Effect of Electrocautery and Laser Treatment on the Composition and Morphology of Surface-Modified Titanium Implants.

The purpose of this study was to investigate the effects of different peri-implantitis treatment methods (Er,Cr:YSGG laser, diode laser, and electrocautery) on various titanium implant surfaces: machined; sandblasted, large-grit, and acid-etched; and femtosecond laser-treated surfaces. Grade 4 titanium (Ti) disks, with a diameter of 10 mm and a thickness of 1 mm, were fabricated and treated using the aforementioned techniques. Subsequently, each treated group of disks underwent different peri-implantitis treatment methods: Er,Cr:YSGG laser (Biolase, Inc., Foothill Ranch, CA, USA), diode laser (Biolase, Inc., Foothill Ranch, CA, USA), and electrocautery (Ellman, Hicksville, NY, USA). Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and wettability were used to characterize the chemical compositions and surfaces of the treated titanium surfaces. Significant changes in surface roughness were observed in both the electrocautery (Sa value of machined surface = 0.469, SLA surface = 1.569, femtosecond laser surface = 1.741, and p = 0.025) and Er,Cr:YSGG laser (Ra value of machined surface = 1.034, SLA surface = 1.380, femtosecond laser surface = 1.437, and p = 0.025) groups. On femtosecond laser-treated titanium implant surfaces, all three treatment methods significantly reduced the surface contact angle (control = 82.2°, diode laser = 74.3°, Er,Cr:YSGG laser = 73.8°, electrocautery = 76.2°, and p = 0.039). Overall, Er,Cr:YSGG laser and electrocautery treatments significantly altered the surface roughness of titanium implant surfaces. As a result of surface composition after different peri-implantitis treatment methods, relative to the diode laser and electrocautery, the Er,Cr:YSGG laser increased oxygen concentration. The most dramatic change was observed after Er:Cr;YSGG laser treatment, urging caution for clinical applications. Changes in surface composition and wettability were observed but were not statistically significant. Further research is needed to understand the biological implications of these peri-implantitis treatment methods.

In Vitro Biofilm Formation on Zirconia Implant Surfaces Treated with Femtosecond and Nanosecond Lasers.

(1) Background: The purpose of this study was to evaluate how a zirconia implant surface treated with laser technology affects the degree of biofilm formation. (2) Methods: Experimental titanium (Ti) disks were produced that were sandblasted with large grit and acid-etched (T), and they were compared with zirconia (ZrO2) discs with a machined (M) surface topography; a hydrophilic surface topography with a femtosecond laser (HF); and a hydrophobic surface topography with a nanosecond laser (HN) (N = 12 per surface group). An in vitro three-species biofilm sample (Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi)) was applied to each disc type, and bacterial adhesion was assessed after 48 and 72 h of incubation using an anaerobic flow chamber model. Statistical significance was determined using the Kruskal-Wallis H test, with Bonferroni correction used for the post-hoc test (α = 0.05). (3) Results: Compared to the T group, the M group exhibited more than twice as many viable bacterial counts in the three-species biofilm samples (p < 0.05). In comparison to the T group, the HF group had significantly higher viable bacterial counts in certain biofilm samples at 48 h (Aa and Pi) and 72 h (Pi) (p < 0.05). The HN group had higher viable bacterial counts in Pi at 48 h (5400 CFU/mL, p < 0.05) than the T group (4500 CFU/mL), while showing significantly lower viable bacterial counts in Pg at both 48 (3010 CFU/mL) and 72 h (3190 CFU/mL) (p < 0.05). (4) Conclusions: The surface treatment method for zirconia discs greatly influences biofilm formation. Notably, hydrophobic surface treatment using a nanosecond laser was particularly effective at inhibiting Pg growth.

The Impact of Mechanical Debridement Techniques on Titanium Implant Surfaces: A Comparison of Sandblasted, Acid-Etched, and Femtosecond Laser-Treated Surfaces.

