[Effect of Using Hydrogen Peroxide for Periodic Disinfection Combined With Continuous Disinfection to Control Contamination in Dental Unit Waterline]. / è¿‡æ°§åŒ–æ°¢å®šæœŸæ¶ˆæ¯’ç»“åˆæŒç»­æ¶ˆæ¯’å¯¹å£è ”ç»¼åˆæ²»ç–—å°æ°´è·¯æ±¡æŸ“æŽ§åˆ¶çš„æœ‰æ•ˆæ€§è§‚å¯Ÿ.

Objective: To observe the effect of using hydrogen peroxide in periodic disinfection combining with continuous disinfection of dental unit waterlines and to provide references for the selection of waterway disinfection measures. Methods: A total of 4 dental units in a hospital of stomatology were selected through convenience sampling. The dental unit waterlines received periodic disinfection once every 4 weeks in addition to continuous disinfection (When the dental units were not used for more than 3 days, an additional periodic disinfection would be performed.). Periodic disinfection referred to filling up the waterlines with a disinfectant solution (1.4% hydrogen peroxide) by using the waterline disinfection device that came with the dental unit, immersing for 24 hours, and then emptying out the disinfectant solution. Continuous disinfection referred to using hydrogen peroxide at a concentration of 0.014% as dental treatment water and using it to flush the waterlines for 2 minutes before any dental treatment in the morning and to flush the waterlines for 30 seconds after each dental treatment. The study lasted for 25 weeks, with periodic disinfection being performed for 7 times and continuous disinfection carried out for the rest of the dental treatment time. During the 25 weeks, water samples were collected from air/water syringes and high-speed handpieces. Then, the water samples were incubated and the bacterial concentration and the qualification rates were calculated accordingly. When the bacterial concentration≤100 CFU/ mL, the water samples were considered to be qualified. Waterline tubes of 1 cm were collected before and after the 25 weeks of disinfection with hydrogen peroxide. Biofilms in the waterline tube were observed under scanning electron microscope. Results: A total of 352 water samples were collected. Eight water samples were collected before disinfection with hydrogen peroxide, with the median of bacterial concentration being 3140 CFU/mL. On the first day of disinfection with hydrogen peroxide, the median bacterial concentration in dental treatment water was 7.5 CFU/mL. There was a significant difference between the bacterial concentration of the water samples before the disinfection and that after the disinfection (P=0.012). A total of 344 water samples were collected after the disinfection, with the median bacterial concentrations for air/water syringes and high-speed handpieces being 11 CFU/mL and 11CFU/mL and the qualified rates being 83.7% and 82.0%, respectively. There was no significant difference in bacterial concentration or the qualification rates. During week 1 through week 9 of the disinfection, the qualification rates of the dental treatment water always exceeded 80% in 8 weeks, with week 3 being the exception. In the two four-week disinfection periods of week 14 through week 17 and week 18 through week 21, the qualification rate was maintained at above 80% for only the first two weeks and started to decrease from the third week. Biofilm morphology was observed under scanning electron microscope. Before the disinfection, the biofilm was found to be a dense structure and the mixture of a large number of bacteria. After 25 weeks of the disinfection, the biofilm structure appeared to be loose and did not show consistent characteristics of a large number of bacteria retained. Conclusion: Periodic disinfection combined with continuous disinfection using hydrogen peroxide can effectively control contamination in dental unit waterlines. But the cycles of periodic disinfection and the concentration of hydrogen peroxide for continuous disinfection should be further discussed according to the actual clinical situation.

Smart hydrogels with high tunability of stiffness as a biomimetic cell carrier.

