Litong Guo

Effect of Surface Modifications on the Bonding Strength of Titanium–Porcelain

Investigations of surface modifications on cast titanium surfaces and titanium–porcelain adhesion were performed. Cast pure titanium was subjected to surface modifications by sandblasting, preoxidation, and SnO x coating by sol-gel process. The adhesion between the titanium and porcelain was evaluated by a three-point flexure bonding test. The X-ray diffraction (XRD) and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) results revealed that failure of the titanium–porcelain predominantly occurred at the titanium–oxide interface after sandblasting and preoxidation treatments. The SnO x film with small spherical pores obtained at 300°C served as an effective oxygen diffusion barrier and improved titanium–porcelain adhesion. With the temperature elevated, SnO was oxidized to SnO2 and the film microcracked, which resulted in the decrease of the titanium–porcelain bonding strength.

Preparation and characterization of a titanium bonding porcelain

The titanium bonding porcelain was synthesized through normal melting-derived route using borate-silicate system. The porcelain was characterized by thermal expansion, X-ray diffraction, scanning electron microscope and cytotoxicity tests. The results of X-ray diffraction showed that the main phase of the bonding porcelain was SnO2. The SnO2 microcrystals precipitated from the glass matrix when the SnO2 content was increased. The thermal expansion coefficient of bonding porcelains decreased with the increasing concentration of SiO2. The thermal expansion coefficient of bonding porcelains first decreased slightly with the increasing of B2O3 concentration (from 0 wt% to 10 wt%) and then increased to about 9.4×10(-6)/°C(from 10 wt% to 12 wt%). As an intermediate, B2O3 can act as both network formers and modifiers, depending on the relationship between the concentration of basic oxides and intermediates. The Vickers hardness of bonding porcelains increased with the increase of SnO2 concentration. When SnO2 concentration was 6 wt%, only Si and Sn elements attended the reaction between titanium and porcelain and mainly adhesive fracture was found at Ti-porcelain interface. When SnO2 concentration was 12 wt%, failure of the titanium-porcelain predominantly occurred in the bonding porcelain and mainly cohesive fracture was found at Ti-porcelain interface. The methyl thiazolyl tetrazolium assay results demonstrated that the cytotoxicity of the titanium porcelain was ranked as 0.

Biological properties of nanostructured Ti incorporated with Ca, P and Ag by electrochemical method

TiO2 nanotube arrays were synthesized on Ti surface by anodic oxidation. The elements of Ca and P were simultaneously incorporated during nanotubes growth in SBF electrolyte, and then Ag was introduced to nanotube arrays by cathodic deposition, which endowed the good osseointegration and antibacterial property of Ti. The bioactivity of the Ti surface was evaluated by simulated body fluid soaking test. The biocompatibility was investigated by in vitro cell culture test. And the antibacterial effect against Staphylococcus aureus was examined by the bacterial counting method. The results showed that the incorporation of Ca, P and Ag elements had no significant influence on the formation of nanotube arrays on Ti surface during electrochemical treatment. Compared to the polished or nanotubular Ti surface, TiO2 nanotube arrays incorporated with Ca, P and Ag increased the formation of bone-like apatite in simulated body fluid, enhanced cell adhesion and proliferation, and inhibited the bacterial growth. Based on these results, it can be concluded that the nanostructured Ti incorporated with Ca, P and Ag by electrochemical method has promising applications as implant material.

Synthesis and Characterization of SiO2 Coating on Cast Pure Titanium

The silicon coating was deposited by sol–gel dipping process as intermediate layer to minimize titanium oxidation for Ti-porcelain restorations. The effect of silicon coating on bonding strength of titanium–porcelain was investigated. The adhesion between the titanium and porcelain was evaluated by three-point flexure bonding test. The result of TG-DSC analysis showed that the optimal treating temperature for SiO2 coating was 300°C. Silicon coating was effective in preventing titanium oxide layer formation and improving bonding strength. The improvement in bonding strength of titanium–porcelain was about 10%. At the same time, the in vitro bioactivity of the titanium and SiO2 coating was studied by cytotoxicity test. The methyl thiazolyl tetrazolium assay results demonstrated that the cytotoxicities of SiO2 coating were ranked as 0. The SEM results revealed the existence of microcrack on the SiO2 coating surface. Failure of the titanium–porcelain predominantly occurred at the titanium-oxide interface. The SiO2 coating increased bonding strength of titanium–porcelain and could be used for dental implant materials.

