Titanium alloy material (TC4) samples were treated with nitriding technique. The dynamic friction and wear behavior of the modified layer were examined on a reciprocating sliding rig in artificial saliva. Microhardness, depth profile and wear mechanisms were investigated by means of MVK-H12, TALYSURF6, XPS and microscopy. The results demonstrate that after being treated with nitriding technique the titanium alloy material (TC4) has better tribological behavior and up-graded wear resistance. The wear mechanism involves adhesion.
Adsorption ; Biocompatible Materials ; Dental Alloys ; chemistry ; Dental Materials ; Dental Prosthesis ; Electricity ; Friction ; Humans ; Materials Testing ; Surface Properties ; Titanium ; chemistry

Objective To understand the types, proportions, and radiation dose levels of pediatric cardiac interventional procedures. Methods A retrospective analysis was conducted using the basic information and radiation dose data from all cases of pediatric cardiac interventional procedures performed at two tertiary medical institutions in Beijing from July 2023 to August 2024. The data included air kerma-area product, reference point air kerma, and fluoroscopy time. Descriptive statistical analysis was conducted to evaluate the basic information and dosimetric indicators of the procedures. Non-parametric tests were employed to examine the differences between variables, and Spearman’s correlation coefficient was utilized to investigate the relationships among various factors. All cases were categorized into the diagnostic group and the therapeutic group. In the diagnostic group, the majority of procedures involved catheter examinations and angiography for identifying the type of disease. In the therapeutic group, the primary procedures included patent ductus arteriosus, atrial septal defect, ventricular septal defect, patent foramen ovale, pulmonary stenosis, radiofrequency catheter ablation, major aortopulmonary collateral arteries, complex congenital heart diseases, and other interventional procedures. Results The survey comprised 1008 cardiac interventional procedures involving 476 males and 532 females. The ages of the participants ranged from 0 to 15 years and the body weights from 4.5 to 105 kg. Among these participants, 92 and 916 were classified in the diagnostic and therapeutic groups, respectively. The proportions of interventional procedures were in the order of atrial septal defect (36.9%), radiofrequency catheter ablation (22.3%), patent ductus arteriosus (15.1%), complex congenital heart disease (4.8%), patent foramen ovale (3.1%), pulmonary stenosis (3.1%), ventricular septal defect (2.2%), other procedures (2.0%), and major aortopulmonary collateral arteries (1.5%). The radiation doses of different interventional procedures were statistically different (P < 0.05), with air kerma-area product ranging from 0.02 to 658.4 Gy·cm², reference point air kerma from 0.1 to 2524 mGy, and fluoroscopy time from 0.2 to 62 min. Conclusion In pediatric cardiac interventional procedures, there is considerable variability in radiation doses for the same type of procedure. Additionally, radiation doses for identical procedures vary between different medical institutions, and a few cases carry a risk of deterministic effects.