ABSTRACT
Objective To investigate effect of a new lumbar dynamic internal fixation system(DIFS)on the stability and intradiscal pressure of lumbar segment.Methods Eight fresh calf lumbar specimens were collected to build test models,which were loaded with pure moments of 8 N·m in flexion/extension,lateral bending,and rotation planes.The test states included intactness,destabilization,dynamic fixation,semi-rigid fixation,and solid fixation.The data were collected from the third loading cycle to determine range of motion and neutral zone of corresponding segments,and the intradiscal pressure.Results Destabilization significantly increased segmental range of motion and neutral zone in three motion planes without obvious influence on intradiscal pressure.The three fixation systems were all able to stabilize and load destabilizing segments.DIFS restored the range of motion of unstable segment to 77％,60％,61％ and 70％ of the intact level in anterior flexion,posterior extension,lateral bending and rotation planes.Meanwhile,DIFS bore 45％,29％ and 40％ of tbe intradiscal load in lateral bending,rotation and flexion directions,but 100％ of the intradiscal load in back extension.The stability and intradiscal pressure of adjacent segments were not affected by the test states.Conclusion DIFS can effectively restore range of motion of unstable segments and share appropriate intradiscal load in most directions.
ABSTRACT
Objective:To study the mechanical properties of a new titanium alloy with lower elastic modulus for prosthodontic use.Methods:Samples of a newly developed Ti-Nb-Zr-Sn alloy with low elastic modulus were prepared.The microstructure,microhardness profile of the specimen cross section were measured by microhardness test meter and metallurgical microscope.Results:The data of the tensile strength(MPa),yield strength(MPa),elongation(%),elastic modulus(GPa) and microhardness(Hv)of Ti-Nb-Zr-Sn alloy were 681.7,410,6,42.1 and 453 respectively.The microstructure was with fine crystal grains.Conclusion: The microstructure and microhardness profile of the Ti-Nb-Zr-Sn alloy may meet the requirement for dental applications.