The purpose of this study was to evaluate effects of fabrication of thermoplastic appliance on the dimensional stability of 3D printed dental models. A digital reference model was printed by different printing materials and densities [acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA); 20, 40 and 60%]. Thermoplastic appliances were then fabricated with printed models for three times and models were scanned at three different stated; following the print out, following the fabrication for one time and three times. Tooth and arch measurements were performed to evaluate the accuracy and dimensional stability of printed models after fabrication of thermoplastic appliances. Printed models were not significantly different from the digital reference model regardless of different materials and densities. After the first fabrication of the appliance, most of measurements were decreased in PLA models ranged from 0.05 to 0.24 mm (p<0.05), whereas only a few measurements were decreased in ABS models (p<0.05). After fabrication for three times, measurements were more decreased in PLA models ranged from 0.04 to 0.42 mm (p<0.05) and some measurements were decreased in ABS models ranged from 0.08 to 0.27 mm (p<0.05). ABS models showed relatively good dimensional stability, but the PLA models showed significant dimensional changes even after initial fabrication of the appliance. Repeated fabrication of the appliances increased dimensional changes in printed models, especially printed with PLA.

The purpose of this study was to fabricate platinum (Pt), one of the plasmonic nanoparticles that induces localized surface plasmon resonance (LSPR) effects caused by the pairing of plasmon with the electric field of visible-near infrared light, coated 100 nm titania (Pt-TiO2) nanotubes to evaluate the surface properties and laser mediated antibacterial effects. From the analysis of UV-VIS-NIR spectrum, the light absorptions of Pt-TiO2 nanotubes were detected at wavelengths 399–429 nm, 527–579 nm, and 806–906 nm, respectively, and one of the detected wavelengths was suitable for the laser used in this study (OCLA, Wavelength: 405). From the observation of FE-SEM, as the platinum coating time increased, the inner diameter of the Pt-TiO2 nanotubes decreased from 68.8 nm to 48.8 nm, and the shape of the platinum nanoparticles coated on the top layer of the titania nanotubes changed from spherical to rod. From the results of contact angle measurement, the contact angle of water increased from 11.94°to 19.84°as the platinum coating time increased from 1 minute to 3 minutes. The Staphylococcus aureus antibacterial test resulted that 98% or more bacterial reduction of all Pt-TiO2 nanotube groups were observed after laser irradiation (P<0.05). Live-dead assay and MTT assay indicated that laser irradiation did not affect cell death. Therefore, Pt–TiO2 nanotube exhibiting a local surface plasmon resonance effect is expected to have many potentials for semi-permanent antimicrobial implant surface treatment without antibacterial drugs.

In this study, clinically applicable methods of improving the bond strength between Y-TZP and the bracket were considered, which the method was confirmed for the durability in a humid oral environment. The bond strength of Y-TZP bonding surface and the surface characteristics were analyzed following the surface treatment of Y-TZP specimens with conditioning by 30 μm tribochemical silica coating, or tribochemical silica coating with one of the following primers: silane, MDP, or an MDP-containing silane primer. It was found that after surface treatment, the surface roughness of all groups increased (p<0.05), and Si was uniformly distributed on the Y-TZP surface after silica coating. The bond strength value of the group treated with silane primer and tribochemical coating was not significantly different after thermocycling (p>0.05). The group treated with MDP primer and tribochemical silica coating showed a significant difference in bond strength values after thermocycling (p<0.05), and it showed the lowest bond strength values except the untreated groups (p<0.05). The group treated with tribochemical silica coating and MDP-containing silane primer showed the highest bond strength values (p<0.05), and was not significantly different after thermocycling (p>0.05). Therefore, the surface treatments of Y-TZP with MDP-containing silane primer after 30 μm tribochemical silica coating enhanced the bond strength to the orthodontic metal bracket; such a clinically applicable method may advance studies on the surface treatment of Y-TZP.

