Preshaped hydroxyapatite tricalcium-phosphate implant using three-dimensional computed tomography in the reconstruction of bone deformities of craniomaxillofacial region

Synthesis of pure and doped nano-calcium phosphates using different conventional methods for biomedical applications: a review

The applications of calcium phosphates (hydroxyapatite, tetracalcium phosphate, tricalcium phosphate (alpha and beta), fluorapatite, di-calcium phosphate anhydrous, and amorphous calcium-phosphate) are increasing day by day. Calcium hydroxyapatite, commonly known as hydroxyapatite (HAp), represents a mineral form of calcium apatite. Owing to its close molecular resemblance to the mineral constituents of bones, teeth, and hard tissues, HAp is often employed in the biomedical domain. In addition, it is extensively employed in various sectors such as the remediation of water, air, and soil pollution. The key advantage of HAp lies in its potential to accommodate a wide variety of anionic and cationic substitutions. Nevertheless, HAp and tricalcium phosphate (TCP) syntheses typically involve the use of chemical precursors containing calcium and phosphorus sources and employ diverse techniques, such as solid-state, wet, and thermal methods or a combination of these processes. Researchers are increasingly favoring natural sources such as bio-waste (eggshells, oyster shells, animal bones, fish scales, etc.) as viable options for synthesizing HAp. Interestingly, the synthesis route significantly influences the morphology, size, and crystalline phase of calcium phosphates. In this review paper, we highlight both dry and wet methods, which include six commonly used synthesis methods (i.e. solid-state, mechano-chemical, wet-chemical precipitation, hydrolysis, sol-gel, and hydrothermal methods) coupled with the variation in source materials and their influence in modifying the structural morphology from a bulky state to nanoscale to explore the applications of multifunctional calcium phosphates in different formats.

Transforming the Degradation Rate of β-tricalcium Phosphate Bone Replacement Using 3-Dimensional Printing

BACKGROUND

β-Tricalcium phosphate (β-TCP) is one of the most common synthetic bone grafting materials utilized in craniofacial reconstruction; however, it is limited by a slow degradation rate. The aim of this study was to leverage 3-dimensional (3D) printing in an effort to accelerate the degradation kinetics of β-TCP.

METHODS

Twenty-two 1-month-old New Zealand white rabbits underwent creation of calvarial and alveolar defects, repaired with 3D-printed β-TCP scaffolds coated with 1000 μM of osteogenic agent dipyridamole. Rabbits were euthanized after 2, 6, and 18 months after surgical intervention. Bone regeneration, scaffold degradation, and bone mechanical properties were quantified.

RESULTS

Histological analysis confirmed the generation of vascularized and organized bone. Microcomputed tomography analysis from 2 to 18 months demonstrated decreased scaffold volume within calvarial (23.6% ± 2.5%, 5.1% ± 2.2%; P < 0.001) and alveolar (21.5% ± 2.2%, 0.2% ± 1.9%; P < 0.001) defects, with degradation rates of 54.6%/year and 90.5%/year, respectively. Scaffold-inducted bone generation within the defect was volumetrically similar to native bone in the calvarium (55.7% ± 6.9% vs 46.7% ± 6.8%; P = 0.064) and alveolus (31.4% ± 7.1% vs 33.8% ± 3.7%; P = 0.337). Mechanical properties between regenerated and native bone were similar.

CONCLUSIONS

Our study demonstrates an improved degradation profile and replacement of absorbed β-TCP with vascularized, organized bone through 3D printing and addition of an osteogenic agent. This novel additive manufacturing and tissue engineering protocol has implications to the future of craniofacial skeletal reconstruction as a safe and efficacious bone tissue engineering method.

Clinical experience of full custom-made artificial bones for the maxillofacial region

Introduction

Autologous, allogeneic, and artificial bones are clinically applied as graft materials for bone reconstruction, with each having their own advantages and disadvantages. Although artificial bones with various shapes are currently available, a product with a morphology that may be freely modified by operators has not yet been developed. In the present study, we developed a full custom-made artificial bone, and applied it to form the maxillofacial region. We herein report treatment outcomes.