Human tissues are sophisticated ensembles of various distinct cell types encapsulated in the biomechanical cues of the extracellular matrix. It has been known matrix stiffness plays a pivot role in cellular events and tissue-scale biological processes. Thus, materials that can mimic mechanical environments of tissues in vitro and possess wide, physiologically relevant elasticity are highly desirable. Hydrogels provide a good cell platform to mimic native cellular environment. However, the limited stiffness tunability, and hinders the efforts to reproduce the biomechanical microenvironment of many in vivo progresses. These problems have been addressed by the recently emerged great quantity of exquisitely designed smart hydrogels. Smart hydrogels that respond sensitively to external stimuli are good choices due to the convenience in regulating their mechanical properties. In this review, we summarize the latest progress in the development of stimuli-responsive hydrogels as a cell carrier (platform for cell culture) which spans a wide range of stiffness. Different kinds of smart hydrogels corresponding to various stimuli, including pH, temperature, light, metal ions, and forces, are introduced and their stiffness modulation through physicochemical procedures are reported.

COD removal efficiency and mechanism of HMBR in high volumetric loading for ship domestic sewage treatment.

The hybrid membrane bioreactor (HMBR) has been applied in ship domestic sewage treatment under high volumetric loading for ship space saving. The mechanism and influence factors on the efficiency, including hydraulic retention time (HRT), dissolved oxygen (DO) of chemical oxygen demand (COD) removal were investigated. The HMBR's average COD removal rate was up to 95.13% on volumetric loading of 2.4 kgCOD/(m3•d) and the COD concentration in the effluent was 48.5 mg/L, far below the International Maritime Organization (IMO) discharge standard of 125 mg/L. DO had a more remarkable effect on the COD removal efficiency than HRT. In addition, HMBR revealed an excellent capability of resisting organics loading impact. Within the range of volumetric loading of 0.72 to 4.8 kg COD/(m3•d), the effluent COD concentration satisfied the discharge requirement of IMO. It was found that the organics degradation in the aeration tank followed the first-order reaction, with obtained kinetic parameters of vmax (2.79 d-1) and Ks (395 mg/L). The original finding of this study had shown the effectiveness of HMBR in organic contaminant degradation at high substrate concentration, which can be used as guidance in the full scale of the design, operation and maintenance of ship domestic sewage treatment devices.

Positive regulation of the PhcB neighbouring regulator PrhX on expression of the type III secretion system and pathogenesis in Ralstonia solanacearum.

Ralstonia solanacearum PhcB and PhcA control a quorum-sensing (QS) system that globally regulates expression of about one third of all genes, including pathogenesis genes. The PhcB-PhcA QS system positively regulates the production of exopolysaccharide (EPS) and negatively regulates hrp gene expression, which is crucial for the type III secretion system (T3SS). Both EPS and the T3SS are essential for pathogenicity. The gene rsc2734 is located upstream of a phcBSR operon and annotated as a response regulator of a two-component system. Here, we demonstrated that RSc2734, hereafter named PrhX, positively regulated hrp gene expression via a PrhA-PrhIR-PrhJ-HrpG signalling cascade. Moreover, PrhX was crucial for R. solanacearum to invade host roots and grow in planta naturally. prhX expression was independent of the PhcB-PhcA QS system. PrhX did not affect the expression of phcB and phcA and the QS-dependent phenotypes, such as EPS production and biofilm formation. Our results provide novel insights into the complex regulatory network of the T3SS and pathogenesis in R. solanacearum.

Polyacrylamide gel with switchable trypsin activity for analysis of proteins.

Trypsin was immobilized on a variety of materials to improve digestion efficiency. However, because the immobilized trypsin will digest proteins during electrophoresis, direct immobilization of active trypsin in polyacrylamide gel will compromise the protein separation. To overcome this problem, here we report a novel polyacrylamide gel with switchable trypsin activity. It was prepared by copolymerization of the PEG-trypsin-aprotinin complex during the gel-casting step. Because the inhibitor aprotinin binds strongly with trypsin at alkaline pH, this novel gel does not display hydrolytic activity during electrophoresis. After electrophoresis, the activity of trypsin embedded in gel could be recovered by simply washing away the bound inhibitor at a low pH. It was demonstrated that this unique switchable activity design allowed high resolution of the complex protein mixture during electrophoresis and highly efficient digestion of the separated proteins in situ in the gel after electrophoresis.

Factors associated with dental behaviour management problems in children aged 2-8 years in Beijing, China.

