The purpose of this study was to evaluate the effectiveness of silane on the surface treatment of silica-based ceramic when silane is incorporated into the universal adhesive versus using silane separately from the adhesive. The materials used in this study are as follows: 1) All-Bond Universal, 2) Silane mixed with All-Bond Universal, 3) Porcelain primer (as a regular silane primer), and 4) Scoth Bond Universal (which is a commercial silane-containing universal adhesive). IPS e-Max press, a lithium disilicate, was used as the silica-based ceramic. Contact angle test was measured to evaluate hydrophobicity on a silica-based ceramic surface. Shear bond strength was tested by universal testing machine. The surfaces of the specimen were polished in order to eliminate any bias from micro mechanical retention due to an uneven surface. The results indicated that only silane applied to the silica based ceramic surface resulted in highest contact angle and shear bond strength. Using silane separately and using silane incorporated into the universal adhesive (contains hydrophobic resin) resulted in different performance on silica-based ceramic. Therefore, it was concluded that the silane should be used separately from a hydrophobic resin monomer in order to maximize its porcelain surface treatment function.

This study investigated the physical properties of dental universal adhesive according to the varying proportions of 10-MDP, a functional monomer that is a representative component of universal adhesives. Experimental dental universal adhesives were made with 5 different proportions of 10-MDP (from 8.906 wt% to 10.500 wt%). Shear bond strength between bovine teeth and composite resin blocks were measured by applying each experimental adhesive between them. Following the shear bond strength test, fractured surfaces were observed for measurement of the fracture modes. Finally, the pH of the liquid experimental adhesives were measured, to understand results from shear bond strength. As the results, bonding strength of the experimental dental universal adhesive increased gradually with increasing amounts of 10-MDP, but showed a tendency to decrease gradually after a certain amount was exceeded. The highest adhesive strength was observed when 9.710 wt% of 10-MDP was added. In terms of pH, results showed that as the amount of 10-MDP in the experimental dental universal adhesive increased, the pH decreased from pH 2.9 to pH 2.76.Based on the results of this study, it was evident that the proportions of 10-MDP resulted in changes in adhesive strength and pH, though the optimal amount of 10-MDP would need a further investigations in the future.

This study investigated reduction of the bandgap of silica by applying nano-silver doping technique and possible application of such silica as a filler in dental resin. Due to reduce band gap, newly fabricated nano-silver doped silica was able to release ROS in accordance with exposure of visible light. Nano-silver doped silica was composed of below 20 nm size crystal silver nanoparticle and 100~500 nm size amorphous silica. These two components were chemically attached to each other (Si-O-Ag). The reduced bandgap was 2.10 eV, which the value could be interpreted as occurrence of surface plasmon resonance generating ROS in visible light exposure conditions. When such nano-silver doped silica was used as a filler in dental resin, increased antibacterial property of nano-silver ion was observed which was related to releasing of ROS when exposed in visible light. The antibacterial properties were statistically significant following exposure to visible light when 0.7 to 1.5 wt% of nano-silver doped silica were incorporated into resin. When the contents of nano-silver doped silica were below 0.7 wt%, minimal ROS release resulted in no significant increase in antibacterial properties as there would be less exposed nano-silver doped silica on the resin surface by visible light. Meanwhile, more than 1.5 wt% of nano-silver doped silica also resulted no significant increase in antibacterial properties following exposure to visible light as the antibacterial effects from nano-silver ion itself were greater than effects from released ROS. Hence, it was concluded that dental resin containing 0.7 to 1.5 wt% of nano-silver doped silica would provide antibacterial properties when exposed to visible light, significantly greater than in dark conditions.

