THE EFFECTS OF MICROMACHINED SURFACES ON FORMATION OF BONELIKE TISSUEON SUBCUTANEOUS IMPLANTS AS ASSESSED BY RADIOGRAPHY AND COMPUTER IMAGE-PROCESSING

Surface topography varies widely among commercially available orthoped ic and dental implants. While it is generally accepted that the surfac e topography of an implant influences the formation of bone and affect s its performance, few systematic studies have dealt with this importa nt feature. Quantification of the mineralized tissue at the implant in terface has typically been attempted using histologic methods or conve ntional radiographic procedures. However, histologic methods are often technically demanding and time consuming, whereas conventional radiog raphic procedures lack resolution and sensitivity to identify small ar eas of mineralization. The objective of this study was to study system atically the effects of micromachined surfaces on bone formation by ap plying digital radiographic techniques to identify and quantify minera lized tissue. Titanium-coated epoxy replicas of 19 different micromach ined grooved or pitted surfaces that ranged between 30 and 120 mu m de ep, as well as smooth control surfaces, were implanted percutaneously and fixed to the parietal bone of rats. After 8 weeks the implants and attached tissue were removed and processed for light and electron mic roscopy. A total of 316 implant surfaces were processed, radiographed using conventional and digital techniques, and sectioned for histologi c observations. The area of the bonelike tissue and its density were c alculated using National Institutes of Health Image software. Minerali zation was frequently noted at the interface of some types of micromac hined surface but rarely on smooth surfaces. The presence of bone in h istologic sections and areas identified as bone through digital radiog raphy and image processing correlated strongly. The frequency of bonel ike foci formation decreased as the depth of the grooves increased. In contrast, mineralization occurred more frequently as the depth of the pit increased. In addition, bonelike foci were oriented along the lon g axis of the grooves. It is thus feasible that the bonelike tissue is shaped, directed, or engineered to a predetermined configuration whic h is dictated by the surface topography. This study indicated that sur face topography influences the frequency as well as the amount of bone deposited adjacent to implants, and mineralized product can be guided by the surface topography. Moreover, digital radiography and image pr ocessing can be used reliably to identify and quantify mineralized tis sue at the implant interface. (C) 1997 John Wiley & Sons, Inc.