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 »  Home  »  Dental Implant 1  »  Effects of a Modified Sandblasting Surface Treatment on Topographic and Chemical Properties of Titanium Surface
Effects of a Modified Sandblasting Surface Treatment on Topographic and Chemical Properties of Titanium Surface
Introduction - Materials and methods.

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Dehua Li, MD, DDS, PhD,
Associate Professor, Dept. of Oral and Maxillofacial Surgery, Qindu Stomatological College, Xi’an 710032, P.R. China.

Baolin Liu, MD, DDS,
Professor and Chairman, Craniofacial Implant Center, Qindu Stomatological College, Xi’an 710032, P.R. China.

Yong Han, PhD,
Associate Professor, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, P.R. China.

Kewei Xu, PhD,
Professor and Dean, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, P.R. China.

To seek ideal osseointegration is a major focus of study in contemporary oral implantology.1 The osseointegration currently achieved is far from ideal. It takes a long time for dental implants to osseointegrate ordinarily from 3–6 months2. Histologically, only capsule-like bone attachment forms at the interface, rather than the real bone-fiber-perpendicularly connecting integration (D.-H. Li, unpublished data). This is reflected clinically with lengthy therapeutics courses for most current dental implant systems (irrespective of submerged or nonsubmerged) and the detrimental periimplant alveolar bone loss resulting from the unfavorable distribution of stress at the bone interface.   Although there are immediately loaded nonsubmerged implants for shortening the time of implant therapy, they are still at the preliminary stage of development.
Surface modification of dental implants is essential for seeking the ideal osseointegration. Regarding the implant-bone interface, it was demonstrated that a rough surface is more beneficial than a smooth surface.   Several methods, such as titanium plasma spraying, sintering, hydroxylapatite coating, electrophoretic deposition, and ion-beam or radiofrequency sputtering, have been adopted with the aim of optimizing the roughness and topography of the implant surface. Nearly all of these methods are coating techniques. To enhance the interfacial biomechanical properties, these methods also present some new problems.  Of these problems, the major one is the existence of an additional interface between the coating and the substrate of the implant, which could further complicate the maintenance of osseointegration, especially with repetitive function.
Presently, as an alternative, the noncoating, surface-roughening method has drawn some attention. In light of the status of coating techniques, a modified sandblasting noncoating surface modification was developed. In vivo experimental studies initially demonstrated that it can improve osseointegration of dental implants and enhance the interfacial shear strength. This paper studies the effects of this newly developed modification on the topographic and chemical properties of the implant surface and is intended to verify its feasibility and reliability in treating titanium dental implants.


Surface Treatments of Titanium and Preparation of Samples.
A total of 27 titanium discs (10-mm diameter and 1-mm thickness) were cut from grade 2 commercially pure titanium plates (ASTM F67, unalloyed titanium for surgical implant applications), which were supplied by the Northwest Nonferrous Metal Institute (Xi’an, P.R. China). Samples were equally divided into three groups: the smooth surface (S) group, the sandblasted surface (SB) group, and the modified sandblasted surface (SBA) group. S group disks were polished through a series of silicon carbide papers to 800 grit, SB group disks were sandblasted by 0.15- to 0.21-mm corundum (Al2O3) at 0.45 MPa, and SBA group disks were etched by oxalic acid after the sandblast treatment. Before use, all samples were degreased by cleaning in trichloroethylene and ethanol using ultrasonics for 10 minutes, respectively, and passivation by immersion in 40% nitric acid for 30 minutes. They were then rinsed with distilled water three times for 5 minutes each time. After air-drying, they were used for the further tests, each of which was done on a separate disc.

Observation of Surface Topography.
Topographic variations of samples (two samples each group) were observed using a S-520 scanning electron microscope (SEM; S-520, Hitachi Co., Japan) with an energy dispersive electron probe x-ray analyzer (TN-5500, Thermo Noran, Middleton, WI) for the element analysis of surface.

Detection of Heteroelement Pollution of Titanium Surface.
Heteroelement pollution of the treated samples (two samples each group) was detected by phase composition analysis with x-ray diffraction (XRD; D/Max-3c, Rigaku Co., Japan), using monochromated CuKa radiation at 40 kV and 20 mA. Data were collected from 20 to 100 degrees, with a step size of 0.02 degrees and a count time of 0.15 second. This examination was used solely to detect the element pollution of Al2O3 on the surfaces.

Assay of Titanium Anti-Corrosiveness.
Anti-corrosiveness of titanium was examined by the in vitro titanium ion-releasing test, which was performed as follows. Samples of various groups, sterilized by autoclaving, were soaked in the sterile simulated body fluid 18 at 37°C, 2 mL per sample, and five samples per group. After soaking for 3 months, the samples were removed, and the concentration of titanium ion in the simulated body fluid was assayed using a standard curve of visible spectrometry (Shanghai 722, the 3rd of Shanghai Analytical Instrument Manufacturer, Shanghai, P.R. China) at 385 nm. A standard curve of Ti-ion concentrations, ranging from 0 to 2 mg/mL, was measured using the same testing method as described below; TiO2 was used to produce the standard solutions, which were done by dissolution of analytically pure TiO2 powder (Beijing Chemical Industry Company, Beijing, P.R. China) in 1:1 HCl.
The principle for this method is that the mixture of Ti ion and diantipyrylmethane in acidic conditions (0.25–2.00 mol/L of H2SO4) causes formation of a yellow complex compound. The measurements were performed three times for each sample, and the final value was the average. In detail, 1.5 mL per sample was transferred to a 25-mL flask, 2 mL of 1:1 H2SO4, and 2 mL of 50% ascorbic acid was added; the solution was incubated for 2 minutes; then 10 mL of 2% diantipyrylmethane was added; and finally the sample was diluted to 25 mL with distilled water. The resultant solution was incubated in a boiling-water bath for 2 minutes then cooled to room temperature. The absorbance of each sample was measured using Shanghai-722 Visible Spectrometry at 385 nm, and the corresponding Ti-ion concentration was calculated from that standard curve.