The Complex, Unique, and Powerful Imaging Instrument for Dynamics (CUPI2D) at the Spallation Neutron Source (invited).

The Oak Ridge National Laboratory is planning to build the Second Target Station (STS) at the Spallation Neutron Source (SNS). STS will host a suite of novel instruments that complement the First Target Station's beamline capabilities by offering an increased flux for cold neutrons and a broader wavelength bandwidth. A novel neutron imaging beamline, named the Complex, Unique, and Powerful Imaging Instrument for Dynamics (CUPI2D), is among the first eight instruments that will be commissioned at STS as part of the construction project. CUPI2D is designed for a broad range of neutron imaging scientific applications, such as energy storage and conversion (batteries and fuel cells), materials science and engineering (additive manufacturing, superalloys, and archaeometry), nuclear materials (novel cladding materials, nuclear fuel, and moderators), cementitious materials, biology/medical/dental applications (regenerative medicine and cancer), and life sciences (plant-soil interactions and nutrient dynamics). The innovation of this instrument lies in the utilization of a high flux of wavelength-separated cold neutrons to perform real time in situ neutron grating interferometry and Bragg edge imaging-with a wavelength resolution of δλ/λ ≈ 0.3%-simultaneously when required, across a broad range of length and time scales. This manuscript briefly describes the science enabled at CUPI2D based on its unique capabilities. The preliminary beamline performance, a design concept, and future development requirements are also presented.

Novel Experimental In-Office Bleaching Gels Containing Co-Doped Titanium Dioxide Nanoparticles.

The present study reports on the development and testing of novel bleaching agents containing co-doped metaloxide nanoparticles (NP; 0%, 5%, 10% v/w) and hydrogen peroxide (HP, 0%, 6%, 15%, and 35%). Bovine blocks (n = 200, A = 36 mm2) were obtained and randomly distributed into experimental groups (n = 10/group). NPs were incorporated into gels before bleaching (3 sessions, 7 days apart, 30 min/session, irradiated with violet light-LT). Color changes (ΔE00, ΔWID), mineral content (CO32−, PO43−), and topography were assessed (spectrophotometer, ATR-FTIR, and AFM) before and after bleaching procedures (14 days). Metabolic status and three-dimensional components of non-disrupted Streptococcus mutans biofilms were investigated using a multimode reader and confocal microscopy. The results indicate that ΔE00 and ΔWID significantly increased with NPs' concentrations and LT. The enamel's mineral ratio was adversely impacted by HP, but alterations were less pronounced when using NP-containing gels. The enamel's topography was not damaged by the bleaching protocols tested. The bioluminescence results show that bleaching protocols do not render latent antibacterial properties to enamel, and the confocal microscopy results demonstrate that the 3-dimensional distribution of the components was affected by the protocols. The proposed nanotechnology improved the bleaching efficacy of experimental materials independent of hydrogen peroxide or irradiation and did not adversely impact the enamel's surface properties or its chemical content.

Shear Bond Strength and Color Stability of Novel Antibacterial Nanofilled Dental Adhesive Resins.

Experimental adhesives containing co-doped metaloxide nanoparticles were demonstrated to display strong and long-term antibacterial properties against Streptococcus mutans biofilms. The present study represents an effort to characterize the shear-bond strength (SBS) and color stability (CS) of these novel biomaterials. Experimental adhesives were obtained by dispersing nitrogen and fluorine co-doped titanium dioxide nanoparticles (NF_TiO2, 10%, 20% or 30%, v/v%) into OptiBond Solo Plus (OPTB). Dentin surfaces were wet-polished (600-Grit). Specimens (n = 5/group) of Tetric EvoCeram were fabricated and bonded using either OPTB or experimental (OPTB + NF_TiO2) adhesives. Specimens were stored in water (37 °C) for twenty-four hours (T1), three months (T2), and six months (T3). At T1, T2, or T3, specimens were removed from water storage and were tested for SBS. Disc-shaped specimens (n = 10/group; d = 6.0 mm, t = 0.5 mm) of adhesives investigated were fabricated and subjected to thermocycling (10,000 cycles, 5−55 °C, 15 s dwell time). Specimens' colors were determined with a VITA Easyshade® V spectrophotometer (after every 1000 cycles). SBS data was analyzed using two-way ANOVA and post-hoc Tukey tests, while CS data was analyzed using one-way ANOVA and post-hoc Tukey tests (α = 0.05). Mean values of SBS ranged from 16.39 ± 4.20 MPa (OPTB + 30%NF_TiO2) to 19.11 ± 1.11 MPa (OPTB), from 12.99 ± 2.53 MPa (OPTB + 30% NF_TiO2) to 14.87 ± 2.02 (OPTB) and from 11.37 ± 1.89 (OPTB + 20% NF_TiO2) to 14.19 ± 2.24 (OPTB) after twenty-four hours, three months, and six months of water storage, respectively. Experimental materials had SBS values that were comparable (p > 0.05) to those from OPTB independently of nanoparticle concentration or time-point considered. Experimental materials with higher NF_TiO2 concentrations had less intense color variations and were more color stable than OPTB even after 10,000 thermocycles. In combination, the results reported have demonstrated that experimental adhesives can establish strong and durable bonds to human dentin while displaying colors that are more stable, thereby suggesting that the antibacterial nanotechnology investigated can withstand the harsh conditions within the oral cavity without compromising the esthetic component of dental restorations.

