NOP53 undergoes liquid-liquid phase separation and promotes tumor radio-resistance.

Aberrant DNA damage response (DDR) axis remains the major molecular mechanism for tumor radio-resistance. We recently characterized liquid-liquid phase separation (LLPS) as an essential mechanism of DDR, and identified several key DDR factors as potential LLPS proteins, including nucleolar protein NOP53. In this study, we found that NOP53 formed highly concentrated droplets in vivo and in vitro, which had liquid-like properties including the fusion of adjacent condensates, rapid fluorescence recovery after photobleaching and the sensitivity to 1,6-hexanediol. Moreover, the intrinsically disordered region 1 (IDR1) is required for NOP53 phase separation. In addition, multivalent-arginine-rich linear motifs (M-R motifs), which are enriched in NOP53, were essential for its nucleolar localization, but were dispensable for the LLPS of NOP53. Functionally, NOP53 silencing diminished tumor cell growth, and significantly sensitized colorectal cancer (CRC) cells to radiotherapy. Mechanically, NOP53 negatively regulated p53 pathway in CRC cells treated with or without radiation. Importantly, data from clinical samples confirmed a correlation between NOP53 expression and tumor radio-resistance. Together, these results indicate an important role of NOP53 in radio-resistance, and provide a potential target for tumor radio-sensitization.

Peri-implant marginal bone changes with implant-supported metal-ceramic or monolithic zirconia single crowns: A retrospective clinical study of 1 to 5 years.

STATEMENT OF PROBLEM: Monolithic zirconia has excellent mechanical and biologic properties. However, evidence of the clinical properties of implant-supported monolithic zirconia prostheses is limited. PURPOSE: The purpose of this retrospective clinical study was to compare the peri-implant marginal bone changes of metal-ceramic and monolithic zirconia single crowns in the posterior region after prosthetic loading. MATERIAL AND METHODS: A total of 224 participants treated with 327 implants restored with either metal-ceramic or monolithic zirconia single crowns in the posterior region between 2012 and 2016 were included in this study. Clinical outcomes, including the plaque index, peri-implant probing depth, and bleeding on probing, were recorded, and the marginal bone level was recorded by using the panoramic radiographs obtained at implant placement, second-stage surgery, and the most recent follow-up visit. The included parameters were analyzed with the nonparametric Mann-Whitney tests (α=.05). RESULTS: The mean follow-up time was 30.4 months, and the cumulative survival rate of implants was 100% and that of the prostheses was 99.1%. The plaque index was 0.46 in the metal-ceramic group, which was significantly higher (P<.05) than 0.37 in the monolithic zirconia group. However, no significant differences (P>.05) were observed in peri-implant probing depth and bleeding on probing between the 2 groups. The marginal bone level at implant placement, second-stage surgery, and the most recent follow-up visit was above the implant platform in both the metal-ceramic and monolithic zirconia groups. The marginal bone changes of the metal-ceramic group was 0.31 mm in the healing period and 0.38 mm in the prosthetic loading period, while in the monolithic zirconia group, it was 0.25 mm in the healing period and 0.43 mm in the prosthetic loading period; no significant differences (P>.05) were observed between the 2 groups. CONCLUSIONS: The peri-implant marginal bone level change was comparable after prosthetic loading for metal-ceramic and monolithic zirconia single crowns, although monolithic zirconia was associated with reduced plaque.

Norovirus shedding among symptomatic and asymptomatic employees in outbreak settings in Shanghai, China.

