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PubMed1998

Isokinetic muscle strength and hiking performance in elite sailors.

The aim of the present study was to describe the isokinetic strength profile and its relation to hiking performance in male (SM, n = 15) and female (SF, n = 6) elite sailors compared to a group of male control subjects (CM, n = 8) similar in age, anthropometry and level of fitness. Eccentric knee extension strength was higher in SM compared to CM (P < 0.01). Furthermore, SM were stronger during trunk extension (P < 0.05), but not during trunk flexion compared to CM. Overall muscle strength was lower in SF compared to SM (P < 0.01) and CM (P < 0.05), except for eccentric knee extension strength, where SF and CM did not differ (P > 0.05). Hiking performance correlated to maximal eccentric and isometric knee extensor strength in SF (rs = 0.83-0.88, P < 0.05) and in CM (rs = 0.73-0.77, P < 0.05) and to maximal eccentric knee extensor strength at high velocity in SM (rs = 0.46-0.54, P < 0.05). For a subgroup of hikers in SM (n = 8), hiking performance correlated to maximal isometric-eccentric knee extensor strength (rs = 0.67-0.74, P < 0.05), whereas no correlations emerged for the non-hikers (n = 7). Few correlations were observed between hiking performance and maximal concentric trunk flexor strength (rs = 0.69-0.92, P < 0.05). Unexpectedly, in SM correlations also were observed between hiking performance and maximal strength of the trunk extensors (rs = 0.46-0.53, hiker subgroup: rs = 0.64-0.67, P < 0.05). In conclusion, notably high levels of maximal eccentric knee extensor strength were observed for the male and female elite sailors examined in the present study. Furthermore, the present results suggest that hiking performance depends in part on maximal isometric-eccentric knee extensor strength. The maximal strength of the trunk extensors, which potentially stabilizes the lower back and spine, also seems to have some importance for the hiking performance of top-level sailors.

Adult↗

PubMed2003

The effect of fiber reinforcement type and water storage on strength properties of a provisional fixed partial denture resin.

Fracture resistance of provisional restorations is an important clinical concern. This property is directly related to transverse strength. Strengthening of provisional fixed partial dentures may result from reinforcement with various fiber types. This study evaluated the effect of fiber type and water storage on the transverse strength of a commercially available provisional resin under two different conditions. The denture resin was reinforced with either glass or aramid fiber or no reinforcement was used. Uniform samples were made from a commercially available autopolymerizing provisional fixed partial denture resin. Sixteen bar-shaped specimens (60 x 10 x 4 mm) were reinforced with pre-treated epoxy resin-coated glass fibers, with aramid fibers, or with no fibers. Eight specimens of each group, with and without fibers, were tested after 24 h of fabrication (immediate group), and after 30-day water storage. A three-point loading test was used to measure the transverse strength, the maximal deflection, and the modulus of elasticity. The Kruskal-Wallis Analysis of Variance was used to examine differences among the three groups, and then the Mann-Whitney U Test and Wilcoxon Signed Ranks Test were applied to determine pair-wise differences. The transverse strength and the maximal deflection values in the immediate group and in the 30-day water storage group were not statistically significant. In the group tested immediately, the elasticity modulus was found to be significant (P = 0.042). In the 30-day water storage group, all the values were statistically insignificant. The highest transverse strength was displayed by the glass-reinforced resin (66.25MPa) in the immediate group. The transverse strength value was 62.04MPa for the unreinforced samples in the immediate group. All the specimens exhibited lower transverse strength with an increase in water immersion time. The transverse strength value was 61.13 MPa for the glass-reinforced resin and was 61.24 MPa for the unreinforced resin. The aramid-reinforced resin decreased from 62.29 to 58.77 MPa. The addition of fiber reinforcement enhanced the physical properties (the transverse strength, the maximal deflection, the modulus of elasticity) of the processed material over that seen with no addition of fiber. Water storage did not statistically affect the transverse strength of the provisional denture resin compared to that of the unreinforced resin. The transverse strength was lowered at water storage but it was not statistically significant. The transverse strength was enhanced by fiber addition compared to the unreinforced resin. The glass fiber was superior to the other fiber. Also the modulus of elasticity was enhanced by fiber addition compared to the unreinforced resin.

