DEVELOPMENT OF A PATIENT-SPECIFIC 3D PRINTED BONE GRAFT FOR ENHANCED ALVEOLAR RIDGE RECONSTRUCTION: INTEGRATING FINITE ELEMENT MODELING AND IN VITRO VALIDATION

Maxillofacial and oral defects originate from congenital conditions such as cleft palate, diseases such as osteosarcoma that cause malignancies, and from injuries due to blasts or vehicular accidents. These defects lead to complications for the patient, including challenges with speech, infections, as well as damaging psychological effects owing to the patient’s distorted physical appearance. The current standard of care uses particulates of freeze-dried auto- or allografts covered by a titanium mesh secured in place by screws. This approach is limited by: 1) variability; 2) the length of time the patient is exposed to potential infection during surgery; and 3) overpacking, often leading to diminished bone regeneration as blood vessels may fail to form. Prior research has demonstrated the benefits of using 3D printed titanium covers to protect the core particulate. Benefits such as reduction in surgical times, more reproducible than an in vitro human design, and patient specific. However, these covers do lead to an increased degree of stress shielding, since 3D printed titanium covers are thicker than the current titanium meshes on the market. Additionally, this does not address the issues that can occur with an overpacked core. To address these fallbacks, we designed a 3D printable, biodegradable, and implantable device with patient-specific shape and a porous core-cover structure. We hypothesized that a 3D printed porous cover-core bone graft, with controlled porosities, would enhance infiltration and osteointegration. By using finite element analysis and in vitro modeling, we fine-tuned the design to withstand possible masticatory forces while designing the hydrogel to maximize cell viability. First, we optimized the FEA model and demonstrated the feasibility of 3D printing the cover and core design. Our results demonstrated that a polycaprolactone (PCL) cover with 1 mm pores, secured with buccal screws, minimized stress shielding while providing stresses within a range that would promote osteogenesis. Additionally, we developed a hybrid core composed of methacrylated alginate, methacrylated gelatin (AlgGelMa), and tricalcium phosphate (TCP), which provided elastic properties within the range of the FEA model, promoted cell infiltration, supported growth factor sequestration and demonstrated osteogenesis through RT-PCR. Overall, we demonstrated the feasibility of a patient-specific resorbable osteoprotective cover with a hydrogel core that facilitates stress propagation and improves bone healing outcomes.