Comparison of laser-induced damage in Ta2O5 and Nb2O5 single-layer films and high reflectors

Ta2O5 and Nb2O5 films are deposited on BK7 glass substrates using an electron beam evaporation method and are annealed at 673 K in the air. In this letter, comparative studies of the optical transmittance, microstructure, chemical composition, optical absorption, and laser-induced damage threshold (LIDT) of the two films are conducted. Findings indicate that the substoichiometric defect is very harmful to the laser damage resistance of Ta2O5 and Nb2O5 films. The decrease of absorption improves the LIDT in films deposited by the same material. However, although the absorption of the Ta2O5 single layer is less than that of the Nb2O5 single layer, the LIDT of the former is lower than that of the latter. High-reflective (HR) coatings have a higher LIDT than single layers due to the thermal dissipation of the SiO2 layers and the decreased electric field intensity (EFI). In addition, the Nb2O5 HR coating achieves the highest LIDT at 25.6 J/cm2 in both single layers and HR coatings.

Sol-gel Synthesis of Hybrid Coating to Improve Titanium–Porcelain Bonding

The hybrid coating was synthesized on titanium by sol-gel process. Three-point flexure test was used to investigate the adhesion between porcelain–Ti. The structure and micromorphology of titanium specimens were tested by X-ray diffraction and scanning electron microscopy. With decreasing the silicon content, the gel time and stability of the sol increased accordingly, indicating the increased stability of the sol. A coherent coating with SnO nanoparticles was deposited on titanium. The porcelain–Ti bonding strength and corrosion resistance were enhanced by the hybrid coating. The porcelain–Ti bonding strength maintained constant during immersion in neutral saliva and neutral saliva containing fluorine ion, respectively. However, bonding strength decreased from 49 to 35 MPa after immersion in acidic saliva containing fluorine ion of 100 ppm.

Mullite Fibers Prepared by Sol-Gel Method Using Aluminum Chloride Aluminum Isopropoxide and Tetraethylorthosilicate

Mullite fibers with good flexibility were prepared from an aqueous water solution of aluminum chloride (AC), aluminum isopropoxide (AIP), tetraethylorthosilicate (TEOS) by the sol-gel process. Aluminosilicate spinnable sol (pH=2) with the stoichiometric mullite composition (Al:Si = 3:1, AIP/AC = 2:1) was prepared. The removal of organic and chlorine was completed at 800°C. The complete transformation to mullite was observed at 1200°C by X-ray diffraction (XRD). The lateral and circumferential cracks were showed in the results of scanning electron microscopy (SEM) when fibers were sintered at 10°C min−1. It was useful for preparation of fibers with smooth surface and uniform diameter by controlling the sintering schedule.

Effect of Anodization on Titanium-Porcelain Bonding

The effects of anodization processes on titanium-porcelain bonding were investigated. The morphologies and phase structures were evaluated by field-emission scanning electron microscopy (F-SEM) and X-ray diffraction (XRD). The bonding strength was investigated by three-point flexure test. The corrosion resistance of titanium in artificial saliva was investigated. The SEM results showed that a titanium oxide film with submicron stripes and nano-pores could be prepared by anodization and HF acid pretreatment. This titanium oxide film increased chemical bonding and mechanical interlocking between titanium and porcelain. The anodization process also enhanced the corrosion resistance of the titanium, which led to the increase of corrosion durability of the Ti-porcelain bonding strength.

Synthesis and characterisation of alumina fibres using organic/inorganic composite sol

Abstract The polyvinyl butyral–Al(NO3)3 composite sols and alumina fibres were synthesised by the sol–gel process in an aqueous solution using the polyvinyl butyral (PVB) and Al(NO3)3.9H2O (AN). The viscosity of PVB–AN composite sol increased with increasing AN content and aging time when it was laid at room temperature. The addition of AN leads to the formation of new weak peak and the deviation of diffraction angle to higher degrees according to the X-ray diffraction patterns (XRD). The exothermic peak of PVB disappeared and a weak endothermic peak was observed in differential scanning calorimetry curves of composite powders. The XRD pattern of fibres sintered at 1200°C showed the formation of α-alumina and the fibres showed smooth surface and uniform diameter.

Surface Roughness and Hydrophilicity of Titanium after Anodic Oxidation

Abstract Anodic oxidation was applied to prepare the nanostructured titanium surface with different roughnesses and hydrophilicities. The morphology was characterized by scanning electron microscopy (SEM). The surface roughness was tested by atomic force microscopy (AFM), and the hydrophilicity was assessed from the contact angle between the deionized water and sample surface at room temperature. The results show that surface morphologies change remarkably with applied voltage and oxidation time during anodic oxidation. Under optimized oxidation conditions, well-ordered nanotube arrays were fabricated on the Ti surface. Roughness values increase with increase of the oxidation time, ranging from several dozen to several hundred nanometers, while the influence of voltage on surface roughness is not obvious. The hydrophilicity increases initially with the increase of oxidation time, but then decrease. The variations of surface morphology, roughness and hydrophilicity are correlated to the reactions occurring during the anodic oxidation.