OBJECTIVE To understand epidemiologic situation of pathogens causing nosocomial infection,their resistance and changing pattern.METHODS A retrospective analysis was made upon the pathogens data from 2002 to 2006.The identification of bacteria was evaluated by VITEK32 and susceptibility test by K-B method.RESULTS The prevalence rate was 6.4%,and main infection sites were lower respiratory tract and urinary tract.Gram-negative bacteria(38.11%) stood first,followed by Gram-positive bacteria(25.25%) and fungi(22.54%).The mean resistance of Gram-negative bacteria was very high,from them Stenotrophomonas maltophilia(72.71%) and Chryseobacterium meningosepticum(68.13%) stood the highest.Besides Enterococcus faecalis,the mean resistance of Gram-positive bacteria exceeded 55.00%.Candida albicans stood first on the list of fungi.CONCLUSIONS The composition of pathogens is changing and showing serious resistances.It is important to strengthen nosocomial infection management and utilize drug rationally.

The application of tooth whitening technology in oral clinical diagnosis and treatment is becoming increasing widespread. Non-invasive tooth whitening based on bleaching technology has become the choice of many patients with tooth discoloration because of its unique advantage of not destroying the hard tissue of the tooth. The whitening effects differ according to the causes and degrees of tooth discoloration The effect of bleaching on tetracycline teeth is not as good as that of fluorosis teeth. The bleaching effect of hydrogen peroxide bleaching agents is similar to that of urea peroxide bleaching agents with the same concentration of hydrogen peroxide. The addition of non-peroxide agents such as bromelain to peroxide bleaching agents can improve the whitening effect on teeth. The whitening effect of a high-concentration bleaching agent can be achieved by using a low-concentration bleaching agent for a prolonged the working time. The effect of pH on tooth whitening is still controversial; the combination of lasers and traditional peroxide bleaching agents can effectively improve the whitening effect of teeth. The combination of enamel micro-grinding and peroxide tooth bleaching agents can improve the whitening effect in cases of dental fluorosis. This review analyzes the causes of tooth staining, the properties of bleaching agents, the application of laser microgrinding and the changes in tooth tissue after bleaching to discuss the influencing factors of the non-invasive tooth whitening effect mainly based on bleaching techniques.