Compositionally Disordered Doped with Cerium Crystalline Garnet Type Materials for Brighter and Faster Scintillations

Ce-doped tetracationic garnets (Gd, M)3Al2Ga3O12(M = Y, Lu) form a family of new multipurpose promising scintillation materials. The aim of this work was to evaluate the scintillation yield in the materials of quaternary garnets activated by cerium ions with partial isovalent substitution of the matrix-forming gadolinium ions by yttrium or lutetium ions.Materials were obtained in the form of polycrystalline ceramic samples, and the best results were shown by samples obtained from the raw materials produced by the coprecipitation method. It was found that ceramics obtained from coprecipitated raw materials ensure a uniform distribution of activator ions in the multi-cationic matrices, which enables the high light yield and fast scintillation kinetics of the scintillation. It was demonstrated that the superstoichiometric content of lutetium/gadolinium in the material is an effective method to suppress phosphorescence accompanied scintillation. For ceramics with the composition (Gd, Lu)3Al2Ga3O12 , a scintillation yield of more than 50.000 ph/MeV was achieved. The scintillation kinetics was measured to be close to the kinetics with a decay constant of 50 ns.In terms of the set of the parameters, the developed scintillation materials are close to the recently developed alkali halide materials LaBr3:Ce, GdBr3:Ce. Moreover, they have high mechanical hardness, are characterized by the absence of hygroscopicity, and are better adapted to the manufacture of pixel detectors used in modern devices for medical diagnostics.

The Impact of Different Types of Orthodontic Appliances and Its Location in Producing CT Scan Artefacts

Fixed orthodontic appliances can produce metal artefacts in CT images which may degrade the diagnostic image quality. The study aimed to evaluate the artefacts based on the types and location of the metallic and non-metallic orthodontic brackets. This is an in-vitro cross-sectional study. Four different types of orthodontic brackets (stainless steel, titanium, monocrystalline, and polycrystalline ceramic bracket) were bonded consecutively in four different locations of the cadaveric skull. All scans were performed by a single operator using the same CT machine followed by a standard scanning protocol. Artefact intensity for all data sets was quantified by calculating the standard deviation (SD) of the grey values within the dataset by following a standard method. The One-way ANOVA Bonferroni test was used for the data analysis. The mean artefact score of the stainless steel bracket was significantly (p < 0.001) high in comparison with other types of the orthodontic brackets. Besides, the mean artefact score was significantly (p=0.002) low when orthodontic brackets were placed unilaterally. Stainless steel brackets produced a significant amount of noise in CT images which can degrade the diagnostic image quality. Thus, the polycrystalline ceramic bracket can be a better alternative of stainless steel brackets for patient need frequent CT scan.

Thermally Resilient Planar Waveguides in Novel nc-YSZ Transparent Ceramic by fs Laser Pulses

We report on thermally resilient planar waveguides fabricated on nc-YSZ by direct fs-laser inscription in transparent nc-yttria stabilized zirconia (nc-YSZ) polycrystalline ceramic. The waveguides consisted of rectangular sections (4.5 × 2 mm2) on the surface of the sample. Optical characterization at 633 and 810 nm was performed. We estimate a laser-induced refractive index contrast of 10–4. Post-waveguide-fabrication thermal annealing treatments at 750°C for 24 h were carried out to test the resilience of the waveguides and to further reduce the waveguide losses. Both micro-Raman spectroscopy and XPS characterization revealed unmodified lattice and steady chemical features, which are consistent with the waveguide thermal resilience. Our results suggest a promising potential use of nc-YSZ in harsh and high temperature demanding photonic environments.

An Engineering Zirconia Ceramic Made of Baddeleyite

Wet high-energy milling and uniaxial pressing are used to fabricate CaO-stabilized tetragonal zirconia polycrystalline ceramic (Ca-TZP) with decent mechanical characteristics, i.e., a hardness of 11.5 GPa, Young’s modulus of 230 GPa, and fracture toughness of 13 MPa·m0.5. The effect of CaO concentration and the sintering temperature on phase composition and mechanical characteristics of CaO-stabilized zirconia ceramic made of baddeleyite is investigated.