The objective of this work was to verify the antimicrobial effect and the characteristics of the tissue conditioner containing silver-chitosan nanocomplex at in vitro level. Nanocomplex was synthesized by the chemical reduction of silver nitrate and chitosan in aqueous solution with sodium borohydride as a reducing agent. Silver-chitosan nanocomplex was incorporated to tissue conditioner as powder to powder ratio with different weight percentage (%) of 0 (control), 1.0, 3.0, 5.0 and 7.0. The antimicrobial effect was assessed by colony forming unit in retrieved two streptococcal suspensions inoculated on specimens and cytotoxicity was measured using human gingival fibroblasts by MTS assay. Surface topography, Ag ion release and ultimate tensile strength tests were conducted for mechanical validity. The significantly reduced bacterial adhesions were observed above 5.0% loading while all of tested samples did not show cytotoxicity when compared to the control. Ag ion releases were detected with the dose-dependent of initial silver loadings with gradual decreasing over time. Modified tissue conditioner revealed similar microscopic surface textures and expressed no significant tensile strength changes (P>0.01) as compared to unmodified. Within some limitations in present study, the tissue conditioner loaded by 5.0% of silver-chitosan nanocomplex can be candidate as a novel denture biomaterial without mechanical hazards. For a clinical specification, future studies including in vivo, multi-strain or factor assays, and additional physical tests were still required.

This study aimed to assess the sustainability of antibacterial agents mixed with experimental fluoride varnish (EFV) against S. mutans. Five antibacterial agents [Xanthorrhizol (XAN), Bakuchiol (BAK), Bavachalcone (BCC), Isobavachromene (IBC), and Bavachromene (BCM)] were used and incorporated into the EFV to make the final concentration of 10 mM. Then, 5 μL of antibacterial agents mixed with EFV were applied on polyethylene terephthalate film disc (5 mm diameter). The positive and vehicle control were ampicillin and DMSO mixed with EFV, respectively. Each group was stored in distilled water in a 37℃ shaking water bath at 80 rpm for 0 hour, 4 hours, 1 day, 2 days, 3 days, 5 days, 10 days, 20 days and 30 days. The sustainability of the antibacterial activities was evaluated with the inhibition zone by the agar diffusion test. The antibacterial activities of all antibacterial agents were sustained for 30 days. Among them, BCC showed relatively higher antibacterial activities up to 30 days compared to other groups. This study suggests that antibacterial agents including BCC can be used with fluoride varnish to have sustained antibacterial activities.

This study aimed to evaluate the antibacterial activities sustainability of antibacterial agents mixed with experimental fluoride varnish on hydroxyapatite disc against Streptococcus mutans (S. mutans). On the hydroxyapatite disc with 4.8 mm of diameter, 5 μL of 1 mM antibacterial agents mixed with experimental fluoride varnish were applied. Positive control and vehicle control were 10 μg/mL ampicillin and dimethyl sulfoxide (DMSO) mixed with fluoride varnish, respectively. The discs were stored in distilled water in a 37℃ shaking water bath at 120 rpm for 30 minutes, 4 hours, 1 day, 5 days, 20 days, and 30 days. Antibacterial activities were evaluated with the inhibition zone by the agar diffusion test. The antibacterial activities of all antibacterial agents were sustained for 30 days. Among them, Bakuchiol, Bavachromene, and Bavachalcone showed higher antibacterial activities for up to 30 days. The antibacterial agents when mixed in the experimental fluoride varnish with increased and prolonged antibacterial activities can be applied to prevent dental caries effectively.

We evaluated the antibacterial, anti-inflammatory, and inhibitory effect of osteoclast differentiation of Brachypodium sylvaticum (BS) to find out the possibility of preventing periodontal disease. The inhibition of Porphyromonas gingivalis (P. gingivalis) growth by BS and the sustainability of the antibacterial activity was assessed. The production of pro-inflammatory cytokines from lipopolysaccharide (LPS)-induced RAW 264.7 cells were measured using enzyme-linked immunosorbent assays (ELISA), and the production of nitric oxide (NO) and cell viability were measured. Osteoclast differentiation was evaluated by Tartrate-resistant acid phosphatase (TRAP) staining, and TRAP activity. BS showed significant antibacterial activity and sustainable antibacterial activity in P. gingivalis. We also found out that the BS significantly decreased secretion of pro-inflammatory cytokines [tumor necrosis factor (TNF-α) and interleukin-6 (IL-6)] and NO production without cytotoxicity. Furthermore, BS inhibited the differentiation of bone marrow macrophages (BMMs) obtained from mouse bone marrow cells into osteoclasts without cytotoxicity. Taken together, BS can be a promising candidate for a preventive and improving agent of periodontal disease having antibacterial, anti-inflammatory, and inhibitory effects of osteoclast differentiation.