Acrylic Resins↗

PubMed2004

Strength training and albuterol in facioscapulohumeral muscular dystrophy.

BACKGROUND: In animals and healthy volunteers beta2-adrenergic agonists increase muscle strength and mass, in particular when combined with strength training. In patients with facioscapulohumeral muscular dystrophy (FSHD) albuterol may exert anabolic effects. The authors evaluated the effect of strength training and albuterol on muscle strength and volume in FSHD. METHODS: Sixty-five patients were randomized to strength training of elbow flexors and ankle dorsiflexors or non-training. After 26 weeks albuterol (sustained-release, 8 mg BID) was added in a randomized, double-blind, placebo-controlled design. Primary outcome was maximum voluntary isometric strength (MVIC) at 52 weeks. Secondary outcomes comprised dynamic strength and muscle volume. RESULTS: Training and albuterol were well tolerated. Training of elbow flexors did not result in a significant effect on MVIC, but dynamic strength improved significantly. Elbow flexor MVIC strength increased significantly in albuterol vs placebo treated patients. Ankle dorsiflexor strength decreased in all groups. Eleven out of twelve non-trained muscles in the albuterol group showed a positive effect on MVIC compared to the placebo group (p < 0.05 in seven muscle groups). Muscle volume decreased in the placebo-treated, and increased in the albuterol-treated patients. No synergistic or antagonistic effects were observed between training and albuterol. CONCLUSIONS: In FSHD strength training and albuterol appear safe interventions with limited positive effect on muscle strength and volume. Consequences of prolonged use are presently unclear, which precludes routine prescription.

Adrenergic beta-Agonists↗

PubMed2003

Assessment and interpretation of isokinetic muscle strength during growth and maturation.

The majority of strength studies examining changes during growth and maturation have investigated isometric actions, which tell us little about the muscle under dynamic conditions. There are numerous methodological issues in the isokinetic testing of paediatric populations that require further investigation. However, several studies have indicated that children can be reliably assessed isokinetically using both concentric and eccentric actions. Most paediatric studies have examined the knee joint and more data are needed to elucidate the reliability of upper body isokinetic strength testing. The age- and sex-associated development of isokinetic strength is less well understood. Studies have indicated that isokinetic strength increases with age but the mechanisms associated with this increase require further investigation. Current data are also conflicting regarding the age at which sex differences become apparent in isokinetic strength. More work is needed to examine the influence of maturation on isokinetic strength development, but available data suggest that maturation is a non-significant contributory factor once stature and body mass are accounted for. Most studies have demonstrated a significant relationship between stature, body mass and isokinetic strength during growth and maturation. The importance that changes in body composition during growth have on isokinetic strength has been investigated using fat-free mass and muscle cross-sectional area. Data have shown that although fat-free mass and muscle cross-sectional area are important contributors to isokinetic strength, other unexplained factors also influence isokinetic strength development. Additional work needs to investigate possible qualitative changes in muscle during growth and maturation. More work is also needed to examine changes in eccentric strength with age and to investigate sex differences in upper body isokinetic strength. Future studies should preferably be longitudinal in nature and examine known covariates simultaneously using appropriate statistical techniques.

Biomechanical Phenomena↗

PubMed2002

Assessment of isokinetic muscle strength in women who are obese.