Methods

An artificial bone was prepared on a 3-dimensional solid model, and data of its shape was collected on CT. A full custom-made artificial bone was prepared by laminating α-tricalcium phosphate powder using an aqueous polysaccharide curing solution and the ink-jet powder-laminating device, Z406 3D Printer (DICO, USA). Subjects comprised patients who underwent maxillofacial plasty using this artificial bone between March 2006 and September 2009.

Results

Maxillofacial plasty using the full custom-made artificial bone was applied to 23 regions in 20 patients (14 females and 6 males). The recipient region was the maxilla in 3, mandibular ramus in 13, mental region in 7, and frontal bone in 1. Postoperative courses were favorable in 18 out of the 23 regions; however, the fit was insufficient in 2 regions and the recipient regions were exposed within 1 year after surgery. Three regions were exposed 1 year or more after surgery.

Conclusion

We developed a novel reconstruction method using a full custom-made artificial bone. Its fit with the recipient bone was considered to be important, since an ill fit between the recipient and artificial bones potentially resulting in the artificial bone being detached. Therefore, fixation is important in order to prevent the detachment, and careful course observations are required when an ill fit is concerned during the follow-up period.

3D Printing of Personalized Artificial Bone Scaffolds

Additive manufacturing technologies, including three-dimensional printing (3DP), have unlocked new possibilities for bone tissue engineering. Long-term regeneration of normal anatomic structure, shape, and function is clinically important subsequent to bone trauma, tumor, infection, nonunion after fracture, or congenital abnormality. Due to the great complexity in structure and properties of bone across the population, along with variation in the type of injury or defect, currently available treatments for larger bone defects that support load often fail in replicating the anatomic shape and structure of the lost bone tissue. 3DP could provide the ability to print bone substitute materials with a controlled chemistry, shape, porosity, and topography, thus allowing printing of personalized bone grafts customized to the patient and the specific clinical condition. 3DP and related fabrication approaches of bone grafts may one day revolutionize the way clinicians currently treat bone defects. This article gives a brief overview of the current advances in 3DP and existing materials with an emphasis on ceramics used for 3DP of bone scaffolds. Furthermore, it addresses some of the current limitations of this technique and discusses potential future directions and strategies for improving fabrication of personalized artificial bone constructs.

Fabrication and evaluation of porous beta-tricalcium phosphate/hydroxyapatite (60/40) composite as a bone graft extender using rat calvarial bone defect model

Beta-tricalcium phosphate ( β -TCP) and hydroxyapatite (HA) are widely used as bone graft extenders due to their osteoconductivity and high bioactivity. This study aims to evaluate the possibility of using porous substrate with composite ceramics ( β -TCP: HA = 60% : 40%, 60TCP40HA) as a bone graft extender and comparing it with Bio-Oss. Interconnectivity and macroporosity of β -TCP porous substrate were 99.9% and 83%, respectively, and the macro-porosity of packed granule after crushing was 69%. Calvarial defect model with 8 mm diameter was generated with male Sprague-Dawley rats and 60TCP40HA was implanted. Bio-Oss was implanted for a control group and micro-CT and histology were performed at 4 and 8 weeks after implantation. The 60TCP40HA group showed better new bone formation than the Bio-Oss group and the bone formation at central area of bone defect was increased at 8 weeks in micro-CT and histology. The percent bone volume and trabecular number of the 60TCP40HA group were significantly higher than those of Bio-Oss group. This study confirms the usefulness of the porous 60TCP40HA composite as a bone graft extender by showing increased new bone formation in the calvarial defect model and improved bone formation both quantitatively and qualitatively when compared to Bio-Oss.

