Search

Objectives: The present study aimed to simulate the influence of palatal extensions for custom-made mouthguards (MGs) on protecting dentoalveolar structures and to provide a theoretical basis for designing a comfortable MG. Materials and methods: Based on finite element analysis (3D-FEA), five groups of maxillary dentoalveolar models of wearing MGs were established: no MG on palatal side (NP), on palatal gingival margin (G0), 2 mm from the palatal gingival margin (G2), 4 mm from the palatal gingival margin (G4), 6 mm from the palatal gingival margin (G6), and 8 mm from the palatal gingival margin (G8). A cuboid was created to simulate the solid ground impacted in falls, a gradually increasing force was applied from 0 to 500 N on the vertical ground, and the distribution and peak values of the Critical modified von-Mises stress, maximum principal stress, and displacement of dentoalveolar models were calculated. Results: Stress distribution range, stress, and deformation peak value of dentoalveolar models increased as the impact strength increased, at 500 N. Maximum critical modified von-Mises stress, peak maximum principal stress and maximum displacement of dentoalveolar models G4, G3, G2, G1, G0, and NP were 154.5 MPa, 154.5 MPa, 154.4 MPa, 154.7 MPa, 154.4 MPa, and 154.7 MPa; 191.65 MPa, 192.11 MPa, 191.62 MPa, 191.81 MPa, 191.56 MPa, and 191.62 MPa; and 88.78 μm, 88.57 μm, 88.19 μm, 88.67 μm, 88.43 μm, and 89.04 μ, respectively. However, the position of the MG palatal edge had little effect on stress distribution, stress, and deformation peak values of the dentoalveolar models. Conclusions: Different extension ranges of the MG palatal edge have little effect on the protective effects of MGs on maxillary teeth and maxilla. An MG with palatal extension on the gingival margin is more appropriate than other models and may help dentists to design a suitable MG and increase its usage. Clinical relevance: MGs with palatal extensions on the gingival margin may provide a more comfortable wearing experience for individuals involved in sports and encourage increased MG usage. [ABSTRACT FROM AUTHOR]

The present paper reports the first stage of the study by the present group on the thermal decomposition of La2Mo2O9 under lower oxygen partial pressure. The stability of La2Mo2O9 at 1473 K in an oxygen partial pressure $$ (p_{{{\rm O}_{2} }} ) $$ ranges from 2.44 × 10 to 4.33 × 10 Pa was studied by XRD. The results showed that La2Mo2O9 could remain stable in a $$ p_{{{\rm O}_{2} }} $$ range greater than 2.44 × 10Pa. While below this $$ p_{{{\rm O}_{2} }} $$, the formation of several reduced and crystallized molybdates were found. By means of XRD, TEM, SAED, and EDS, the decomposition process of La2Mo2O9 at 1473 K under $$ p_{{{\rm O}_{2} }} $$ of 9.75 × 10Pa was investigated. The intermediate and final products formed during the thermal decomposition were characterized. It was found that the La2Mo2O9 decomposition consisted of two steps. La2Mo2O9 first decomposed to intermediate products like LaMo2O5, La5Mo4O14, and La12Mo6O35 and then to final products like La5Mo3O16 and a new Mo-rich compound. Tilt series of SAED patterns of this new structure were recorded. These measurements were used for the reconstruction of the reciprocal space. The cell attained was monoclinic with parameters: a ≈ 1.195 nm, b ≈ 4.133 nm, c ≈ 1.314 nm, and β ≈ 95°. [ABSTRACT FROM AUTHOR]

The tetragonal TbPO was controlled synthesized via a simple solvothermal route by using glycol as solvent. The structures and micromorphologies of the as-synthesized TbPO have been investigated by means of X-ray powder diffraction (XRD) and field-emission scanning electronic microscopy (FE-SEM). The results showed that the tetragonal TbPO are composed of square-like particles about 200 nm in diameter. The photoluminescence spectra exhibited that the emission spectra of the sample could be divided into two parts, representing the D → F (J = 6, 5, 4, 3) transitions and D → F (J = 6, 5, 4, 3) transitions of Tb. [ABSTRACT FROM AUTHOR]