AIM: This study determined the prevalence of children's dental behaviour management problems (BMP) in our clinic, investigated the influence of non-dental and dental background variables on BMP, and analysed the predictive power of these variables. DESIGN: The study group included 209 children aged 2-8 years who received dental treatment. Interviews were conducted with accompanying guardians. Children's dental behaviour was rated by a modified Venham's clinical anxiety scale and a cooperative behaviour rating scale. Regression models were used to analyse behavioural and interview data and to calculate the power of background variables to predict children's dental behaviour. RESULTS: During the first treatment, 29.7% of children displayed BMP. Four variables were found to predict BMP in 87.9% of cases. The risk factors for BMP were younger age, negative guardian expectations of the child's behaviour during treatment, anxiety or shyness around strangers, and presence of toothache. Children aged 2.5-3.5 years who attended kindergarten showed better dental behaviour than those who did not. CONCLUSIONS: This study is the first to report BMP prevalence in mainland China. Our results indicate that a simple pre-treatment interview could provide data allowing the dentist to identify children with special dental behavioural needs.

[Clinical evaluation of oral midazolam sedation for dental treatment in children].

OBJECTIVE: To assess the safety, effectiveness and acceptability of oral midazolam sedation for dental treatment in children. METHODS: Twenty-three health children aged 4 to 14 (ASA I), who were classified as 4 or 5 by modified Venham's clinic anxiety and cooperative behavior rating scale, referred for dental treatment were included in the study. Each child was treated under sedation with oral midazolam (0.15-0.70 mg/kg), and totally 45 sedations were conducted. At each visit, heart rate, arterial oxygen saturation, respiration rate, sedation and behavioral scores were recorded. The level of acceptance and satisfaction of the patients and their guardians were recorded after the treatment. RESULTS: Among the 23 children, 19 were boys and 4 were girls with mean age of 6.2 years old. In all the 45 treatments, the heart rate, respiratory rate and arterial oxygen saturation levels were within acceptable clinical limits. Forty planned treatments were completed satisfactorily. Oral sedation was ineffective in 3 children, and they were treated under general anesthesia. Only 2 guardians refused to have oral midazolam sedation again. Six of seven children who had regular dental check-up could be treated under normal condition. CONCLUSION: Oral midazolam (0.15-0.70 mg/kg) could be a safe and acceptable approach of sedation for pediatric dental patients.

[Biodiversity and enzyme screening of actinomycetes from Hami lake].

OBJECTIVE: In order to study the biodiversity of actinomycetes isolated from salt lakes in Hami, Xinjiang, and the characteristics of enzymes thereof. METHODS: Soil samples in salt lakes Hami were isolated with 4 isolation media containing 5% and 10% NaCl (w/v) by dilution-plate method. The activities of lipase, galactosidase, amylase, esterase and cellulose from isolated strains were qualitatively detected by using five selective media. Based on morphological characteristics, test of salt tolerance, antibacterial activitity, enzymatic characters and sequencing of 16S rRNA gene, strains were selected for phylogenetic analysis. RESULTS: A total of 63 actinomycetes were isolated from salt lake in Hami, of which 47 strains were halophilic actinomycetes. The antibacterial activity results showed that 23 strains had antibacterial activity toward Bacillus subtilis and other pathogens. Three strains produced proteinase, 46 strains produced amylase, 14 strains produced esterase, 34 strains produced galactosidase, and 5 strains produced cellulase. Analysis of 16S rRNA gene sequence indicated relatively rich genotypic diversity among these actinomycetes. CONCLUSION: There were abundant actinomycetes resources in the salt lakes in Hami, Xinjiang. The strains had very promising enzyme activities.

Transoral Atlantoaxial Release and Posterior Reduction by Occipitocervical Plate Fixation for the Treatment of Basilar Invagination with Irreducible Atlantoaxial Dislocation.

