Objective:To observe the artifacts produced by dental metal crown made from different materials on magnetic resonance imaging (MRI).Methods:Mental crows made from Co-Gr,Ni-Gr,low-Ti alloy and Pure-Ti were respectively fabricated for upper right second premolar of a ripe crossbreed dog.The 4 different casting crowns were respectively put on experimental tooth and head MRI scan was carried out with 4 sequences of 1.5 T and 6 sequences of 3.0 T MRI respectively.The existence and extent of the arti-facts were assessed and compared.Results:On both 1.5 T and 3.0 T MRI,the Go-Gr alloy crown exhibited significantly wider arti-facts than the others (ANAVO analysis,P<0.01).There were no significant differences among Ni-Gr,low-Ti alloy and Pure-Ti on 1.5 T MRI(P>0.05).On 3.0 T MRI the artifacts produced by Ni-Gr was larger than that by low-Ti alloy or Pure-Ti(P<0.05,be-tween low-Ti alloy and pure-Ti,P>0.05).By any of the test sequence either on 1.5 T or on 3.0 T,the Co-Gr alloy produced arti-facts in the most slices of MRI imaging and Pure-Ti in the least.Conclusion:Go-Gr alloy may produce larger artifacts than Ni-Gr, low-Ti alloy and Pure-Ti on MRI.

Objective To study plasmid-mediated transfer,plasmid replicon typing,and genetic environment of blaNDM-1 gene in Enterobacteraerogenes(E.aerogenes).Methods E.aerogenes HN-NDM0711 was used as the subject of this research,the transferable properties of plasmid were analyzed by conjugation testing,conjugant was performed stability testing,plasmid type was determined by PCR-based replicon typing (PBRT),downstream and upstream of blaNDM-1 were sequenced using chromosome walking method,genetic context was analyzed by BLASTN and BALSTP,as well as annotated using Vector NTI 11.5.1 software,sequence pipeline graph was made,the sequence was submitted to Genbank through software Banklt.Results The conjugation testing of E.aerogenes pHN-NDM0711 was positive,after positive conjugant was conducted 4-day passage,minimal inhibitory concentrations (MICs) of imipenem and meropenem to all the cloned strains didn't change,blaNDM-1 were all positive.The replicon type was IncA/C;blaNDM-1 gene was localized between ISAba14 and IS91,at upstream of the blaNDM-1,class 1 integron and Tn3 transposon were identified,class 1 integron contained a new mosaic structure of a drug-resistant resistance gene cassette.Conclusion E.aerogenes pHN-NDM071 1,bearing blaNDM-1 gene in IncA/C plasmid,derived from gene recombination under different antimicrobial selection pressure.Antimicrobial use in clinical,industrial and agricultural area should be strictly controlled,so as to reduce the emergence of such bacteria.

Taking Shinshu University of Japan for example,we attempted to introduce the postgraduate clinical education system for new oral surgeons by analyzing the management of clinical training programs,studies of oral maxillofacial and associated medicine,and practices of scientific research in the department of oral surgery.Their experiences may be useful for us to improve our medical continuing education for young oral surgery residences.