68 / 2018-07-31 10:00:50

Custom Repair of Mandibular Bone Defects with 3D Printed Bioceramic Scaffolds

3D print; bone repair; oral implant

全体主题 > vi. BAMOS (Biomaterials and Additive Manufacturing: Osteochondral Scaffold innovation)

Introduction
The great demand for bone graft in maxillofacial surgery(1, 2) is rising with the increase of bone defects caused by infection, tumor resection, and traffic trauma(3), especially in oral implantation, where poor alveolar bone condition does not meet the demand for implant repair(4-6). Due to its varied forms and support needs, alveolar bone defect repair is still a difficult procedure in oral implant therapy. The 3D printing technology has an enormous advantage in satisfying individual requirements of the implants(7). It has been used to fabricate porous material with both accurate outline dimensions and complex internal morphology(8). Many materials have been selected for trial manufacture.(9) However, which kind of materials and manufacturing process should be chosen to produce customized mandibular alveolar bone scaffolds with high strength and appropriate degradation remains to be verified.
Materials and methods
In this study, our objective is to investigate the effect of different material substrates of the 3D printed Ca-silicate–based bioceramics, such as CSi, CSi-Mg10, and bredigite (Bred), on the repair of the alveolar bone defects of the specific shape. The latter is a stoichiometric compound with the lowest Mg content in the Ca-Mg-silicate family. The β-tricalcium phos- phate (TCP), as a typical bioresorbable Ca-phosphate bioc- eramic, was included as a control. A bone defect in the rabbit mandibular alveolar bone was made in advance, and thus the external shape of the implants was defined in line with it. As the alveolar bone is mainly cancellous bone, a square pore size of 250 to 300 μm was designed to fit the bone ingrowth in this study. All the implants were manufactured by 3D printing and divided into 4 groups according to their different components.
All the samples were test in vitro degradation, and mechanical test. The rabbit mandible defect model was used to investigate the in situ osteogenic capacity of the 4 groups of bioceramic scaffolds (TCP, CSi, CSi-Mg10, and Bred). To custom repair the mandible defect area, a cuboid-like critical-size bone defect (10 × 6 × 4 mm3) was first created in the alveolar bone defects of New Zealand male rabbits.
To determine the geometry and dimensions of the required porous implants, the head of the live rabbit was scanned with the 3D microfocus computed tomography (CT) system (vivaCT100; Scanco Medical) at a voltage of 80 kVp and an electric current of 80 mA. The CT scan images in the Digital Imaging and Communications in Medicine (DICOM) file format were imported into the medical image-processing software (Mimics 16.0; Materialise). Then the DICOM images were reconstructed into a 3D model, and a STL file was generated. Following the postprocessing by the CAD software (Magics 13.0; Materialise), the 3D model was subjected to Boolean operation to generate the defect model.
All the data presented above were expressed as the mean ± standard deviation (SD) and analyzed with the 1-way analysis of variance (ANOVA). In all cases, the results were considered statistically significant at a P < 0.05.
Results

Figure 1. Schematic illustration of the design of porous scaffolds and alveolar bone defect operation. (A) Flow chart of the custom bone defects repair. (B) Representative optical images of surgical operation for implantation with scaffolds.

Figure 2. Characterization of the TCP, CSi, CSi-Mg10, and Bredigite powders and porous bioceramic scaffolds. (A) Scanning electron microscopy (SEM) images of the powders. (B) X-ray diffraction patterns of the powders. (C) SEM images of the fracture surface of the porous scaffolds. CSI, wollastonite; CSI-Mg10, ~10% Mg-substituted wollastonite; TCP, β-tricalcium phosphate.

Figure 3. In vitro biodissolution test for the 4 groups of bioceramic scaffolds (n = 6) in Tris buffer. (A) Schematic illustration of the scaffolds soaking in the Tris buffer. (B) Weight decrease (%) of the scaffolds with time. (C) Flexural strengths of the scaffolds with time. (D) Ca concentration in Tris buffer. (E) Si concentration in Tris buffer. (F) Mg concentration in Tris buffer. (G) Scanning electron microscopy images of the as-immersed scaffolds. Bred, bredigite; CSI, wollastonite; CSI-Mg10, ~10% Mg-substituted wollastonite; TCP, β-tricalcium phosphate.

Figure 4. Macroscopic observation, radiographic analysis, and histological analysis of bone defect sites in rabbit mandibles at 8 and 16 wk after implantation of 4 different types of bioceramic scaffolds (n = 4). (A) Histological analysis of bone defect site in rabbit mandibles, ×20. Bred, bredigite; BV, blood vessel; CSI, wollastonite; CSI-Mg10, ~10% Mg-substituted wollastonite; DP, degraded particles; OC, osteocytes; OI, osteoid; HC, Haversian canal-like structure; NB, new bone; M, materials; TCP, β-tricalcium phosphate. (B) Images of the specimens. (C) Radiographs of the specimens. (D) Two-dimensional, 3-dimensional micro–computed tomography (CT) images of the scaffolds implanted in the rabbit alveolar defects with different time, separately. (E) Morphometric analysis of the volume of the newly formed bone (BV/TV) by micro-CT (*P < 0.05). (F) The new bone (%) in the alveolar bone defect area (*P < 0.05). (G) The relative residual material (%) of specimens using micro-CT analysis (*P < 0.05).
Conclusions
The 3D printed CSi-Mg10 scaffolds has high strength, suitable degradation rate, and can be a customized mandibular repair scaffolds for dental implant in the future.
References
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