ABSTRACT
BACKGROUND: The vibration of high speed handpiece during tooth preparation may have adverse effect on the continuous force of the bonding interfaces among the cement, dentin, and post core. OBJECTIVE: To find the effect of different types of cements on the coronal microleakage of fiber post under different tooth preparation timings, and to provide evidence for the clinical operation. METHODS: The extracted mandibular premolars were divided into 3 groups, and they were cemented by Rely X luting, Panavia F and Paracora 5 mL, respectively. Each group was averagely divided into 3 subgroups: A, B, C groups which were prepared 15 minutes, 45 minutes, and 90 minutes after the cements mixed. All roots were then dyed and transparented. The teeth were observed under stereoscopic microscope and the dyeing scores were also recorded. RESULTS AND CONCLUSION: Rely X luting caused the highest coronal microleakage of fiber post, followed by Panavia F, while Paracore 5 mL, brought about the lowest under the same tooth preparation timing. Different tooth preparation timing caused no significant effect on the coronal microleakage of fiber post when the cement had been completely set.
ABSTRACT
BACKGROUND:Under different induction conditions,bone marrow mesenchymal stem cells can differentiate into the mesodermal tissues such as osteoblasts,chondroblasts,muscle cells,adipocytes and so on.OBJECTIVE:To verify the effect on repairing the rabbit articular cartilage injury using bone marrow mesenchymal stern cells (MSCs)induced by tissue engineering method.DESIGN,TIME AND SETTING:Randomized controlled animal experiment was performed in the Clinical Center Laboratory of Shenyang Medical College between May 2005 and December 2007.MATERIALS:Twenty health New Zealand rabbits,irrespective of genders,aged 2-3 months,were used.METHODS:①Rabbit bone marrow MSCs were cultured in vitro,experiment group was cultured for one week withdexamethasone,basic fibroblast growth factor and vitamin C,then for additional 3 weeks with transforming growth factor-β instead of basic fibroblast growth factor;calls without inductors served as controls;②Twenty rabbits were used to establish knee articular cartilage defect models,which were then divided into three groups at random. Experiment group (n=5) was transplanted with the induced bone marrow MSCs;control group with the non-induced cells;blank control group with saline. At 2,4,6,8 weeks postoperation,two rabbits in the experiment group were killed,while one animal in control group and blank control group was killed for the index determination.MAIN OUTCOME MEASURES:①Cell morphology. ②Alkaline phosphatase activities.③General observation. ④X-ray observation.⑤Histological observation.RESULTS:①The morphology of the induced bone marrow MSCs was changed,from long fusiform to polygon,which was similar to cartilage calls-like morphology.②After the bone marrow MSCs were induced for 4 weeks,the alkaline phosphatase activities were obviously enhanced(P＜0.05).③Eight weeks after transplantation,the specimens in the experiment group exhibited smooth surface and unclear outlines with surrounding cartilage;X-ray results showed joint space broadened,subchondral bone sack was improved;histological slices observation revealed similarity with normal chondrocytes.CONCLUSION:Autologous MSCs transplantation can repair articular cartilage injury.