Liza Pelyhe

Investigation of the mechanical and chemical characteristics of nanotubular and nano-pitted anodic films on grade 2 titanium dental implant materials

OBJECTIVE The objective of this study was to investigate the reproducibility, mechanical integrity, surface characteristics and corrosion behavior of nanotubular (NT) titanium oxide arrays in comparison with a novel nano-pitted (NP) anodic film. METHODS Surface treatment processes were developed to grow homogenous NT and NP anodic films on the surface of grade 2 titanium discs and dental implants. The effect of process parameters on the surface characteristics and reproducibility of the anodic films was investigated and optimized. The mechanical integrity of the NT and NP anodic films were investigated by scanning electron microscopy, surface roughness measurement, scratch resistance and screwing tests, while the chemical and physicochemical properties were investigated in corrosion tests, contact angle measurement and X-ray photoelectron spectroscopy (XPS). RESULTS AND DISCUSSION The growth of NT anodic films was highly affected by process parameters, especially by temperature, and they were apt to corrosion and exfoliation. In contrast, the anodic growth of NP film showed high reproducibility even on the surface of 3-dimensional screw dental implants and they did not show signs of corrosion and exfoliation. The underlying reason of the difference in the tendency for exfoliation of the NT and NP anodic films is unclear; however the XPS analysis revealed fluorine dopants in a magnitude larger concentration on NT anodic film than on NP surface, which was identified as a possible causative. Concerning other surface characteristics that are supposed to affect the biological behavior of titanium implants, surface roughness values were found to be similar, whereas considerable differences were revealed in the wettability of the NT and NP anodic films. CONCLUSION Our findings suggest that the applicability of NT anodic films on the surface of titanium bone implants may be limited because of mechanical considerations. In contrast, it is worth to consider the applicability of nano-pitted anodic films over nanotubular arrays for the enhancement of the biological properties of titanium implants.

Review: the potential impact of surface crystalline states of titanium for biomedical applications

Abstract In many biomedical applications, titanium forms an interface with tissues, which is crucial to ensure its long-term stability and safety. In order to exert control over this process, titanium implants have been treated with various methods that induce physicochemical changes at nano and microscales. In the past 20 years, most of the studies have been conducted to see the effect of topographical and physicochemical changes of titanium surface after surface treatments on cells behavior and bacteria adhesion. In this review, we will first briefly present some of these surface treatments either chemical or physical and we explain the biological responses to titanium with a specific focus on adverse immune reactions. More recently, a new trend has emerged in titanium surface science with a focus on the crystalline phase of titanium dioxide and the associated biological responses. In these recent studies, rutile and anatase are the major two polymorphs used for biomedical applications. In the second part of this review, we consider this emerging topic of the control of the crystalline phase of titanium and discuss its potential biological impacts. More in-depth analysis of treatment-related surface crystalline changes can significantly improve the control over titanium/host tissue interface and can result in considerable decreases in implant-related complications, which is currently a big burden on the healthcare system.

Kinking Resistance of Guidewires

The guidewire is a small diameter, steerable wire which facilitates the navigation of the interventional devices such as stent, balloon, or coil in endovascular intervention. The guidewire has an elongated flexible body and a relatively more flexible ribbon tip. The elongated body (shaft) is tapered to the ribbon tip. The composition of the helical coil formed ribbon tip is different than the elongated body. In this article we demonstrate the correlation between the material composition and the kinking resistance of guidewire. The identified metal composition of the core wire was 18-8 stainless steel and the helical coil composed of platinum-nickel alloy and the material of tip bond was tin. The kink angle which caused permanent deformation were significantly higher on the helical coil (=68,3o) due to the higher flexibility of the helical coil than that was found on the shaft portion (=55o) (p=0,00032). The remnant angel induced by 90o kinking on the helical coil was significantly lower (=15o) than that was observed on the shaft portion (=23,9o) (p=0,00046). The deformation of the helical coil was smaller due to the higher flexible properties of the platinum-nickel alloy material against the stainless steel.

Determination of the Guidewire’s Visibility

The purpose of our research was the development of a new algorithm to the objective quantification of guidewire’s visibility; which is suitable for the classification and comparison of different guidewires, according to this property. The guidewire is a flexible medical device, over which the catheter or the dilator is lead into the vascular system to assist the insertion and position of these devices. During the insertion and the removal of guidewire the movement of distal end is monitored under fluoroscopy. At the beginning of our experiments two algorithms were developed and applied: the first one investigated the total distal end, while the second one investigated two parts of the distal end. Both algorithms were tested on ten guidewires made of same brand and material, so their relative visibility (the visibility of guidewire’s investigated part compared the background) were determined by both method. The average relative visibility was 19.8%±3.0% in case of algorithm for total distal end, and it was 21.5%±2.9% in case of algorithm for two part of distal end. The coefficient of variation was calculated in case of both algorithms, thus characterized by their reliability. Both coefficient of variation were low (0.15 and 0.13), so the algorithms were considered to be reliable. The two algorithm were no significant different (p=0.15), therefore the investigation of the total distal end might be replaced by the investigation of two parts.

Determination of the Reliability of Guidewires' Visibility Measurement

In this study, the repeatability (variation in measurements) and reproducibility (precision between measuring persons) of a measuring method, developed by us, for quantifying the visibility of guidewires was investigated. Visibility was determined on a percentage scale against the background. The measuring method was tested by two persons with three repeats using X-ray images. Images were made from ten guidewires with the same material and type. X-ray images were made with the same settings on different days. Coefficients of variation (standard deviation as a proportion of the mean) for three repeats did not exceed 0.10 in measurement. Therefore, our method was repeatable. The average difference between the persons was 4 %, therefore our method was reproducible. Coefficients of variation for the mean of the ten images were under 0.10. Therefore, the images made with the same settings on different days could be averaged in case of the same samples. Significantly, there was a difference (p = 0.04) between the three tests by the first person. There were no significant differences in case of the second person (p = 0.74), and between the three-three test (p = 0.21). Using this method, available guidewires can be tested under laboratory conditions, so they may become comparable based on their visibility.

FLEXIBILITY TEST OF THE TOOLS OF ANGIOPLASTY

Coronary angioplasty is a procedure used to treat the narrowed coronary arteries. Physicians operate with many different tools during the intervention, the main devices are the following: guidewires, guiding catheters, balloon catheters and stents. One of the most important properties of the tools of angioplasty is flexibility. This article introduces a flexibility measuring device and a testing method. With the help of this the flexibility of the tools of angioplasty can be compared easily.

Pliability and deflection of diagnostic catheters

INTRODUCTION The cardiac catheter is an intravascular catheter, which is introduced or implanted into the heart for diagnostic or therapeutic reasons. The catheters may break or king during their introduction and/or removal. AIM The aim of the authors was to study the pliability of two catheters with the same material but different diameters according to the Food and Drug Administrations recommendation. METHOD The bending points, diameter decrease, deflection, and their correlation and dependence on the distance from the tip, as well as the influence of the initial diameter of the catheters were determined. The bending of catheters was performed on 9 bending points (120-280 mm from the tip by 20 mm) on 16 gauges with different radius (10-2.5 mm by 0.5 mm). RESULTS A linear dependency between the diameter decrease and deflection was observed, which was independent from the placement of the measurement in both catheters examined. The larger initial diameter had significant (p = 0.05) greater diameter decrease than the smaller, but the curves characteristic of the diameter decrease and deflection were similar. CONCLUSIONS The applied method seems to be useful for the examination of weak points of cardiac catheters.