ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

interaction. Previous studies on this subject lacked the trabecular architecture and
usually used very simplified geometry [3, 4]. Our aim is to introduce more complex
model which includes the detailed trabecular architecture and which is in this respect
much closer to the reality than ever before.
In assessing the implant/bone interaction one has to deal with the fact that no criteria
have been formulated yet. The aim of this paper is not to develop such a criterion,
nevertheless the applicability of the model and also results of the calculations should be
somehow assessed. For this purpose, mechanical quantities such as implant
displacements and bone strains will be analyzed, and the latter also compared to
physiological values introduced by Frost in his Mechanostat hypothesis [5].
2. MATERIALS AND METHODS
The computational model proposed for the implant/bone interaction assessment
basically consists of four parts: Model of geometry, model of material properties, model
of loading, and model of boundary conditions. In this paper, the most complex and also
the most novel is the model of geometry which is based on the modern visualization
methods, specifically the µCT device.
The conventional CT devices with a typical spatial resolution of 0.2 -5 mm do not allow
visualization of the complex trabecular architecture. In order to get the geometry model
of the cancellous bone tissue including this architecture the µCT device must be used
(resolution 1-100 µm). Fig. 1 demonstrates the difference between a conventional CT
image (pixel size of 295x295µm 2 ) and a µCT image (pixel size of 16x16µm 2 ) of the
same bone at the specific region of a human mandible. The inner structure of the
cancellous bone is poorly distinguishable via the conventional CT while the µCT
provides fundamentally better image quality which makes the trabecular architecture
clearly recognizable.
Two series of images of mandible segments were made using the µCT device (GE 130
keV 76mA). The 6mm-thick segments were taken from two cadavers. These segments
represent the left premolar region with healed alveolar processes after a tooth extraction;
this is the typical state allowing the implant application. These two bone segments differ
in bone density which is quantified here by the bone volume fraction (BVF). BVF of the
analyzed segments are 0.145±0.036 and 0.377±0.056. The first segment has relatively
poor bone density which is caused by long-range bone atrophy. The second one can be
classified as bone with a normal bone density.
6 mm
a) b) c) d)
Fig. 1. a) CT image; b) µCT image; c) Model (BVF=0.149); b) Model: (BVF=0.377)
The µCT slices were preserved as TIFF files, and were imported into an image