This study evaluated the effects of various mechanical debridement methods on the surface roughness (Ra) of dental implants, comparing femtosecond laser-treated surfaces with conventionally machined and sandblasted with large-grit sand and acid-etched (SLA) implant surfaces. The fabrication of grade 4 titanium (Ti) disks (10 mm in diameter and 1 mm thick) and the SLA process were carried out by a dental implant manufacturer (DENTIS; Daegu, Republic of Korea). Subsequently, disk surfaces were treated with various methods: machined, SLA, and femtosecond laser. Disks of each surface-treated group were post-treated with mechanical debridement methods: Ti curettes, ultrasonic scaler, and Ti brushes. Scanning electron microscopy, Ra, and wettability were evaluated. Statistical analysis was performed using the Kruskal-Wallis H test, with post-hoc analyses conducted using the Bonferroni correction (α = 0.05). In the control group, no significant difference in Ra was observed between the machined and SLA groups. However, femtosecond laser-treated surfaces exhibited higher Ra than SLA surfaces (p < 0.05). The application of Ti curette or brushing further accentuated the roughness of the femtosecond laser-treated surfaces, whereas scaling reduced the Ra in SLA surfaces. Femtosecond laser-treated implant surfaces, with their unique roughness and compositional attributes, are promising alternatives in dental implant surface treatments.

Influence of Dental Titanium Implants with Different Surface Treatments Using Femtosecond and Nanosecond Lasers on Biofilm Formation.

This study aimed to evaluate the impact of different surface treatments (machined; sandblasted, large grit, and acid-etched (SLA); hydrophilic; and hydrophobic) on dental titanium (Ti) implant surface morphology, roughness, and biofilm formation. Four groups of Ti disks were prepared using distinct surface treatments, including femtosecond and nanosecond lasers for hydrophilic and hydrophobic treatments. Surface morphology, wettability, and roughness were assessed. Biofilm formation was evaluated by counting the colonies of Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), and Prevotella intermedia (Pi) at 48 and 72 h. Statistical analysis was conducted to compare the groups using the Kruskal-Wallis H test and the Wilcoxon signed-rank test (α = 0.05). The analysis revealed that the hydrophobic group had the highest surface contact angle and roughness (p < 0.05), whereas the machined group had significantly higher bacterial counts across all biofilms (p < 0.05). At 48 h, the lowest bacterial counts were observed in the SLA group for Aa and the SLA and hydrophobic groups for Pg and Pi. At 72 h, low bacterial counts were observed in the SLA, hydrophilic, and hydrophobic groups. The results indicate that various surface treatments affect implant surface properties, with the hydrophobic surface using femtosecond laser treatment exerting a particularly inhibitory effect on initial biofilm growth (Pg and Pi).

Retina-Inspired Color-Cognitive Learning via Chromatically Controllable Mixed Quantum Dot Synaptic Transistor Arrays.

Artificial photonic synapses are emerging as a promising implementation to emulate the human visual cognitive system by consolidating a series of processes for sensing and memorizing visual information into one system. In particular, mimicking retinal functions such as multispectral color perception and controllable nonvolatility is important for realizing artificial visual systems. However, many studies to date have focused on monochromatic-light-based photonic synapses, and thus, the emulation of color discrimination capability remains an important challenge for visual intelligence. Here, an artificial multispectral color recognition system by employing heterojunction photosynaptic transistors consisting of ratio-controllable mixed quantum dot (M-QD) photoabsorbers and metal-oxide semiconducting channels is proposed. The biological photoreceptor inspires M-QD photoabsorbers with a precisely designed red (R), green (G), and blue (B)-QD ratio, enabling full-range visible color recognition with high photo-to-electric conversion efficiency. In addition, adjustable synaptic plasticity by modulating gate bias allows multiple nonvolatile-to-volatile memory conversion, leading to chromatic control in the artificial photonic synapse. To ensure the viability of the developed proof of concept, a 7 × 7 pixelated photonic synapse array capable of performing outstanding color image recognition based on adjustable wavelength-dependent volatility conversion is demonstrated.

Large-Area Pixelized Optoelectronic Neuromorphic Devices with Multispectral Light-Modulated Bidirectional Synaptic Circuits.