The purpose of this study was to examine the effect of hardness and optical properties of dental zirconia in accordance to sintering condition and aging. 10.0 mm×10.0 mm×1.5 mm zirconia specimens were prepared using Luxen Enamel E2.According to aging, zirconia specimens were sintered under fifteen different conditions. Specimens were divided into six subgroup and sintered with various durations (4 h, 5 h, 6 h, 7 h, and 12 h) at the various maximum temperature (1,500℃, 1,530℃, and 1,560℃). The hardness was measured four times per specimen using a Micro Vickers hardness tester, CIE L * , a * , b * values of each specimen were measured using a spectrophotometer and the TP values were calculated for translucency comparison.In the specimen with aging, there was a difference in hardness according to the sintering temperature, but there was no difference in hardness according to the sintering time. In the specimen with aging, as sintering temperature increased, CIE L * , a * , b * values decreased, resulting in a decrease in brightness and tendency of green and blue trends. In the specimen with aging, there was no change in L * value with decreasing sintering time and as sintering time decreased, CIE a * , b * values decreased, resulting in tendency of green and blue. In the specimen with aging, even if the sintering time decreases from 12 hours to 5 hours, there was no reduce in TP values.

The purpose of this study was to evaluate the effect of the reaction between investment material and zirconia on the strength of zirconia in the application of heat-pressing method. Sixty specimens were cut (24 mm×4 mm×0.5 mm) into plates from Zirtooth ™ Multi O-9814 block (∅98×14T, HASS, Gangwondo, Korea) and sintered at 1450℃. Specimens were divided into 6 subgroups according to the depending on the investement material; (a) UN group (Control), (b) PH group (Prime vest HS), (c) CP group (Calibra-press), (d) BV group (BC-Vest), (e) MH group (Microstar-HS), (f) F1 group (Formula 1). Five investment materials were buried according to the procedure recommended by the manufacturer and left at room temperature for 30 minutes. The investment mold was dried and maintained at an elevated temperature of 850℃ for 50 minutes. Then, Amber Lisi-POZ LT (HASS) was placed in a thermoformed electric furnace (Programat EP3000/G2, Ivoclar Vivadent, Schaan, Liechtenstein) together with the mold, heated to 915℃ at an elevation temperature of 45℃/min, and moored for 15 minutes. The specimens were loaded to fracture in a universal testing machine and the fracture surface was examined by a field-emission scanning electron microscopy (FE-SEM). The surface of the zirconia specimen with the investment material was analyzed by energy dispersive X-ray spectroscopy (EDS). The 3-point flexural strength test showed the highest value (1265.5 MPa) in the UN group and the lowest value (756.1 MPa) in the F1 group. As a result of EDS analysis, the largest amount of Si was detected in the F1 group, and the most interfacial changes occurred as a result of FE-SEM analysis. It was concluded that when the zirconia is buried with the investment material and the heat press molding is performed, the state of the interface is changed due to the investment material at the bonding interface while the strength is lowered.

The purpose of this study was to evaluate the sustainability of antibacterial effect against Streptococcus mutans of experimental fluoride varnish mixed with 2-hydroxyethyl methacrylate (HEMA) and/or glutaraldehyde. Experimental fluoride varnish (EX1) was fabricated. To make fluoride varnish with adhesive materials, EX1 was mixed with 5 wt% of glutaraldehyde (EX2), 35 wt% of HEMA (EX3) or both 5 wt% of glutaraldehyde and 35 wt% of HEMA (EX4). 5 μL of each experimental group was applied to 6 mm diameter polyethylene terephthalate film discs. Disks were stored in distilled water in a shaking incubator at 37℃ for 1 hour, 3 hours, 8 hours, 12 hours, 24 hours, 5 days and 10 days. The antibacterial activities against S. mutans were evaluated by agar diffusion test with the discs at each time. The antibacterial activities were sustained up to 10 days in all groups. The antibacterial activities of EX3 and EX4 were significantly higher than other groups from 8 hours to 10 days and there were no significant differences from EX2 at 10 days. HEMA with and without glutaraldehyde can be applied to fluoride varnish to increase the sustainability of antibacterial activities.