STUDY DESIGN: Cross-sectional study of isokinetic trunk and knee muscle strength in women who are obese. OBJECTIVE: To provide reference values, to identify variables that affect peripheral muscle strength, and to provide recommendations for isokinetic testing of trunk and knee muscles in women who are obese and morbidly obese. BACKGROUND: The assessment of peripheral muscle strength is useful for the quantification of possible loss of strength, for exercise prescription, and for the evaluation of the effect of training programs in obese individuals. METHODS AND MEASURES: Isokinetic trunk and leg muscle strength was assessed in 241 women who were obese (18-65 years, body mass index (BMI) > or = 30 kg/m2). Trunk flexion and extension peak torque (PT) was measured using the Cybex TEF dynamometer; trunk rotation (TR) PT was measured using the Cybex TORSO dynamometer; and knee flexion/extension (KFE) PT was measured using the Cybex 350 dynamometer. Body composition was assessed using the bioelectrical impedance method; physical activity was assessed using the Baecke questionnaire; and peak VO2 was assessed using an incremental exercise capacity test on a bicycle ergometer. To identify variables related to muscle strength, Pearson correlations were computed and a stepwise multiple regression analysis was performed. RESULTS: Pearson correlation coefficients of all strength measurements at 60 degrees/s revealed low-to-moderate negative associations with age and positive associations with mass, height, fat free mass (FFM), and peak VO2 (P < 0.05), except for gravity-uncorrected trunk extension strength, which was not related to mass. The sports index of the Baecke questionnaire was associated with TR PT (r = 0.20, P < 0.01) and KFE PT (r = 0.18, P < 0.05). CONCLUSION: The weight of the trunk accounts largely for the measured trunk extensor and flexor strength in women who are obese. Contributing variables of isokinetic trunk flexion and extension strength in women who are obese are age, height, and FFM; whereas sports activities and aerobic fitness are contributing factors for trunk rotational and knee extension strength. Recommendations for measuring isokinetic muscle strength in individuals who are obese are provided.

Adult↗

PubMed2000

Knee isokinetic strength and body fat analysis in university students.

Many factors such as anthropometric variables influence strength performance. This study is to determine the relationship between knee isokinetic strength and body composition, and to compare the gender differences. Test-retest reliability had been performed within one week for all measurement methods before the formal study. Fifty-eight 20-25 year-old university students, 32 females and 26 males, participated in this study. Isokinetic strength of the knee flexion and extension was measured at two angular velocities of 60 degrees/sec and 120 degrees/sec. Body composition was measured by bioelectrical impedance analysis (BIA) and skinfold caliper. The others variables including height, body weight, body mass index (BMI), and waist to hip ratio were measured or calculated. The results showed that the intra-class correlation coefficients for isokinetic knee strength were between 0.83 and 0.93, and body composition and anthropometric variables were between 0.83 and 0.98. Isokinetic knee strength was significantly correlated with body height, body weight, BMI, waist and hip ratio and percent of body fat estimated by skinfold caliper (r = -0.56 to 0.64). The correlation between isokinetic strength with percent of body fat estimated by BIA (r = -0.60 to -0.74; p < 0.001) and with fat free mass (r = 0.64 to 0.78; p < 0.001) was even higher. Although male subjects had significantly greater mean values in body height, body weight, waist to hip ratio and isokinetic strength than female subjects, the MANCOVA showed that the effect of gender on knee isokinetic strength would be eliminated when the covariant variable, the percent of body fat measured by BIA and BMI was controlled in the analysis model. In conclusion, knee isokinetic strength was significantly negatively correlated with proportion of fat and positively correlated with fat free mass. The magnitude of strength difference between males and females could be explained by differences in body fat proportion and BMI in this study. Therapist would take the body fat composition, fat free mass, and BMI into consideration in knee muscle strength measurement. Less body fat and higher BMI will contain more fat free mass that produces more muscle strength.

Adipose Tissue↗

PubMed2001

Effects of strength exercise and training on the natural killer cell counts in elderly humans.

