Ji-Myung Bae

Inhibition of osteoclast differentiation and bone resorption by rotenone, through down-regulation of RANKL-induced c-Fos and NFATc1 expression

Osteoclasts are responsible for bone erosion in diseases as diverse as osteoporosis, periodontitis, and rheumatoid arthritis. Natural plant-derived products have received recent attention as potential therapeutic and preventative drugs in human disease. The effect of rotenone in RANKL-induced osteoclast differentiation was examined in this study. Rotenone inhibited RANKL-mediated osteoclast differentiation in bone marrow macrophages (BMMs) in a dose-dependent manner without any evidence of cytotoxicity. The mRNA expression of c-Fos, NFATc1, TRAP, and OSCAR in RANKL-treated BMMs was inhibited by rotenone treatment. Rotenone strongly inhibited p38 and ERK phosphorylation and I-kappaB degradation in RANKL-stimulated BMMs, and did not inhibit JNK phosphorylation. Further, RANKL-induced c-Fos and NFATc1 protein expression was suppressed by rotenone. Rotenone additionally inhibited the bone resorptive activity of differentiated osteoclasts. A lipopolysaccharide (LPS)-induced bone erosion study was also performed to assess the effects of rotenone in vivo. Mice treated with rotenone demonstrated marked attenuation of bone erosion based on Micro CT and histologic analysis of femurs. These results collectively suggested that rotenone demonstrated inhibitory effects on osteoclast differentiation in vitro and suppressed inflammatory bone loss in vivo. Rotenone may therefore serve as a useful drug in the prevention of bone loss.

Microleakage and fracture patterns of teeth restored with different posts under dynamic loading

STATEMENT OF PROBLEM Many studies concerned with the microleakage of endodontically treated teeth restored with posts and cores and subjected to loading can be found in the literature. However, no studies have investigated microleakage under dynamic loading with simultaneous dye penetration, which is more relevant to clinical situations. PURPOSE The purpose of this study was to compare microleakage and to classify fracture patterns of endodontically treated teeth restored with various post systems under dynamic loading. MATERIAL AND METHODS The crown portions of 40 human mandibular incisors were sectioned at the cementoenamel junction, and the teeth were endodontically treated. Teeth were divided into 4 groups (n=10): teeth restored with a cast post and core, prefabricated metal post (ParaPost), fiber-reinforced composite resin post (FRC Postec), and ceramic post (Cosmopost). After preparing the post space, each post was cemented with dual-polymerized resin cement (DuoLink). With the exception of the cast post-and-core group, the cores were formed directly using a light-polymerized composite resin (Light-Core). An intermittent load of 98 N at 1 Hz was applied for 50,000 cycles at an angle of 135 degrees to the long axis of the restored teeth, which were immersed in a 0.5% basic fuchsin solution. The ratio of the dyed surface area to the total area of the sectioned root surface was determined using an image analysis program. The data were analyzed by a 1-way ANOVA and Duncans multiple range test (alpha =.05). The fracture patterns of the teeth were classified according to their fracture propagation lines. RESULTS The cast post group showed a significantly higher level of microleakage compared to the other groups (P=.001). Regarding the failure mode, the FRC Postec and Cosmopost groups showed fracture patterns that would favor retreatment. The number of cycles of repeated loading was not significantly different among the groups (P=.161). CONCLUSIONS Both FRC Postec and Cosmopost groups showed less microleakage under dynamic loading and fracture patterns favoring a retreatment of fractured specimens.

Microleakage of different sealing materials in access holes of internal connection implant systems

STATEMENT OF PROBLEM Current implant systems cannot completely prevent microleakage from the access holes of screw-retained implant prostheses, which may constitute risks to the clinical success of the implants. PURPOSE The purpose of this study was to evaluate the levels of microleakage through the access holes of screw-retained implant prostheses sealed with different materials. MATERIAL AND METHODS An implant with an internal hexagonal configuration was connected to a temporary abutment with an acrylic resin crown. The apical 6.5 mm of the access hole was filled with 1 of the following materials: cotton pellet, silicone sealing material, vinyl polysiloxane, or gutta-percha. The remaining coronal 3 mm was sealed with composite resin. Cyclic loading with 21 N at 1 Hz was applied 16,000 times to the specimens in 0.5% basic fuchsin solution according to the long axis of the tooth. Basic fuchsin dye which penetrated into the internal wall of the abutment through the access hole was dissolved with methyl alcohol. Then the absorbance was measured by a spectrophotometer at 540 nm to evaluate the degree of microleakage. The results were statistically analyzed with 1-way ANOVA and the Tukey HSD test. RESULTS From greatest to least, the levels of microleakage were in the following order: cotton pellet, silicone sealing material, vinyl polysiloxane, and gutta-percha. The microleakage associated with gutta-percha was not significantly different from that of vinyl polysiloxane. CONCLUSIONS When sealing the access holes of screw-retained implant prostheses, gutta-percha or vinyl polysiloxane would help reduce microleakage.

