ABSTRACT
<p><b>OBJECTIVE</b>This study was about the influence of porcelain thickness on crack at interface.</p><p><b>METHODS</b>The effect of porcelain thickness on the flaw at the interface between porcelain and metal was studied in three groups with porcelain thickness of 0.5 mm, 1.5 mm and 2.5 mm (metal thickness of 0.5 mm) by means of moire interferometre and interfacial fracture mechanics. The parameter Jc was compared among the three groups and the growing of the flaw was observed.</p><p><b>RESULTS</b>Jc and the extreme strength of group with porcelain thickness of 0.5 mm (2.813 N/m and 9.979 N) were lower than those of the groups with porcelain thickness of 1.5 mm and 2.5 mm (5.395 N/m, 19.134 N and 5.429 N/m, 19.256 N). Flaws extend along the interface in the groups with porcelain thickness of 1.5 mm and 0.5 mm.</p><p><b>CONCLUSIONS</b>(1) Fracture resistance of the interface in the groups with porcelain thickness of 1.5 mm and 2.5 mm is similar and it decreases in the group with 0.5 mm thick porcelain. (2) When porcelain is 1.5 mm or 0.5 mm thick, flaws will extend along the interface. When porcelain is 2.5 mm thick, flaws will extend into the porcelain layer.</p>
Subject(s)
Humans , Dental Porcelain , Dental Stress AnalysisABSTRACT
Objective:To study the biomechanical basis of swan like memory compressive connector (SMC) for treating fractures and nonunions of humerus. Methods:The study was performed by electrometric, two and three dimensional (3D) photoelasticity techniques. By gauging and multiple time standardization, load strain curve was got, then the dynamic memory force of SMC was calculated. The dynamically compressive force of swan neck compressive part was calculated by 2D photoelasticity. By precision moulding, the epoxy resin 3D photoelasticity humeral model was established, then it was fixated by SMC, meanwhile, an epoxy resin cirque was used to share the continuously memorial compress. The 3D stress distribution of humeral model was got, and 6 space component stress of the inspected node was divided by Leize polarizing microscope. Results:The continuously memory force of SMC was 110.35 N. The longitudinal dynamical compressive memory force was 163.88 N. 3D photoelasticity method showed that the swan neck compressive part of SMC, swan body connecting part of SMC and swan wing holding part of SMC were in consistent with each other, memorably holding bone, 3D fixation style was formed, and overall stress distribution was produced.. Conclusion:The stress field produced by 3D memory fixation of SMC is good for the treatment of fractures and nonunions. Early function exercises are allowed, and the fracture healing is prompted.