BACKGROUND: It has been reported that 26-1 ferrite stainless steel has excellent biological characteristics, but the report of its biocompatibility is rare, especially the evaluation of biocompatibility by apoptosis mechanism. OBJECTIVE: To study the pattern of call death induced by magnetic-attached 26-1 ferrite stainless steel and to evaluate whether 26-1 ferrite stainless steal meats the biocompatibility in clinical application. DESIGN, TIME AND SETTING: A contrast observational study at the level of molecular biology was performed at Central Laboratory of China Medical University from June 2004 to June 2005.MATERIALS: 26-1 ferrite stainless steel (Fe - 26% Cr - 1% Mo), Tilite [70% Ni - 16% Cr - (4%-6%) Ti - ether alloy elements] and Co-Cr alloy (Co - 30% Cr - 5% Mo) were used in this study. Embed and cast metal materials then were cut into roll discs whose diameters were 12 mm.METHODS: ① The fibroblast L929 cells were co-cultured with the three materials, while cells in the negative control group were cultured in RPMI1640 media. At 18 and 24 hours after culture, types of cell death were quantitatively detected using fluorescein isothiocyanate and propidium iodide (PI) staining. ② Apoptosis rate and cycle distribution of L929 cells were detected using flow cytometry and Pl staining at 24 hours after respectively culturing in 25%, 50%, and 100% leaching liquor. MAIN OUTCOME MEASURES: Ratio between apoptosis and necrosis of L929 cells induced by different materials; apoptotic rate and cycle distribution of L929 cells.RESULTS: All the three materials could decrease the survival rate of L929 cells: in particular, there was no significant difference in necrosis rate between different concentration material groups and negative control group, suggesting that call apoptosis was the major factor to induce cytopathic effect, but there was no significant difference between the three material groups. Apoptosis of L929 cells indicated a great fashion of time- and concentration-dependence. There was no significant difference in apoptosis rate of L929 cells betwean the three material groups.CONCLUSION: Cell apoptosis is a major pattern induced by 26-1 ferrite stainless steel which meets the biocompatibility as a clinical material and can be safely applied in dinic.

BACKGROUND: Nickel-chromium ceramic alloy with well anti-causticity has been widely used in clinic; however, it should be paid much attention to the toxic and side effects of the released nickel and glucinium ions. Therefore, studies about modifying alloy component, enhancing physical and chemical performance, and improving biocompatibility are hot topics recently. OBJECTIVE: To measure the in vitro cytotoxicity of self-made nickel-chromium ceramic alloy comparing with nickel-chromium alloy and pure titanium metal. DESIGN, TIME AND SETTING: A contrast observational experiment was performed at Central Laboratory of China Medical University from May to December 2006. MATERIALS: L-929 cells at logarithmic phase were used in this study. Self-made nickel-chromium ceramic alloy was provided by Metal Institute of Chinese Academy of Science, pure titanium was provided by Matsukaze Japan Co., Ltd., and nickel-chromium alloy was provided by Heraeus Kulzer Dental Co., Ltd. METHODS: L-929 cells were assigned into nickel-chromium ceramic alloy, pure titanium, nickel-chromium alloy, positive control, and negative control groups. The cells were cultured in 96-well culture plate. Every five wells were randomly selected from each group, and 12 wells were used for the duplication. Cell suspension (100 μL) at concentration of 1.0×108/L was added in each well. Leaching liquor (100 μL) was added in self-made nickel-chromium ceramic alloy, pure titanium alloy, and nickel-chromium alloy groups, respectively, lead leaching liquor (100 μL) was added in positive control group to make the final concentration at 50%, and RPMI 1640 culture solution (100 μL) was added in the negative control group. MAIN OUTCOME MEASURES: Absorbance was measured at day 1, 2, 3, 4 and 5 using MTT colorimetric assay to calculate relative growth rate. RESULTS: There were no significant differences in absorbance between three metal groups and negative control group (P > 0.05), but there were significant differences in absorbance between three metal groups and positive control group (P < 0.05 or P < 0.01). Cell growth rate was > 100% and cytotoxicity was grade 0 in the pure titanium group; while, cell growth rate ranged from 86.36% to 99.49% and cytotoxicity was grade 1 in both self-made nickel-chromium ceramic alloy and nickel-chromium alloy groups. At day 3 after culture, cytotoxicity was grade 2 in the positive control group. CONCLUSION: Self-made nickel-chromium ceramic alloy has a little cytotoxicity and requires for the clinical application.