BACKGROUND: Norovirus (NoV) is recognized as a leading cause of acute gastroenteritis (AGE) outbreaks in settings globally. Studies have shown that employees played an important role in the transmission mode during some NoV outbreaks. This study aimed to investigate the prevalence of NoV infection and duration of NoV shedding among employees during NoV outbreaks, as well as factors affecting shedding duration. METHODS: Specimens and epidemiological data were collected from employees who were suspected of being involved in the transmission or with AGE symptoms during NoV outbreaks in Xuhui District, Shanghai, from 2015 to 2017. Specimens were detected using real-time RT-PCR to determine whether or not employees had become infected with NoV. Specimens were collected every 3-7 days from NoV-infected employees until specimens became negative for NoV. RESULTS: A total of 421 employees were sampled from 49 NoV outbreaks, and nearly 90% of them (377/421) were asymptomatic. Symptomatic employees showed significantly higher prevalence of NoV infection than asymptomatic ones (70.5% vs. 17.0%, P < 0.01). The average duration of NoV shedding was 6.9 days (95% confidence interval: 6.1-7.7 days) among 88 NoV-infected individuals, and was significantly longer in symptomatic individuals than in asymptomatic ones (9.8 days vs. 5.6 days, P < 0.01). In Cox proportional-hazards model, after adjusting age and gender, symptoms was the only factor associated with duration of NoV shedding. CONCLUSIONS: Compared with asymptomatic employees, symptomatic employees had higher prevalence of NoV infection and longer durations of NoV shedding. Since NoV shedding duration among NoV-infected employees tends to be longer than their isolation time during outbreaks, reinforcement of hygiene practices among these employees is especially necessary to reduce the risk of virus secondary transmissions after their return to work.

Unusual and Highly Bioactive Sesterterpenes Synthesized by Pleurotus ostreatus during Coculture with Trametes robiniophila Murr.

Candida albicans and Cryptococcus neoformans, human-pathogenic fungi found worldwide, are receiving increasing attention due to high morbidity and mortality in immunocompromised patients. In the present work, 110 fungus pairs were constructed by coculturing 16 wood-decaying basidiomycetes, among which coculture of Trametes robiniophila Murr and Pleurotus ostreatus was found to strongly inhibit pathogenic fungi through bioactivity-guided assays. A combination of metabolomics and molecular network analysis revealed that 44 features were either newly synthesized or produced at high levels in this coculture system and that 6 of the features that belonged to a family of novel and unusual linear sesterterpenes contributed to high activity with MICs of 1 to 32 µg/ml against pathogenic fungi. Furthermore, dynamic 13C-labeling analysis revealed an association between induced features and the corresponding fungi. Unusual sesterterpenes were 13C labeled only in P. ostreatus in a time course after stimulation by the coculture, suggesting that these sesterterpenes were synthesized by P. ostreatus instead of T. robiniophila Murr. Sesterterpene compounds 1 to 3 were renamed postrediene A to C. Real-time reverse transcription-quantitative PCR (RT-qPCR) analysis revealed that transcriptional levels of three genes encoding terpene synthase, farnesyl-diphosphate farnesyltransferase, and oxidase were found to be 8.2-fold, 88.7-fold, and 21.6-fold higher, respectively, in the coculture than in the monoculture, indicating that biosynthetic gene cluster 10 was most likely responsible for the synthesis of these sesterterpenes. A putative biosynthetic pathway of postrediene A to postrediene C was then proposed based on structures of sesterterpenes and molecular network analysis.IMPORTANCE A number of gene clusters involved in biosynthesis of secondary metabolites are presumably silent or expressed at low levels under conditions of standard laboratory cultivation, resulting in a large gap between the pool of discovered metabolites and genome capability. This work mimicked naturally occurring competition by construction of an artificial coculture of basidiomycete fungi for the identification of secondary metabolites with novel scaffolds and excellent bioactivity. Unusual linear sesterterpenes of postrediene A to C synthesized by P. ostreatus not only were promising lead drugs against human-pathogenic fungi but also highlighted a distinct pathway for sesterterpene biosynthesis in basidiomycetes. The current work provides an important basis for uncovering novel gene functions involved in sesterterpene synthesis and for gaining insights into the mechanism of silent gene activation in fungal defense.

Toxicity testing of four silver nanoparticle-coated dental castings in 3-D LO2 cell cultures.

