Impact of internal design on the accuracy of 3-dimensionally printed casts fabricated by stereolithography and digital light processing technology.

STATEMENT OF PROBLEM: Altering the internal design of 3-dimensionally (3D) printed dental casts may help to reduce material and time consumption. However, it remains unclear whether such changes would compromise the accuracy of the casts. Further research is also needed to determine the optimal internal design that would maximize printing accuracy. PURPOSE: The purpose of this in vitro study was to evaluate the impact of internal design on the accuracy (trueness and precision) of 3D printed dental casts fabricated by stereolithography (SLA) and digital light processing (DLP) technology. MATERIAL AND METHODS: A reference digital cast was obtained by scanning a maxillary typodont with an intraoral scanner to create 4 types of internal designs, including hollow interior with perforated base (HWB), hollow interior without base (HB), all solid (S), and internal support structure with perforated base (SWB). Digital casts with different internal designs were printed by two 3D printers with different technologies (SLA and DLP). The printed casts were scanned by a desktop scanner to obtain standard tessellation language (STL) format research digital casts. All reference and research digital casts were imported into a software program for comparison and analysis of accuracy. Differences between the reference and research digital casts were quantitatively indicated by the root mean square (RMS) value. The Kruskal-Wallis 1-way ANOVA was used to test significant differences between the different internal design types and the Mann-Whitney U test was used to test significant differences between the two 3D printers (α=.05). RESULTS: The Kruskal-Wallis 1-way ANOVA revealed significant differences in the trueness and precision of different internal design types (all P<.001) for casts printed by both 3D printers. The trueness and precision were significantly worse for the HB design than for the other design types for casts printed by both 3D printers (all P<.05). Regardless of the design type, the trueness was significantly better for casts printed by the SLA-based printer than for casts printed by the DLP-based printer (all P<.05). The precision was significantly worse for casts printed by the SLA-based printer than for casts printed by the DLP-based printer (all P<.05). CONCLUSIONS: The internal design may affect the accuracy of 3D printing. The base is necessary to ensure the accuracy of 3D printed dental casts, whereas the internal support structure did not affect the accuracy of 3D printed dental casts. An all-solid design led to higher precision, but not higher trueness. Dental casts printed with SLA technology have higher trueness and lower precision than those printed with DLP technology.

Abutment removal torque and implant conical surface morphological changes after standardized artificial aging: An in vitro study.

STATEMENT OF PROBLEM: Zirconia abutments have become popular as they provide favorable esthetic outcomes. However, studies investigating how abutment material affects abutment screw torque performance and implant conical surface morphological changes in internal conical connection systems are scarce. PURPOSE: The purpose of this in vitro study was to investigate the influence of abutment material on abutment removal torque and implant conical surface morphological changes in internal conical connection implant-abutment assemblies of 2 diameters after simulated long-term oral use. MATERIAL AND METHODS: Thirty abutments of 3 materials (1-piece titanium, 1-piece zirconia, zirconia with alloy base) and 2 diameters (regular, narrow) made by the original manufacturer were connected to internal conical connection implants and subjected to a standardized artificial aging process consisting of thermal cycling and mechanical cyclic loading with parameters corresponding to anterior and posterior mastication scenarios simulating long-term oral use. An abutment removal torque test was done before and after aging. Morphological changes in the implant conical contact surface were observed with a scanning electron microscope (SEM). Initial and after-aging torque loss values were calculated and analyzed separately with 1-way ANOVA and Tukey HSD post hoc tests (α=.05). RESULTS: All specimens survived artificial aging. For initial and after-aging torque loss, the 1-piece zirconia groups showed significantly greater values (P<.001) for both diameters. In the SEM observation, the 1-piece zirconia groups showed distinct widespread surface damage while the other groups exhibited only minor damages. CONCLUSIONS: Regardless of diameter, 1-piece zirconia abutments tend to induce more abutment removal torque loss and implant conical surface morphological changes than those with metal connections, both initially and after simulated long-term oral use. Zirconia abutments with an alloy base performed similarly to 1-piece titanium abutments.

Influence of Liquid on the Tooth Surface on the Accuracy of Intraoral Scanners: An In Vitro Study.