The complete hardware implementation of an optoelectronic neuromorphic computing system is considered as one of the most promising solutions to realize energy-efficient artificial intelligence. Here, a fully light-driven and scalable optoelectronic neuromorphic circuit with metal-chalcogenide/metal-oxide heterostructure phototransistor and photovoltaic divider is proposed. To achieve wavelength-selective neural operation and hardware-based pattern recognition, multispectral light modulated bidirectional synaptic circuits are utilized as an individual pixel for highly accurate and large-area neuromorphic computing system. The wavelength selective control of photo-generated charges at the heterostructure interface enables the bidirectional synaptic modulation behaviors including the excitatory and inhibitory modulations. More importantly, a 7 × 7 neuromorphic pixel circuit array is demonstrated to show the viability of implementing highly accurate hardware-based pattern training. In both the pixel training and pattern recognition simulation, the neuromorphic circuit array with the bidirectional synaptic modulation exhibits lower training errors and higher recognition rates, respectively.

Non-Invasive Optical Coherence Tomography Data-Based Quantitative Algorithm for the Assessment of Residual Adhesive on Bracket-Removed Dental Surface.

The aim of this study was to quantitatively assess the residual adhesive on orthodontic ceramic bracket-removed dental surface. In orthodontic process, ceramic bracket was repeated debonding physically, then the adhesive remained on the dental surface. The residual adhesive caused a lack of adhesive strength between dental and ceramic bracket. Since commonly used adhesive in orthodontics is translucent, residual adhesive is hard to be detected with conventional microscopes. Therefore, 1310 nm center wavelength swept-source OCT system based on laboratory customized image processing algorithm was used for the precise detection of residual adhesive on tooth surface. The algorithm separates residual adhesive from dental surface by comparing the height of adjacent B-scan images, while providing color-scaled images emphasizing the thickness information of residual adhesive. Finally, the acquired results were compared with microscopic and adhesive remnant index scoring gold standards, while the comparison confirmed the potential merits and the improvements of the proposed method over gold standards.

Influence of Sandblasting Particle Size and Pressure on Resin Bonding Durability to Zirconia: A Residual Stress Study.

The influence of residual stress induced by sandblasting the zirconia ceramic surface on the resin bonding to the ceramic is still unclear. The effect of four different sandblasting conditions (with 50 and 110 µm alumina at pressures of 0.2 and 0.4 MPa) on the bonding of adhesive resin cement (Panavia F 2.0) to zirconia (Cercon® ht) was investigated in terms of residual stress. The surface roughness and water contact angle of the zirconia surfaces were measured. The tetragonal-to-monoclinic (t-m) phase transformation and residual stresses (sin2ψ method) were studied by X-ray diffraction. The resin-bonded zirconia specimens were subjected to shear bond strength (SBS) tests before and after thermocycling (10,000 and 30,000 cycles) (n = 10). As the particle size and pressure increased, the roughness gradually and significantly increased (p = 0.023). However, there were no significant differences in roughness-corrected contact angle among all the sandblasted groups (p > 0.05). As the particle size and pressure increased, the m-phase/(t-phase + m-phase) ratios and compressive residual stresses gradually increased. After thermocycling, there were no significant differences in SBS among the sandblasted zirconia groups (p > 0.05). In conclusion, increased surface roughness and residual stress do not directly affect the resin bonding durability.

Measurement of Exciton and Trion Energies in Multistacked hBN/WS2 Coupled Quantum Wells for Resonant Tunneling Diodes.

Quantum confinements, especially quantum in narrow wells, have been investigated because of their controllability over electrical parameters. For example, quantum dots can emit a variety of photon wavelengths even for the same material depending on their particle size. More recently, the research into two-dimensional (2D) materials has shown the availability of several quantum mechanical phenomenon confined within a sheet of materials. Starting with the gapless semimetal properties of graphene, current research has begun into the excitons and their properties within 2D materials. Even for simple 2D systems, experimental results often offer surprising results, unexpected from traditional studies. We investigated a coupled quantum well system using 2D hexagonal boron nitride (hBN) barrier as well as 2D tungsten disulfide (WS2) semiconductor arranged in stacked structures to study the various 2D to 2D interactions. We determined that for hexagonal boron nitride-tungsten disulfide (hBN/WS2) quantum well stacks, the interaction between successive wells resulted in decreasing bandgap, and the effect was pronounced even over a large distance of up to four stacks. Additionally, we observed that a single layer of isolating hBN barriers significantly reduces interlayer interaction between WS2 layers, while still preserving the interwell interactions in the alternative hBN/WS2 structure. The methods we used for the study of coupled quantum wells here show a method for determining the respective exciton energy levels and trion energy levels within 2D materials and 2D materials-based structures. Renormalization energy levels are the key in understanding conductive and photonic properties of stacked 2D materials.