Morphometric evaluation of the slot of aesthetic orthodontic brackets.

Introduction: : Dental malocclusion is a public health problem and orthodontics is the specialty in charge of diagnosing and treating it, aesthetic brackets are an alternative, the costs are varied, which makes its precision doubtful. Objective: Evaluate the measurement and geometry of the slot of three brands of aesthetic brackets and verify their precision. Material and Methods: Twenty-four aesthetic Roth prescription 0.022” slot polycrystalline ceramic brackets were evaluated in three brands: American Orthodontics (United States), Morelli (Brazil) and Class One (China). Eight samples were measured per group in a specialized laboratory certified in measurement and calibration, the measurements of internal and external height were verified, per mesial and distal; and the parallelism of the slot of each bracket. The results were processed with SPSS 22 and tests of variance (ANOVA), Tukey and Student's t were used. Results: The measurements of the brackets' grooves do not correspond to the measurements announced by the manufacturers, these are greater, however, American Orthodontics is within the tolerance range (p<0.01); the slots in the mesio-distal direction and the lingual vestibule are not parallel in Morelli and Class One. Conclusion: The results of this study indicate that the slots of the supports are oversized, their geometry is not precise and varies greatly between brands and prices. The three-dimensional control of the tooth could be compromised.

Effectiveness of Nanohydroxyapatite on Demineralization of Enamel and Cementum Surrounding Margin of Yttria-Stabilized Zirconia Polycrystalline Ceramic Restoration

Introduction. Prosthetic dentistry has shifted toward prevention of caries occurrence surrounding restorative margin through the anti-demineralization process. This study examines the ability of nanohydroxyapatite (NHA) gel and Clinpro (CP) on enhancing resistance to demineralization of enamel and cementum at margin of restoration. Materials and Methods. Thirty extracted mandibular third molars were segregated at 1 mm above and below cementoenamel junction (CEJ) to separate CEJ portions and substituted with zirconia disks by bonding to crown and root portions with resin adhesive. The enamel and cementum area of 4 × 4 mm2 neighboring zirconia was applied with either NHA or CP, while one group was left no treatment (NT) before demineralized with carbopal. Vickers hardness (VHN) of enamel and cementum was evaluated before material application (BM), after material application (AM), and after demineralization (AD). Analysis of variance (ANOVA) and post hoc multiple comparisons were used to justify for the significant difference (α = 0.05). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were determined for surface evaluations. Results. The mean ± SD of VHN for BM, AM, and AD for enamel and cementum was 393.24 ± 26.27, 392.89 ± 17.22, 155.00 ± 5.68 and 69.89 ± 4.59, 66.28 ± 3.61, 18.13 ± 0.54 for NT groups, respectively, 390.10 ± 17.69, 406.77 ± 12.86, 181.55 ± 7.99 and 56.01 ± 9.26, 62.71 ± 6.15, 19.09 ± 1.16 for NHA groups, respectively, and 387.90 ± 18.07, 405.91 ± 9.83, 188.95 ± 7.43 and 54.68 ± 7.30, 61.81 ± 4.30, 19.22 ± 1.25 for CP groups, respectively. ANOVA indicated a significant increase in anti-demineralization of enamel and cementum upon application of NHA or CP ( p < 0.05 ). Multiple comparisons indicated the capability in inducing surface strengthening to resist demineralization for enamel and cementum of NHA which was comparable to CP ( p > 0.05 ) as evidenced by SEM and XRD data indicating NHA and CP deposition and crystallinity accumulation. Conclusion. NHA and CP were capable of enhancing anti-demineralization for enamel and cementum. The capability in resisting the demineralization process of NHA was comparable with CP. NHA was highly recommended for anti-demineralization for enamel and cementum surrounding restorative margin.