[The effect of fluoride on electrochemical corrosion of the dental pure titanium before and after adhesion of Streptococcus mutans].

PURPOSE: To investigate the effect of fluoride on electrochemical corrosion of the dental pure titanium before and after adhesion of Streptococcus mutans. METHODS: The dental pure titanium specimens were tested by electrochemical measurement system including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PD) methods in artificial saliva with 0 g/L and 1.0 g/L sodium fluoride before and after dipped into culture medium with Streptococcus mutans for 24 h. The corrosion parameters, including the polarization resistance (R(ct)), corrosion potential (E(corr)), pitting breakdown potential (E(b)), and the difference between E(corr) and E(b) representing the "pseudo-passivation" (ΔE) obtained from the electrochemical tests were used to evaluate the corrosion resistance of dental pure titanium. The data were statistically analyzed by 2×2 factorial statistical analysis to examine the effect of sodium fluoride and adhesion of Streptococcus mutans using SPSS 12.0 software package. RESULTS: The results showed that the corrosion parameters including R(ct), Ecorr, E(b), and ΔE of pure titanium had significant difference between before and after adhesion of Streptococcus mutans in the same solution(P<0.05), and in artificial saliva with 0 g/L and 1.0 g/L sodium fluoride(P<0.05). CONCLUSIONS: The dental pure titanium was prone to corrosion in artificial saliva with sodium fluoride. The corrosion resistance of pure titanium decreased distinctly after immersed in culture medium with Streptococcus mutans.

[The effect of fluoride on adhesion of Streptococcus mutans and Streptococcus sanguis on the dental pure titanium surface].

PURPOSE: This study was to investigate the effect of fluoride on adhesion of Streptococcus mutans and Streptococcus sanguis on the dental pure titanium surface. METHODS: The adhesion of Streptococcus mutans and Streptococcus sanguis on the dental pure titanium surface were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after soaked in artificial saliva containing different concentrations of sodium fluoride for 24 h. Then the surface roughness and surface morphology of the pure titanium were analyzed by atomic force microscope after bacterial adhesion experiments. The data was statistically analyzed by analysis of variance(ANOVA) with SPSS11.0 software package. RESULTS: After soaked in artificial saliva containing different concentrations of sodium fluoride for 24 h, the sequence of OD values showed the adhesion of Streptococcus mutans and Streptococcus sanguis on dental pure titanium surface was 0 g/L < 0.5 g/L < 1.0g/L < 2.0 g/L (P<0.05). In addition, the sequence of Ra values showed the surface roughness of pure titanium after bacterial adhesion experiments was 0 g/L < 0.5 g/L < 1.0g/L < 2.0 g/L (P<0.05). And the surface morphology of pure titanium was consistent with the changes of OD value and Ra value. CONCLUSIONS: The results of adhesion of Streptococcus mutans and Streptococcus sanguis, surface roughness and surface morphology reveal that fluoride aggravates the corrosion of pure titanium, increases the surface roughness, and thus promots the adhesion of Streptococcus mutans and Streptococcus sanguis on the titanium surface.

[The effect of epigallocatechin gallate (EGCG) on the surface properties of nickel-chromium dental casting alloys after electrochemical corrosion].

PURPOSE: To investigate the effect of epigallocatechin gallate (EGCG) on the surface properties of nickel-chromium dental alloys after electrochemical corrosion. METHODS: The surface morphology and surface structure of nickel-chromium dental alloys were examined by stereomicroscope and scanning electron microscopy before and after electrochemical tests in 0 g/L and 1.0 g/L EGCG artificial saliva. The surface element component and chemical states of nickel-chromium dental alloys were analyzed by X-ray photoelectron spectrograph after electrochemical tests in 0 g/L and 1.0 g/L EGCG artificial saliva. RESULTS: More serious corrosion happened on the surface of nickel-chromium alloy in 1.0 g/L EGCG artificial saliva than in 0 g/L EGCG. The diameters of corrosion pits were smaller, and the dendrite structure of the alloy surface was not affected in 0 g/L EGCG. While the diameters of corrosion pits were larger, the dendritic interval of the alloy surface began to merge, and the dendrite structure was fuzzy in 1.0 g/L EGCG. In addition, the O, Ni, Cr, Be, C and Mo elements were detected on the surface of nickel-chromium alloys after sputtered for 120 s in 0 g/L EGCG and 1.0 g/L EGCG artificial saliva after electrochemical corrosion, and the surface oxides were mainly NiO and Cr(2)O(3). Compared with 0 g/L EGCG artificial saliva, the content of O, NiO and Cr(2)O(3) were lower in 1.0 g/L EGCG. CONCLUSIONS: The results of surface morphology and the corrosion products both show that the corrosion resistance of nickel-chromium alloys become worse and the oxide content of corrosion products on the surface reduce in 1.0 g/L EGCG artificial saliva.

[An in vitro comparison of the influence of different surface treatment on shear bond strength between zirconia and enamel].