PURPOSE: To assess the influence of liquid attached on the tooth surfaces on the accuracy (trueness and precision) of intraoral scanners and the effectiveness of the drying method (using compression air) to exclude the influence of liquid on the scanning results. MATERIALS AND METHODS: A mandibular jaw model was scanned using an industrial computed tomography scanner to obtain a reference model. A scanning platform was designed to simulate three specific tooth surface states (dry, wet, blow-dry). Two kinds of liquids (ultra-pure water and artificial saliva) were used for the test. Two intraoral scanners (Trios 3 and Primescan) were used to scan the mandibular jaw model 10 times under each condition. All scanning data were processed and analyzed using dedicated software (Geomagic Control 2015). Trueness and precision comparison were conducted within the 12 groups of 3D models divided based on different intraoral scanners and liquids used under each condition. The root mean square (RMS) value was used to indicate the difference between the aligned virtual models. The color maps were used to evaluate and observe the deviation distribution patterns. The 3-way ANOVA (condition, intraoral scanner, liquid) followed by the Tukey test were used to assess precision and trueness. The level of significance was set at 0.05. RESULTS: The mean RMS values obtained from wet condition were significantly higher than those of the dry and blow-dry condition (p < 0.001, F = 64.033 for trueness and F = 54.866 for precision), which indicates less accurate trueness and precision for wet condition. For two different types of liquids, the mean RMS value was not significantly different on trueness and precision. The deviations caused by liquid were positive and mainly distributed in the pits and fissures of the occlusal surface of posterior teeth, the interproximal area of the teeth, and the margin of the abutments. CONCLUSIONS: Liquid on the tooth surface could affect intraoral scanning accuracy. Blow-drying with a three-way syringe can reduce scanning errors.

The Tumorgenicity of Glioblastoma Cell Line U87MG Decreased During Serial In Vitro Passage.

Established cancer cell lines are routinely used to study cancer. Several factors such as serial passage may affect the reproducibility of experiments with cancer cell lines, but few researches focused on these changes. In the present study, different morphology and decreased tumorigenicity were observed in late passage U87MG cells. In vitro experiments further revealed that late passage U87MG cells possessed lower invasion properties than early passage, whereas no significant differences of proliferation and migration were found between early and late passage U87MG cells. In particular, we confirmed that late passage U87MG cells exhibited more epithelial phenotype with decreased PI3K/Akt pathway and TGF-ß pathway expressions at protein level. In summary, our results focused on the changes of U87MG cells during serial in vitro passage, suggested that passage-induced changes may lead to notable changes of biological characteristics and several molecular transitions in cancer cell lines, indicating the necessity to shorten experiment-span and accomplish experiments with the same or similar passage cancer cell strains.

Effects of Herpud1 in Methamphetamine-Induced Neuronal Apoptosis.

INTRODUCTION: Methamphetamine (METH) is an illicit psychoactive substance that can damage various organs in the body, especially the nervous system. We hypothesized that expression of homocysteine-inducible endoplasmic reticulum-resident with ubiquitin-like domain member 1 (Herpud1) protein would alleviate the induction of apoptosis following METH administration. METHODS: To test this hypothesis, we analysed the changes in Herpud1 expression and apoptosis in PC12 cells under different concentrations and exposure times of METH. Moreover, we examined the effects of Herpud1 knockdown on METH-induced neuronal apoptosis. Flow cytometry and Western blot analyses were used to evaluate apoptosis levels and the expression of apoptotic markers (cleaved caspase-3) in PC12 cells following Herpud1 knockdown by synthetic small interfering RNA (siRNA). RESULTS: Our results showed that Herpud1 expression was upregulated in PC12 cells following METH treatment, while endoplasmic reticulum stress (ERS) and apoptosis were also increased. Conversely, Herpud1 knockdown reduced METH-induced ERS and apoptosis levels in vitro. CONCLUSIONS: These results suggest that Herpud1 plays an essential role in METH-induced neuronal ERS and apoptosis and may represent a potential therapeutic gene target in METH-induced neurotoxicity.

Implant deformation and implant-abutment fracture resistance after standardized artificial aging: An in vitro study.

BACKGROUND AND PURPOSE: Zirconia abutments have been widely adopted in clinical implant practice. The unique mechanical properties of zirconia may significantly affect the long-term prognosis of implant treatments. The purpose of this study was to investigate the influence of abutment material on implant deformation and fracture resistance of internal conical connection implant-abutment complexes of two diameters after standardized artificial aging. MATERIALS AND METHODS: Thirty original abutments (one-piece titanium, one-piece zirconia, zirconia with alloy base) with two diameters (regular, narrow) were connected to internal conical connection implants and subjected to a standardized artificial aging process consisting of thermal cycling and mechanical cyclic loading. Microcomputed tomography (µCT) scans of implant bodies were performed before and after aging. 3-dimensional images of implant bodies were generated from the µCT scans and aligned for before and after aging to calculate the volumetric deformation amount. Finally, fracture resistance was measured using a mechanical static loading test for the surviving aged and 30 brand-new specimens. RESULTS: All specimens survived artificial aging. No significant difference in implant deformation was found in the regular groups (p = 0.095). In narrow groups, the one-piece zirconia group showed significantly less deformation (p < 0.0001). For fracture resistance, no significant decrease was observed after aging in any group (p > 0.05). One-piece zirconia abutments showed significantly lower strength than the other two materials for both diameters (p < 0.0001). CONCLUSIONS: In the regular diameter system, abutment material had no significant influence on the tested mechanical property degradation after simulated long-term oral use. The mechanical performance of narrow diameter one-piece zirconia abutments differed from the other two materials. For optimal performance, one-piece zirconia abutments should be adopted only in anterior regions.