To address the controversial issue of the toxicity of dental alloys and silver nanoparticles in medical applications, an in vivo-like LO2 3-D model was constructed within polyvinylidene fluoride hollow fiber materials to mimic the microenvironment of liver tissue. The use of microscopy methods and the measurement of liver-specific functions optimized the model for best cell performances and also proved the superiority of the 3-D LO2 model when compared with the traditional monolayer model. Toxicity tests were conducted using the newly constructed model, finding that four dental castings coated with silver nanoparticles were toxic to human hepatocytes after cell viability assays. In general, the toxicity of both the castings and the coated silver nanoparticles aggravated as time increased, yet the nanoparticles attenuated the general toxicity by preventing metal ion release, especially at high concentrations.

Effects on cytotoxicity and antibacterial properties of the incorporations of silver nanoparticles into the surface coating of dental alloys.

The aim of this study was to research the changes in cytotoxicity and antibacterial properties after silver nanoparticles (AgNPs) were incorporated into the surface coating of dental alloys. AgNPs were attached to cobalt chromium alloys and pure titanium using a hydrothermal method, according to the reaction: AgNO3+NaBH4→ Ag+1/2H2+1/2B2H6+NaNO3. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate the cytotoxicity of the alloys when in contact with osteogenic precursor cells (MC3T3-E1) from mice and mesenchymal stem cells (BMSC) from rats. The antibacterial properties of dental alloys incorporating three different concentrations (10, 4, and 2 µmol/L) of AgNPs were tested on Staphylococcus aureus (SA) and Streptococcus mutans (MS). High cytotoxicity values were observed for all dental alloys that contained 0% of AgNPs (the control groups). The incorporation of AgNPs reduced cytotoxicity values. No significant difference was observed for antibacterial performance when comparing dental alloys containing AgNPs to the respective control groups. The results demonstrated that the cobalt chromium alloys and pure titanium all had cytotoxicity to MC3T3-E1 and BMSC and that the incorporation of AgNPs could reduce this cytotoxicity. The concentrations of AgNPs adopted in this study were found to have no antibacterial action against SA or MS.

Metabolomics Investigation of an Association of Induced Features and Corresponding Fungus during the Co-culture of Trametes versicolor and Ganoderma applanatum.

The co-culture of Trametes versicolor and Ganoderma applanatum is a model of intense basidiomycete interaction, which induces many newly synthesized or highly produced features. Currently, one of the major challenges is an identification of the origin of induced features during the co-culture. Herein, we report a 13C-dynamic labeling analysis used to determine an association of induced features and corresponding fungus even if the identities of metabolites were not available or almost nothing was known of biochemical aspects. After the co-culture of T. versicolor and G. applanatum for 10 days, the mycelium pellets of T. versicolor and G. applanatum were sterilely harvested and then mono-cultured in the liquid medium containing half fresh medium with 13C-labeled glucose as carbon source and half co-cultured supernatants collected on day 10. 13C-labeled metabolome analyzed by LC-MS revealed that 31 induced features including 3-phenyllactic acid and orsellinic acid were isotopically labeled in the mono-culture after the co-culture stimulation. Twenty features were derived from T. versicolor, 6 from G. applanatum, and 5 features were synthesized by both T. versicolor and G. applanatum. 13C-labeling further suggested that 12 features such as previously identified novel xyloside [N-(4-methoxyphenyl)formamide 2-O-beta-D-xyloside] were likely induced through the direct physical interaction of mycelia. Use of molecular network analysis combined with 13C-labeling provided an insight into the link between the generation of structural analogs and producing fungus. Compound 1 with m/z 309.0757, increased 15.4-fold in the co-culture and observed 13C incorporation in the mono-culture of both T. versicolor and G. applanatum, was purified and identified as a phenyl polyketide, 2,5,6-trihydroxy-4, 6-diphenylcyclohex-4-ene-1,3-dione. The biological activity study indicated that this compound has a potential to inhibit cell viability of leukemic cell line U937. The current work sets an important basis for further investigations including novel metabolites discovery and biosynthetic capacity improvement.

