the TMG signal to three separate muscle fiber phenotypes, we provided a non-invasive insight in the contribution of each muscle fiber phenotype to the PAP of the whole muscle.
Screw loosening is one of the most common clinical problems of dental implants. Research on the influencing factors of screw loosening is very important to prevent screw loosening. The purpose of this in vitro study was to evaluate the influence of liquid contamination on the screw loosening. According to the contamination condition, forty-five abutment screws were divided into three groups (n = 15): no contamination, artificial saliva contamination, and mouthwash contamination. The preload and friction coefficient of the abutment screws were recorded. Then, the reverse torque values (RTVs) and settlement were measured after 3.0 × 105 and 6.0 × 105 cycles. The surface wear of the screws was analyzed. Finally, the stress distribution of the abutment screws was calculated by finite element analysis (FEA). The results showed that fluid contamination reduced the friction coefficient, increased the preload, decrease the settlement, improved resistance to screw loosening, and reduced wear on the thread surface. Appropriate antimicrobial lubrication may improve the anti-loosening performance of abutment screws and prevent excessive wear on the threaded surface.
Biomechanical performance plays an important role in the long-term service of dental implants. Loosening and fatigue damage of the central screw are the most common problems. This research investigated the effect of the central screw taper angle on the loosening performance and fatigue characteristics of dental implants. Central screws with four taper angles, 30°, 60°, 90° and 180°, were processed and tested. The loosening performance of the screws under initial and postload conditions was compared. Then, the fatigue characteristics of dental implants was measured. Finally, the wear and fracture modes of the screws were observed. The damage locations were verified by finite element analysis (FEA). The results showed that the central screws with 30° taper had substantially better anti-loosening performance and less fretting wear. The central screws with 180° taper had a higher preload, resulting in a longer fatigue life. Furthermore, the fatigue fracture of the central screw occurred at the level of the first thread position, consistent with the FEA results. In the future clinical applications, central screws with a 30° taper angle may improve anti-loosening performance and prolong fatigue life by increasing the tightening torque.
BACKGROUND: It is not clear if soccer training affected the development of muscle strength positively in children. We hypothesize that soccer training could positively affect the isokinetic concentric muscle strength and anthropometric characteristics in different ages of adolescents of the same biological age. METHODS: A total of 126 young soccer players (N.=66) and untrained boys (N.=60) throughout the developmental ages of 12, 14 and 16 years volunteered to participate in the study. Sexual maturation was classified according to Tanner's stages. Soccer players, except from their school's physical education program, participate also in a soccer training program. All participants underwent anthropometric measurements. The isokinetic-concentric peak torque values of the hamstrings (H) and quadriceps (Q), as well as the conventional strength ratios of H:Q, were measured on an isokinetic dynamometer at angular velocities of 60, 180, and 300°·s-1. RESULTS: Anthropometric differences in the same age group, between trained and untrained, were presented only for 12-year-olds (height, P<0.001 and BMI, P<0.01). Between groups, differences were observed in almost all anthropometric measurements, probably as result of development. The absolute isokinetic-concentric muscle strength was significantly higher (P<0.001) in the 12- and 16-year-old trained group, compared to untrained, for the knee-flexors and knee-extensors. However, no significant differences were found between the trained and untrained 14-year-olds, for the muscle groups of Q and H. The H:Q strength ratios did not differ between groups at all angular velocities. CONCLUSIONS: The results of this study showed that systematic soccer training has a positive effect in the peripheral system, expressed as an increased lower limb muscle strength; specifically, Q and H.
- MeSH
- dítě MeSH
- fotbal * MeSH
- kosterní svaly MeSH
- lidé MeSH
- mladiství MeSH
- stárnutí MeSH
- svalová síla MeSH
- točivý moment MeSH
- zadní stehenní svaly * MeSH
- Check Tag
- dítě MeSH
- lidé MeSH
- mladiství MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
The research aims to analyze the tibial component rotation using the finite element method by resecting the tibia in a transverse plane at an angle between 1.5° (external rotation) and -1.5° (internal rotation). We used a three-dimensional scanner to obtain the tibia's geometrical model of a cadaveric specimen. We then exported the surfaces of the tibial geometrical model through the Computer-Aided Three-dimensional Interactive Application (CATIA), which is a Computer-Aided Design (CAD) program. The CAD program three-dimensionally shaped the tibial component, polyethylene, and cement. Our analysis determined that the maximum equivalent stress is obtained in the case of proximal tibial resection at -1.5° angle in a transverse plane (internal rotation) with a value of 12.75 MPa, which is also obtained for the polyethylene (7.693 MPa) and cement (6.6 MPa). The results have shown that detrimental effects begin to occur at -1.5°. We propose the use of this finite element method to simulate the positioning of the tibial component at different tibial resection angles to appreciate the optimal rotation.
