ABSTRACT
OBJECTIVE: To evaluate a simple static test (i.e. a slow strain rate test) designed to measure Young's modulus and the bulk modulus of polymeric materials (The NOL Test). Though it is a 'mature' test as yet it has never been applied to dental materials. METHODS: A small cylindrical specimen is contained in a close-fitting steel constraining ring and compressive force applied to the ends by steel pistons. The initial (unconstrained) deformation is controlled by Young's modulus. Lateral spreading leads to constraint from the ring and subsequent deformation is controlled by the bulk modulus. A range of dental materials and reference polymers were selected and both moduli measured. From these data Poisson's ratios were calculated. RESULTS: The test proved be a simple reliable method for obtaining values for these properties. For composite the value of Young's modulus was lower, bulk modulus relatively similar and Poisson's ratio higher than that obtained from high strain rate techniques (as expected for a strain rate sensitive material). SIGNIFICANCE: This test does fulfil a requirement for a simple test to define fully the elastic properties of dental polymeric materials. Measurements are made at the strain rates used in conventional static tests and values reflect this test condition. The higher values obtained for Poisson's ratio at this slow strain rate has implications for FEA, in that analysis is concerned with static or slow rate loading situations.
Subject(s)
Compomers , Dental Materials/chemistry , Dental Stress Analysis/methods , Materials Testing/methods , Polymers/chemistry , Benzophenones , Chemical Phenomena , Chemistry, Physical , Compliance , Composite Resins/chemistry , Dental Impression Materials/chemistry , Elasticity , Ketones , Methacrylates/chemistry , Poisson Distribution , Polyethylene Glycols , Polymethyl Methacrylate , Polytetrafluoroethylene , Silicates/chemistry , Silicone Elastomers/chemistry , Tensile StrengthABSTRACT
285 cases of salpingoplasty are reported and studied. Only 172 patients could be followed up recently. The percentage of pregnancies was 27-7, 20 per cent were intra-uterine pregnancies. The percentage of successful pregnancies was 45-93 if only those patients who were seen again were reviewed. The results are best when the operation is carried out in the most conservative and most anatomically restorative fashion. This fine surgery, which must be carried out so delicately and with such detail, which will appeal more and more to modern technicians using micro-surgery, should stay in the hands of specialists because there is no doubt that the level of success rises with the experience of the operator.
