Objective : To observe the clearance of smear layer on the root canal wall in different action time by scanning electron microscope (SEM), and to determine the optimal amount of time using sonically activated irrigation to wash root canal in clinic. Methods: Fifty-six ex vivo human anterior teeth with single straight root canal were selected. After routine mechanical preparation, they were divided into two experimental groups according to different irrigating agents: saline group and EDTA group. Each group was assisted by VDW sonic activation EDDY. The saline group was divided into three subgroups according to the irrigating time: 5 s, 30 s and 50 s; EDTA group was divided into six subgroups according to the irrigating time: 5 s, 10 s, 20 s, 30 s, 40 s and 50 s. The control group did not undergo root canal irrigation. After irrigation, the root was cut longitudinally. The smear layer of crown, middle and apical of root canal wall was observed by SEM. Results: After irrigating for 30 seconds, there was a significant difference between the normal saline group and the control group and the 5 second group (P<0.05), and there was no difference in the middle and apical part (P>0.05). After 50 seconds, there was a significant difference in the score of the smear layer between the apical area and the other groups (P<0.05). After irrigating for 5 seconds or 10 seconds in EDTA group, there was a significant difference between the scores of the crown and middle area of the root canal and the control group (P<0.05), and there was no significant difference in the apical area (P>0.05). There was a significant difference between the 20-40 second group and the first two groups (P<0.05). There was a significant difference between the 50 second group and the other groups (P<0.05). Comparing the cleaning effect on the smear layer after 50 seconds of irrigating between the two experimental groups, the whole root canal showed significant statistical difference (P<0.05). Conclusion The EDTA-assisted sonic activated device used for 50 seconds has the best cleaning effect.

Objective To report a new method of fluorescent labeling technique in microarray studies: universal primer U2 labeling( UPL). The efficiency was compared of the UPL with that of random primer, restriction display labeling method and the reverse transcription coupled random primer spiking labeling method(RT-PSL). Methods Influenza viral RNA was labeled with both UPL and the conventional random primer labeling method as well as two other more laborious labeling methods( RD-direct and RD-incorporate), and hybridized with influenza virus oligonucleotide microarrays. The signals extracted from the microarrays were analyzed using SPSS 10.0 software. Results The fluorescent intensity, signal-to-noise ration(SNR), true positive ratio(TPR) of probes and labeling reproducibility of UPL were demonstrated to be higher than those of the Random primer approaches.Conclusion These results established that UPL is a valid new labeling protocol, which may have wide applications in the research and development of the microarray technology.