A review of focused ion beam milling techniques for TEM specimen preparation

Cubic boron nitride (cBN) has a number of highly desirable mechanical, thermal, electrical, and optical properties. Because of this, there has been an extensive worldwide effort to synthesize thin films of cBN. Film synthesis is difficult in that without significant levels of ion bombardment during growth, only sp2-bonded BN forms, not sp3-bonded cBN. Recently there has been considerable progress in improving the deposition techniques and cBN film quality. In addition, progress has been made in understanding how energetic deposition conditions can lead to cBN formation. However, unanswered questions remain and process improvements are still needed. In this paper we critically and comprehensively review recent developments in cBN film synthesis and characterization. First, the structures and stability of the BN phases and characterization techniques are described. Next, the key experimental parameters controlling cBN film formation and synthesis techniques are discussed. Following a review of microstructure, the proposed mechanisms of cBN formation and the observed mechanical and electrical properties of cBN films are analyzed. We conclude by highlighting the current impediments to the practical realization of cBN-film technology.

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Review of advances in cubic boron nitride film synthesis

The Guided Bone Regeneration (GBR) treatment concept advocates that regeneration of osseous defects is predictably attainable via the application of occlusive membranes, which mechanically exclude non-osteogenic cell populations from the surrounding soft tissues, thereby allowing osteogenic cell populations originating from the parent bone to inhabit the osseous wound. The present review discusses the evolution of the GBR biological rationale and therapeutic concept over the last two decades. Further, an overview of the GBR research history is provided with specific focus on the evidence available on its effectiveness and predictability in promoting the regeneration of critical size cranio-maxillo-facial defects, the neo-osteogenesis potential and the reconstruction of atrophic alveolar ridges before, or in conjunction with, the placement of dental implants. The authors conclude that future research should focus on (a) the investigation of the molecular mechanisms underlying the wound healing process following GBR application; (b) the identification of site and patient related factors which impact on the effectiveness and predictability of GBR therapy and (c) the evaluation of the pathophysiology of the GBR healing process in the presence of systemic conditions potentially affecting the skeletal system.To cite this article:Retzepi M, Donos N. Guided Bone Regeneration: biological principle and therapeutic applications.Clin. Oral Impl. Res. 21, 2010; 567-576.doi: 10.1111/j.1600-0501.2010.01922.x.

Guided Bone Regeneration: biological principle and therapeutic applications

Use of titanium as biomaterial is possible because of its very favorable biocompatibility with living tissue. Titanium implants having calcium phosphate coatings on their surface show good fixation to the bone. This review covers briefly the requirements of typical biomaterials and narrowly focuses on the works on titanium. Calcium phosphate ceramics for use in implants are introduced and various methods of producing calcium phosphate coating on titanium substrates are elaborated. Advantages and disadvantages of each type of coating from the view point of process simplicity, cost-effectiveness, stability of the coatings, coating integration with the bone, cell behavior, and so forth are highlighted. Taking into account all these factors, the efficient method(s) of producing these coatings are indicated finally.

Calcium phosphate-based coatings on titanium and its alloys

New promising techniques for depositing biocompatible hydroxyapatite-based coatings on biocompatible metal substrates for biomedical applications have continuously been exploited for more than two decades. Currently, various experimental deposition processes have been employed. In this review, the two most frequently used deposition processes will be discussed: a sol-gel dip coating and an electrochemical deposition. This study deliberates the surface morphologies and chemical composition, mechanical performance and biological responses of sol-gel dip coating as well as the electrochemical deposition for two different sample conditions, with and without coating. The review shows that sol-gel dip coatings and electrochemical deposition were able to obtain the uniform and homogeneous coating thickness and high adherent biocompatible coatings even in complex shapes. It has been accepted that both coating techniques improve bone strength and initial osseointegration rate. The main advantages and limitations of those techniques of hydroxyapatite-based coatings are presented. Furthermore, the most significant challenges and critical issues are also highlighted.