BACKGROUND: To investigate the effects of strength exercise and training on the natural killer cell counts in elderly humans. METHODS: The study examined strength exercise-induced changes in the number of NK cells and changes in stress hormones in 16 sedentary elderly subjects before and after a 8-week strength training intervention. Blood samples were obtained before, immediately and 6 hours after a standardized strength test. Blood samples were also obtained from ten sedentary young subjects, under the same conditions and from ten resting elderly subjects serving as time controls. RESULTS: Prior to training, older adults immediately decreased (from 165.4+/-19.5 microL to 110.6+/-14.3 microL; mean+/-SEM) their NK cell count in response to the standardized strength test, whereas young controls increased their count (from 157.6+/-28.8 microL(-1) to 241.4+/-39.8 microL(-1)). After strength training, the same old subjects slightly increased (from 159+/-19.8 microL(-1) to 166.6+/-19.7 microL(-1)) their NK cell counts in response to the standardized strength test. In elderly subjects, no increase in stress hormone was observed following the strength test either before or after the strength training programme. CONCLUSIONS: The results suggest that in sedentary older adults, unlike young subjects, strength exercises can induce a transient decrease in NK cell count which can be cancelled by a short-term strength conditioning. Therefore, caution should be taken regarding immunocompetence of older adults when initiating a rehabilitation programme based on strength.

Adult↗

PubMedDate not supplied

Effects of simulated vastus medialis strength variation on patellofemoral joint biomechanics in human cadaver knees.

Selective strengthening of the vastus medialis (VM) muscle is a conservative treatment used to address some patellofemoral joint (PFJ) problems. The objective of this study was to examine the effects of varying VM strength on PFJ kinematics and contact pressures and areas. We tested five fresh-frozen cadaveric knees using a custom knee jig, which permits the simulation of physiologic quadriceps loading while also allowing the VM force to be varied. PFJ kinematics were measured with a magnetic tracking device. PFJ contact pressures and areas were measured with Fuji pressure-sensitive film. For PFJ kinematics, the change in the medial-lateral and superior-inferior translation was significant at 0% of VM strength and 150% of VM strength with respect to the 100% of VM strength condition (p < 0.05). Extreme changes in the VM force had a statistically significant effect on patellofemoral contact pressures (0% of VM strength (19 +/- 10%) and 150% of VM strength (17 +/- 3%) with respect to 100% of VM strength condition (p < 0.05)). No statistically significant differences were shown in the patellofemoral contact areas (p > 0.05). The functional range of VM strength is between 75% and 125% of total VM strength. The PFJ kinematics and contact pressures were not significantly influenced by VM strength except at extreme conditions (0% of VM strength or 150% of VM strength) in human cadaveric knees.

Analysis of Variance↗

PubMed1983

Thigh muscle strength in below-knee amputees.

The aim of this investigation has been to study the magnitude of the reduction of thigh muscle strength of below-knee amputees and to correlate the strength to the degree of atrophy and to the clinical function. Thirty-two below-knee amputees participated in examinations of the isometric and isokinetic knee extension and flexion strength using an isokinetic dynamometer (Cybex II). The atrophy was evaluated by measuring the mean muscle fibre area on muscle biopsies of the vastus lateralis and the cross-sectional area of the quadriceps and hamstring muscles measured with computed tomography. The isometric and isokinetic knee extension and flexion strength in the amputated leg with and without prosthesis was significantly lower than the strength in the non-amputated leg (p less than 0.01). Knee extension strength was significantly correlated to the mean muscle fibre area of the vastus lateralis. There was no correlation between strength and the cross-sectional area of the quadriceps muscles. There was, however, a significant correlation between the side differences (amputated leg versus non-amputated leg) in isometric knee extension and flexion strength and the side differences in cross-sectional areas. The reduction in isometric and isokinetic knee extension and flexion strength in the amputated leg both with and without prosthesis compared with the non-amputated leg was larger than the reduction in cross-sectional areas of the quadriceps and hamstring muscles and in muscle fibre areas of the vastus lateralis. This indicates that besides muscle atrophy changes in motor unit recruitment pattern may be of importance for the reduction in muscle strength. Isometric and isokinetic knee extension and flexion strength values in the amputated leg with prosthesis were significantly correlated to step length, maximal walking speed and circumference of the thigh. These results indicate that below-knee amputees with a better preserved thigh muscle strength have a good walking capacity.