BACKGROUND: There have been no reports in CNKI database addressing the cellular apoptosis caused by stainless steel materials used in the dental magnetic attachment. OBJECTIVE: To observe the effects of 3 stainless steel materials used in the dental magnetic attachment, cobalt-chromium alloy, titanium alloy, and austenitic stainless steel on L-929 cell apoptosis. DESIGN, TIME AND SETTING: A comparative observation was performed at the Central Laboratory of China Medical University between June and December 2007. MATERIALS: Mouse L-929 fibroblasts in logarithmic growth phase were provided by Institute of Tumor, First Affiliated Hospital of China Medical University, China. Cobalt-chromium (Co-Cr) alloy was purchased from Heraeus-Kulzer Corporation, China. Titanium alloy was obtained from Morita Company, Japan. Austenitio stainless steel was provided by Institute of Mental Research Chinese Academy of Sciences, China. METHODS: The leaching liquor of Co-Cr alloy, titanium alloy, and austenitic stainless steel was made by culturing 3 kinds of round-slice mental materials in 24-well plate with RPMI-1640 medium at 0.1 mL/cm2 (leaching liquor volume: specimen surface area). L-929 fibroblasts were divided into 5 groups: Co-Cr alloy, titanium alloy, austenitic stainless steel, negative control, and positive control. The Co-Cr alloy, titanium alloy, and austenitic stainless steel groups were cultured with corresponding leaching liquor (250, 500, and 1 000 g/L). Cells from the negative control and positive control groups were cultured with simple RPMI 1640 medium and 100 mg/L mitomycin-treated L-929 cells. MAIN OUTCOME MEASURES: Following 24-hour culture, the effects of 3 kinds of leaching liquor (at different concentrations) on L-929 fibroblasts were examined through the use of flow cytometer. RESULTS: There was significant difference in cellular apoptosis between Co-Cr alloy, titanium alloy, and austenitic stainless steel groups at the same concentration or between different concentrations for the same dental material (P < 0.01), but no significant difference existed between titanium-alloy (250 g/L) and negative control groups (P > 0.05). CONCLUSION: Co-Cr alloy, titanium alloy, and austenitic stainless steel have apparent influence on cellular apoptosis. The apoptosis rate is the greatest in the Co-Cr alloy group, followed by austenitic stainless steel group, and lastly titanium alloy group.

OBJECTIVETo compare the shear bond strength(SBS) of cast Co-Cr alloys and selective laser melting(SLM) Co-Cr alloys with those of dental porcelain.

METHODSA dental porcelain (Vita) was applied on cast and SLM Co-Cr alloy specimens (n = 10). SBS test was conducted, and fracture mode analysis was determined. Student's t-test by SPSS 13.0 software was employed to analyze the data.

RESULTSThe SLM Co-Cr alloy specimens had lower SBS values than the cast Co-Cr alloy specimens (P > 0.05). The metal-porcelain bond strength value of the cast group was (33.11 +/- 4.98) MPa, and that of the SLM group was (30.94 +/- 5.98) MPa. The specimens in both test groups exhibited mixed failure.

CONCLUSIONThe metal-porcelain system processed by SLM exhibit a bond strength that is similar to that of the cast group. This system also display a high precision.

Alloys ; Chromium Alloys ; Dental Alloys ; Dental Porcelain ; Lasers ; Materials Testing ; Metal Ceramic Alloys ; Metals

BACKGROUND:BIOSSN4 nickel-free stainless steel is an austenitic medical stainless steel material, which has passed the standard hemolysis test, cytotoxicity assays and sensitization test of the National Institute for the Control of Pharmaceutical and Biological Products. OBJECTIVE:To evaluate theinvitro cytotoxicity and corrosion resistance of a new medical BIOSSN4 nickel-free stainless steel. METHODS:The L929 mouse fibroblasts suspension was seeded in 96-wel plates at a concentration of 1×108 /L, and were divided into five groups. BIOSSN4 nickel-free stainless steel extract, 316L stainless steel extract, gold aloy extract, lead material extract (positive control) and RPMI1640 medium (negative control) were added respectively. After 1, 2 and 3 days of culture, cel morphology was observed. The absorbance value in each group was determined using MTT assay. The relative cel proliferation rate was calculated. Toxicity grading was evaluated. In the simulated oral environment, the eletric potential of corrosion, current density of corrosion and polarization resistance of BIOSSN4 no-nickel stainless steel, 316L stainless steel and gold aloy were determined. RESULTS AND CONCLUSION:Within 3 days of culture, in lead material extract group, cels shrunk; the number of cels significantly reduced; the relative growth rate was lower than that in the other four groups (P < 0.05). In the other four groups, the cel morphology was good, and the relative growth rate was over 75%. The toxicity of BIOSSN4 nickel-free stainless steel extract, 316L stainless steel extract and gold aloy extract was grade 1. The toxicity of lead material extract was grades 2-3. These results demonstrate that BIOSSN4 nickel-free stainless steel has good biocompatibility. The corrosion resistance of BIOSSN4 nickel-free stainless steel is higher than that of the 316L stainless steel but lower than that of the gold aloys.

BACKGROUND:The residual alveolar ridge in edentulous patients with osteoporosis always presents with a poor shape,which increases the difficulty in complete denture restoration.Until now,there are no predictors for residual alveolar ridge resorption or guidelines on the frequency of denture relines.OBJECTIVE:To investigate the correlation between the frequency of complete denture relines and serum bone turnover markers,osteocalcin (OC) and cross-linked carboxy-terminal telopeptide of type Ⅰ collagen (CTX),in elderly edentulous patients with osteoporosis,in order to provide reference for complete denture repair.METHODS:According to inclusion criteria,50 elderly edentulous patients with osteoporosis who had complete dentures were recruited in the study randomly.The frequency of complete denture relines was surveyed by related questionnaire and medical record,and the serum OC and CTX levels were detected by electrochemiluminescence immunoassay.Related data were analyzed statistically via Pearson correlation analysis.RESULTS AND CONCLUSION:It showed a strong positive correlation between the frequency of complete denture relines and the serum OC level (r=0.517,P ＜ 0.01).No significant correlation between relines frequency and the serum CTX level was observed (r=0.278,P=0.051 ＞ 0.05),but it showed a similar tendency between them.These findings indicate that to detect the levels of serum bone turnover markers may be conducive to evaluating curative effect of complete dentures in elderly edentulous patients with osteoporosis as well as to making subsequent diagnostic and therapeutic strategies.