A review of hydroxyapatite-based coating techniques: Sol-gel and electrochemical depositions on biocompatible metals.

Many techniques for the surface modification of titanium and its alloys have been proposed from the viewpoint of improving bioactivity. This paper contains an overview of surface treatment methods, including coating with hydroxyapatite (HAp), an osteoconductive compound. There are two types of coating methods: pyroprocessing and hydroprocessing. In this paper, hydroprocessing for coating on the titanium substrate with HAp, carbonate apatite (CO3–Ap), a CO3–Ap/CaCO3 composite, HAp/collagen, and a HAp/gelatin composite is outlined. Moreover, evaluation by implantation of surface-modified samples in rat tibiae is described.

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Hydroxyapatite Coating of Titanium Implants Using Hydroprocessing and Evaluation of Their Osteoconductivity

A new hydrocoating method (the thermal substrate method) is proposed for coating calcium phosphates such as hydroxyapatite (HA), on titanium substrates in an aqueous solution. Several factors (e.g., the type of ion source, the heating time and temperature, and the surface roughness of the substrate) affected the characteristics of the precipitate formed by this method. The solution used included 3 mmol dm−3 Ca(H2PO4)2 and 7 mmol dm−3 CaCl2, and its pH was adjusted to 6.5. The experimental studies were conducted under the following conditions: temperature 45–160°C, heating time 10–20 min, and surface roughness of substrate #120–#2000 grid ground using energy paper. A high quality of precipitate, whose predominant component was HA, was obtained on titanium substrates by the thermal substrate method in an aqueous solution. No significant difference in the precipitates was found with the type of ion source. The amount of HA precipitate increased with increasing temperature and with increasing heating time. The features of the precipitate were different, depending on the surface roughtness of the substrate: HA regularly nucleated along the grooves of the rough surface (#120 and #400 grid), and in the case of the fine surface (#1200–#2000 grid), a uniform precipitation occurred. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 390–397, 2002

Hydroxyapatite coating on titanium by thermal substrate method in aqueous solution

New insights into the interaction between heavy metals and struvite: Struvite as platform for heterogeneous nucleation of heavy metal hydroxide

Hydroxyapatite coating on titanium by means of thermal substrate method in aqueous solutions

A new hydrocoating method (the thermal sub- strate method) has been proposed for coating calcium phos- phates, such as hydroxyapatite, onto titanium substrates in an aqueous solution. The influences of several solution properties on the thermal substrate method were examined. The solutions used included 3 mmol dm �3 Ca(H2PO4)2 and 7 mmol dm �3 CaCl2 as a reference concentration solution. The ion concentration was changed from 0.1 to 2 times with respect to the reference concentration. The experimental studies were conducted under the following conditions: temperature = 140°C, heating time = 10-20 min., pH = 4-8 and Ca/P = 0.0167-16.7. The type of precipitate changed, depending on the pH and ion concentration. In the reference solution with pH > 6, predominantly hydroxyapatite was precipitated onto titanium. By contrast, only CaHPO4 was formed in the solution of pH 4. In the solution with an ion concentration of one-tenth the reference solution, CaHPO4 was also precipitated. The addition of H3PO4 to the 0.1-times solution accelerated the precipitation rate of HA. It is sug- gested that the PO4 3� concentration was insufficient to form HA in the Ca/P = 1.67 solution. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 354-359, 2002

Kensuke Kuroda

Papers

Hydroxyapatite Coating of Titanium Implants Using Hydroprocessing and Evaluation of Their Osteoconductivity

Hydroxyapatite coating on titanium by thermal substrate method in aqueous solution

New insights into the interaction between heavy metals and struvite: Struvite as platform for heterogeneous nucleation of heavy metal hydroxide

Hydroxyapatite coating on titanium by means of thermal substrate method in aqueous solutions

Effects of ion concentration and pH on hydroxyapatite deposition from aqueous solution onto titanium by the thermal substrate method.