Multiphasic 3D-printed Bone Structures for Site-specific dental and Craniomaxillofacial Implants

Professor Cho, Kiho   (Principal Investigator (PI))

Professor Tsoi Kit Hon   (Co-Investigator)

Professor Dissanayaka Waruna Lakmal   (Co-Investigator)

30

2022-06-01

150000

Multiphasic 3D-printed Bone Structures for Site-specific dental and Craniomaxillofacial Implants

3D printing, Biocomposite, Dental implant, Functionally graded implant, Multiphase

Dentistry

202107185047

Seed Fund for Basic Research for New Staff

2021

Completed

The main goal of this research is to develop multiphasic implants with desirable mechanical and biological performance for the site-specific treatments in dental and craniomaxillofacial rehabilitation. To overcome the limitations raised from many conventional implants, new materials and methods are required. This research will address the current shortcomings of biomaterials, implant structures, and their manufacturing technologies by accomplishing three research objectives (RO) as follows: [RO-1] to synthesize resin-based and collagen-based multifunction biocomposites to be applicable for 3D printing; [RO-2] to develop new 3D-printing methods for fabricating novel multiphasic and functionally graded implant (MFGI) structures; [RO-3] to investigate the combined reliability assessments for predicting and optimizing the mechanical properties of the complex multiphase structures. [RO-1] To synthesize resin- and collagen-based multifunction biocomposites to be applicable for 3D printing. From a clinical applications perspective, one of the major challenges in dental and craniomaxillofacial implants is fabricating an engineered structure that can mimic the complex multiphasic bone-to-tendon or alveolar bone-to-gingiva system. The mechanobiological optimized biocomposites are a promising alternative to treat gingiva and alveolar bone degeneration by replacing the damaged unit with engineered implants. In this study, new multifunctional biocomposites with photocurable dental monomers for mimicking hard tissue, collagen hydrogels for soft tissue, and mineral nano-fillers such as nano-hydroxyapatites (nHAPs) and halloysite nanotubes (HNTs) will be developed to enhance mechanical and biological properties of the resultant biocomposites. Also, to improve the dispersion of nanofillers in the monomer matrix, mechanochemical mixing methods will be employed in this study. The optimal mixing fraction of monomers/fillers and collagen/fillers can be evaluated through the mechanical and physical characterization and tests including flexural bending, compression, fracture toughness, wear, thermal cycle shock, shrinkage, degree of conversion tests, and computational simulations by creating accurate prediction models (in RO-3). It hypothesizes that nHAPs in the composites will increase osteoconductivity by increasing cell attachment and growth on the surface of the implants. Also, HNTs has a high potential as a nano-carrier of bone growth factors and related agents which lead to enhancement in the osteoinductive properties. The optimized composites will ultimately be applied to stereolithography 3D printing to develop multiphasic and multipurpose medical implants (in RO-2). Key tasks in RO-1 include the following: • Development of multiphasic and multifunctional biocomposites using methacrylate-based photocurable monomers, collagen hydrogel, and biocompatible nano-fillers for applications in dental and craniomaxillofacial implants. • Study on the bone growth factors and the related biological agents that can be embedded inside nHNTs or grafted on the HAPs. • Mechanical, physical, and biological characterization of the resulting biocomposites. [RO-2] To develop new 3D-printing methods for fabricating novel MFGI structures. In this research, the advanced 3D printing technologies utilizing polymer-based stereolithography (SLA) printings will be investigated to fabricate the novel MFGI structures using the newly developed biocomposites (in RO-1). 3D-biofabrication techniques would drive to increase the precision and accuracy of the complex implant structures and also allow to rapidly manufacturing the site-specific implants. Also, a multiphasic structure can be fabricated by layering the developed composites with different characteristics such as hard-soft materials composition, structural gradient, and biological functionalization. Especially, to improve the load-bearing capabilities at the hard-soft transition area, hierarchical porous architecture in micro-/nano-scale can be designed. This can enhance the resulted structure’s mechanical, physical, and biological properties compared to conventional implants and scaffolds. For practical dental applications, the proposed technologies can be used to mimic the complex structure of the periodontium, consisting of both hard (alveolar bone and cementum) and soft (gingiva, periodontal ligament) tissues, and can be applied for surgical periodontal treatments by primarily enhancing biomechanical stability of implantation over time and as well osteoconductive and osteoinductive nature of the MFGI. Key tasks in RO-2 include the following: • Material and structural design of MFGI that shows high mechanical performance. • Optimization of the hierarchical structure of MFGI and interface between hard and soft composite materials. • Mechanical, physical, and biological characterization of the 3D-printed MFGIs. [RO-3] To investigate the combined reliability assessments for predicting and optimizing the mechanical properties of the complex multiphase structures. This study will investigate the static and dynamic mechanical properties and the failure mechanism of the 3D-printed MFGI (in RO-2) via experimental and computational simulation approaches. To minimize the localized stress, which usually causes crack initiation, at the interface between the different material layers, it is necessary to optimize interfacial geometry in the multiphase structures. The main factors which can affect the interfacial bonding strength would be the interfacial design between the layers, the thickness of each layer, and the effective elastic modulus of the faced two layers based on the contact layer model. The results of the finite element method (FEM) simulations will be compared with the experimental measurements to confirm the effectiveness of the designed model. Key tasks in RO-3 include the following: • Interfacial structure optimization of MFGI by mimicking the dentin-enamel junction and microstructure of enamel. • Biomechanical design and computational simulations to analyse the dynamic behaviour of MFGI under biomechanical loadings. • The strategic framework of the comparative analysis studies of FEM simulation and theoretical and experimental examination.