PURPOSE: To compare the shear bond strength of zirconia to enamel using different surface treatments, in order to provide evidence for clinical practice. METHODS: Forty cut and fully sintered Lava frame zirconia blocks (2.7 mm × 2.7 mm × 5 mm) were randomly divided into 4 groups and subjected to 4 different surface treatments: no treatment (control), airborne-particle abrasion; airborne-particle abrasion and silane; airborne-particle abrasion and CoJet sand (silica coating with 30 µm silica-modified alumina particles) and silane. After surface treatment, the zirconia blocks were bonded to acid-etched enamel with self-adhesive resin cement (RelyX Unicem). Half of the specimens in each group were stored in 37 degrees centigrade distilled water for 24 h and the others were thermocycled (5 degrees centigrade and 55 degrees centigrade) for 5000 cycles. All specimens were subjected to shear bond strength (SBS) test. The data was analyzed with SPSS 20.0 software package for two-way ANOVA and t test. Failure mode was observed and analyzed by scanning electron microscope (SEM). RESULTS: Airborne-particle abrasion and CoJet Sand and silane group resulted in a significantly higher SBS than those in other groups (P<0.001), while no significant difference existed between the specimens which were submerged in 37 degrees centigrade water stored and thermocycled (P=0.595) within this group. No adhesive failures were observed by SEM in this group. CONCLUSIONS: The combination of tribo-chemical silica coating with silane coupling can improve the bond of zirconia when self-adhesive resin cement is used and it is recommended as a pre-treatment to increase zirconia retention.

[The effect of hydrogen peroxide on the electrochemical corrosion properties and metal ions release of nickel-chromium dental alloys].

PURPOSE: To investigate the effect of hydrogen peroxide on the electrochemical corrosion and metal ions release of nickel-chromium dental alloys. METHODS: The corrosion resistance of nickel-chromium dental alloys was compared by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curve (PD) methods in artificial saliva after immersed in different concentrations of hydrogen peroxide for 112 h. The metal ions released from nickel-chromium dental alloys to the artificial saliva were detected after electrochemical measurements using inductively coupled plasma mass spectrometry (ICP-MS). The data was statistically analyzed by analysis of variance (ANOVA) using SPSS 13.0 software package. RESULTS: The electrochemical experiment showed that the sequence of polarization resistance in equivalent circuit (Rct), corrosion potential (Ecorr), pitting breakdown potential (Eb), and the difference between Ecorr and Eb representing the "pseudo-passivation" (δE) of nickel-chromium alloys in artificial saliva was 30% < 10% < 0%(P<0.05). Furthermore, the metal ions including Ni, Cr, and Mo were released from the Ni-Cr alloys to the artificial saliva, and the order of the concentrations of metal ions was 0% < 10%< 30% (P<0.05). CONCLUSIONS: The corrosion resistance of nickel-chromium dental alloys decrease after immersed in different concentrations of hydrogen peroxide for 112 h. Nickel-chromium dental alloys are more prone to corrosion in the artificial saliva with the concentration of hydrogen peroxide increased, and more metal ions are released in the artificial saliva.

[Expression of Ki67 and P53 proteins in gingival tissue after wearing casting alloy crowns].

OBJECTIVE: The aim of the study was to detect the expression of Ki67 and P53 proteins in the gingival tissue before and after wearing three kinds of dental casting alloy crowns. METHODS: The three kinds of dental casting alloys (58% golden alloy, NiCr alloy, NiCr alloy excluding Be) were used to make full crowns for 3 dogs in each group. Another 3 dogs were taken as control. The immunohistochemistry Envision method was used to measure the expression of Ki67 and P53 proteins in the gingival tissue before wearing the crowns, 2 weeks, 1 month, 2 months, 3 months after wearing the crowns. RESULTS: The expression of Ki67 and P53 proteins in gingival tissue increased 1 month after wearing NiCr alloy and NiCr alloy excluding Be, then decreased gradually. And the expression of Ki67 and P53 proteins in 58% golden alloy group was similar to that in control. No pathological change was observed in all samples. CONCLUSION: Two kinds of NiCr alloy crowns both can increase the expression of Ki67 and P53 proteins in gingival tissue, but 58% golden alloy crowns can not. So compared with NiCr alloy crowns, 58% golden alloy crowns have better biological properties. And none of three kinds of dental alloy crowns may induce long-term abnormal proliferation in gingival tissue.

[Study on cytotoxicity of three kinds of dental ceramic alloys on L929 mouse fibroblasts in vitro].