Purpose: Measuring viability of a three-dimensional in vitro organotypic human oral tissue model has been suggested as an alternative test method to the oral mucosa irritation test of oral care products. The aim of this study was to investigate the production of two different cytokines using organotypic human oral tissue model following exposure to chemicals that are commonly used in oral care products. Materials and Methods: The organotypic human oral tissues were exposed to ethanol, sodium lauryl sulphate or hydrogen peroxide for 90 minutes. Following exposure, interleukin (IL)-1α and IL-8 productions were assessed and correlated with cell viability testing as well as histology of the organotypic human oral tissues.Result: High levels of IL-8 were released from organotypic human oral tissues in all of the test and control groups without any significant differences between them. In contrast, differences were found in IL-1α release between the test and control groups. Additionally, the trend of IL-1α release corresponded to the phenotypes observed in histological analysis while different trend existed between IL-1α release and cell viability. Conclusion The study concluded the non-specific release of IL-8 for the assessment of oral care product chemicals’ toxicity, while potential of measuring IL-1α cytokine level as the possible alternative test method.

The study aims to analyze the compressive strength, pH, and surface properties of mineral trioxide aggregates (MTA), which can be used as a pulp capping and root canal filling material. The tests were performed after immersing premixed types of MTA for seven days into three different solutions: simulated body fluid (SBF), saline, and distilled water (DW). A universal testing machine was used to measure the compressive strength after one and seven days of immersion. The un-immersed MTA was used as the control. To investigate the pH variation, MTA specimens were immersed in each solution and the pH was measured using a pH meter after 3, 6, 12, 24, 72, and 168 h. Changes on the MTA surface were also observed by SEM-EDS after seven days of immersion. Moreover, statistical analysis was performed by one-way ANOVA, Tukey's post-hoc test, and independent sample t-test. All experimental groups showed significantly higher compressive strengths compared to the control group (p<0.05). In addition, as the immersion time increased, the compressive strength gradually and significantly increased among all the groups. On the other hand, the difference was insignificant among solutions with the same immersion time (p>0.05). As the immersion time increased, the pH increased among all the groups, and the pH of samples immersed in saline and DW was significantly higher than that in SBF. The MTA surface immersed in each solution for seven days showed precipitates which mainly composed of Ca and Zr ions. Therefore, the type of contact solution does not significantly affect the compressive strength of MTA, but it significantly influences both the pH and surface condition

Conventional dental resins for crown and bridge fulfill ISO 10477 and ISO 10993 before clinical application. Although 3D printing or rapid prototyping (RP) for the fabrication of temporary crown and bridge have been proposed, a little studies were reported for 3D printing resin for temporary crown and bridge. The purpose of this study was to evaluate the physical properties (such as water sorption and solubility, color stability and flexural strength) of the various 3D printing temporary crown and bridge resin following the ISO 10477:2018 and estimate the effect of chemical composition of resin on the physical properties. Four resins approved by KFDA and 4 experimental resins developed by different manufacturer were tested in this study. Samples were prepared with DLP typed 3D Printer (G-Printer) and post-cured using UV-light Cure Unit (Cure M). Proper 3D printing and post-curing conditions were selected for different 3D printing resins. Each test was performed according to the ISO 10477 and results were statistically analyzed using Tukey-multiple comparison test (p=0.05). Only group-B did not satisfied the ISO requirement (< 40 µg/ mm³) in water sorption test, but 3 groups (C, E and F) showed high solubility which exceeds the ISO requirement (< 7.5 µg/mm³). For color stability, the color difference were detected at 5 groups (A, E, F, G and H). Group-D and F showed the low flexural strength and some building direction did not satisfied the ISO requirement (> 60 MPa). Resin components may affect the flexural strength, then user should check the components of 3D printing resin. Deficient degree of polymerization may lead to large water sorption, water solubility and color changes. Further study should be done comparison between specimens printed with specific 3D printer recommended by manufacturer and specimens used in this study.
Crowns ; Polymerization ; Polymers ; Printing, Three-Dimensional ; Resins, Synthetic ; Solubility ; Water

