Hydroxyapatite cement (BoneSource®) and brushite calcium phosphate cement (chronOS™ Inject) were tested for fixation of glass ceramic implants (Bioverit®) in experimentally created cranial defects in 24 adult New Zealand White rabbits. Aim of the in vivo study was to assess and compare the biocompatibility and osseointegration of the implanted materials. Macroscopic and histological evaluations were performed 1 month, 3 months, and 6 months postoperatively. All implanted materials were well tolerated by the surrounding tissue. Both bone cements exhibited osteoconductive properties. Differences could be detected regarding to the rates of cement resorption and new bone formation. The brushite cement was resorbed faster than the hydroxyapatite cement. The chronOS™ Inject samples exhibited a higher rate of connective tissue formation and an insufficient osseointegration. BoneSource® was replaced by bone with minimal invasion of connective tissue. New bone formation occurred faster compared to the chronOS™ Inject group. Bioverit® implants fixed with BoneSource® were successfully osseointegrated.
Introduction: For functional and structural restoration of bone deficiencies, various resorbable and nonresorbable alloplastic materials have been introduced, including metals, polymers and ceramics. However, an "optimal" artificial replacement for craniofacial bone has not been found yet and the search for improved reconstruction methods and alternative materials is going on. To assess and compare biocompatibility and osseointegration of these materials, adequate animal test models are indispensable. Methods: In a rabbit cranial defect model, biocompatibility and osseointegration of polymeric and composite bone replacement materials were evaluated at different time points after implantation. Calvaria including implants and surrounding tissue were explanted and embedded in methacrylate resin. The samples were scanned with a nanotom® (phoenix|x-ray) µCT scanner and proceeded for histological examination by sawing-grinding technique. Avizo® Fire (vsg) software was used for visualisation and processing of µCT data. Qualitative and morphometric evaluation of osseointegration and fibrous encapsulation was performed on undecalcified histologic preparations of the explants, and on 3D reconstructions plus virtual slices derived from corresponding 3D µCT datasets. Results: The obtained 3D µCT data enabled a comprehensive qualitative and quantitative assessment of osseointegration and biodegradation of radioopaque composite implants. Prerequisite for visualization and discrimination of materials by µCT is a significant difference of their hounsfield values. Due to this limitation, radiolucent polymeric implant materials and soft tissue could not be distinguished from embedding resin. In contrast, histologic preparations of undecalcified hard tissue and implant materials enabled detailed visualization and examination of all tissues and implant materials. The substantial disadvantage of hard tissue histology was the inevitable loss of information due to small number of slices and large gaps between specimens yielded by this method. Conclusion: To obtain comprehensive and quantifiable information about biodegradation, biocompatibility and osseointegration of alloplastic bone replacement materials, µCT scans as well as histologic evaluation should be performed.
Objective: Evaluation of μCT scans of bone implant complexes often shows a specific problem: if an implant material has a very similar radiopacity as the embedding medium (e.g. methacrylate resin), the implant is not visible in the μCT image. Segmentation is not possible, and especially osseointegration as one of the most important parameter for biocompatibility is not evaluable. Methods: To ensure μCT visualisation and contrast enhancement of the evaluated materials, the embedding medium Technovit® VLC7200 was doped with an iodine monomer for higher radiopacity in different concentrations and tested regarding to handling, polymerisation, and histological preparation, and visualisation in µCT. Six different µCT devices were used and compared with regard to scan conditions, contrast, artefacts, image noise, and spatial resolution for the evaluation of the bone-implant blocks. Results: Visualisation and evaluation of all target structures showed very good results in all μCT scans as well as in histology and histological staining, without negative effects caused by iodine doping. Subsequent evaluation of explants of in vivo experiments without losing important information was possible with iodine doped embedding medium. Conclusion: Visualisation of implants with a similar radiopacity as the embedding medium could be considerably improved. µCT scan settings should be selected with the highest possible resolution, and different implant materials should be scanned individually for optimal segmentation. µCT devices with higher resolutions should be preferred. Advances in knowledge: Iodine doped embedding medium is a useful option to increase radiopacity for better visualisation and evaluation of special target structures in µCT.
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