Comparison of fracture resistance and fit accuracy of customized zirconia abutments with prefabricated zirconia abutments in internal hexagonal implants.

BACKGROUND Customized zirconia abutments are increasingly applied for the fabrication of esthetic implant restorations aimed at imitating the natural situation. These abutments are individually shaped according to the anatomical needs of the respective implant site. PURPOSE This study sought to compare the fracture resistance and fit accuracy of prefabricated and customized zirconia abutments using an internal hexagonal implant system (TSV®, Zimmer, Carlsbad, CA, USA). MATERIALS AND METHODS Two zirconia abutment groups were tested: prefabricated zirconia abutments (ZirAce, Acucera, Seoul, Korea) and customized zirconia abutments milled by the Zirkonzahn milling system. Twenty zirconia abutments per group were connected to implants on an acrylic resin base with 30-Ncm torque. The fracture resistance of zirconia abutments was measured with an angle of 30° at a crosshead speed of 1 mm/min using the universal testing machine (Z020, Zwick, Ulm, Germany). Marginal and internal gaps between implants and zirconia abutments were measured after sectioning the embedded specimens using a digital microhardness tester (MXT70, Matsuzawa, Tokyo, Japan). RESULTS The customized abutments were significantly stronger (1,430.2 N) than the prefabricated abutments (1,064.1 N). The mean marginal adaptation of customized abutments revealed a microgap that was increased (11.5 µm) over that in prefabricated abutments (4.3 µm). CONCLUSION Within the limitations of this study, the customized abutments are significantly stronger than prefabricated abutments, but the fit is less accurate. The strength and fit of both abutments are within clinically acceptable limit.

Push-out bond strengths of fiber-reinforced composite posts with various resin cements according to the root level

PURPOSE The aim of this study was to determine whether the push-out bond strengths between the radicular dentin and fiber reinforced-composite (FRC) posts with various resin cements decreased or not, according to the coronal, middle or apical level of the root. MATERIALS AND METHODS FRC posts were cemented with one of five resin cement groups (RelyX Unicem: Uni, Contax with activator & LuxaCore-Dual: LuA, Contax & LuxaCore-Dual: Lu, Panavia F 2.0: PA, Super-Bond C&B: SB) into extracted human mandibular premolars. The roots were sliced into discs at the coronal, middle and apical levels. Push-out bond strength tests were performed with a universal testing machine at a crosshead speed of 0.5 mm/min, and the failure aspect was analyzed. RESULTS There were no significant differences (P>.05) in the bond strengths of the different resin cements at the coronal level, but there were significant differences in the bond strengths at the middle and apical levels (P<.05). Only the Uni and LuA cements did not show any significant decrease in their bond strengths at all the root levels (P>.05); all other groups had a significant decrease in bond strength at the middle or apical level (P<.05). The failure aspect was dominantly cohesive at the coronal level of all resin cements (P<.05), whereas it was dominantly adhesive at the apical level. CONCLUSION All resin cement groups showed decreases in bond strengths at the middle or apical level except LuA and Uni.

Biphasic osteogenic characteristics of human mesenchymal stem cells cultured on TiO 2 nanotubes of different diameters

We cultured human mesenchymal stem cells (hMSCs) on TiO2 nanotubes with diameters of 30-100nm to assess the size-effect of TiO2 nanotubes on the behavior and osteogenic functionality of hMSCs. Most studies of the expression of genes encoding alkaline phosphatase (ALP), osteocalcin (OCN), osteopontin (OPN), and integrin-β (INT-B), after 1 week of incubation, supported the results of cell viability and MTT assays at 48 hrs of plating. However, after 2 weeks of incubation, expression of ALP, OPN, INT-B, and protein kinase R-like ER kinase (PERK) genes were significantly higher in cells cultured on 70nm TiO2 nanotubes than that in cells cultured on other TiO2 nanotubes and Ti. This biphasic osteogenic characteristic of hMSCs is supposed to relating to the nature of the hMSCs adhering to the substrate at the beginning of incubation, and the nanostructural stimulation caused by the topography of TiO2 nanotubes at a later stage of incubation. The discovery of these biphasic characteristics of hMSCs cultured on different-sized TiO2 nanotubes may contribute to resolving the discrepant results relating to the size-effect of TiO2 nanotubes on the adhesion, proliferation, and functionality of cells.