PURPOSE: To investigate the cytotoxicity in vitro of three kinds of dental ceramic alloys on L929 mouse fibroblasts. METHODS: CCK-8 assay was a quick method to study the cell relative proliferation rate or cytotoxicity. L929 mouse fibroblasts were used to detect the cell relative proliferation rate of the three kinds of dental ceramic alloys(NiCr,CoCr and golden alloys containing 58% of gold) by CCK-8 assay. The DNA damage of L929 mouse fibroblasts was determined by single cell gel electrophoresis(SCGE). The data was statistically analyzed with SAS 9.0 software package. RESULTS: The relative growth rate induced by NiCr, CoCr and golden dental ceramic alloys was (75.9510+/-7.6244)%, (84.8920+/-8.2660)% and (88.5420+/-12.3611)%, respectively. NiCr ceramic alloys caused the most marked cytotoxicity(P<0.05), and there was no difference between CoCr ceramic alloys and 58% golden ceramic alloys(P>0.05). The cytotoxicity of the three kinds of metal ceramic alloys was all grade 1, i.e. mild cytotoxicity. The DNA damage of L929 mouse fibroblasts induced by NiCr ceramic alloys was most serious(P<0.05). There was no difference in the DNA damage between CoCr ceramic alloys and 58% golden ceramic alloys(P>0.05). CONCLUSIONS: NiCr ceramic alloys can suppress the proliferation of the L929 mouse fibroblasts and promote DNA damage. While CoCr ceramic alloys which are similar to 58% golden ceramic alloys show less cytotoxicity than NiCr ceramic alloys. CoCr or 58% golden ceramic alloys should be used as crown and bridge for patients instead of NiCr ceramic alloy clinically.

[Cytotoxicity of three kinds of temporary crown and bridge materials on mouse fibroblasts in vitro].

PURPOSE: This study was to investigate the cytotoxicity in vitro of three kinds of common temporary crown and bridge materials, i.e.,self-curing resin, heat-curing resin, and DMG-TEMP bi-acrylic composite. METHODS: L-929 mouse fibroblasts were used to evaluate the cytotoxicity of three kinds of temporary crown and bridge materials by agar overlay assay to test the cell death rate through trypan blue dyeing. RESULTS: The agar overlay assay showed that the value of Zone/Lysis of self-curing resin was 2/3, heat-curing resin was 1/0, and DMG-TEMP bi-acrylic composite was 1/2. Self-curing resin caused the most significant cytotoxicity (P<0.05), followed by heat-curing resin and DMG-TEMP composite, and the latter two showed no significant difference(P>0.05). The results of trypan blue dyeing were in accordance with the above. CONCLUSIONS: Self-curing resin, heat-curing resin, and DMG-TEMP bi-acrylic composite could decrease L-929 fibroblasts proliferation. Of all, self-curing resin caused most marked cytotoxicity, so we should avoid using self-curing resin as temporary crown and bridge to protect pulp.

[Study of DNA damage of buccal mucosal cells after wearing casting alloy crowns].

OBJECTIVE: To test the corrosion behavior of three kinds of dental casting alloys and to investigate the effect of the released metal ions on the DNA damage of dog buccal mucosal cells. METHODS: Three kinds of frequently used dental casting alloys were used to make full crowns for dogs. The concentration of the released metal ions was measured after the restoration of 2 weeks, 1 month, 2 months and 3 months. The DNA damage of buccal mucosal cells was studied by the method of SCGE. RESULTS: The metal ions released from NiCr and NiCrBe were detected in buccal mucosal cells while the amount of the ions released from noble alloy (gold 58%) was too small to be detected. The DNA damage of mucosal cells increased after restoration of NiCr and NiCrBe crowns. CONCLUSION: The noble alloy (gold 58%) is most corrosion resistant of the three alloys and has good biocompatibility. The NiCr and NiCrBe are prone to corrode and have cytotoxicity to cells.

Promoting hepatic growth factor in the treatment of heavy type hepatitis and severe chronic hepatitis: a multicenter clinical study.

BACKGROUND: The mortality rate of heavy type hepatitis is high. No special treatment is available except general treatment. This multicenter clinical study was designed to observe the safety and efficacy of promoting hepatic growth factor (PHGF) in the treatment of heavy type hepatitis and severe chronic hepatitis. METHODS: 347 patients with heavy type hepatitis and 324 with severe chronic hepatitis were subjected to administration of 120 microg of PHGF per day for 4 weeks on the basis of general treatment. Those who were being effectively treated would last additional 2 to 4 weeks. Blood routine, urine routine, blood urea nitrogen (BUN), blood creatinine (Cr), blood ammonia, alpha fetoprotein (AFP), electrolyte, alanine transaminase (ALT), aspartate transaminase (AST), serum total bilirubin (TBIL), serum direct bilirubin (DBIL), prothrombin time activity (PTA), total protein (TP) and albumin (ALB) were detected in the patients before treatment, 2 weeks after treatment, and at the end of the treatment. Any side-effect would be recorded. RESULTS: In the patients with severe chronic hepatitis, the total effective rate of the treatment was 88.9%. The levels of ALT, AST and TBIL decreased significantly (P<0.001), whereas those of PTA and ALB increased significantly (P<0.001), and the level of AFP increased slightly. In patients with heavy type hepatitis, the total effective rate of this treatment was 78.4%, and patients at different stage showed different results. The total effective rates of patients with early, medium and terminal stage heavy type hepatitis were 89.9%, 84.8% and 27.5%, respectively. No severe side-effect was shown. CONCLUSION: PHGF is effective and safe in the treatment of patients with heavy type hepatitis and severe chronic hepatitis. But it should be administered early in patients with heavy type hepatitis so as to get better curative effects.