Effects of Implant Microtopography on Osteoblast Cell Attachment

Effects of Implant Microtopography on Osteoblast Cell Attachment
June 2003
Keller, John C. PhD*; Schneider, Galen B. DDS, PhD**; Stanford, Clark M. DDS, PhD***; Kellogg, Bradley BSÇƒÜ
Implant Dentistry: Volume 12(2) June 2003 pp 175-181
Lippincott Williams & Wilkins
*Professor, Dows Institute for Dental Research, College of Dentistry, Iowa City, Iowa.
** Assistant Professor, Department of Prosthodontics, Dows Institute for Dental Research, Iowa City, Iowa.
***Centennial Fund Professor, Department of Prosthodontics, Dows Institute for Dental Research, Iowa City, Iowa.
ÇƒÜDental Student, College of Dentistry, The University of Iowa, Iowa City, Iowa
Reprint requests and correspondence to:
John C. Keller, PhD
Dows Institute for Dental Research
College of Dentistry
N407 Dental Science Building
The University of Iowa
Iowa City, IA 52242-1010
Phone: (319) 335-7375
Fax: (319) 335-8895
E-mail: John-Keller@uiowa.edu
Abstract
Purpose: The overall aim of this project was to study osteoblast cell attachment on titanium surfaces with varying surface roughness.
Materials and Methods: Commercially pure titanium surfaces were prepared by polishing through 600-grit sandpaper, sandblasting, or sandblasting followed by acid etching to produce surfaces of varying roughness, as determined by scanning electron microscopy and atomic force microscopy. In vitro cell attachment of MC3T3-E1 osteoblasts was performed on the prepared surfaces in both serum-containing and serum-free media conditions.
Results: Cell attachment was directly related to the average surface roughness, with the highest levels of cell attachment observed on sandblasted and sandblasted-acid-etched surfaces. Similar patterns of cell attachment were observed when serum-free conditions were employed.
Conclusions: Combined surface analytical and cell/molecular biological techniques are powerful tools to broaden our understanding of biological events occurring at the implant-tissue interface. Data acquired from these in vitro techniques provide a translational application to in vivo clinical models leading to the next generation of dental implants.
With the continuing and increasing use of dental implants, it has become increasingly apparent that the interaction of host-tissue with the implant surface is critically important for the long-term success of the implant. 1 Anatomically speaking, although the implant must be firmly integrated into host bone tissue (by osseointegration) to maintain mechanical rigidity, the appropriate integration of implant materials must also occur in the connective and epithelial tissue regions in order to maintain the permucosal seal for prevention of bacterial ingress leading to periodontal-like disease adjacent to the implant. From this biological viewpoint, the characteristics of the implant substrate that permit hard and soft tissue integration and prevent bacterial invasion need continued development. As a more complete understanding of the basic biological responses of host tissues becomes known, refinements in the currently employed materials are likely to lead to incremental advances in the development of dental implants.
From a materials viewpoint, the factors that affect the biological properties of dental implants can be divided into the effects of materials selection and the effects of the surface properties of the individual materials. Discussion of the effects of materials selection (eg, metallic systems, Ti and Ti alloys, and ceramics and ceramic coatings based on hydroxyapatite chemistries) are presented in recent reviews and are not the specific focus of this report. 2,3 Over the past decade the effects of implant surface properties such as surface chemistry and surface topography have attracted the attention of numerous in vitro and in vivo reports. Although not the focus of this report, implant chemistry is affected by a variety surface-preparation treatments, including coating methodologies, roughening procedures, cleaning operations, and sterilization procedures. 4-7 These preparation treatments affect the overall oxide chemistry of selected metallic systems and the composition and chemical structure of ceramic coatings. 8-10
Interest has continued on the role and effects of surface topography on the subsequent interaction of the dental implant with the respective host tissues. The effects of surface topography are related to, but different than, the overall three-dimensional design or geometry of the implant. For example, the geometrical design of the implant may be cylindrical in the case of root-form implants or narrow rectangular for bladelike implants. Implants may be press-fit (solid body or sintered bead technology) or have a screwlike (self-tapping) shape to maximize initial tissue contact upon implantation. 1,7 In this particular report, we refer to surface topography as the texture of the implant on a microtopographic basis, where the intimate cell and tissue interactions leading to osseointegration are based.
The effects of surface topography on in vitro and in vivo osteoblast cell and tissue responses have been a field of intense study for the past decade. 4,11-15 Early in vitro studies by Bowers et al 4 established that the levels of short-term (osteoblast) attachment were higher on rough, compared to smooth, surfaces and that the resulting cell morphology was directly related to the nature of the underlying substrate. Increased surface roughness provided by such techniques as sand (grit) blasting and/or acid treatments seem to provide the necessary surface texture for optimum cell behavior. Anselme et al 11 expanded this in vitro work further and suggested that osteoblast cells prefer surfaces with a high level of microroughness (Ra values approximately 0.5 ¨µm).
Subsequent work by a number of authors, including Brunette et al, 12 have focused on the relationship between surface topography and the resultant cell morphology, intracellular organization, or development of extracellular matrix. Their work suggests that microtextured surfaces produced by micromachining or nanofabrication techniques can help orchestrate cellular activity including mineralization by osteoblasts. Reports from a number of laboratories 13-15 have also indicated that cell attachment and expression of extracellular matrix proteins are affected by surface micromorphology.
In this work we continued our studies by combining surface analytical techniques, such as scanning electron microscopy and atomic force microscopy, to better understand the relationship between surface topography and in vitro cellular attachment. The overall goal of this work is to identify surface topographies that mimic the natural substrata in order to permit tissue integration and improve the clinical performance of the implant. The results from such in vitro studies have proven invaluable in setting parameters from which in vivo animal and in situ human clinical studies have been designed. 16-18
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