Characterization of the surface properties of commercially available dental implants using scanning electron microscopy, focused ion beam, and high-resolution transmission electron microscopy.

BACKGROUND: Since osseointegration of the respective implant is claimed by all manufacturing companies, it is obvious that not just one specific surface profile including the chemistry controls bone apposition. PURPOSE: The purpose was to identify and separate out a particular set of surface features of the implant surfaces that can contribute as factors in the osseointegration process. MATERIAL AND METHODS: The surface properties of several commercially available dental implants were extensively studied using profilometry, scanning electron microscopy, and transmission electron microscopy. Ultrathin sections prepared with focused ion beam microscopy (FIB) provided microstructural and chemical data which have not previously been communicated. The implants were the Nobel Biocare TiUnite (Nobel Biocare AB, Göteborg, Sweden), Nobel Biocare Steri-Oss HA-coated (Nobel Biocare AB, Yorba Linda, CA, USA), Astra-Tech OsseoSpeed (Astra Tech AB, Mölndal, Sweden), Straumann SLA (Straumann AG, Waldenburg, Switzerland), and the Brånemark Integration Original Fixture implant (Brånemark Integration, Göteborg, Sweden). RESULTS: It was found that their surface properties had differences. The surfaces were covered with crystalline TiO(2) (both anatase and rutile), amorphous titanium oxide, phosphorus doped amorphous titanium oxide, fluorine, titanium hydride, and hydroxyapatite, respectively. CONCLUSION: This indicates that the provision of osseointegration is not exclusively linked to a particular set of surface features if the implant surface character is a major factor in that process. The studied methodology provides an effective tool to also analyze the interface between implant and surrounding bone. This would be a natural next step in understanding the ultrastructure of the interface between bone and implants.

Forearm bone-anchored amputation prosthesis: a case study on the osseointegration.

BACKGROUND AND PURPOSE: Bone-anchored titanium implants have been used for anchorage of amputation prostheses for more than one and a half decades. Histo-logical and ultrastructural analyses were performed on a forearm amputation prosthesis after being in use for more than 11 years. MATERIAL, METHODS AND RESULTS: The implant was retrieved from the ulnar bone after a fatigue fracture of the titanium implant, and was clinically stable at the time of removal. The histological findings showed a large amount of bone within the threads and a high degree of apposition of mineralized bone to the implant surface. Ultrastructural analysis of thin samples prepared by focused ion-beam microscopy revealed an electron-dense layer at the interface and direct apposition of crystalline hydroxyapatite at the implant surface. INTERPRETATION: Our observations in this retrieval study provide a structural correlate to the functional properties and clinical results of amputation prostheses.

Technique for preparation and characterization in cross-section of oral titanium implant surfaces using focused ion beam and transmission electron microscopy.

The surface properties of materials are believed to control most of the biological reactions toward implanted materials. To study the surface structure, elemental distribution, and morphology, using transmission electron microscopy (TEM) techniques, thin foils of the surface (in cross-section) are needed. These have been cumbersome to produce, in particular, from the normally irregular screw-shaped metal implants. Focused ion beam (FIB) microscopy has been developed partly for TEM sample preparation, mainly within the microelectronics industry. Our study describes a method based on FIB for producing electron transparent foils/sections from a metal implant for TEM analysis. Using a screw-shaped titanium dental implant, it was demonstrated that thin foils can be prepared with submicron specificity and from almost any surface geometry. A comparison of different lift-out techniques showed that the in situ lift-out preparation technique allowed plasma cleaning and produced particularly good samples with excellent yield. The titanium oxide on the implant surface was analyzed using energy-filtered TEM (EFTEM) and high-resolution TEM (HRTEM) and the TiO(2) rutile phase being determined via the lattice parameters. This study provides the first set of data for the optimization of a new route for preparation and analysis of biomaterial surfaces and interfaces.

A novel method for producing electron transparent films of interfaces between cells and biomaterials.

Transmission electron microscopy (TEM) investigations of intact interfaces of cells and brittle biomaterials have proven difficult using common TEM preparation techniques. This paper describes a technique to fabricate thin sections for TEM investigation of intact interfaces between human monocytes and sintered hydroxylapatite by the use of focused ion beam (FIB) microscopy. The interfaces were examined using energy filtered TEM.

A comparative study of the bioactivity of three materials for dental applications.

OBJECTIVES: The aim of this work was to investigate the in vitro bioactivity of two different experimental dental luting cement formulations based on calcium aluminate (CA) in comparison with glass ionomer cement (GIC). One of the CA-based formulations was a hybrid between CA and GIC. METHODS: Samples were submerged in phosphate buffered saline and stored at 37 degrees C for four periods of time: 1 h, 1 day, 7 days and 4 weeks. After storage the samples were analyzed in order to investigate if a surface layer of hydroxyapatite had formed. The analysis techniques used included grazing incidence X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. RESULTS: Both the CA-containing formulations were found to be bioactive. The highest degree of bioactivity was found on the sample with only CA as active substance. A relatively thick and totally covering layer was already formed after 24 h. On the hybrid material hydroxyapatite was found after 7 days. The GIC showed no bioactivity during the test period. SIGNIFICANCE: The utilization of a bioactive material for tooth restorations will give an opportunity for remineralization and a natural and durable seal of the tooth-material interface. Materials based on CA exhibit bioactivity.

Formation and adhesion of biomimetic hydroxyapatite deposited on titanium substrates.

This study has been carried out to investigate the bioactivity of rutile and to deposit hydroxyapatite (HA) on heat-treated titanium through a biomimetic method. Biomimetic deposition of HA has gained large interest because of its low deposition temperature and good step coverage; however, it demands a substrate with bioactive properties. Commercially pure titanium is not bioactive but it can acquire bioactive properties through various surface treatments. In the present study, titanium plates were heat-treated at 800 degrees C to achieve rutile TiO(2) surfaces. These samples were immersed in a phosphate-buffered saline solution for seven days in order to deposit a HA layer on the surface. The rutile TiO(2) surfaces were found to be highly bioactive: after seven days of immersion, a layer of HA several micrometers thick covered the plates. The HA surfaces were confirmed by electron microscopy and X-ray diffraction. A scratch test was used to assess the adhesion of the HA coatings. This is a standard method to provide a measure of the coating-to-substrate adhesion and was found to be a useful method to test the thin HA coatings deposited on the bioactive surfaces. The critical pressure of the layer was estimated to be 2.4+/-0.1GPa.