BACKGROUND: The shear bond strength between ceramic orthodontic brackets and teeth is so large that ceramic brackets are not easily eliminated safely. Whether the shear bond strength of self-etching primer/adhesive can be decreased and the injuries to enamel can be reduced has been always concerned by orthodontists. OBJECTIVE: To evaluate the bond strength between self-etching primer/adhesive system and ceramic orthodontic brackets and make a comparison with Jingjin enamel adhesive most commonly used by clinicians in China.DESIGN, TIME AND SETTING: Controlled observation, performed at Hebei University of Science and Technology in March 2006.MATERIALS: Twenty permanent premolars extracted due to orthodontic treatment were selected. The premolars were required to have excellent enamel and gloss, no cracks or carious lesions, and have not been given any chemotherapy. Ceramic orthodontic brackets were arch wire ceramic premolar brackets with 0.022-inch standard edgewide (3M company,USA). The bottom bracket area was 12.16 mm2. Self-etching sealant and TransbondTM fight-cure adhesive were purchased from 3M company, USA. Jingjin enamel adhesive, a conventional self-etching adhesive, was provided by Tianjin Institute of Synthetic Materials Industry, China.METHODS: The 20 premolars were randomly evenly divided into a self-etching primer/adhesive group, in which,self-etching sealant and TransbondTM fight-cure adhesive were applied, and a Jingiin enamel adhesive group, in which,Jingjin enamel adhesive was used.MAIN OUTCOME MEASURES: After 24 hours, shear bond strength was determined respectively in the two groups using anti-shearing testing machine. Simultaneously, residual adhesive remaining on the teeth was examined. RESULTS: The mean shear bond strength was lower in the self-etching primer/adhesive group than in the Jingjin enamel adhesive group, but there was no significant difference (P > 0.05). The mean shear bond strength in the two groups was clinically acceptable. The residual adhesive remaining on the teeth was significantly less in the self-etching prime/adhesive group than in the Jingjin enamel adhesive group (P < 0.01).CONCLUSION: Self-etching prime/adhesive system used for bonding ceramic orthodontic brackets can satisfy clinical requirements. Moreover, its bond strength can be appropriately decreased and ceramic brackets are easily removed, thereby,injuries to enamel can be reduced.

Objective To investigate the related factors that affect the valid period of sterile items. Methods Sterile items after well cleaning and disinfection were stored in the supply room with a standard storage conditions,as well as in different storage conditions such as neural therapy room,general surgery dressing room, outpatient and emergency injection room,clean operating room with 120 items respectively. Bacterial culture was performed regularly on the sterile items in different storage rooms.Results At 90 d after sterilization, 3 sterile items stored in the outpatient and emergency injection room with paper-plastic packaging had the bacterial growth. At 105 d after sterilization,2 samples in the general surgery dressing room with paper-plastic packaging were found to have the bacterial growth. At 150 d after sterilization,1 sample in the general surgery dressing room with non-woven packaging had the bacterial growth. Up to the end of the experiment,no bacterial growth was observed in the sterile items stored in disinfection supply center,neural therapy room and clean operating room. Conclusions The factors that affect the valid period of the sterilized items are related to the time. It is necessary to evaluate influencing factors of the valid period of sterile items from various perspectives. Specification,industry standards and provision should be executed to ensure the quality of the sterilized items and prevent nosocomial infection.

Objective:To investigate the characteristics of natural killer (NK) cell subsets and function in methicillin-resistant staphylococcus aureus (MRSA) sepsis, and to assess the influence of matrix metalloproteinase (MMP) to NK cell function in MRSA sepsis patients.Methods:Twenty-one MRSA sepsis patients who were hospitalized in our department between January 2017 and June 2018 were enrolled. Eleven healthy individuals were served as healthy controls. Peripheral blood mononuclear cells (PBMCs) were isolated. NK cell subsets were investigated by flow cytometry. NK cell function was assessed by measuring CD107a, CD69, and CD16 expression in co-culture system between PBMCs and different target cells. MMP mRNA was semi-quantified by real-time PCR in purified NK cells. The influence of NK cell function was assessed by measuring CD107a expression in co-culture system between NK cells with MMP inhibitor stimulation and target cells.Results:There was no significant difference of total NK cell percentage between healthy controls and MRSA sepsis patients ( P>0.05). CD56brightCD16 -NK [(5.36±1.02)% vs (4.30±0.89)%] and CD56 -CD16 +NK [(24.04±2.92)% vs (9.70±1.54)%] percentage was elevated ( P<0.05), while CD56dimCD16 +NK percentage [(71.22±13.03)% vs (87.64±7.05)%, P<0.01] was reduced in MRSA sepsis. NK cells recognized and killed target cells via different receptors upon activation. CD107a [(33.55±3.84)% vs (25.34±6.20)%] and CD69 percentage [(14.96±1.47)% vs(18.80±1.49)%] was decreased ( P<0.0001), while CD16 MFI was increased [(247.1±50.31) vs (189.4±57.54), P<0.01] in MRSA sepsis patients in comparison with healthy controls. MMP-1/2/3/9 mRNA relative levels were elevated in purified NK cells from MRSA sepsis patients ( P<0.01). Inhibition of MMP in NK cells from MRSA sepsis patients promoted CD107a percentage [(33.67±8.03)% vs (25.87±6.23)%, P=0.018]. Conclusions:NK cell subsets imbalance and exhaustion is existed in MRSA sepsis, which might be due to the MMP-induced down-regulation of antibody-dependent cell-mediated cytotoxicity.