Two-Dimensional and 3-Dimensional Analysis of Bone/Dental Implant Interfaces With the Use of Focused Ion Beam and Electron Microscopy

Abstract

To assess the usefulness of a dual-beam focused ion beam (FIB) and scanning electron microscope (SEM) instrument and FIB-based transmission electron microscopy (TEM) specimen preparation techniques to characterize bone/dental implant interfaces. The FIB was used to site specifically polished cross-sections for direct FIB, SEM, and TEM imaging of bone osseointegration into a Nobel Biocare TiUnite failed dental implant (Nobel Biocare, Yorba Linda, CA). Bone was observed to grow into the porous structure of the coating, yielding direct evidence of a mechanical locking mechanism of the bone/implant interface. Multiple SEM images obtained from sequential FIB cross-sections were reconstructed into 3-dimensional tomograms that showed partial and full bone growth into the porous structure of the TiUnite coating. Sections thinned by FIB techniques were observed by transmission electron microscope (TEM) and related methods. Conventional bright field TEM showed that the coating, which was more than 2 microm thick, consisted of a nanocrystalline and porous structure. High-resolution TEM (HRTEM) showed the presence within the bone of hydroxyapatite crystallites that measured approximately 7 nm. TEM images showed that the bone does not form an intimate and homogenous interface with the implant coating in all regions. X-ray energy dispersive spectrometer (XEDS) line scans that used scanning TEM (STEM) methods showed interdiffusion of Ti, P, and Ca between the bone and the coating where intimate bone/coating contact was observed, suggesting that chemical bonding also exists within this interface. FIB methods for SEM and TEM were used to characterize bone/implant surfaces.