Background Prior studies have mainly assessed transoral odontoidectomy for basilar invagination with irreducible atlantoaxial dislocation. However, studies evaluating transoral release and posterior reduction with occipitocervical fixation in this setting are scarce. Methods From 2008 to 2013, 11 patients (6 men and 5 women; 23-67 years of age) with basilar invagination and irreducible atlantoaxial dislocation underwent surgery. They presented signs and symptoms of myelopathy or significant spinal cord injury, and were treated by transoral soft tissue release without odontoidectomy, under skull traction with heavy weight and by posterior reduction with occipitocervical plate fixation. Results Patients were followed up for 10 to 42 months (average: 25.4 months). All achieved bony fusion; radiologically complete reduction was achieved in 10 cases, and partial reduction in 1. All patients showed an improved postoperative neurologic condition, indicated by increased muscle strength and decreased or now absent pathologic symptoms. The average Japanese Orthopaedic Association preoperative score of 10.5 points increased to 15.5 points postoperatively. These findings indicated an improvement rate of 76.1%. The efficiency rate was 90.9%. Conclusions Anterior transoral atlantoaxial release without odontoidectomy and posterior fixation is an efficient treatment of basilar invagination with irreducible atlantoaxial dislocation.

An improved polymeric sponge replication method for biomedical porous titanium scaffolds.

Biomedical porous titanium (Ti) scaffolds were fabricated by an improved polymeric sponge replication method. The unique formulations and distinct processing techniques, i.e. a mixture of water and ethanol as solvent, multiple coatings with different viscosities of the Ti slurries and centrifugation for removing the extra slurries were used in the present study. The optimized porous Ti scaffolds had uniform porous structure and completely interconnected macropores (~365.1µm). In addition, two different sizes of micropores (~45.4 and ~6.2µm) were also formed in the skeleton of the scaffold. The addition of ethanol to the Ti slurry increased the compressive strength of the scaffold by improving the compactness of the skeleton. A compressive strength of 83.6±4.0MPa was achieved for a porous Ti scaffold with a porosity of 66.4±1.8%. Our cellular study also revealed that the scaffolds could support the growth and proliferation of mesenchymal stem cells (MSCs).

Construction of surface HA/TiO2 coating on porous titanium scaffolds and its preliminary biological evaluation.

A simple approach to fabricating hydroxyxapatite/titanium dioxide (HA/TiO2) coating on porous titanium (Ti) scaffolds was developed in the present study. Surface TiO2 layer was firstly formed on porous Ti scaffolds with multi-scale pores by acid-alkali (AA) treatment. The outer HA layer was then formed on the TiO2 layer by subsequent pulse electrochemical deposition (ED) technique. All the three main process parameters, i.e. deposition times, current density and mass transfer mode affected the properties of the HA coating notably. Under the conditions of 90 deposition cycles, -10mA/cm2 of pulse current density and stirring, a thin layer of homogeneous and nanorod-like HA sediments was formed on the substrate surface of porous Ti scaffolds. The results of protein adsorption and cellular experiments showed that compared to the single TiO2 surface, the HA/TiO2 surface allowed more adsorption of serum proteins and further enhanced the alkaline phosphatase (ALP) activity of MC3T3-E1 osteoblasts.

Fabrication of porous titanium scaffolds by stack sintering of microporous titanium spheres produced with centrifugal granulation technology.

Microporosity plays a key role in bioactivity and osteoinductivity of a biomaterial scaffold. A simple new approach to fabricating load-bearing porous titanium (Ti) scaffolds with uniform porous structure, highly controllable pore size and excellent biocompatibility was developed in the present study. This method was based on stack sintering of microporous Ti spheres produced with centrifugal granulation of commercial Ti powders. Macropores (180.0-341.8 µm) and micropores (6.1-11.8 µm) of the scaffolds were dependent on the sizes of the Ti spheres and the Ti powders, respectively. The compressive strength of the scaffolds (83.4-108.9 MPa) was high enough for the repair of load-bearing bone defects. Besides, the abundant micropores occurred on the rough and convex surface of the Ti spheres in the scaffolds were more favorable for adsorption of serum proteins, and thus promoted the growth of mesenchymal stem cells (MSCs).

[Confirmatory study on the regression equation for children dental behavior in Beijing].

