PubMed · 11085082
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
T Takemiya. 2000. [Muscle exercise and microcirculation].. https://pubmed.ncbi.nlm.nih.gov/11085082/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Additives that provide stress relief may be incorporated into dental composites to reduce contraction stress (CS). This study attempted to test the hypothesis that conventional fillers could be replaced by high-density polyethylene (HDPE) spheres in hybrid and nanofill composites to reduce CS, but with minimal effect on mechanical properties. Nanofill and hybrid composites were made from a Bis-GMA/TEGDMA resin having either all silica nanofiller or 75 wt.% strontium glass + 5 wt.% silica and replacing some of the nanofiller or the glass with 0%, 5% (hybrid only), 10% or 20 wt.% HDPE. The surface of the HDPE was either left untreated or had a reactive gas surface treatment (RGST). Contraction stress (CS) was monitored for 10 min in a tensilometer (n = 5) after light curing for 60 s at 390 mW/cm(2). Other specimens (n = 5) were light cured 40 s from two sides in a light-curing unit and aged 1 d in water before testing fracture toughness (K(Ic)), flexure strength (FS), and modulus (E). Results were analyzed by ANOVA with Tukey's multiple comparison test at p < 0.05. There was no difference between composites with RGST and untreated HDPE except for FS-10% HDPE hybrid (RGST higher). An increased level of HDPE reduced contraction stress for both types of composites. Flexure strength, modulus (hybrid only), and fracture toughness were also reduced as the concentration of HDPE increased. SEM showed evidence for HDPE debonding and plastic deformation during fracture of the hybrid composites. In conclusion, the addition of HDPE spheres reduces contraction stress in composites, either through stress relief or a reduction in elastic modulus.
OBJECTIVES: To measure the strength at tearing of pelvic ligaments used in the cure of prolapse and urinary incontinence. MATERIAL AND METHODS: We performed our measurements on pelvis ligaments from cadaveric specimens. We dissected 29 human female pelvis cadavers of which storage conditions differed. Ten were frozen, 10 fresh and 9 were stored in formalin. In each cadaver we dissected pre-vertebral ligaments at promontory and right and left symmetrical ligaments. These were the iliopectineal, sacrospinous and arcus tendineus of pelvic fascia. A subjective clinical evaluation of the ligament properties was performed by visual observation as well as finger palpation. Ligaments were classified into three groups. Group A contained high quality ligaments, in terms of thickness and apparent strength following finger palpation. Ligaments of doubtful quality were classified in group B and low apparent quality ligaments in group C. Then the ligaments were stitched by a suture taking the entire ligament and a force was applied on the vagina axis until tearing. The device used for strength measurement during traction was a SAMSON type force gauge, model EASY, serial number SMS-R-ES 300N manufactured by Andilog that was developed for the purpose of our study. Measurements were given in Newton (N). RESULTS: There was a great variability in the values obtained at tearing with minimal values at around 20N and maximal values at 200N. Individually measured, ligament strength varied between individuals, and for the same patient between the type of ligaments and the side. The pre-vertebral ligament was on average the strongest. There was no significant difference according to the storage condition except for the pre-vertebral ligament in formalin cadavers. For bilateral ligaments, there was no difference between the left and right side. The iliopectineal ligament was statistically significantly stronger than the sacrospinous and arcus tendineus of pelvic fascia. There was a correlation between subjective evaluation and objective strength measurements. DISCUSSION: No papers have been published on the strength of pelvic ligaments at tearing. These are however routinely used in the cure of prolapse and urinary incontinence. Our results show that there is a great variability in strength between individuals, and for a same patient between the types of ligaments and side. These observations could explain some of the surgical intervention failures and demonstrate the importance of per-operative strength evaluation. Per-operative subjective evaluation of strength is related to objective measurements and could be used to determine the type of ligaments to be used for surgical suspension. Freezing does not damage pre-vertebral ligament strength and further studies are required to evaluate elasticity of pelvic ligaments.
INTRODUCTION: Advances continue to improve direct reconstruction of the dorsal scapholunate (SL) ligament, which is the strongest part of the entire SL ligament and is known as the turning point between the scaphoid and lunate. This study was designed to compare the biomechanical properties of the dorsal SL ligament with those of a periosteal flap of the iliac crest, which is a new graft candidate for dorsal SL reconstruction. MATERIALS AND METHODS: A bone-ligament-bone complex was harvested for biomechanical testing from the iliac crest and the dorsal SL complex. Ten specimens could be prepared in each group. After potting the bone blocks in methylmethacrylate for stable fixation, the specimens were tested, using a servohydraulic testing system, at a rate of 10 mm/min. RESULTS: Failure displacement, failure force, failure stress, energy to failure, and stiffness were assessed for both groups. Eight specimens in each group were tested successfully. In the ligament group, six specimens failed at the ligament level, whereas two failed at the insertion of the scaphoid. In the periosteum group, all eight specimens failed at the ligament level. The failure force of the dorsal SL ligament averaged 171.8 N, failure stress was 10.3 N/mm2, and failure displacement amounted to 2.9 mm. Energy to failure was 269.1 N-mm, and stiffness averaged 77.2 N/mm. Failure force of the periosteal flap amounted to 144.3 N, failure stress was 9.9 N/mm2, failure displacement was 3.0 mm, and energy to failure was 217.9 N-mm. Stiffness of the periosteal flap measured 60.5 N/mm. Comparison of the dorsal SL ligament and the periosteal flap of the iliac crest revealed no significant biomechanical differences. CONCLUSION: Therefore, the biomechanical properties of the periosteal flap recommend its use for reconstruction of the dorsal SL ligament.