Adult↗

PubMed1995

A study of different postures on isometric lifting strength in normal college students.

The purpose of this study was to describe norms of isometric lifting strength for normal college students and to investigate the effects of gender, body weight, height, and upper and lower limb length on lifting strength. Three types of lifting (i.e., arm, back, and leg lifting) were measured in a sample of 104 college students aged between 18 and 26 years. A Force Evaluation and Testing System (FET 5000) was used for strength measurements with three standard lifting positions. The average of three trials for each lifting strength test was used as the subject's test score. The results showed that the highest mean lifting strength was recorded for leg lifting in both males and females. Both groups also had the lowest score in arm lifting. Of the total sample, there was a difference of strength of nearly three- times between leg and arm lifting. Males were stronger than females in all lifting patterns. In addition, lifting strengths were significantly affected by such variables as sex, weight and height. Body weight was an effective predictor of arm lifting strength, and height an effective predictor of leg lifting strength. Finally, we found that strength in one position had positive relations with strength in other positions. These findings and the establishment of data base can in future provide therapists with an objective evaluation regarding lifting strength of individuals for clinical use.

Adolescent↗

PubMedDate not supplied

Strength measurements of the intrinsic hand muscles: a review of the development and evaluation of the Rotterdam intrinsic hand myometer.

Numerous neurological diseases are accompanied by atrophy of the intrinsic muscles of the hand. Muscle strength testing of these muscles is frequently used for clinical decision making. Traditionally, these strength measurements have focused on manual muscle testing (MMT) or on grip and pinch strength dynamometry. We have developed a hand-held dynamometer, the Rotterdam Intrinsic Hand Myometer (RIHM), to measure this intrinsic muscle strength. The RIHM was designed such that it can measure a wide range of muscle groups, such as the abduction and adduction strength of the little finger and index finger, the opposition, palmar abduction (anteposition) and opposition strength of the thumb, and intrinsic muscles of the fingers combined in the intrinsic plus position. We found that the reliability of RIHM measurements in nerve injury patients was comparable to grip and pinch strength measurements and is appropriate to study the functional recovery of the intrinsic muscles of the hand in isolation. We have applied the RIHM in a recent study on the long-term outcome of muscle strength in patients with ulnar and median nerve injuries and found that while recovery of grip and pinch strength was relatively good, recovery of the ulnar nerve innervated muscles measured with the RIHM was poor. This poor recovery could not be detected with manual muscle strength testing or with grip and pinch dynamometry. We conclude that the RIHM provides an accurate clinical assessment of the muscle strength of the intrinsic hand muscles that adds valuable information to MMT and grip and pinch dynamometry.

Equipment Design↗

PubMed2006

Maintenance of muscle strength may counteract weight-loss-related postmenopausal bone loss--a population-based approach.

INTRODUCTION: Weight loss significantly increases postmenopausal bone loss, but the effects of muscle strength change on weight-loss-associated bone loss remain unclear. The study population, 587 peri- and postmenopausal women, was a random sample of the original Osteoporosis Risk Factor and Prevention Study (OSTPRE) study cohort (n=14,220) in Kuopio, Finland. Bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN) was measured with dual x-ray absorptiometry, and grip strength was measured with a pneumatic squeeze dynamometer at baseline in 1989-1991 and at the 10-year follow-up in 1999-2001. METHODS: Women were divided into three groups according to change in age-grouped grip-strength quartile in both of the measurements: "decreased" (n=133), "maintained" (n=300), and "improved" (n=154). In addition, the study sample was divided into two groups according to weight change during the follow-up: weight losers (n=156) and weight gainers (n=431). RESULTS: There were no differences in the change status of grip (muscle) strength between the weight loss and weight gain groups (p>0.500, Pearson chi-square test). Women losing weight during the follow-up and within the improved grip-strength-change group had a significantly lower bone loss rate compared with those in the maintained and decreased grip-strength-change groups (p<0.01 in comparison to the decreased group). This was in contrast to women who gained weight during the follow-up (not significant between any grip-strength-change groups). Furthermore, women who lost body weight and were in the improved grip-strength-change group had a bone loss rate comparable with that of the women who gained body weight (not significant). This was in contrast to the maintained (p<0.05 between weight losers versus gainers in LS) and decreased grip-strength-change groups (p<0.01 weight losers versus gainers in LS and FN). CONCLUSION: The present study suggests that maintaining muscle strength may counteract postmenopausal bone loss related to weight loss. Accordingly, exercise that improves muscle strength may be encouraged for postmenopausal women with weight loss intentions for other health reasons.