Assessment of Streptococcus mutans biofilms on orthodontic adhesives over 7 days.

INTRODUCTION: The purpose of this study was to compare the metabolism of Streptococcus mutans biofilms after 1-7 days of growth on different orthodontic adhesives. METHODS: Specimens of 6 commercial orthodontic adhesives were fabricated in custom-made molds and polymerized using a light-emitting diode light-curing unit. Bioluminescent S mutans (UA159:JM10) biofilms were grown on ultraviolet-sterilized specimens for 1, 3, 5, and 7 days (n = 18 biofilms/d/product) in anaerobic conditions at 37°C. The metabolism of biofilms (relative luminescence unit [RLU]) was measured 0, 2, 4, and 6 minutes after exposure to D-luciferin solution using a microplate reader. A linear mixed-effects model was used to analyze the logarithm of RLU (log RLU). The model included fixed effects of products, days, and minutes. Tukey-Kramer post-hoc tests were then performed on the significant predictors of log RLU (α = 0.05). RESULTS: Days (P <0.0001) and minutes (P <0.0001) were independent predictors of log RLU, but the products were not (P = 0.5869). After adjusting for minutes, the log RLU was analyzed with a post-hoc test, and all differences between days were significant with the exceptions of day 3 from day 5 (P = 0.0731) and day 5 from day 7 (P = 0.8802). After adjusting for day, log RLU was analyzed with a post-hoc test and all differences in minutes were significant. CONCLUSIONS: No significant differences in the metabolism of S mutans biofilms were observed among the 6 orthodontic adhesives. Biofilms that were grown for 3 days demonstrated the highest levels of biofilm metabolism as evidenced by higher mean log RLU values relative to 1, 5, and 7-day growth durations.

Pairing orthodontic adhesive resins and light-curing units for optimal degree of conversion.

OBJECTIVES: The purpose of this study was to identify the combination of orthodontic adhesive resins and light-emitting diode (LED) light-curing units (LCUs) that result in the highest degree of resin conversion (DC). The hypothesis tested was that pairing orthodontic resins with LCUs from the same manufacturer produces higher DC versus unpaired resins and LCUs. METHODS: Pre-polymerization spectra of adhesive resins (Transbond XT [3M Unitek], BracePaste [American Orthodontics] or Opal Bond MV [Opal by Ultradent]) were obtained at oral temperature (37°C) using an attenuated total reflectance (ATR) diamond crystal (Golden Gate, Specac) in a Fourier-transform infrared (FTIR) spectrometer (Nicolet IS50). Resin specimens were polymerized using various LCUs (Ortholux Luminous [3M Unitek], Blue Ray 3 [American Orthodontics], or VALO Ortho Cordless [Ultradent Products, Inc.]) before obtaining post-polymerization infrared (IR); spectra. Twelve LCU-resin combinations were tested (n = 20/combination), half with a bracket present (Mini Diamond Twin, Ormco) and half without. DC values (%) were calculated using the two-frequency method and tangent-baseline technique. Data for each resin were statistically analyzed using General Linear Models and Student-Newman-Keuls post hoc tests (α = 0.05). RESULTS: Statistically significant differences were found within each resin for the groups without brackets present (P < 0.0001), the groups with brackets present (P < 0.0001), and the groups with brackets when compared with the manufacturer-paired group without a bracket (P < 0.0001). CONCLUSIONS: Adhesive resins and LCUs from the same manufacturer did not consistently result in statistically higher mean DC values than unpaired combinations. Metal brackets do not uniformly reduce the degree of conversion of adhesive resins when assessed using IR spectrometry.