OBJECTIVE: The aim of this systematic multiscale analysis was to evaluate the effects of thermoforming on the physical and mechanical properties of thermoplastic materials used to fabricate transparent orthodontic aligners (TOAs). METHODS: Specimens were fabricated using four types of thermoplastic materials with different thicknesses under a thermal vacuum. Transparency, water absorption and solubility, surface hardness, and the results of three-point bending and tensile tests were evaluated before and after thermoforming. Data were analyzed using one-way analysis of variance and Student's t-test. RESULTS: After thermoforming, the transparency of Duran and Essix A+ decreased, while the water absorption ability of all materials; the water solubility of Duran, Essix A+, and Essix ACE; and the surface hardness of Duran and Essix A+ increased. The flexure modulus for the 0.5-mm-thick Duran, Essix A+, and eCligner specimens increased, whereas that for the 0.75-/1.0-mm-thick Duran and eClginer specimens decreased. In addition, the elastic modulus increased for the 0.5-mm-thick Essix A+ specimens and decreased for the 0.75-mm-thick Duran and Essix ACE and the 1.0-mm-thick Essix ACE specimens. CONCLUSIONS: Our findings suggest that the physical and mechanical properties of thermoplastic materials used for the fabrication of TOAs should be evaluated after thermoforming in order to characterize their properties for clinical application.
Elastic Modulus ; Hardness ; Solubility ; Vacuum ; Water

OBJECTIVE: This study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on time-dependent viscoelastic properties. METHODS: Orthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated. RESULTS: The degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length. CONCLUSIONS: Although prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.
Elastomers* ; Relaxation* ; Tooth Movement

OBJECTIVE: The aim of this study was to compare recycled and unused orthodontic miniscrews to determine the feasibility of reuse. The comparisons included both miniscrews with machined surfaces (MS), and those with etched surfaces (ES). METHODS: Retrieved MS and ES were further divided into three subgroups according to the assigned recycling procedure: group A, air-water spray; group B, mechanical cleaning; and group C, mechanical and chemical cleaning. Unused screws were used as controls. Scanning electron microscopy, energy-dispersive X-ray spectrometry, insertion time and maximum insertion torque measurements in artificial bone, and biological responses in the form of periotest values (PTV), bone–implant contact ratio (BIC), and bone volume ratio (BV) were assessed. RESULTS: Morphological changes after recycling mainly occurred at the screw tip, and the cortical bone penetration success rate of recycled screws was lower than that of unused screws. Retrieved ES needed more thorough cleaning than retrieved MS to produce a surface composition similar to that of unused screws. There were no significant differences in PTV or BIC between recycled and unused screws, while the BV of the former was significantly lower than that of the latter (p < 0.05). CONCLUSIONS: These results indicate that reuse of recycled orthodontic miniscrews may not be feasible from the biomechanical aspect.
Microscopy, Electron, Scanning ; Recycling* ; Spectrum Analysis ; Torque

OBJECTIVE: The purpose of this study was to examine the effect of commercially available fluoride-containing oral rinses on the corrosion behavior of titanium alloys, which are the main components of orthodontic miniscrews. METHODS: Four commercially available oral rinses (solution A, pH 4.46/260 ppm fluoride; solution B, pH 4.41/178 ppm fluoride; solution C, pH 6.30/117 ppm fluoride; and solution D, pH 4.17/3.92 ppm fluoride) were tested on titanium alloy (Ti-6Al-4V) circular plates, and saline was used as the control. The open-circuit potential and potentiodynamic polarization of these materials were measured. Thereafter, all samples were evaluated under a field-emission scanning electron microscope. RESULTS: Among the tested oral rinses, except solution D, the more the fluoride content was, the greater was the corrosion potential downtrend; the corrosion resistance of the titanium alloy sample was also lowered significantly (p < 0.05). Field-emission scanning electron microscopic analysis of the surface morphology of the titanium alloy samples revealed that all samples had some defects, crevices, or pitting after exposure to the oral rinses than before treatment. In particular, the samples in solution A showed the most changes. CONCLUSIONS: Commercially available oral rinses having a high fluoride concentration and a low pH may reduce the corrosion resistance of titanium alloys used in dental appliances such as orthodontic titanium miniscrews and brackets.
Alloys* ; Corrosion* ; Fluorides ; Hydrogen-Ion Concentration ; Titanium*