Effect of CO2 laser power intensity on the surface morphology and friction behavior of alumina ceramic brackets

Tailoring an Interface Microstructure for High-Performance Reversible Protonic Ceramic Electrochemical Cells via Soft Lithography

Micropatterning is considered a promising strategy for improving the performance of electrochemical devices. However, micropatterning on ceramic is limited by its mechanically fragile properties. This paper reports a novel imprinting-assisted transfer technique to fabricate an interlayer structure in a protonic ceramic electrochemical cell with a micropatterned electrolyte. A dense proton-conducting electrolyte, BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3-δ, is micropatterned in a chevron shape with the highest aspect ratio of patterns in electrode-supported cells to the best of our knowledge, increasing surface areas of both electrode sides more than 40%. The distribution of relaxation time analysis reveals that the chevron-patterned electrolyte layer significantly increases the electrode contact areas and active electrochemical reaction sites at the vicinity of the interfaces, contributing to enhanced performances of both the fuel cell and electrolysis operations. The patterned cell demonstrates improved fuel cell performance (>45%) and enhances electrolysis cell performance (30%) at 500 °C. This novel micropatterning technique is promising for the facile production of layered electrochemical cells, further opening a new route for the performance enhancement of ceramic-based electrochemical cells.

Effects of Diode and Nd:YAG Laser Irradiation on Friction Forces Between Two Types of Ceramic Brackets and Rhodium-Coated Archwires

Introduction: Ceramic brackets have gained increasing popularity among dental clinicians and orthodontic patients but friction is a major concern when using them. This study sought to assess the effects of diode and Nd:YAG (neodymium-doped yttrium aluminum garnet) laser irradiation on friction forces between two types of ceramic brackets and rhodium-coated esthetic archwires. Methods: Thirty polycrystalline and 30 poly-sapphire brackets were divided into 6 groups (n=10) as follows: (I) control polycrystalline brackets (no laser irradiation), (II) polycrystalline brackets subjected to diode laser irradiation, (III) polycrystalline brackets subjected to Nd:YAG laser irradiation, (IV) control poly-sapphire brackets (no laser irradiation), (V) poly-sapphire brackets subjected to diode laser irradiation, and (VI) poly-sapphire brackets subjected to Nd:YAG laser irradiation. The bracket slots were laser-irradiated on a custom-made table. Sixty 5-cm pieces of rhodium-coated archwires were used for the friction test in a universal testing machine at a speed of 10 mm/min. Ten brackets from the six groups underwent scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). Results: The frictional resistance value of polycrystalline brackets was significantly higher than that of poly-sapphire brackets, irrespective of laser type (P <0.05). Irradiation of diode and Nd:YAG lasers, compared with the control group, had no significant effect on friction, irrespective of bracket type (P >0.05). Conclusion: It appears that diode and Nd:YAG laser irradiation cannot significantly decrease the friction. Future studies are warranted on different laser types with variable exposure.

Comparison of force loss due to friction of different wire sizes and materials in conventional and new self-ligating orthodontic brackets during simulated canine retraction

AIMS

The aim of this study was to compare force loss due to friction (Fr) during simulated canine retraction using different archwire dimensions and materials between conventional and new self-ligating brackets.

METHODS

The tested brackets were (1) conventional brackets (Victory series, GAC twin and FLI twin), (2) self-ligating brackets (Damon-Q, FLI-SL, new/improved FLI-SL (I FLI-SL), SPEED, GAC innovation (R) and Ortho Classic) and (3) a low-friction bracket (Synergy). All brackets had a 0.022″ slot size. The tested archwires were stainless steel (0.018″; 0.016″x0.022″; 0.017″x0.025″; 0.018″x0.025″ and 0.019″x0.025″); nickel titanium (NiTi; 0.016″x0.022″; 0.017″x0.025″; 0.018″x0.025″ and 0.019″x0.025″) and titanium molybdenum alloy (TMA; 0.016″x0.022″; 0.017″x0.025″; 0.018″x0.025″ and 0.019″x0.025″). Canine retraction was experimentally simulated in a biomechanical set-up using a NiTi coil spring that delivered a force of 1 N. The simulated retraction path was up to 4 mm. Force loss due to friction was compared between groups using the Welch t‑test.

RESULTS

Force loss due to friction increased with increasing archwire size. Also, TMA showed the highest and stainless steel the lowest force loss due to friction. FLI-SL brackets showed the lowest Fr (31%) and Ortho Classic showed the highest (67%).

CONCLUSIONS

Increasing wire size generally showed increasing force loss due to friction. FLI-SL brackets showed the lowest, while Ortho Classic showed the highest friction.