Discovery of novel xylosides in co-culture of basidiomycetes Trametes versicolor and Ganoderma applanatum by integrated metabolomics and bioinformatics.

Transcriptomic analysis of cultured fungi suggests that many genes for secondary metabolite synthesis are presumably silent under standard laboratory condition. In order to investigate the expression of silent genes in symbiotic systems, 136 fungi-fungi symbiotic systems were built up by co-culturing seventeen basidiomycetes, among which the co-culture of Trametes versicolor and Ganoderma applanatum demonstrated the strongest coloration of confrontation zones. Metabolomics study of this co-culture discovered that sixty-two features were either newly synthesized or highly produced in the co-culture compared with individual cultures. Molecular network analysis highlighted a subnetwork including two novel xylosides (compounds 2 and 3). Compound 2 was further identified as N-(4-methoxyphenyl)formamide 2-O-ß-D-xyloside and was revealed to have the potential to enhance the cell viability of human immortalized bronchial epithelial cell line of Beas-2B. Moreover, bioinformatics and transcriptional analysis of T. versicolor revealed a potential candidate gene (GI: 636605689) encoding xylosyltransferases for xylosylation. Additionally, 3-phenyllactic acid and orsellinic acid were detected for the first time in G. applanatum, which may be ascribed to response against T.versicolor stress. In general, the described co-culture platform provides a powerful tool to discover novel metabolites and help gain insights into the mechanism of silent gene activation in fungal defense.

[Combination of multiple displacement amplification with short tandem repeat polymorphismin preimplantation genetic diagnosis].

OBJECTIVE: To explore the application of multiple displacement amplification (MDA) combined with short tandem repeats (STRs) in preimplantation genetic diagnosis (PGD). METHODS: MDA was applied to amplify the whole genome of a single cell and to retrieve and assemble the highly heterogeneous STR loci among human population. Haplotype analytic system was established with aiming at diagnosis of the single gene diseases by selecting the STR loci located within the pathogenic genes or on both bounding sides of the pathogenic genes. At the same time, allele specific amplification, PCR-reverse dot-blotting hybridization methods and gene sequencing methods were employed for direct detection of the pathogenic genes. The STR loci located at related chromosomes were selected to carry out allele number analysis on the basis of chromosome number and structural abnormality. RESULTS: In the study, 12 PGD systems were set up including 6 different monogenic diseases (spinal muscular atrophy, Duchenne muscular dystrophy, X-linked chronic granulomatous disease, osteopetrosis, achondroplasia, X-linked severe combined immunodeficiency), Robertsonian translocations, α-thalassemia combined with Robertsonian translocation, α- and ß-double thalassemia, ß-thalassemia with HLA typing and DMD with HLA typing. Then 44 PGD cycles were performed for 35 couples with different kinds of inherited diseases, which resulted in 20 healthy liveborns (12 singletons and 4 twins) and 5 ongoing pregnancies. The clinical pregnancy rate was 47.7% (21/44) per PGD cycle. The overall diagnostic rate was 94.6% (367/388). The MDA failed in 3.6% (14/388) single blastomeres. The amplification rate of the subsequent PCR was 97.1% and the average allele drop out (ADO) rate was 12.6% (range: 0-47.5%). CONCLUSION: The application of MDA combined with STRs provided a generic PGD approach for different genetic disorders, especially for simultaneous diagnosis of two or more hereditary statuses. The method could greatly shorten the time of developing PGD system of new diseases, which broadens the indications of PGD.

Prevalence of hepatitis C infection among intravenous drug users in Shanghai.