Maxillofacial reconstruction using custom-made artificial bones fabricated by inkjet printing technology

Ideally, artificial bones should be dimensionally compatible with deformities, and be biodegradable and osteoconductive; however, there are no artificial bones developed to date that satisfy these requirements. We fabricated novel custom-made artificial bones from alpha-tricalcium phosphate powder using an inkjet printer and implanted them in ten patients with maxillofacial deformities. The artificial bones had dimensional compatibility in all the patients. The operation time was reduced due to minimal need for size adjustment and fixing manipulation. The postsurgical computed tomography analysis detected partial union between the artificial bones and host bone tissues. There were no serious adverse reactions. These findings provide support for further clinical studies of the inkjet-printed custom-made artificial bones.

Delivery of bone morphogenetic proteins for orthopedic tissue regeneration

Carriers for bone morphogenetic proteins (BMPs) are used to increase retention of these factors at orthopedic treatment sites for a sufficient period of time to allow regenerative tissue forming cells to migrate to the area of injury and to proliferate and differentiate. Carriers can also serve as a matrix for cell infiltration while maintaining the volume in which repair tissue can form. Carriers have to be biocompatible and are often required to be bioresorbable. Carriers also have to be easily, and cost-effectively, manufactured for large-scale production, conveniently sterilized and have appropriate storage requirements and stability. All of these processes have to be approvable by regulatory agencies. The four major categories of BMP carrier materials include natural polymers, inorganic materials, synthetic polymers, composites of these materials. Autograft or allograft carriers have also used. Carrier configurations range from simple depot delivery systems to more complex systems mimicking the extracellular matrix structure and function. Bone regenerative carriers include depot delivery systems for fracture repair, three-dimensional polymer or ceramic composites for segmental repairs and spine fusion and metal or metal/ceramic composites for augmenting implant integration. Tendon/ligament regenerative carriers range from depot delivery systems to three-dimensional carriers that are either randomly oriented or linearly oriented to improve regenerative tissue alignment. Cartilage regenerative systems generally require three-dimensional matrices and often incorporate cells in addition to factors to augment the repair. Alternative BMP delivery systems include viral vectors, genetically altered cells, conjugated factors and small molecules.

Comparison of 2 methods of making surgical models for correction of facial asymmetry

PURPOSE

Stereolithography is useful in reconstructive surgery in that the surgical template or customized implant can be prefabricated on the models. To correct facial asymmetry, prior reshaping of the replica of the original structures is frequently required before it can be used as a surgical model. This is traditionally accomplished by direct sculpturing. This method has its limitations in clinical use. Recently, we developed a method using computer techniques to reconstruct the required structures. We herein report several of its applications in a variety of clinical situations and compare this virtual method with the traditional method.

PATIENTS AND METHODS

With the traditional method, reconstruction of the models was handmade on the replica of the original structures. In the virtual method, the anticipated reconstructions were completed on the computer using various image-processing tools and were verified by the surgeons before sending to stereolithography. Thirteen patients who had undergone surgical correction of facial asymmetry using models made by either method were retrospectively reviewed. The traditional method was used in 5 of them while the virtual method was applied in the other 8 patients. The surgical models and the patients following the reconstruction were evaluated for symmetry and esthetics.

RESULTS

To construct implants or to precontour fixation plates, an average of 1.4 models was fabricated for each patient using the traditional method, whereas only 1.1 models were made for each patient in the virtual method group. Both methods worked satisfactorily in restoring symmetry of the bony structures on the models. However, the projection of the chin on the model created by the traditional method was inadequate, as showed postoperatively in 1 patient. There was surface roughness on the customized area of the models made by the virtual method. The surgical result was poor in symmetry in 1 case in the traditional method group. One patient in the virtual method group showed irregularities on the temporal region following augmentation with prefabricated bone cement implant.

CONCLUSIONS

Both methods of making models were useful and effective in surgical reconstruction for facial symmetry in selected cases. The virtual method was preferred in cases where midline structures had already been deformed, or when soft tissue was involved in reconstruction. From the technical standpoint, the virtual method was superior because of its versatility, predictability, precision, communicability, and the convenience of storage and documentation.