Understanding the effect of scan spans on the accuracy of intraoral and desktop scanners.

OBJECTIVES: This study aimed to measure and compare the accuracy (trueness and precision) of intraoral scanners and desktop scanners when scanning different spans. METHODS: Three plaster models representing different spans (full arch, half arch, and three teeth) were obtained from conventional silicone impressions of a maxillary typodont and used as the scanning objects. An industrial scanner (ATOS III Triple Scan) was used to scan the three plaster models to obtain reference digital models. The plaster models were then scanned using two intraoral scanners (Trios 3 and Primescan) and two desktop scanners (LS3 and D2000) to obtain test digital models. The reference and test models were imported into professional reverse engineering software for processing and analysis. The root mean square value indicated differences between the reference and test models. Two-way ANOVA and Bonferroni multiple comparison tests were used for statistical analysis. RESULTS: Two-way ANOVA tests revealed significant differences in trueness and precision for different scan spans (p < 0.001) and different scanners (p < 0.001), which indicates that the scanner types and scan spans affect the accuracy of the scanner. There was no significant difference in the accuracy of the D2000 at three different scan spans (trueness: 23.82 ± 0.22 µm, 21.53 ± 0.18 µm, and 21.02 ± 0.27 µm respectively; precision: 7.86 ± 0.83 µm, 7.87 ± 1.11 µm, and 7.82 ± 0.84 µm respectively). For the LS3 and the two intraoral scanners, the accuracy of the full arch scan (LS 3, trueness: 33.35 ± 0.47 µm, precision:15.36 ± 3.10 µm; Trios 3, trueness: 46.92 ± 9.23 µm, precision:20.79 ± 3.08 µm; Primescan, trueness: 28.73 ± 0.77 µm, precision:15.74 ± 2.45 µm) was significantly lower than that of the half arch (LS 3, trueness: 27.27 ± 0.43 µm, precision:5.62 ± 0.88 µm; trios 3, Trueness: 22.29 ± 1.50 µm, precision:14.12 ± 2.25 µm; Primescan, trueness: 18.91 ± 0.70 µm, precision:7.94 ± 1.09 µm) and three teeth scans (LS 3, trueness: 24.68 ± 0.36 µm, precision:5.29 ± 0.62 µm; Trios 3, trueness: 16.92 ± 0.78 µm, precision:11.95 ± 2.22 µm; Primescan, trueness: 15.79 ± 0.65 µm, precision:7.68 ± 0.62 µm). CONCLUSIONS: The scan span affected the accuracy of the intraoral scanners, but not necessarily the accuracy of the desktop scanners.

One-Step In Situ Self-Assembly of Cypress Leaf-Like Cu(OH)2 Nanostructure/Graphene Nanosheets Composite with Excellent Cycling Stability for Supercapacitors.

Transition metal hydroxides and graphene composite holds great promise to be the next generation of high performance electrode material for energy storage applications. Here we fabricate the cypress leaf-like Cu(OH)2 nanostructure/graphene nanosheets composite through one-step in situ synthesis process, employed as a new type of electrode material for high efficiency electrochemical energy storage in supercapacitors. A solution-based two-electrode system is applied to synthesize Cu(OH)2/graphene hybrid nanostructure, where anodic graphene nanosheets firmly anchor cathodic Cu(OH)2 nanostructure due to the electrostatic interaction. The in situ self-assembly of Cu(OH)2/graphene ensures good structural robustness and the cypress leaf-like Cu(OH)2 nanostructure prompt to form the open and porous morphology. The hybrid structure would facilitate charge transport and effectively mitigate the volume changes during long-term charging/discharging cycles. As a consequence, the Cu(OH)2/graphene composite exhibits the highest capacitance of 317 mF/cm2 at the current density of 1 mA/cm2 and superior cyclic stability with no capacitance decay over 20,000 cycles and remarkable rate capability at increased current densities.

NiO/Ni x Co3-x O4 porous ultrathin nanosheet/nanowire composite structures as high-performance supercapacitor electrodes.

The demand for a new generation of high-safety, long-lifespan, and high-capacity power sources increases rapidly with the growth of energy consumption in the world. Here we report a facile method for preparing architecture materials made of NiO/Ni x Co3-x O4 porous nanosheets coupled with NiO/Ni x Co3-x O4 porous nanowires grown in situ on nickel foams using a hydrothermal method without any binder followed by a heat treatment process. The nanosheet-shaped NiO/Ni x Co3-x O4 species in the nanosheet matrix function well as a scaffold and support for the dispersion of the Ni x Co3-x O4 nanowires, resulting in a relatively loose and open structure within the electrode matrix. Among all composite electrodes prepared, the one annealed in air at 300 °C displays the best electrochemical behavior, achieving a specific capacitance of 270 mF cm-2 at 5 mA cm-2 while maintaining excellent stability (retaining ≈ 89% of the max capacitance after 20 000 cycles), demonstrating its potential for practical application in power storage devices.