OBJECTIVE: To test and verify the regression equation got before for children's dental behavior management problems(BMP). METHODS: The study group included 279 children aged 2- < 8 years who received dental treatment by 16 pediatric dentists in the Department of Pediatric Dentistry, Peking University School of and Hospital of Stomatology. Interviews were conducted with accompanying guardians and children's dental behavior was rated by a modified Venham's clinical anxiety scale and a cooperative behavior rating scale. The variables were put into the regression equation and the results were compared with their dental behavior scale. RESULTS: The accuracy rate of regression equation reached 84.2% (235/279) , sensitivity was 0.613 (95%CI:0.514-0.712) and specificity was 0.957 (95%CI:0.928-0.986). CONCLUSIONS: The regression equation is characterized by its accuracy rate at a good level. Younger age, negative guardian expectations of the child's behavior during treatment, anxiety or shyness around strangers, and presence of toothache were four risk factors for children's dental BMP.

High production of ß-glucosidase by Aspergillus niger on corncob.

Using low-cost raw material is an effective approach for reducing the cost of cellulolytic enzymes. The farmland waste corncob was found in this study to be the best carbon source for the production of ß-glucosidase by Aspergillus niger. The maximum yield of ß-glucosidase activity was 48.7 IU ml(-1) by using 50 g l(-1) of corncob powder as the substrate. It was found that the water-soluble components of the corncob could increase ß-glucosidase production significantly only when mixed with Avicel or wheat bran. The soluble components could not enhance the biomass and ß-glucosidase production when used alone. On the other hand, the water-insoluble components of the corncob still produced high level of ß-glucosidase (30 IU ml(-1)) although lower than that of using whole corncob. The results suggested that the water-insoluble components of corncob were beneficial for ß-glucosidase production. It was further demonstrated that the xylan in the water-insoluble parts of corncob was the important factor in producing ß-glucosidase by A. niger.

[Atlanto-axial screw-plate fixation and bone fusion for the treatment of atlanto-axial instability].

OBJECTIVE: To explore the clinical outcomes of atlanto-axial screw-plate fixation and bone fusion for the treatment of atlanto-axial instability. METHODS: From June 2003 to June 2008,15 cases with atlanto-axial instability were treated with atlanto-axial lateral mass screw-plate fixation and self-cancellous bone graft fusion. There were 10 males and 5 females with the mean age of 41.7 years (range, from 19 to 72 years). Six cases were old odontoid fracture, 3 cases rheumatoid arthritis, 6 cases odontoid developmental deformity. All patients had symptoms and signs of upper cervical myelopathy and the imaging displayed atlanto-axial instability. JOA scores before operation were from 6 to 11 with an average of 7.4. RESULTS: All patients were followed up with the mean of 28 months (range, from 9 to 40 months). The follow-up data indicated solid fusion in all patients, posterior reductions were satisfactory, no loosening or screw-plate broken was found. There were 10 cases which spinal cord function improved obviously, 4 cases improved slightly, 1 case no changed in the study. The postoperative JOA scores were from 13 to 17 with an average of 15.6. CONCLUSION: Atlanto-axial screw-plate fixation and self-cancellous bone graft can stabilize atlas and axis, and promote fusion of atlanto-axial joint, which is an effective method for the treatment of atlanto-axial instability.

[Establishment and evaluation of a scale method for rating children's behavior in dental clinic in China].

OBJECTIVE: To establish and evaluate a scale method for rating children's behavior in dental clinic in China. METHODS: DV records were taken for 210 children under 8-year-old, who visited the department of pediatric dentistry of Peking University School and Hospital of Stomatology during Jun to Aug in 2004. The Venham's clinic anxiety rating scale and cooperative behavior rating scale were translated into Chinese, and modified according to these records. Twenty-four pieces of records were selected randomly, and 11 pediatric dentists and assistants assessed the child behavior in the 24 records. The intraclass correlation coefficient (ICC) and Spearman's correlation coefficient (SCC), which denoted inter-rater reliability and intra-rater reliability, were calculated. RESULTS: The ICC was 0.929 and the SCC was 0.963. CONCLUSIONS: The scale has good inter-rater reliability and excellent intra-rater reliability, and it is competent for rating the children's behavior in dental clinic in China.