Biomineralized diamond-like carbon films with incorporated titanium dioxide nanoparticles improved bioactivity properties and reduced biofilm formation.

Recently, the development of coatings to protect biomedical alloys from oxidation, passivation and to reduce the ability for a bacterial biofilm to form after implantation has emerged. Diamond-like carbon films are commonly used for implanted medical due to their physical and chemical characteristics, showing good interactions with the biological environment. However, these properties can be significantly improved when titanium dioxide nanoparticles are included, especially to enhance the bactericidal properties of the films. So far, the deposition of hydroxyapatite on the film surface has been studied in order to improve biocompatibility and bioactive behavior. Herein, we developed a new route to obtain a homogeneous and crystalline apatite coating on diamond-like carbon films grown on 304 biomedical stainless steel and evaluated its antibacterial effect. For this purpose, films containing two different concentrations of titanium dioxide (0.1 and 0.3g/L) were obtained by chemical vapor deposition. To obtain the apatite layer, the samples were soaked in simulated body fluid solution for up to 21days. The antibacterial activity of the films was evaluated by bacterial eradication tests using Staphylococcus aureus biofilm. Scanning electron microscopy, X-ray diffraction, Raman scattering spectroscopy, and goniometry showed that homogeneous, crystalline, and hydrophilic apatite films were formed independently of the titanium dioxide concentration. Interestingly, the diamond-like films containing titanium dioxide and hydroxyapatite reduced the biofilm formation compared to controls. A synergism between hydroxyapatite and titanium dioxide that provided an antimicrobial effect against opportunistic pathogens was clearly observed.

A new silica-infiltrated Y-TZP obtained by the sol-gel method.

OBJECTIVE: The aim of this study was to evaluate silica infiltration into dental zirconia (VITA In-Ceram 2000 YZ, Vita Zahnfabrik) and its effects on zirconia's surface characteristics, structural homogeneity and bonding to a resin cement. METHODS: Infiltration was performed by immersion of the pre-sintered zirconia specimens in silica sols for five days (ZIn). Negative (pure zirconia specimens, ZCon-) and positive controls (specimens kept in water for 5 days, ZCon+) were also performed. After sintering, the groups were evaluated by X-ray diffraction (XRD), grazing angle X-ray diffraction (DRXR), scanning electron microscopy (SEM), contact angle measurements, optical profilometry, biaxial flexural test and shear bonding test. Weibull analysis was used to determine the Weibull modulus (m) and characteristic strength (σ0) of all groups. RESULTS: There were no major changes in strength for the infiltrated group, and homogeneity (m) was also increased. A layer of ZrSiO4 was formed on the surface. The bond strength to resin cement was improved after zirconia infiltration, acid conditioning and the use of an MDP primer. CONCLUSION: The sol-gel method is an efficient and simple method to increase the homogeneity of zirconia. Infiltration also improved bonding to resin cement. CLINICAL SIGNIFICANCE: The performance of a zirconia infiltrated by silica gel improved in at least two ways: structural homogeneity and bonding to resin cement. The infiltration is simple to perform and can be easily managed in a prosthesis laboratory.

Quantitative phase analysis from X-ray diffraction in Y-TZP dental ceramics: a critical evaluation.

UNLABELLED: The dentistry literature shows consensus to use the Garvie and Nicholson equation modified by Toraya to quantify the Y-TZP phase transformation. However, this method does not include the possibility of cubic phase transformation and crystallographic texture after artificial ageing, and in this case, it is possible to observe errors of quantification. OBJECTIVES: The aim of this study was to evaluate a dental Y-TZP ageing kinetic of phase transformation under pressure and hydrothermal conditions (130°C, 2bar) and to compare the methods of quantification by the equation of Garvie and Nicholson modified by Toraya and the Rietveld refinement method. METHODS: Discs of Y-TZP (12mm Ø×1.2mm in height) were divided into groups (n=4) according to the ageing times (in the range of 6 and 138h). The superficial characterisation was made using SEM and the XDR for crystallographic analysis. RESULTS: An aggressive superficial degradation process at the beginning of phase transformation in 6-10h of ageing was observed by SEM. The phase transformation quantification showed differences between the methods. It was observed the increase and stabilisation of monoclinic phase until 80% at 40h of ageing by the Garvie and Nicholson modified by Toraya equation, compared to 60% of monoclinic phase and approximately 30% of cubic phase observed by the Rietveld method. CONCLUSION: The Toraya equation showed an overestimated result of monoclinic quantification compared to the Rietveld method. CLINICAL SIGNIFICANCE: The overestimated result of monoclinic phase could lead to different interpretation about the dental Y-TZP ageing process.

Biomimetic calcium phosphate coating on Ti-7.5Mo alloy for dental application.

Titanium and its alloys have been used as bone-replacement implants due to their excellent corrosion resistance and biocompatibility. However, a titanium coating is a bioinert material and cannot bond chemically to bone tissue. The objective of this work was to evaluate the influence of alkaline treatment and heat treatment on the formation of calcium phosphate layer on the surface of a Ti-7.5Mo alloy after soaking in simulated body fluid (SBF). Thirty six titanium alloy plates were assigned into two groups. For group I, samples were immersed in a 5.0-M NaOH aqueous solution at 80°C for 72 h, washed with distilled water and dried at 40°C for 24 h. For group II, after the alkaline treatment, samples were heat-treated at 600°C for 1 h in an electrical furnace in air. Then, all samples were immersed in SBF for 7 or 14 days to allow the formation of a calcium phosphate coating on the surface. The surfaces were characterized using SEM, EDS, AFM and contact angle measurements.