6 research outputs found
Effects of the development changes in dentition on the retention of mouthguards
Summary The use of mouthguards is one of the main strategies that are considered effective in preventing sports–related trauma.Although mouthguards are recommended for use in children during sports activities,little is known as to how growth and developmental changes in the oral cavity, jaw, and dentition affect the retention of mouthguards. In the present study, we designed mouthguards for primary,mixed(4 types),and permanent detention stages and performed tensile testing to determine the effects of dental growth and development on their retention.We also designed mouthguards for the left maxillary second milk molar,left maxillary second premolar, and left maxillary first molar to determine how the shape of the teeth affects their retention.Data was analyzed statistically,and the following results were obtained:1.Mouthguards for permanent detention stage had a significantly higher level of retention than those for primary and mixed detention stages.2.Mouthguards for primary detention stage had a significantly lower level of retention than those for mixed and permanent detention stages. 3.The retention of mixed detention stage mouthguards became poorer with the number of teeth requiring relief.4.Differences in the shape of the teeth(left maxillary second milk molar, left maxillary second premolar, left maxillary first molar)had no significant effect on the retention of mouthguards.These findings indicate that the level of mouthguard retention is lower in children at primary and mixed detention stages than in adults and children with complete eruption of central incisor to second molar.This difference may be attributed to the differences in the coverage areas of mouthguard
Single-Step Synthesis of W2C Nanoparticle-Dispersed Carbon Electrocatalysts for Hydrogen Evolution Reactions Utilizing Phosphate Groups on Carbon Edge Sites
Single-Step Synthesis of W<sub>2</sub>C Nanoparticle-Dispersed Carbon Electrocatalysts for Hydrogen Evolution Reactions Utilizing Phosphate Groups on Carbon Edge Sites
A novel, one-step
protocol for the selective synthesis of W<sub>2</sub>C nanoparticles
from phosphotungstic acid (H<sub>3</sub>PW<sub>12</sub>O<sub>40</sub>), a low-cost and commercially available tungsten
compound, was developed. The nanoparticles had diameters of 1–50
nm and were dispersed on a carbon substrate. The W<sub>2</sub>C nanoparticles
were prepared by a simple operation sequence, involving impregnation
of carbon black with H<sub>3</sub>PW<sub>12</sub>O<sub>40</sub> followed
by calcination at 1000 °C. X-ray diffraction study revealed the
selective formation of the W<sub>2</sub>C phase in the samples prepared,
whereas the tungsten carbide (WC) phase was present in the control
prepared from H<sub>2</sub>WO<sub>4</sub>. Stable W<sub>2</sub>C nanoparticles
were obtained using this method owing to the presence of phosphate
at the interfaces between the W<sub>2</sub>C nanoparticles and the
carbon substrates, which inhibited the diffusion of carbon atoms from
the carbon substrates to the W<sub>2</sub>C nanoparticles, leading
to the formation of WC. The W<sub>2</sub>C nanoparticles prepared
showed an excellent catalytic activity for the hydrogen evolution
reaction (HER), with low Tafel slopes of ∼50 mV/decade. The
HER catalytic activity was notably high, being comparable to that
of MoS<sub>2</sub>, which is a promising alternative to Pt. The present
method can potentially be applied to produce highly effective, low-cost,
Pt-free electrocatalysts for the HER