Catalytic Metal-Accelerated Crystallization of High-Performance Solution-Processed Earth-Abundant Metal Oxide Semiconductors.

As an alternative strategy for conventional high-temperature crystallization of metal oxide (MO) channel layers, the catalytic metal-accelerated crystallization (CMAC) process using a metal seed layer is demonstrated for low-temperature crystallization of solution-processed MO semiconductors. In the CMAC process, the catalytic metal layer plays the role of seed sites for initiating and accelerating the crystallization of amorphous MO films. Generally, the solution-processed crystalline-TiO2 (c-TiO2) films required high-temperature crystallization conditions (≥500-600 °C), showing low electrical performance with a high defect density. In contrast, the suggested CMAC process could effectively lower crystallization temperature of the a-TiO2 films, enabling high-quality c-TiO2 films with well-aligned anatase grains and low-defect density. The various crystalline catalytic layers were deposited over the earth-abundant n-type amorphous titanium oxide (a-TiO2) films. Also, then, the CMAC process was performed for facile low-temperature translation of solution-processed a-TiO2 to a highly crystallized state. In particular, the Al-CMAC process using the crystalline thin-aluminum (Al) catalytic metal seed layer facilitates low-temperature (≥300 °C) crystallization of the solution-processed a-TiO2 films and the fabrication of high-performance solution-processed c-TiO2 thin-film transistors with superior field-effect mobility, good on/off switching behavior, and improved operational stability.

Highly Efficient Photo-Induced Charge Separation Enabled by Metal-Chalcogenide Interfaces in Quantum-Dot/Metal-Oxide Hybrid Phototransistors.

Quantum dot (QD)-based optoelectronics have received great interest for versatile applications because of their excellent photosensitivity, facile solution processability, and the wide range of band gap tunability. In addition, QD-based hybrid devices, which are combined with various high-mobility semiconductors, have been actively researched to enhance the optoelectronic characteristics and maximize the zero-dimensional structural advantages, such as tunable band gap and high light absorption. However, the difficulty of highly efficient charge transfer between QDs and the semiconductors and the lack of systematic analysis for the interfaces have impeded the fidelity of this platform, resulting in complex device architectures and unsatisfactory device performance. Here, we report ultrahigh detective phototransistors with highly efficient photo-induced charge separation using a Sn2S64--capped CdSe QD/amorphous oxide semiconductor (AOS) hybrid structure. The photo-induced electron transfer characteristics at the interface of the two materials were comprehensively investigated with an array of electrochemical and spectroscopic analyses. In particular, photocurrent imaging microscopy revealed that interface engineering in QD/AOS with chelating chalcometallate ligands causes efficient charge transfer, resulting in photovoltaic-dominated responses over the whole channel area. On the other hand, monodentate ligand-incorporated QD/AOS-based devices typically exhibit limited charge transfer with atomic vibration, showing photo-thermoelectric-dominated responses in the drain electrode area.

A skin-like two-dimensionally pixelized full-color quantum dot photodetector.

Direct full-color photodetectors without sophisticated color filters and interferometric optics have attracted considerable attention for widespread applications. However, difficulties of combining various multispectral semiconductors and improving photon transfer efficiency for high-performance optoelectronic devices have impeded the translation of these platforms into practical realization. Here, we report a low-temperature (<150°C) fabricated two-dimensionally pixelized full-color photodetector by using monolithic integration of various-sized colloidal quantum dots (QDs) and amorphous indium-gallium-zinc-oxide semiconductors. By introducing trap-reduced chelating chalcometallate ligands, highly efficient charge carrier transport and photoresistor-free fine-patterning of QD layers were successfully realized, exhibiting extremely high photodetectivity (>4.2 × 1017 Jones) and photoresponsivity (>8.3 × 103 A W-1) in a broad range of wavelengths (365 to 1310 nm). On the basis of these technologies, a wavelength discriminable phototransistor circuit array (>600 phototransistors) was implemented on a skin-like soft platform, which is expected to be a versatile and scalable approach for wide spectral image sensors and human-oriented biological devices.