Background and objective: Type of physical activity may influence morphological and muscular asymmetries in the young population. However, less is known about the size of this effect when comparing various sports. The aim of this study was to identify the degree of bilateral asymmetry (BA) and the level of unilateral ratio (UR) between isokinetic strength of knee extensors (KE) and flexors (KF) among athletes of three different types of predominant locomotion in various sports (symmetric, asymmetric and hybrid). Material and methods: The analyzed group consisted of young elite athletes (n = 50). The maximum peak muscle torque of the KE and KF in both the dominant (DL) and non-dominant (NL) lower limb during concentric muscle contraction at an angular velocity of 60°·s-1 was measured with an isokinetic dynamometer. Results: Data analysis showed a significant effect of the main factor (the type of sport) on the level of monitored variables (p = 0.004). The type of sport revealed a significant difference in the bilateral ratio (p = 0.01). The group of symmetric and hybrid sports achieved lower values (p = 0.01) of BA in their lower limb muscles than those who played asymmetric sports. The hybrid sports group achieved higher UR values (p = 0.01) in both lower limbs. Conclusions: The results indicate that sports with predominantly symmetrical, asymmetrical, and hybrid types of locomotion affected the size of the BA, as well as the UR between KE and KF in both legs in young athletes. We recommend paying attention to regular KE and KF strength diagnostics in young athletes and optimizing individual compensatory exercises if a higher ratio of strength asymmetry is discovered.
- MeSH
- koleno MeSH
- kosterní svaly MeSH
- lidé MeSH
- sportovci MeSH
- sporty * MeSH
- svalová síla * MeSH
- točivý moment MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Šestaosmdesátiletý aktivní muž na antikoagulační terapii dabigatranem s nesprávným dávkováním byl přijat na chirurgické oddělení spádové nemocnice pro bolesti břicha. Vstupně byla zjištěna renální insuficience, prodloužený aktivovaný parciální tromboplastinový čas (APTT). Byla zvažována operace. Přivolaný interní konziliář provedl tuto rozvahu: je-li operace urgentní, podat před dní specifickou protilátku proti dabigatranu idarucizumab. Je-li odložitelná, následující den je třeba zkontrolovat test na dilutovaný trombinový čas a aPTT a v případě nutnosti operace učinit rozhodnutí o podání idarucizumabu dle zjištěných hodnot. Na CT břicha zjištěna torze mezenteria. Rozhodnuto o akutním provedení operace. Před ní byl podán idarucizumab. Operace a následný průběh se obešly bez větších komplikací. Rekonvalescence byla rychlá. Při propuštění byla opět nasazena vyšší dávka dabigatranu nežli doporučená. Náprava byla provedena při kontrole v kardiologické ambulanci. Dabigatran je jediné nové antikoagulans, jehož účinek je možné okamžitě zrušit pomocí specifické monoklonální protilátky idarucizumabu. Operace se mohla provést okamžitě po podání přípravku Praxbind, ischemie střeva tím pádem byla krátká, nebyla nutná jeho resekce, zkrátila se i doba rekonvalescence. Idarucizumab dobře funguje i u předávkovaných pacientů s renální insuficiencí. Je možná alespoň částečná monitorace účinků dabigatranu pomocí aPTT (i v podmínkách okresní nemocnice). Je nutné důsledně kontrolovat, jestli užívá pacient vhodnou antikoagulační léčbu a ve správné dávce.
86-year-old active man on anticoagulation therapy with dabigatran in non adequately high dose was hospitalised at surgery, department of regional hospital for the sake of abdominal pain. The operation was considered. Senior consultant from internal department advised to administer the specific antidote idarucizumab in the case of urgent surgery or, in the case the surgery could be postponed, wait and the next day control dilute thrombin time and aPTT and after receiving the results to administer idarucizumab or not. After that the CT of abdomen revealed mesenteric torsion. Urgent surgery was done after immediate administration of specific antidote of dabigatran idarucizumab. The operation and other development passed without serious complications. Recovery was rapid. The patient was dismissed with too high dose of dabigatran. The correction was made during the control in cardiologist outpatients. Dabigatran is the only new anticoagulans, whose effect can be immediately cancelled by its specific monoclonal antidote idarucizumab. The surgery could have been done soon, the ischemia of intestine was short, resection was not needed, recovery was short. Idarucizumab works reliably even in cases of overdosage and renal failure. We can monitor more or less the effect of dabigatran by aPTT even in the conditions of regional hospital.
- Klíčová slova
- idarucizumab,
- MeSH
- antikoagulancia * aplikace a dávkování MeSH
- bolesti břicha etiologie MeSH
- dabigatran aplikace a dávkování MeSH
- fibrilace síní farmakoterapie MeSH
- humanizované monoklonální protilátky aplikace a dávkování MeSH
- lidé MeSH
- medikační omyly * škodlivé účinky MeSH
- mezenteriální ischemie chirurgie diagnóza etiologie MeSH
- mezenterium patologie MeSH
- renální insuficience MeSH
- senioři nad 80 let MeSH
- torze mechanická MeSH
- vyšetření krevní srážlivosti MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- Publikační typ
- kazuistiky MeSH
