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Objective To investigate the effect of en-masse retraction of maxillary anterior teeth by rocking-chair archwire (RCA) in sliding mechanics. Methods The three dimensional finite element model of maxillary teeth was created based on spiral CT data of a patient by ANSYS software. The forces on each tooth and the torques on the six center of resistance (CR) of the anterior teeth induced by the deformation of RCA with different depth and anterior retraction hook (ARH) with different height were calculated when retracted from a mini-implant between the first molar and the second premolar. The movements of anterior teeth were observed eonthining different depth of RCA with different height of ARH. Results The clockwise torque in sliding mechanics to realize en-masse retraction of the anterior teeth could be counterbalanced by RCA of certain depth. The combination of 7.2 mm ARH and 2 mm RCA can be used to intrude and retract maxillary anterior teeth under the condition of applying mini-implant. Conclusion The excessive retraction that usually exists in traditional treatments can be avoided by RCA in sliding mechanics and intrusion and torque control during anterior segment retraction can also be achieved by this method. [ABSTRACT FROM AUTHOR]

Objective To evaluate the feasibility of identifying oral mucosa pathogenic bacteria by comparing the metabolic profiling of Sciccharomyces and try to find a convenient and rapid way to discriminate oral micro-organisms. Methods Saccharomyces albicams ATCC 10231 and Saccharomyces tropicalis ATCC 13803 and Saccharomyces glabrata ATCC 15126 were respectively inoculated in sabouraud medium. The growth quantity were measured periodically by a spectrophotometer. And the growth curves of the inoculated bacteria were completed. The culture solutions in stationary phases of the three bacteria were respectively tested with ¹H-nuclear magnetic resonance (¹H-NMR) spectroscopy. The data of H-NMR spectroscopy results were analyzed by principal components analysis (PCA). Results The PCA showed respectively a obvious clustering phenomena and the points of every two groups' data stayed separately. Therefore, the NMR-based metabonornics profiles could discriminate the three kinds of mucosa pathogenic bacteria. Conclusion The metabonomics can be expected to be a kind of promising useful method in quick discrimination of oral pathogenic bacteria. [ABSTRACT FROM AUTHOR]