Environment-Adaptable Artificial Visual Perception Behaviors Using a Light-Adjustable Optoelectronic Neuromorphic Device Array.

Emulating the biological visual perception system typically requires a complex architecture including the integration of an artificial retina and optic nerves with various synaptic behaviors. However, self-adaptive synaptic behaviors, which are frequently translated into visual nerves to adjust environmental light intensities, have been one of the serious challenges for the artificial visual perception system. Here, an artificial optoelectronic neuromorphic device array to emulate the light-adaptable synaptic functions (photopic and scotopic adaptation) of the biological visual perception system is presented. By employing an artificial visual perception circuit including a metal chalcogenide photoreceptor transistor and a metal oxide synaptic transistor, the optoelectronic neuromorphic device successfully demonstrates diverse visual synaptic functions such as phototriggered short-term plasticity, long-term potentiation, and neural facilitation. More importantly, the environment-adaptable perception behaviors at various levels of the light illumination are well reproduced by adjusting load transistor in the circuit, exhibiting the acts of variable dynamic ranges of biological system. This development paves a new way to fabricate an environmental-adaptable artificial visual perception system with profound implications for the field of future neuromorphic electronics.

Corrugated Heterojunction Metal-Oxide Thin-Film Transistors with High Electron Mobility via Vertical Interface Manipulation.

A new strategy is reported to achieve high-mobility, low-off-current, and operationally stable solution-processable metal-oxide thin-film transistors (TFTs) using a corrugated heterojunction channel structure. The corrugated heterojunction channel, having alternating thin-indium-tin-zinc-oxide (ITZO)/indium-gallium-zinc-oxide (IGZO) and thick-ITZO/IGZO film regions, enables the accumulated electron concentration to be tuned in the TFT off- and on-states via charge modulation at the vertical regions of the heterojunction. The ITZO/IGZO TFTs with optimized corrugated structure exhibit a maximum field-effect mobility >50 cm2 V-1 s-1 with an on/off current ratio of >108 and good operational stability (threshold voltage shift <1 V for a positive-gate-bias stress of 10 ks, without passivation). To exploit the underlying conduction mechanism of the corrugated heterojunction TFTs, a physical model is implemented by using a variety of chemical, structural, and electrical characterization tools and Technology Computer-Aided Design simulations. The physical model reveals that efficient charge manipulation is possible via the corrugated structure, by inducing an extremely high carrier concentration at the nanoscale vertical channel regions, enabling low off-currents and high on-currents depending on the applied gate bias.

Reliable Multivalued Conductance States in TaO x Memristors through Oxygen Plasma-Assisted Electrode Deposition with in Situ-Biased Conductance State Transmission Electron Microscopy Analysis.

Transition metal oxide-based memristors have widely been proposed for applications toward artificial synapses. In general, memristors have two or more electrically switchable stable resistance states that device researchers see as an analogue to the ion channels found in biological synapses. The mechanism behind resistive switching in metal oxides has been divided into electrochemical metallization models and valence change models. The stability of the resistance states in the memristor vary widely depending on: oxide material, electrode material, deposition conditions, film thickness, and programming conditions. So far, it has been extremely challenging to obtain reliable memristors with more than two stable multivalued states along with endurances greater than ∼1000 cycles for each of those states. Using an oxygen plasma-assisted sputter deposition method of noble metal electrodes, we found that the metal-oxide interface could be deposited with substantially lower interface roughness observable at the nanometer scale. This markedly improved device reliability and function, allowing for a demonstration of memristors with four completely distinct levels from ∼6 × 10-6 to ∼4 × 10-8 S that were tested up to 104 cycles per level. Furthermore through a unique in situ transmission electron microscopy study, we were able to verify a redox reaction-type model to be dominant in our samples, leading to the higher degree of electrical state controllability. For solid-state synapse applications, the improvements to electrical properties will lead to simple device structures, with an overall power and area reduction of at least 1000 times when compared to SRAM.