Absorptiometry, Photon↗

PubMed1987

The effects of fibre reinforcement and gold plating on the flexural and tensile strength of PGA/PLA copolymer materials in vitro.

Changes in the flexural and/or tensile strength of plates and rods made of PGA/PLA copolymer submerged in water for a period of 4 wk were investigated. During this time, the effects of PGA/PLA fibre self-reinforcement, carbon fibre reinforcement and gold plating on tensile and/or flexural strength were examined. The results were used for evaluation of the surgical applications of PGA/PLA copolymer and its composites. The initial tensile strength of non-reinforced material was 45 Mpa and its flexural strength was 150 MPa: the flexural strength of self-reinforced material was 265 MPa. The tensile strength of carbon fibre reinforced material was 90 MPa and its flexural strength 190 MPa. The initial strengths of plated and unplated samples were the same but plating delayed the loss of the mechanical strength of carbon fibre reinforced samples. After 4 wk the flexural strength of self-reinforced and carbon fibre reinforced samples was decreased to the level of cancellous bone (10-20 MPa) while the flexural strength of non-reinforced samples was below that level (less than or equal to 5 MPa). The results suggested that self-reinforced PGA/PLA composites may be used for the treatment of fractures in cancellous bone. Positive animal experiments led to clinical studies in vivo. These studies showed that there was no difference in outcome between 2 groups of patients with displaced fractures of the ankle treated with metallic implants or PGA/PLA fibre self-reinforced implants, respectively. Self-reinforced biodegradable implants are now used routinely in Helsinki University Central Hospital.

Biocompatible Materials↗

PubMed2006

Factors associated with decreased muscle strength after anterior cruciate ligament reconstruction with hamstring tendon grafts.

PURPOSE: To identify factors associated with decreased muscle strength and activity after anterior cruciate ligament (ACL) reconstruction with semitendinosus-gracilis tendon (ST-G) grafts. TYPE OF STUDY: Retrospective review. METHODS: Eighty-five patients who underwent ACL reconstruction with ST-G grafts were evaluated at a mean of 44.4 months after surgery. Patients underwent isokinetic testing, physical examination, radiographs, instrumented laxity testing, and Lysholm, Cincinnati, and International Knee Documentation Committee (IKDC) ratings. Cartilage and meniscal pathology at surgery was reviewed. Strength group 1 (n = 30) showed greater than 20% deficits in strength; strength group 2 (n = 55) had less than 20% strength deficits. Activity group 1 (n = 60) maintained their IKDC activity level at final follow-up relative to preinjury level; activity group 2 (n = 25) decreased activity by 1 or more levels. RESULTS: With all patients combined, there was less than a 4% difference in mean hamstring and quadriceps strength between the reconstructed and contralateral legs at follow-up. Knee flexion deficits were associated with decreased hamstring strength. Subjective giving way and squatting/kneeling discomfort were associated with decreased quadriceps strength. Patients in strength group 1 were more likely to have squatting/kneeling discomfort and lower Cincinnati Function scores. Activity group 2 had a longer interval from injury to surgery and more chondromalacia at surgery. At follow-up, activity group 2 had lower subjective scores and was more likely to have pain, swelling, giving way, and flexion deficits. Activity group 2 also had greater deficits in quadriceps strength. CONCLUSIONS: Articular cartilage injury and meniscal pathology were not associated with decreased muscle strength. ACL reconstruction with ST-G grafts has a 38% incidence of squatting/kneeling pain that occurs secondary to patellofemoral crepitus, harvest site symptoms, and tibial hardware sensitivity. LEVEL OF EVIDENCE: Level IV, therapeutic, case series, no control group.