Physicochemical, Mechanical, and Antimicrobial Properties of Novel Dental Polymers Containing Quaternary Ammonium and Trimethoxysilyl Functionalities.

The aims of this study were to evaluate the physicochemical and mechanical properties, antimicrobial (AM) functionality, and cytotoxic potential of novel dental polymers containing quaternary ammonium and trimethoxysilyl functionalities (e.g., N-(2-(methacryloyloxy)ethyl)-N,N-dimethyl-3-(trimethoxysilyl)propan-1-aminium iodide (AMsil1) and N-(2-(methacryloyloxy)ethyl)-N,N-dimethyl-11-(trimethoxysilyl)undecan-1-aminium bromide (AMsil2)). AMsil1 or AMsil2 were incorporated into light-cured (camphorquinone + ethyl-4-N,N-dimethylamino benzoate) urethane dimethacrylate (UDMA)/polyethylene glycol-extended UDMA/ethyl 2-(hydroxymethyl)acrylate (EHMA) resins (hereafter, UPE resin) at 10 or 20 mass %. Cytotoxic potential was assessed by measuring viability and metabolic activity of immortalized mouse connective tissue and human gingival fibroblasts in direct contact with monomers. AMsil-UPE resins were evaluated for wettability by contact angle measurements and degree of vinyl conversion (DVC) by near infra-red spectroscopy analyses. Mechanical property evaluations entailed flexural strength (FS) and elastic modulus (E) testing of copolymer specimens. The AM properties were assessed using Streptococcus mutans (planktonic and biofilm forms) and Porphyromonas gingivalis biofilm. Neither AMsil exhibited significant toxicity in direct contact with cells at biologically relevant concentrations. Addition of AMsils made the UPE resin more hydrophilic. DVC values for the AMsil-UPE copolymers were 2%-31% lower than that attained in the UPE resin control. The mechanical properties (FS and E) of AMsil-UPE specimens were reduced (11%-57%) compared to the control. Compared to UPE resin, AMsil1-UPE and AMsil2-UPE (10% mass) copolymers reduced S. mutans biofilm 4.7- and 1.7-fold, respectively (p ≤ 0.005). Although not statistically different, P. gingivalis biofilm biomass on AMsil1-UPE and AM AMsil2-UPE copolymer disks were lower (71% and 85%, respectively) than that observed with a commercial AM dental material. In conclusion, the AM function of new monomers is not inundated by their toxicity towards cells. Despite the reduction in mechanical properties of the AMsil-UPE copolymers, AMsil2 is a good candidate for incorporation into multifunctional composites due to the favorable overall hydrophilicity of the resins and the satisfactory DVC values attained upon light polymerization of AMsil-containing UDMA/PEG-U/EHMA copolymers.

Synthesis and characterization of silver phosphate/calcium phosphate mixed particles capable of silver nanoparticle formation by photoreduction.

Silver phosphate is a semi-conductor sensitive to UV-Vis radiation (<530nm). Exposure to radiation removes electrons from the oxygen valence shell, which are scavenged by silver cations (Ag+), forming metallic silver (Ag0) nanoparticles. The possibility of silver nanoparticle formation in situ by a photoreduction process was the basis for the application of mixed calcium phosphate/silver phosphate particles as remineralizing and antibacterial fillers in resin-based dental materials. Mixed phosphate particles were synthesized, characterized and added to a dimethacrylate resin in 20% or 30% mass fractions to investigate their efficacy as ion-releasing fillers for dental remineralization and antibacterial activity. The formation of metallic silver nanoparticles after exposure to visible radiation from a dental curing unit (peak emission: 470nm) was demonstrated by particle X-ray diffraction and scanning electron microscopy analysis of the composite fractured surface. Calcium and phosphate release from materials containing the mixed particles were similar to those containing pure CaP particles, whereas Streptococcus mutans colonies were reduced by three orders of magnitude in relation to the control, which can be attributed to silver release. As expected, the optical properties of the materials containing mixed phosphate particles were compromised by the presence of silver. Nevertheless, materials containing mixed phosphate particles presented higher fracture strength and elastic modulus than those with pure CaP particles.