AIM: To characterize the prevalence of hepatitis C virus (HCV) infection among Chinese intravenous drug users (IDUs). METHODS: A total of 432 adult IDUs (95 women and 337 men) in Shanghai were included in the study. The third-generation Elecsys Anti-HCV assay (Roche Diagnostics GmbH, Sandhofer Strasse 116, D-68305, Mannheim, Germany) was used to screen for antibodies against HCV. The RIBA strip, a supplemental anti-HCV test with high specificity, was performed on all of the samples that tested positive during the initial screening. All of the anti-HCV positive samples were analyzed with a Cobas TaqMan 48 Analyzer (Roche Diagnostics) for direct detection of HCV RNA. All of the HCV RNA-positive samples were sequenced for genotype determination. RESULTS: The preliminary screening identified 262 (60.6%) subjects who were seropositive for HCV. Of the 62 females and 200 males seropositive subjects, 16 (16.7%) and 65 (19.3%), respectively, were confirmed by RIBA, yielding an overall HCV seropositive rate of 18.8%. Four female (6.5%) and 14 male (7.0%) subjects tested positive for HCV RNA, indicating an active infection rate of 4.2% for the entire study population. The 18 HCV RNA-positive serum samples were genotyped. Seven individuals were genotype 1b, and four were genotype 1a. One individual each was infected with genotypes 2a, 2b and 3a. Four subjects were co-infected with multiple strains: two with genotypes 1a and 2a, and two with genotypes 1b and 2a. The active infection rate among HCV-seropositive individuals was 22.2%, which was significantly lower than most estimates. CONCLUSION: The prevalence of HCV is relatively low among IDUs in Shanghai, with a spontaneous recovery rate much higher than previous estimates.

A further exploration of the impact of antinuclear antibodies on in vitro fertilization-embryo transfer outcome.

OBJECTIVE: To determine the presence of antinuclear antibodies (ANAs) in follicular fluid (FF) and embryos as to their potential impact on IVF outcome. METHODS: A total of 100 women presenting to IVF/ICSI program were recruited in this study, wherein 50 women sero-positive for ANA served as study group (ANA+ group) and 50 women seronegative for ANA served as control group (ANA- group), and patients were age-matched in the two groups. ANA level in serum and FF were examined by ELISA, and immunofluorescence assay was employed to detect IgG within embryos. RESULTS: In ANA+ group, 36 women showed positive ANA both in serum and FF on the day of ovum pick-up (OPU), wherein 34 exhibited fluorescence of IgG in embryos. All the 50 women in control group showed negative results in serum and FF ANA on OPU day and in embryo immunofluorescence. Serum ANA level positively correlated with FF ANA level. IVF outcomes were significantly poorer in ANA+ group, mainly reflecting the less number of high-quality embryos, reduced rates of pregnancy, clinical pregnancy, and implantation. CONCLUSION: These data demonstrated the existence of ANA in FF and embryos, which may exert detrimental impact on IVF outcome.

A retrospective study on IVF outcome in patients with anticardiolipin antibody: effects of methylprednisolone plus low-dose aspirin adjuvant treatment.

Patients undergoing in vitro fertilization-embryo transfer have a high prevalence of anticardiolipin antibody (ACA). However, the relationship between ACA and IVF outcome is still controversial. The aim of the present study was to evaluate the potential effect of anticardiolipin antibody on IVF outcome and determine the role of adjuvant treatment in these ACA positive patients. The study included a total of 116 infertile women (116 IVF-ET cycles) positive for ACA, including 56 women pretreated with methylprednisolone plus low-dose aspirin before IVF (treated ACA+ group) and 60 patients without treatment (untreated ACA+ group). In addition, 518 infertile women (518 IVF-ET cycles) negative for ACA were enroled as controls (ACA- group). The results show that ACA+ patients who did not receive any adjuvant treatment showed a significantly lower fertilization rate, less high-quality embryos, as well as a markedly lower pregnancy rate and implantation rate than controls. Moreover, ACA+ patients who received methylprednisolone plus aspirin achieved significantly higher fertilization, pregnancy and implantation rates than untreated ACA+ patients (FR 69.0%, PR 46.4% and IR 25.4% vs. FR 60.0%, PR 33.3% and IR 17.9%, respectively). The overall IVF results in the treated ACA+ group were comparable to patients negative for ACA (PR 53.9% and IR 32.3%). Thus, while the presence of ACA exerts a detrimental effect on IVF outcome, ACA+ patients have a better outcome if given methylprednisolone for immunosuppression and low-dose aspirin as an anti-thrombotic agent.