Anterior Cruciate Ligament↗

PubMed2006

The evaluation of microleakage and bond strength of a silicone-based resilient liner following denture base surface pretreatment.

STATEMENT OF PROBLEM: The failure of adhesion between a silicone-based resilient liner and a denture base is a significant clinical problem. PURPOSE: The purpose of this study was to examine the effects of denture base resin surface pretreatments with different chemical etchants preceding the silicone-based resilient liner application on microleakage and bond strength. The initial effects of chemical etchants on the denture base resin in terms of microstructural changes and flexural strength were also examined. MATERIAL AND METHODS: Forty-two polymethyl methacrylate (PMMA) denture base resin (Meliodent) specimens consisting of 2 plates measuring 30 x 30 x 2 mm were prepared and divided into 7 groups (n = 6). Specimen groups were treated by immersion in acetone for 30 (A30) or 45 (A45) seconds, methyl methacrylate monomer for 180 (M180) seconds, and methylene chloride for 5 (MC5), 15 (MC15) or 30 (MC30) seconds. Group C had no surface treatment and served as the control. Subsequently, an adhesive (Mollosil) and a silicone-based resilient denture liner (Mollosil) were applied to the treated surfaces, and all specimens were immersed in the radiotracer solution (thalium-201 chloride) for 24 hours. Tracer activity (x-ray counts), as a parameter of microleakage, was measured using a gamma camera. For bond-strength measurement, 84 rectangular PMMA specimens (10 x 10 x 40 mm) were surface-smoothed for bonding and treated with the different chemical etchants using the same previously described group configurations. The adhesive and the silicone-based denture liner were applied to the treated surfaces. Tensile bond-strength (MPa) was measured in a universal testing machine. Flexural strength measurement was performed with 49 PMMA specimens (65 x 10 x 3.3 mm according to ISO standard 1567) in 7 groups (n = 7), with 1 flat surface of each treated with 1 of the chemical etchants preceding adhesive application. The flexural strength (MPa) was measured using a 3-point bending test in a universal testing machine. The data were analyzed by 1-way analysis of variance and the Tukey HSD test (alpha = .05). RESULTS: Significant differences were found between the groups in terms of microleakage (P < .0001). The lowest microleakage was observed in group M180 (30,000 x-ray counts) and the highest in the control group (44,000 x-ray counts). The mean bond strength to PMMA resin ranged from 1.44 to 2.22 MPa. All treated specimens showed significantly higher bond strength than controls (P < .01). The flexural strength values all significantly differed (P < .05). All experimental specimens that had chemical surface treatments showed lower flexural strength than controls (P < .05). CONCLUSION: Treating the denture base resin surface with chemical etchants increased the bond strength of silicone-based resilient denture liner to denture base and decreased the microleakage between the 2 materials. Considering the results of both tests together, the use of methyl methacrylate monomer for 180 seconds was found to be the most effective chemical treatment.

Acid Etching, Dental↗

PubMed2001

Age, sex, and grip strength determine architectural bone parameters assessed by peripheral quantitative computed tomography (pQCT) at the human radius.

