[Influence of surface modification of titanium on OPG/RANKL mRNA expression in MG-63 human osteoblast-like cells].

OBJECTIVE: To investigate the influence of surface modification of titanium on OPG/RANKL mRNA expression in human osteoblast-like cells. METHODS: MG-63 osteoblast-like cells were seeded on the titanium plates with surface polishing and with surface modification by sandblasting plus acid-base treatment, with the cells on glass slides as the control. On days 2, 4, 6, and 8 following cell seeding, the cells were harvested for examination of OPG/RANKL mRNA expression using RT-PCR and real-time PCR. RESULTS: The expression of OPG/RANKL mRNA was sensitive to the surface microphotography. Compared with the other groups, the cells on the titanium plates with sandblasting plus acid-base treatment, which resulted in a porous micro-structure and high roughness, showed significantly up-regulated expression of OPG mRNA. OPG mRNA expression also showed a time-dependent up-regulation, and was the highest on day 8. The expression of the RANKL mRNA in cells on both of the titanium plates was higher than that in the control cells. The peak level of RANKL mRNA expression occurred on day 6 followed by a gradual decrease. CONCLUSION: A rough and porous surface of the culture plates and prolonged culture time can synergistically up-regulate the ratio of OPG/RANKL mRNA.

[Influence of zirconia content on translucency of zirconia-toughened alumina glass-infiltrated ceramic].

OBJECTIVE: The objective of this study is to investigate the influence of zirconia content which is 0-30.0% weight percentage of matrix on translucency of zirconia-toughened alumina glass-infiltrated ceramics. METHODS: Seven groups were divided according to different weight percentage of zirconia (0, 2.5%, 5.0%, 7.5%, 10.0%, 20.0% and 30.0%). After sintering, infiltrating and polishing, spectral transmittance was determined with spectrophotometer under D65 standard source. Contrast ratio was also tested by whiteness colorimeter. RESULTS: With mass fraction of zirconia increasing from 0 to 30.0%, spectral transmittance reduced from 0.406% to 0.058%, while contrast ratio value increased from 0.849 +/- 0.005 to 1.015 +/- 0.006. When zirconia content was 10.0%, contrast ratio was 0.990 +/- 0.008. When it was more than 10.0%, transmission rate of the downward trend and contrast ratio of the rising trend became flat. CONCLUSION: Zirconia content has a direct impact on translucency of zirconia-toughened alumina glass-infiltrated ceramic, which is essentially opaque when zirconia content is 10.0%. When mass fraction of zirconia is more than 10.0%, the influence of zirconia content is reduced.

[Observation on osteoblasts responded to fluid induced shear cultured on different surfaces with scanning electron microscope].

OBJECTIVE: To investigate morphological change of osteoblasts cultured on titanium plates with different microarchitecture structure when exposured to fluid shear stress. METHODS: 14 dynes x cm(-2) fluid shear stress was applied on osteoblasts cultured on 3 different commercially pure titanium plates: Polished treatment (PT), sandblast (SB), sandblasting and acid-base (SB-AB) surfaces. Scanning electron microscope (SEM) was adopted to observe the morphological changes after 0.5, 4, 7.5 h time point respectively. RESULTS: Morphologically, no significant changes were observed after 0.5 h and few osteoblasts were seen after 7.5 h on all 3 type of different surfaces, and significant changes could only be observed after 4 h. Osteoblasts were elongated and rearranged along the flow way on different levels on PT surface. Shape of cells was altered, from long fusiform suspending over depressed areas into polygon stretching out many synapsises tightly attached to pits on SB-AB surface. Osteoblasts on SB surface displayed similar change as SB-AB surface, besides, some cells were elongated along the way of flow, stretching out threadlike synapsises attached to edges of pits. CONCLUSION: Morphological change of osteoblast responding to fluid shear stress in physiological range depends on substrate microarchitecture and varies with the time of fluid shear stress application.

[Characterization and antibacterial effect of Ag-nHA-nTiO2/polyamide 66 nanocomposite membrane on oral bacteria].

OBJECTIVE: Undried silver-hydroxyapatite-titania (Ag-nHA-nTiO2) nanoparticles slurry was used to make membrane with polyamide 66 (PA66) by co-polymerization method. The purpose of this study is to test the physical and chemical characteristics and antibacterial ability. METHODS: The morphology, chemical components and structures of the membrane were characterized by atomic absorption spectrometer (AAS), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDX). Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Porphyromonas gingivalis (P. gingivalis), Fusobacterium nucleatum (F. nucleatum) and Streptococcus mutans (S. mutans) were utilized to test the antibacterial effect. RESULTS: XRD results demonstrated that the membrane have characteristic diffraction peaks of pure hydroxyapatite (HA). A homogeneous distribution of the Ca, P, Ti and Ag element in the membrane was confirmed by EDX. Both surface and section showed porous structure which was confirmed by SEM and the average hole size was 20-30 microm. The bacteria assay reflected to the antibacterial effect, 50.10% of S. aureus and 56.31% of E. coli were killed. However, 91.84% of P. gingivalis, 90.64% of F. nucleatum and 90.49% of S. mutans were killed and pictures of SEM showed obviously fewer cells on the surface. CONCLUSION: The nanocomposite membrane could be one of the bioactive materials with antibacterial properties for oral guided bone regeneration technique.

[Investigation of the function of the glass colorant on the machinable infiltrated ceramics color].

OBJECTIVE: To investigae the function of the glass colorant on the color of the machinable infiltrated ceramics(MIC). METHODS: Five kinds of glass with different colorant were infiltrated through the aluminous matrix by heating the components to 1 100 degrees C for 2 hours. The specimens surface was polished, and their thickness was 0.5 mm. RESULTS: The refractive index of the MIC infiltration glass was 1.59691 (587.6 nm, nd) . The most different parameter of the MIC color were L*, then a*, and b* had little difference . The parameters of the color space of MIC were: L*(64.55-71.46), a*(3.35-7.38), b*(10.00-12.41), Ca*b*(11.38-13.95), ha*b*(54.07-73.00). These were almost close to the color parameters of Vita In-ceram. CONCLUSION: This experiment proved that the glass colorant was changed the MIC color parameters, and the main function was on L*, then a*. The ceramic color was up to the requirement of clinic.

[Experimental study of periosteal osteoblasts adhesion to artificial bone scaffolds based on rapid prototype].

OBJECTIVE: To study the biocompatibility of bone engineering scaffolds designed and fabricated by CAD and Rapid Prototyping techniques. METHODS: Infant rat calvarias osteoblasts were isolated and expanded in vitro and the cells (2nd passage) were seeded onto scaffolds with porosity 80%, 90%, 95% at a density of 2.06 x 10(9)/L. Cell adhesion number and morphology were measured with SEM after 4 days, 10 days co-culture. RESULTS: (1) The osteoblasts' adhesion amounts increased with culture time in three porosity group (P < 0.05), but the increase were different among three groups, 80% group was 0.35 x 10(5), 90% group was 2.84 x 10(5); (2) Through SEM observations, it showed that osteoblasts adhered to all scaffolds well. CONCLUSION: The scaffolds designed and fabricated by CAD and rapid prototyping own a good cellular biocompatibility. The results suggest the feasibility of using such scaffold fabricating method for bone tissue engineering research and clinical therapy.