Comparison of Endocrine Profile and In Vitro Fertilization Outcome in Patients with PCOS, Ovulatory PCO, or Normal Ovaries.

Aim. To compare the basic endocrine profile and outcomes of in vitro fertilization (IVF) in women with polycystic ovary syndrome (PCOS), ovulatory polycystic ovaries (PCO), or normal ovaries (NO). Methods. The basic clinical features and in vitro fertilization and embryo transfer outcome in patients receiving IVF or intracytoplasmic sperm injection (ICSI) were retrospectively analyzed. Results. The body mass index, basal luteinizing hormone, and testosterone levels were significantly lower in patients with ovulatory PCO compared to those in patients with PCOS. The PCOS patients exhibited the shortest duration of ovarian stimulation and lowest dose of gonadotropin, followed by the ovulatory PCO and NO patients. The ovulatory PCO and PCOS patients showed similar levels of E2 on the human chorionic gonadotropin treatment day and numbers of oocytes, which were both significantly higher than those of the NO patients. The fertilization rate of the PCOS patients was significantly lower than the other two groups. Compared to NO patients, the cleavage rate was lower in both PCOS and ovulatory PCO patients, however, the number of available embryos was significantly more in these two groups. The incidence of the moderate to severe ovarian hyperstimulation syndrome (OHSS) was markedly higher in the PCOS and ovulatory PCO patients. Conclusion. Ovulatory PCO patients do not express similar endocrine abnormalities as PCOS patients. Although the fertilization rate and cleavage rate were relatively low in PCOS patients, ultimately, all the three groups showed similar transferred embryo numbers, clinical pregnancy rates, and implantation rates. Since the incidence of OHSS was much higher in the PCOS and ovulatory PCO patients, we should take more care of these patients and try to prevent severe OHSS.

Antinuclear antibodies predicts a poor IVF-ET outcome: impaired egg and embryo development and reduced pregnancy rate.

To investigate the impact of anti-nuclear antibodies (ANAs) on the outcome of in vitro fertilization-embryo transfer (IVF-ET), 66 (96 cycles) infertile women positive for anti-nuclear antibodies (ANA+ group), and 233(285 cycles) infertile women negative for ANAs (ANA- group) were enrolled. The clinical characteristics and IVF outcome were compared between the two groups. In the ANA+ group, the proportion of MII oocytes and two-pronuclear zygotes (2PN), cleavage rate, number of available embryos and proportion of available embryos, number of high-quality embryos and proportion of high-quality embryos were significantly lower than those in the ANA- group. In addition, the pregnancy rate and implantation rate in patients positive for ANA was markedly lower than the ANA- patients (28.1% vs 46.4%, 15% vs 25.7%, respectively). Thus, our findings suggest that the presence of ANAs significantly interfere with the oocyte and embryo development, as well as reduce implantation and pregnancy rate in patients undergoing IVF treatment.

Relationship between antithyroid antibody and pregnancy outcome following in vitro fertilization and embryo transfer.

OBJECTIVE: To investigate the impact of antithyroid antibody on pregnancy outcome following the in vitro fertilization and embryo transfer (IVF-ET). METHODS: A total of 90 patients (156 cycles) positive for antithyroid antibody (ATA+ group) and 676 infertile women (1062 cycles) negative for antithyroid antibody (ATA- group) undergoing IVF/ICSI from August 2009 to August 2010 were retrospectively analyzed. RESULTS: There was no significant difference in the days of ovarian stimulation, total gonadotropin dose, serum E2 level of HCG day and number of oocytes retrieved between the two groups. The fertilization rate, implantation rate and pregnancy rate following IVF-ET were significantly lower in women with antithyroid antibody than in control group (64.3% vs 74.6%, 17.8% vs 27.1% and 33.3% vs 46.7%, respectively), but the abortion rate was significantly higher in patients with antithyroid antibody (26.9% vs 11.8%). CONCLUSION: Patients with antithyroid antibody showed significantly lower fertilization rate, implantation rate and pregnancy rate and higher risk for abortion following IVF-ET when compared with those without antithyroid antibody. Thus, the presence of antithyroid antibody is detrimental for the pregnancy outcome following IVF-ET.

