Effects of the surface characteristics of nanoporous titanium oxide films on Ti-24Nb-4Zr-8Sn alloy on the initial adhesion of osteoblast-like MG-63 cells.

The aim of the present study was to investigate the effects of the surface characteristics of nanoporous titanium oxide films, formed by anodization on Ti-24Nb-4Zr-8Sn (Ti2448) alloy, on the early adhesion of osteoblast-like MG-63 cells. Nanoporous titanium oxide films with two different pore sizes (30 and 90 nm) were formed by anodization in NH4F solution on Ti2448 alloy. The surface roughness of the nanoporous titanium oxide films was determined using a Surftest Formtracer and field emission scanning electron microscopy (FESEM). Cell viability was evaluated at different time points using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. To investigate the regulatory mechanisms involved in the focal adhesion of osteoblasts to Ti2448 alloy, we quantified the expression levels of integrin ß1 and paxillin mRNAs on the nanoporous titanium oxide films during early osteoblast adhesion using real-time RT-PCR. Samples with a 30-nm nanoporous film exhibited a greater number of overlapping microporous structures with microprojections compared with the 90-nm nanoporous film samples. The MTT assay indicated that cell viability on the 30-nm nanoporous surface following 24 and 48 h of cell culture was higher than those observed on the unanodized control and 90-nm nanoporous surfaces. Integrin ß1 mRNA expression levels on the 30-nm nanoporous surface following cell culture for 48 h were also significantly higher compared with those on the unanodized control and 90-nm nanoporous surfaces. The results demonstrated that a 30-nm nanoporous titanium oxide film on Ti2448 alloy may provide the optimum bioactive implant surface for the initial adhesion of osteoblasts.

Changes of caspase-1 after the application of orthodontic forces in the periodontal tissues of rats.

OBJECTIVE: To investigate the changes of caspase-1 in orthodontic tooth movement and to determine whether the changes are phase-specific. MATERIALS AND METHODS: Eighty Wistar rats were included in this study. Sentalloy closed-coil springs were placed to induce a mesial traction force on the lower right first molar. The animals were killed after 1, 3, 7, and 14 days (n = 20 at each time point). The mandibles of 10 rats were sampled for histomorphometric analysis and immunohistochemical assay, and the periodontal tissues of 10 other rats were sampled for detecting caspase-1 mRNA and protein by real-time RT-PCR and by Western blotting, respectively. RESULTS: The inflammatory reaction was evident in paraffin sections with hematoxylin-eosin staining. The immunohistochemical assay showed that orthodontic forces significantly increased the number of caspase-1-positive cells in the periodontal ligament (PDL). Mechanical force triggered an increase of caspase-1 mRNA in periodontal tissues. The expression of caspase-1 mRNA increased from day 1, reached the peak on day 3, and then decreased. The results of Western blotting indicated that the levels of both procaspase-1 and P20 subunit significantly increased after the application of orthodontic forces, compared with those in controls (P < .05). CONCLUSION: Caspase-1 level increases during orthodontic tooth movement and changes with different phases, which might play a significant role in orthodontic tooth movement.

[Single cell gel electrophoresis of a magnesium alloy coated with beta-tricalcium phosphate].

OBJECTIVE: To evaluate the genotoxicity of a magnesium alloy coated with beta-tricalcium phosphate (beta-TCP). METHODS: Four groups were designed. In the first group, AZ31B magnesium alloy surface was coated with beta-TCP using chemical bath deposition, and in the second group magnesium alloy was tested. The other two groups were negative control (pure titanium) and positive control groups (0.5 mg/L bleomycin). Single cell gel electrophoresis was adopted to investigate genotoxicity of the alloy samples in different groups, and 60 cells from each group were analysed. Tail moment and tail DNA percentage were used as reliable indicators to show DNA damage in lymphocytes induced by every testing sample. Student-Newman-Keuls (SNK) test was used to compare results from 4 groups. RESULTS: There were no significant differences in tail moment and tail DNA percentage between magnesium alloy group [(0.52 +/- 0.12), (6.82 +/- 1.81)%] and magnesium alloy coated with beta-TCP group [(0.51 +/- 0.12), (6.89 +/- 1.93)%, P > 0.05]. Tail moment and tail DNA percentage in negative group were (0.47 +/- 0.14) and (6.29 +/- 1.64)%, and tail moment and tail DNA percentage in positive group were (5.17 +/- 1.23) and (22.09 +/- 4.51)%. CONCLUSIONS: No significant increase was found in DNA damage in lymphocytes induced by magnesium alloy coated with beta-TCP.

[Weibull analysis and flexural strength of glass-infiltrated alumina composite machined by CAD/CAM].

PURPOSE: To explore the structural reliability of machined infiltrated ceramic made from ultrafine alumina powder for dental CAD/CAM by means of flexural strength together with Weibull analysis. METHODS: Ultrafine grain-sized alumina powder made from ammonium aluminum sulfate was sintered into one kind of porous machined ceramic block. After being infiltrated by lanthanum glass powder, a glass infiltrated alumina composite was produced. Thirty bar specimens were prepared. The flexural strength was measured with the three-point bending test. The fracture stress values were analyzed by Weibull analysis to determine the Weibull modulus values(m). The strength values at failure probabilities of 1% and 5% failure were also calculated. X ray diffraction analysis (XRD) and scanning electron microscopy (SEM) analysis were conducted. RESULTS: The mean flexural strength and standard deviation were (375.5+/-66.88) MPa coupled with Weibull modulus of 6.2. Strength values at failure probability of 1% and 5% were 191.79 MPa and 249.83 MPa, respectively. The micrograph under SEM indicated the prefabricated sintered alumina block retained a structure of continuous three-dimensional open pores, whereas the composite characterized itself as a pore-free structure after glass infiltration. XRD indicated the major crystal phase was alpha-alumina. CONCLUSIONS: The average fracture strength can not be used reliably as a design parameter for brittle all-ceramic crown materials. Compared with the average fracture strength alone, the use of flexure strength test combined with the Weibull analysis as a method of predicting survival rates from the strength data could be favorable in identifying the failure mechanisms involved in ceramic crown fracture, which would result in an improved validation of the strength data.