High-performance and scalable metal-chalcogenide semiconductors and devices via chalco-gel routes.

We report a general strategy for obtaining high-quality, large-area metal-chalcogenide semiconductor films from precursors combining chelated metal salts with chalcoureas or chalcoamides. Using conventional organic solvents, such precursors enable the expeditious formation of chalco-gels, which are easily transformed into the corresponding high-performance metal-chalcogenide thin films with large, uniform areas. Diverse metal chalcogenides and their alloys (MQ x : M = Zn, Cd, In, Sb, Pb; Q = S, Se, Te) are successfully synthesized at relatively low processing temperatures (<400°C). The versatility of this scalable route is demonstrated by the fabrication of large-area thin-film transistors (TFTs), optoelectronic devices, and integrated circuits on a 4-inch Si wafer and 2.5-inch borosilicate glass substrates in ambient air using CdS, CdSe, and In2Se3 active layers. The CdSe TFTs exhibit a maximum field-effect mobility greater than 300 cm2 V-1 s-1 with an on/off current ratio of >107 and good operational stability (threshold voltage shift < 0.5 V at a positive gate bias stress of 10 ks). In addition, metal chalcogenide-based phototransistors with a photodetectivity of >1013 Jones and seven-stage ring oscillators operating at a speed of ~2.6 MHz (propagation delay of < 27 ns per stage) are demonstrated.

Resin Bonding to Type IV Gold Alloy Conditioned with a Novel Mercapto Silane System: Effect of Incorporation of a Phosphate Monomer.

Self-assembled monolayers of thiols have been used to link a range of materials to planar gold surfaces or gold nanoparticles in nanoscience and nanotechnology. Novel mercapto silane systems are a promising alternative to dental noble metal alloys for enhanced resin bonding durability Goldbased alloys for full-cast restorations contain various base metal elements, which may bond to acidic functional monomers chemically, in addition to noble metal elements. This study examined how the additional incorporation of a phosphate monomer (di-2-hydroxyethyl methacryl hydrogenphosphate, DHP) into novel mercapto silane primer systems affected the resin bond strength to a type IV gold alloy pretreated with the primers. One of three commercial primers (Alloy Primer and M. L. Primer) and three experimental primer systems ((1) blend of γ-mercaptopropyltrimethoxysilane (SPS) and γ-methacryloxypropyltrimethoxysilane (MPS) (both 1.0 wt%), (2) 1.0 wt% DHP-containing primer, and (3) blend of SPS, MPS, and DHP (each 1.0 wt%)) was applied to the alloy surfaces after sandblasting. Resin cylinders (diameter: 2.38 mm) were bonded to the surfaces and light-cured. All bonded specimens were stored in water at 37 °C for 24 h and then half of them additionally water immersed for 7 days (37 °C) and thermocycled 10,000 times before the shear bond strength test (n = 10). The mercapto silane systems (SPS + MPS) were found to show superior resin bonding durability to the commercial primers and the only DHP-containing primer, regardless of additional incorporation of the phosphate monomer.

Global analysis of gene expression profiles in the submandibular salivary gland of klotho knockout mice.

Salivary dysfunction commonly occurs in many older adults and is considered a physiological phenomenon. However, the genetic changes in salivary glands during aging have not been characterized. The present study analyzed the gene expression profile in salivary glands from accelerated aging klotho deficient mice (klotho-/-, 4 weeks old). Microarray analysis showed that 195 genes were differentially expressed (z-score > 2 in two independent arrays) in klotho null mice compared to wild-type mice. Importantly, alpha2-Na+ /K+ -ATPase (Atp1a2), Ca2+ -ATPase (Atp2a1), epidermal growth factor (EGF), and nerve growth factor (NGF), which have been suggested to be regulators of submandibular salivary gland function, were significantly decreased. When a network was constructed from the differentially expressed genes, proliferator-activated receptor-γ (PPAR γ), which regulates energy homeostasis and insulin sensitivity, was located at the core of the network. In addition, the expression of genes proposed to regulate various PPAR γ-related cellular pathways, such as Klk1b26, Egfbp2, Cox8b, Gpx3, Fabp3, EGF, and NGFß, was altered in the submandibular salivary glands of klotho-/- mice. Our results may provide clues for the identification of novel genes involved in salivary gland dysfunction. Further characterization of these differentially expressed genes will be useful in elucidating the genetic basis of aging-related changes in the submandibular salivary gland.

