Strength analysis of selectively laser sintered titanium alloy dental implant-scaffolds for immediate implantation applications

<ns3:p>The article presents an analysis of the design assumptions of innovative implant-scaffolds developed by the Authors, which constitute an alternative to implantation directly after tooth extraction for typical screw implants designed according to the Brannemark concept.The scope of work was divided into modelling using the digital twin method and manufacturing these implantable elements in real conditions. The computational analysis of bone base models obtained to create a digital twin for real conditions prevailing in the oral cavity was presented and the finite element method FEM analysis of the implant-scaffolds state after installation in the patient's bone under different occlusal conditions was performed to determine the maximum loads and compare them with the strength properties of these implantable elements manufactured by selective laser sintering from TiAl4V6 Extra Low Interstitials (ELI) grade 23 alloy.The results of the simulation studies performed using the FEM method when loading the bone-implant-scaffold model with occlusal forces with an integrated prosthetic crown abutment-screw illustrate the stress distribution occurring in the entire system, in particular those acting on the implant-scaffold. Extreme cases of these forces occurring directly on the tooth cusp at angles of 0, 15, 30 degrees with different forces of 200, 500 or 1500 N were taken into account, simulating the average and maximum forces obtained using the masticatory muscles and in the case of external impact forces acting in the adopted system. The analysis performed confirms that the use of the new additive manufacturing technology and the introduction of unique geometric features guarantees the correct transfer of occlusal forces in the bone-implant system in various load cases simulating the situation of premature contact, which is usually a critical situation for the durability of the implant-prosthetic restoration.In subsequent studies, the Authors plan to compare the results obtained in this work with models of bone-screw implants, prosthetic abutments, and prosthetic crowns according to the Brannemark concept. This will allow the determination of the optimal parameters for using individual solutions depending on the clinical conditions of different types of teeth.The developed innovative implant-scaffold, thanks to the use of an innovative design of the prosthetic connector and the placement of the prosthetic screw in the supragingival zone of the implant-scaffold, can easily transfer stress without damaging the element even with a force of 1500 N applied directly to the cusp of the prosthetic crown without destroying its structure. This force simulates an extreme situation that will cause the patient's bone to break. Despite this, the implant-scaffold will not be damaged. Therefore, the studies confirm that the use of additive manufacturing technology by the selective laser sintering (SLS) method and the innovative design of the implant-scaffold allow for the high strength properties of prosthetic elements and the surrounding bone tissues to be obtained.An original patent by the Authors for implant-scaffolds construction was developed, which is particularly useful in the case of immediate implantation in the same procedure in which the damaged natural tooth was extracted. Optimization of manufacturing conditions and their correct selection, especially laser power, enables precise reproduction of specific geometric solutions from the project. In particular, the possibilities of additive technology, the selective laser sintering method, allows the use of a laser spot diameter of 30-40 micrometres and a single layer height of 25 micrometres, which allows for achieving print accuracy concerning the project with an error not exceeding 50 micrometres, making this technology optimal for the production of dental implants.</ns3:p>