Effect of CO2 Laser on Glazed Zircon Surface Complemented by ZrO2 Oxide

In this paper, the effect of CO2 laser on glaze-dental Zirconia ceramics after adding ZrO2 nanoparticles to glaze is introduced, and its improvement methods are studied. Specimens have been prepared using CAD/CAM dental machines and sintered at 1530o-C. Then the surface was glazed with VITA glaze plus (5% and 10%) Nano ZrO2. A 15W continuous CO2 laser was used as the indicator power to irradiate the glaze layer. The main phase of the ceramic substrate is tetragonal Zirconia, and the alumina content in the corundum phase is a certain percentage. The appearance of the varnish on the ceramic substrate changes the X-ray diffraction pattern through the appearance of new phases, which changes the crystallite size and the percentage of lattice strain. The range of grain size measured by atomic force microscopy was 88.46 nm to 62.18nm. In addition, the surface roughness was changed due to the appearance of crystal cores and grain growth. In addition, the addition of ZrO2 and laser irradiation changed the residual stress on the surface, which was reflected in the hardness value increased from 575 kg/mm2 to 1215 kg/mm2 after the laser treatment with the addition of 5% ZrO2. Generally, in terms of the structure and hardness of the surface of the glaze layer, the addition of 5% ZrO2 is better than 10%. SEM tests also showed no cracks in the central part of the treated area. These characteristics increase hardness.

The Impact of CO2 Laser Treatment and Acidulated Phosphate Fluoride on Enamel Demineralization and Biofilm Formation

Introduction: This study evaluated the impact of CO2 laser treatment and acidulated phosphate fluoride (APF) on enamel demineralization and biofilm formation, using in vitro and in situ designs. Methods: Demineralized enamel slabs were distributed among 8 groups: placebo, placebo + continuous CO2 laser, placebo + repeated CO2 laser, placebo + ultrapulsed CO2 laser, 1.23% APF, APF + continuous CO2 laser, APF + repeated CO2 laser and APF + ultrapulsed CO2 laser. In the in vitro study, 15 enamel slabs from each group were subjected to a pH-cycling regimen for 14 days. In the cross over in situ design, 11 volunteers wore palatal appliances with demineralized enamel slabs for 2 periods of 14 days each. Drops of sucrose solution were dripped onto enamel slabs 8×/day. Biofilms formed on slabs were collected and the colony-forming units (CFU) of Streptococcus mutans and Lactobacillus were determined. Results: For both in vitro and in situ studies, there was no significant difference between treatments (P>0.05). However, all treatments increased microhardness of demineralized enamel (P<0.05). After a further in situ cariogenic challenge, with the exception of the placebo, all treatments maintained microhardness values (P<0.05). Microbiological analysis showed no difference in Streptococcus mutans (P>0.05) or Lactobacillus (P>0.05) counts between groups. Conclusion: The results suggest that APF gel combined with the CO2 laser, regardless of the pulse emission mode used, was effective in controlling enamel demineralization, but none of the tested treatments was able to prevent bacterial colonization.

Study on the Properties of the Laser Cladded Cobalt-Based Alloy Coating on T10 Tool Steel

Co-based alloy coating was cladded on T10 tool steel by the powder feeding and continuous CO2 laser. The results showed that compared to the unreinforced T10 tool steel substrate, the microhardness of the Co-based reinforced composite was significantly enhanced and the maximum value was existed in the middle of the cladding coating. The corrosion resistance of the cladding coating was also improved. After cryogenic treatment, there is no obvious change for the structure of the cladding coating while the phase is transformed, leading to an increase in the microhardness of the cladding coating.

Experimental Study on Residual Stresses of Al2O3 Coating by Laser Re-Melting

The surface of Al2O3 coating sprayed on 40Cr substrate was re-melted with high power continuous CO2 laser, and its micro-hardness and residual stresses were measured, respectively. The strengthening mechanism of Al2O3 coating by laser re-melting was analyzed and discussed. The experimental results shown that the surface of Al2O3 coating by laser re-melting is neat and smooth, and its compositions are even, its structures are compact, and Al2O3 coating is evenly distributed in its surface with grain forms, and its micro-hardness increases about 200%; Residual stress of Al2O3 coating by laser re-melting is changed into compressive stress from tensile stress, which is benefit to improving bonding strength of coating-substrate interface.