Effects of glass fiber mesh with different fiber content and structures on the compressive properties of complete dentures

STATEMENT OF PROBLEM No study has yet evaluated the strength of complete dentures reinforced with glass fiber meshes with different content and structures. PURPOSE The purpose of this study was to compare the reinforcing effects of glass fiber mesh with different content and structures with that of metal mesh in complete dentures. MATERIAL AND METHODS Two types of glass fiber mesh were used: SES mesh (SES) and glass cloth (GC2, GC3, and GC4). A metal mesh was used for comparison. The complete dentures were made by placing the reinforcement 1 mm away from the tissue surface. A control group was prepared without any reinforcement (n=10). The compressive properties were measured by a universal testing machine at a crosshead speed of 5 mm/min. The results were analyzed with the Kruskal-Wallis test and the Duncan multiple range test (α=.05). RESULTS The fracture resistance of the SES group was significantly higher than that of the control, GC4, and metal groups (asymptotic P=.004), but not significantly different from the GC2 and GC3 groups. The toughness of the SES and GC3 groups was significantly higher than that of the others (asymptotic P<.001), but not significantly different from that of the GC4 group. CONCLUSIONS SES and GC3, which have different structures but similar volume content, were the most effective in reinforcing complete dentures. The content of the glass fiber mesh seemed more important than the structures.

Infrared-Mediated drug elution activity of gold nanorod-grafted TiO 2 nanotubes

The purpose of this research was to prepare gold nanorod- (GNR-) grafted TiO2 nanotubes by thiolactic acid treatment and evaluate remote-controlled drug elution and antibacterial activity by infrared (IR) light irradiation. Tetracycline used as an antibiotic was loaded into GNR-grafted TiO2 nanotubes by using 2w/v% polylactic acid solutions. A near-IR laser (830 nm) was used for remote-controlled IR light irradiation. Results of SEM, TEM, XRD, and EDX revealed that GNR chemically bonded to the whole surface of the TiO2 nanotubes. An antibiotic release test revealed that on-off drug elution was triggered effectively by the photothermal effect of GNR grafted on TiO2 nanotubes. Furthermore, an antibacterial agar zone test indicated that the annihilated zone of Streptococcus mutans in the experimental group with IR light irradiation was significantly larger than that of the corresponding group without IR light irradiation (p < 0.05). Therefore, GNR-grafted TiO2 nanotubes would be expected to extend the limited usage of TiO2, which show photocatalytic activity only within the ultraviolet (UV) to IR region, thereby allowing the development of novel fusion technologies in the field of implant materials.

Visible light irradiation-mediated drug elution activity of nitrogen-doped TiO 2 nanotubes

We have developed nitrogen-doped TiO2 nanotubes showing photocatalytic activity in the visible light region and have investigated the triggered release of antibiotics from these nanotubes in response to remote visible light irradiation. Scanning electron microscopy (SEM) observations indicated that the structure of TiO2 nanotubes was not destroyed on the conditions of 0.05 and 0.1 M diethanolamine treatment. The results of X-ray photoelectron spectroscopy (XPS) confirmed that nitrogen, in the forms of nitrite (NO2-) and nitrogen monoxide (NO), had been incorporated into the TiO2 nanotube surface. A drug-release test revealed that the antibiotic-loaded TiO2 nanotubes showed sustained and prolonged drug elution with the help of polylactic acid. Visible light irradiation tests showed that the antibiotic release from nitrogen-doped TiO2 nanotubes was significantly higher than that from pure TiO2 nanotubes (P < 0.05).

Near-infrared laser-mediated drug release and antibacterial activity of gold nanorod–sputtered titania nanotubes:

The infection control of implants is one of the hot issues in the field of medicine and dentistry. In this study, we prepared gold nanorod–sputtered titania nanotubes on titanium surface, which is the main component of implant material, and aimed to estimate the remote-controlled tetracycline release and resulting antibacterial effects of gold nanorod–sputtered titania nanotubes using near-infrared laser irradiation. Gold nanorods prepared by ion plasma sputtering (aspect ratio = 1:3) showed optical properties like those of chemically synthesized gold nanorods, exhibiting photothermal effects in the near-infrared region, as demonstrated using field-emission scanning electron microscopy, transmission electron microscopy, and diffuse ultraviolet–visible–near-infrared spectrophotometry. In addition, a 2 wt% tetracycline/polycaprolactone mixture was found to be the most suitable experimental group to demonstrate the biological compatibilities and antibacterial activities. The results of antibacterial agar diffusion tests and near-infrared-mediated tetracycline release tests in vivo confirmed that remote-controlled tetracycline elution using near-infrared laser irradiation was highly effective. Therefore, gold nanorod–sputtered titania nanotubes would be expected to enable the continued use of the photothermal therapy of gold nanorods and extend the limited use of titania showing photocatalytic activity only within the ultraviolet-to-near-infrared region.