[Application of digital photography in color matching in dentistry].

OBJECTIVE: To develop a new color matching method in dentistry by application of digital photography. METHODS: Digital photographs were obtained of Vitapan 3D-Master shade guide and natural teeth under the same condition, the L*a*b* values of each digital photography were assessed and analyzed by Photoshop CS4. RESULTS: The Vitapan 3D-Master shade guide was divided into 5 groups, the L* values were similar in each group, but decreased from group 1 to 5. The a* values of L1.5 and L2.5 were minimum, R1.5 and R2.5 were maximum and M1-M3 were intermediate. Compared with Vitapan 3D-Master shade guide, the L*a*b* values of natural teeth were higher. CONCLUSION: Digital photography can basically reflect the color of Vitapan 3D-Master shade guide, and provides a reference for color matching in dentistry.

[Effect of pH value and fluoride ions on corrosion resistance of pure Ti and Ni-Cr-Ti alloy in artificial saliva].

OBJECTIVE: To investigate the effect of pH value and fluoride ions on the corrosion resistance of pure Ti and Ni-Cr-Ti alloy in the artificial saliva. METHODS: Electrochemical technique was used to measure the electric potential of corrosion (Ecorr), current density of corrosion (Icorr) and polarization resistance (Rp) of pure titanium and Ti-Ni-Cr alloy in the artificial saliva with different pH value and fluoride concentrations. After electrochemical analysis, microstructure and phase diffraction were examined by FSEM. RESULTS: With the lower pH value, the Ecorr and Icorr of pure titanium and Ti-Ni-Cr alloy increased, the Rp decreased, there was a significant difference (P<0.05). The Ecorr and Icorr increased markedly, the Rp significantly reduced in the artificial saliva containing 0.2% NaF (P<0.01). FSEM showed that pure titanium and Ti-Ni-Cr alloy surface corrosion, pure titanium in the artificial saliva containing 0.2% NaF was most serious. CONCLUSION: Lower pH value decreases the corrosion resistance of pure titanium and Ti-Ni-Cr alloy and the artificial saliva containing fluoride ions decreases the corrosion resistance of pure titanium.

[Study of the correlation between Streptococcus mutans' adhesion and surface corrosion in casting titanium and Ti alloy].

PURPOSE: To investigate the correlation between Streptococcus mutans' adhesion and surface corrosion of the casting titanium and Ti alloy with different kinds of polishing. METHODS: The casting titanium and Ti alloy were respectively processed into size of 30 mm x 8mm x 1mm in tablets. Each material was prepared for 32 specimens, randomly divided into two groups, dealt with mechanical polishing and electrochemistry polishing, and then randomly divided into four groups (blank control, media control, inoculated media control for three months and six months).Four specimens were used in each group under hypoxia conditions. The labeled specimen surfaces were then aseptically placed in the test tube with one transfer per week. The specimens were removed and sterilized. The surface roughness of specimens was measured by FTS i120 contourgraph and the alteration of the surface was observed under SIRION scanning electron microscope. One-way ANOVA was performed with SPSS11.O software package. RESULTS: In casting titanium, blank control media control, inoculated media control for three months and six months showed no influence on Ra value(P>0.05).In Ti alloy, the Ra value of the inoculated media control group was significantly different from those of blank control group(P<0.05) and metal control group(P<0.05). All the specimen surfaces had pits in disorder and in different size. CONCLUSIONS: Streptococcus mutans' adhesion causes surface corrosion of the casting titanium and Ti alloy, and mechanical polishing and electrochemistry polishing have no influence on corrosion.