The purpose of this study was to estimate the relation of some noninvasively derived mechanical characteristics of radial bone including architectural parameters for bone strength to grip strength and muscle cross-section. Sixty-three males between 21 and 78yr of age and 101 females between 18 and 80yr of age were measured at the nondominant forearm using peripheral quantitative computed tomography (pQCT). We assessed the integral bone mineral density (BMD(I)) and content (BMC(I)) by pQCT at the distal and at the mid-shaft radius. Integral bone area (Area(I)), cortical thickness (C-th), and a newly proposed index for bone strength; the stress-strain index (SSI) were also calculated. The dynamometrically measured maximum grip strength was taken as a mechanical loading parameter and muscle cross-section as a substitute for it. Sex, grip strength, BMC(I) and BMD(I) (distal radius) were identified in a multiple regression analysis to significantly predict bone strength as expressed by SSI, after adjusting for all other independent variables, including age and sex (p<0.0001). Grip strength was closest related to age, sex, BMD(I) and SSI(p) of the distal radius. The cross-sectional area of muscle was not significantly determining the grip strength within the analysis model. In conclusion, our results suggested that architectural parameters at the distal radius were better related to grip strength than to cross-sectional muscle area in both males and females. Maximum muscle strength as estimated by grip strength might be a stronger determinant of mechanical characteristics of bones as compared with cross-sectional muscle area.

Adult↗

PubMedDate not supplied

Factors affecting grip strength testing.

The rodent grip strength test was developed decades ago and is a putative measure of muscular strength. This test has been included in the functional observational battery (FOB) to screen for neurobehavioral toxicity, and changes in grip strength have been interpreted as evidence of motor neurotoxicity. Despite its widespread use, questions remain about what the grip strength test actually measures. In this study, potential confounders of the grip strength test were identified and tested, including operational parameters, disruption of peripheral sensory function and changes in body weight. Operational parameters (sampling rate, system type and trial angle but not trial speed) had dramatic effects on grip strength data. Doxorubicin (DX, 10 mg/kg iv) was used to cause sensory impairment. It decreased forelimb and hindlimb grip strength (by 27% and 32%, respectively, compared with controls), an effect that was correlated with degeneration of peripheral and central sensory components (distal tibial and sural nerves, dorsal funiculus of the spinal cord and dorsal, but not ventral, spinal roots). Feed restriction-induced loss of body weight (26% compared with controls) and muscle mass (20% compared with controls) reversibly decreased both forelimb and hindlimb grip strength (18% and 17%, respectively, compared with controls). Ignoring these confounding factors could potentially lead to increased data variability and inconsistency within single studies, across studies and in historical control data sets. To assist in data interpretation and evaluation of grip strength results, it is suggested that exact conditions of application of the test be reported in greater detail. Furthermore, given that the grip strength test can be influenced by factors other than true muscular strength, use of the term grip performance is proposed to better reflect the apical nature of this test.

Analysis of Variance↗

PubMed2000

Comparison of in vitro fracture strength of metallic and tooth-coloured posts and cores.

In root-treated anterior teeth a better aesthetic can be achieved by using translucent and tooth-coloured post and core restorations instead of traditional metal post systems. The aim of this in vitro study was to compare the fracture strength of tooth-coloured ceramic and fibre-reinforced posts as well as titanium posts with clinically proven gold alloy posts as a control. Two all-ceramic, one gold alloy and three combined post restoration systems (titanium and ceramic, respectively, fibre-reinforced posts with composite core) were each applied to upper incisors and after thermal cycling and mechanical loading (TCML) the fracture strength was determined. The variant providing the most reliable fracture strength values and the experimental fibre-reinforced composite (FRC) posts were - in combination with adhesively luted crowns - used to determine the fracture strength of the restoration after thermal cycling and mechanical loading. The median fracture strength of the luted posts and cores fluctuated between 114 and 546 N. Posts with composite cores demonstrate a higher fracture strength in comparison to the all-ceramic and gold alloy systems. Typical failure of metal systems was marked by loosening of the bonding and pulling out of the post in contrast to fracture of the ceramic posts. After the application of the crowns the ceramic system with composite core provided a fracture strength of 338 N and the FRC system a fracture strength of 228 N. Regarding fracture strength, the ceramic posts with composite cores are an alternative to commonly used gold posts and cores. A standardized technical manufacture of FRC posts and cores would provide better fracture strength results of this new dental material. Post and core restorations with tooth-coloured, translucent material offer an improved aesthetic especially in anterior restorations. Because of the high fracture strength prefabricated ceramic posts in combination with composite cores should prove their clinical applicability.

Aluminum Silicates↗