A microcomputed tomography evaluation of the marginal fit of cobalt-chromium alloy copings fabricated by new manufacturing techniques and alloy systems.

STATEMENT OF PROBLEM: Although new digital manufacturing techniques are attracting interest in dentistry, few studies have comprehensively investigated the marginal fit of fixed dental prostheses fabricated with such techniques. PURPOSE: The purpose of this in vitro microcomputed tomography (µCT) study was to evaluate the marginal fit of cobalt-chromium (Co-Cr) alloy copings fabricated by casting and 3 different computer-aided design and computer-aided manufacturing (CAD-CAM)-based processing techniques and alloy systems. MATERIAL AND METHODS: Single Co-Cr metal crowns were fabricated using 4 different manufacturing techniques: casting (control), milling, selective laser melting, and milling/sintering. Two different commercial alloy systems were used for each fabrication technique (a total of 8 groups; n=10 for each group). The marginal discrepancy and absolute marginal discrepancy of the crowns were determined with µCT. For each specimen, the values were determined from 4 different regions (sagittal buccal, sagittal lingual, coronal mesial, and coronal distal) by using imaging software and recorded as the average of the 4 readings. For each parameter, the results were statistically compared with 2-way analysis of variance and appropriate post hoc analysis (using Tukey or Student t test) (α=.05). RESULTS: The milling and selective laser melting groups showed significantly larger marginal discrepancies than the control groups (70.4 ±12.0 and 65.3 ±10.1 µm, respectively; P<.001), whereas the milling/sintering groups exhibited significantly smaller values than the controls (P=.004). The milling groups showed significantly larger absolute marginal discrepancy than the control groups (137.4 ±29.0 and 139.2 ±18.9 µm, respectively; P<.05). In the selective laser melting and milling/sintering groups, the absolute marginal discrepancy values were material-specific (P<.05). Nonetheless, the milling/sintering groups yielded statistically comparable (P=.935) or smaller (P<.001) absolute marginal discrepancies to the control groups. CONCLUSIONS: The findings of this in vitro µCT study showed that the marginal fit values of the Co-Cr alloy greatly depended on the fabrication methods and, occasionally, the alloy systems. Fixed dental prostheses produced by using the milling/sintering technique can be considered clinically acceptable in terms of marginal fit.

Snakebite in Korea: A Guideline to Primary Surgical Management.

PURPOSE: Snakebite is an emergency which causes local symptoms such as pain and edema around the bite. Systemic symptoms may also develop, such as dizziness or renal failure, and may even cause death. The purpose of this research was to assess the validity and safety of snakebite protocol for surgery when treating snakebite patients. MATERIALS AND METHODS: Retrospective research was performed on patients who were admitted after being treated at the emergency center from January 2008 to December 2012. When necessary, debridement was also performed, and 46 of 111 patients (41.4%) underwent debridement. Those who had received debridement without antivenom administration due to a positive skin reaction test were classified as group A, and group B received antivenom and delayed debridement. We reviewed the emergency and admission charts of the patients in each group and recorded and compared their age, sex, bite site, severity of local and general symptoms, time to receive antivenin, and complications. RESULTS: Of the ten patients (21.7%) in group A, two (66.6%) developed cellulites, and one of them experienced skin necrosis, resulting in a skin graft. In group B, there were 36 patients (78.2%), 19 (52.7%) of whom developed cellulitis. Skin necrosis occurred in two patients, and one of these patients received a skin graft. Compartment syndrome was found in one patient, and fasciotomy and a skin graft were performed. CONCLUSION: The treatment protocol implemented to treat snakebite patients admitted to the emergency center during this research was safely and properly followed during surgical treatment.