ABSTRACT
Objective To evaluate the clinical efficacy of combined use of Pathfile and Mtwo in the preparation of curved root canals.Methods This study enrolled a total of 90 teeth(313 root canals)that need root canal therapy because of pulpitis or apical periodontitis from December 2013 to February 2014.All root canals were randomly divided into three groups.In group A,both Pathfile and Mtwo NiTi files were used in root canal preparation.In group B,Pathfile and ProTaper were used.ProTaper was employed alone in root canal preparation in group C.The high temperature thermaplasticized inj ectable ver-tical condensation technique was applied in all the three groups.The time of root canal preparation,the number of separated de-vices,root canal transportation and the quality of root canal filling were obtained and compared among the 3 groups.Results In group A,the time of root canal preparation was shortest,(6.01±1.12)min ;there were no instrument separation and ledge for-mation,and the filling rate was highest in group A.The differences were significantly noted in these indexes between group A and groups B,C.Conclusion Combined use of Pathfile and Mtwo for preparation of curved root canals is fast and safe,and the root canal filling is satisfactory.This method is suitable for clinical application.
ABSTRACT
BACKGROUND:Based on variational principle and weighting technology of three-dimensional finite element method, human teeth with a complex morphology can be modeled, which helps to understand the stress distribution of dental hard tissue and prosthesis during the dynamic repair process. OBJECTIVE:To comprehensively analyze the three-dimensional finite element studies concerning biomechanics of dental prostheses, focusing on the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. METHODS:A computer-based search of PubMed (1993-04/2012-09), China Academic Journal Network Publishing Database (2001-2008), and VIP (2001-2008) was performed by the first author to retrieve articles concerning the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. The keywords were“porcelain-fused-to-metal, finite element method, stress analysis, root canal”in English and Chinese. Articles with repetitive contents or meta-analysis were ruled out. Then 40 articles were suitable for further analysis.RESULTS AND CONCLUSION:Finite element method has important significance to establish high-fidelity and high-accuracy models in oral medicine, thereby providing effective biomechanical information for the root canal treatment and post-treatment repair. Scholars continue to explore the stress distribution of dental prostheses during chewing. This review summarizes the stress changes of post and core crowns, supporting reference for further research. Three-dimensional finite element method can be used to build nonlinear three-dimensional finite element models with anisotropic biomechanical characteristics, and can gradual yimprove the transition from static analysis to a dynamic analysis, truly achieving accurate simulation of oral biology and dental morphology as wel as chewing function of the teeth.
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This study was aimed to assess the stress distribution of different capacity of class I cavity after composite resin filling. A three-dimensional finite element made of the maxillary second molar was constructed by spiral CT scan technology. Based on this model, stress distribution in tooth was analyzed before and after post-core restorations with 5 different capacities of class I cavity. When the circle triangle of class I cavities being under 50N vertical pressures, the cavity capacity increased from 3.3 mm to 3.7 mm, the maximum tensile stress values of the composite resin restorations being 3 times those of normal tooth, which were 14.872 MPa, 16.682 MPa and 17.589 MPa, 17.307 MPa and17.912 MPa. Obviously, the effect of different capacities of class I cavity on the maximum stress value enduring ability of teeth was samll, but in the analysis model, the enduring ability of teeth was reduced when the molars were filled with resin.
Subject(s)
Humans , Composite Resins , Chemistry , Computer Simulation , Dental Stress Analysis , Finite Element Analysis , Imaging, Three-Dimensional , Models, Biological , Molar , Diagnostic Imaging , Pathology , Post and Core Technique , Root Canal Filling Materials , Chemistry , Tomography, Spiral ComputedABSTRACT
Objective To investigate the protective effect of exogenous oxygen and superoxide dismutase (SOD) on acute spinal cord injury. Methods A rabbit model of L2 spinal cord injury was produced by Allen's method, and then the rabbits were randomly divided into experimental group and control group. In the experimental group, the rabbits received exogenous oxygen, SOD or both 30 min after injury. 12h after injury, the amount of MDA and SOD of spinal tissues were determined, and pathological changes of spinal cord were observed at the fourth weeks after injury. Results Combinant administration of exogenous oxygen and SOD could inhibit MDA production and increase SOD activities, effect of which was stronger that single administration (P