Cavitation erosion: an efficient method for promoting osteogenesis of titanium surfaces.

Description

Abstract Objective: Surface treatments of titanium dental implants may improve osseointegration and reduce the incidence of peri-implantitis. This study provides a new approach for surface modification by utilising the principle of cavitation, which can generate high temperature and pressure with micro-jets acting on the surface. Methods: Titanium surfaces were treated by cavitation (CAV), and compared with a control group (large-grit acid-etched and sand-blasted; SLA). The microscopic morphology and roughness of the titanium surfaces, as well as their effect on osteoblast and macrophage biocompatibility were measured. Results: Characteristic cavitation pits were formed on the surface following CAV treatment, and roughness was significantly increased compared to the SLA surface (p<0.05). The CAV treatment not only promoted adhesion, proliferation, and osteogenic differentiation of osteoblasts more effectively, but also facilitated the polarization of macrophages towards an anti-inflammatory phenotype. Conclusion: An innovative titanium implant surface treatment that utilises the cavitation effect has been developed and demonstrates superior biocompatibility and ability to promote osteogenesis and immunomodulation compared with conventional surface treatment methods.

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Titanium discs (15 mm diameter, 1 mm thickness) were prepared from commercially pure grade 4 (c.p. 4) Ti titanium cylinders (Baoji Titanium Industry Company, Shanxi, China) and randomly assigned randomly to each of the two study groups. Firstly, the titanium discs were immersed in acetone for 10 to 15 minutes to remove any oil stains on their surface. Subsequently, the titanium discs were rinsed with deionized water for 3 to 5 times. After that, the titanium discs were placed into ethanol and soaked for 5 to 10 min for further cleaning. Finally, it was rinsed thoroughly with deionized water and then dried with a hair dryer in cold air mode. The discs were assigned randomly to the two study groups. For the SLA group, Ti discs were subjected to grit-blasting with large-grit alumina (Al2O3, 0.2-0.5 mm diameter) at 5 bar for 1 min and etched with 1:1 mixture of H2SO4 and HCl solution for 30min at 65 °C to generate the sandblasted, large grit and acid-etched (SLA) surface. For CAV group, deionized water was added into the anti-corrosion container to completely submerge the titanium discs. The titanium discs were fixed under the probe of the ultrasonic generator, and the distance between the titanium discs and the probe was ensured to be 5 mm. In this way, the surface of the titanium discs could be effectively acted upon by the ultrasonic cavitation effect (Fig. 2). Ultrasonic cavitation is produced by the ultrasonic processor Sonics VCX 130 (Sonics, USA) which has a probe with a diameter of 6 mm and a length of 137 mm. The initial frequency was set at 20 kHz with the amplitude of 123 μm. The output power of was 130 W, and each titanium disc was treated for 20 minutes. As time passed, it could be observed that the surface of the titanium discs gradually became rough. After the experiment was completed, the titanium discs were taken out, and the residues on their surface were rinsed off with deionized water first. Then, they were soaked in anhydrous ethanol for 5 to 10 minutes for dehydration treatment, and finally, they were dried with a hair dryer in cold air mode.

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