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PURPOSE: To study the distribution of stress of simulating teeth with wedge-shaped defects in the cervical region. METHODS: The models of anisotropic enamel of the mandibular first premolar and the opposite maxillary first premolar crown were created. A defect was introduced into the model of mandibular premolar in the buccal cervical region along the enamelo-dentinal junction. The stress distribution in the cervical region of the mandibular premolar was investigated with regard to different loading conditions simulating working, nonworking and vertical micromotions. In each case, the stroke was applied to the mandibular premolars in a stepping procedure using nonlinear contact analysis. RESULTS: The stresses were concentrated in the defect of the enamel and dentin at the enamelo-dentinal junction (EDJ) in the condition of different loading, especially in the condition of simulating lateral excursion on one contact. CONCLUSION: Undermined cervical EDJ had a significant effect on the stress distribution in the buccal cervical region. [ABSTRACT FROM AUTHOR]

Objective To study the distribution of stress of simulating teeth with wedge shaped defects in the cer-vical region. Methods The models of anisotropic enamel of the mandibular first premolar and the opposite maxillary first premolar crown were created. A deffect was introduced into the model of mandibular premolar in the buccal cervical region along the enamelo-dentinal junction (DEJ). The stress distribution in the cervical region of the mandibular premolar was investigated considering lateral condition simulating working micromotions. In this case, the stroke was applied to the maxillary first mandibular in a stepping procedure using nonlinear contact analysis. Results The stresses were concentrated in the defect of the enamel and dentin at the DEJ in the condition of lateral loading. As the defect length increased in size, the peak maximum principal stress (MPS) value and the magnitude of the stress field along the DEJ both increased. Conclusion Undermined cervical DEJ had a significant effect on the stress distribution in the buccal cervical region. [ABSTRACT FROM AUTHOR]

Purpose: To study the distribution of stress of simulating teeth with wedge-shaped defects in the cervical region., Methods: The models of anisotropic enamel of the mandibular first premolar and the opposite maxillary first premolar crown were created. A defect was introduced into the model of mandibular premolar in the buccal cervical region along the enamelo-dentinal junction. The stress distribution in the cervical region of the mandibular premolar was investigated with regard to different loading conditions simulating working, nonworking and vertical micromotions. In each case, the stroke was applied to the mandibular premolars in a stepping procedure using nonlinear contact analysis., Results: The stresses were concentrated in the defect of the enamel and dentin at the enamelo-dentinal junction(EDJ) in the condition of different loading, especially in the condition of simulating lateral excursion on one contact., Conclusion: Undermined cervical EDJ had a significant effect on the stress distribution in the buccal cervical region.

The ultraviolet absorption spectra of pyrazoles and 1-carboxamidepyrazoles were studied. The results indicated that substitution in the 3 or the 5 position it leads to a bathochromic shift of the position of the maximum absorption by about 3-4 nm, whereas in the 4 position leads to a much larger bathochromic shift (> 10 nm). The introduction of carboxamide causes a bathochromic shift of the position of the maximum absorption by about 20-26 nm. Its also leads to an increase in molar extinction coefficient by about 2-3 times. So UV methods were established for determining the contents of pyrazoles and their derivations. Using these methods, the content of 3,4-dimethylpyrazole phosphate (DMPP) in stabilized urea was determined to be 1.15% of urea-N, the hydrolytic half lives of 1-carboxamide-3-methylpyrazole (CMP) in water solution at 20, 25 and 30 degrees C were 48, 30 and 18 h, respectively, and the extraction percentage of nitrification inhibitor 3-methylpyrazole phosphate (MPP) in 3 soils by 3 different extractants were ranged from 63.2% to 89.2%.