title: Structural and mechanical implications of PMMA implant shape and interface geometry in cranioplasty--A finite element study.
abstract: This computational study investigates the effect of shape (defect contour curvature) and bone-implant interface (osteotomy angle) on the stress distribution within PMMA skull implants. Using finite element methodology, 15 configurations--combinations of simplified synthetic geometric shapes (circular, square, triangular, irregular) and interface angulations--were simulated under 50N static loads. Furthermore, the implant fixation devices were modelled and analysed in detail. Negative osteotomy configurations demonstrated the largest stresses in the implant (275 MPa), fixation devices (1258 MPa) and bone strains (0.04). The circular implant with zero and positive osteotomy performed well with maximum observed magnitudes of--implant stress (1.2 MPa and 1.2 MPa), fixation device stress (11.2 MPa and 2.2 MPa), bone strain (0.218e-3 and 0.750e-4). The results suggest that the preparation of defect sites is a critical procedure. Of the greatest importance is the angle at which the edges of the defect are sawed. If under an external load, the implant has no support from the interface and the stresses are transferred to the fixation devices. This can endanger their material integrity and lead to unphysiological strains in the adjacent bone, potentially compromising the bone morphology required for anchoring. These factors can ultimately weaken the stability of the entire implant assembly.
authors.affiliation: Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center, Amsterdam, The Netherlands; Department of Maxillofacial Prosthodontics, Center for Special Care in Dentistry, Amsterdam, The Netherlands.
authors.forename: Angela
authors.initials: A
authors.lastname: Ridwan-Pramana
authors.affiliation: Institute of Solid Mechanics, Mechatronics and Biomechanics, Brno University of Technology, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Marcián
authors.affiliation: Institute of Solid Mechanics, Mechatronics and Biomechanics, Brno University of Technology, Czech Republic.
authors.forename: Libor
authors.initials: L
authors.lastname: Borák
authors.affiliation: Department of Electronics and Communications Engineering, Tampere University of Technology, BioMediTech, Finland. Electronic address: nathaniel.narragirish@tut.fi.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Narra
authors.affiliation: Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Forouzanfar
authors.affiliation: Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Wolff
mesh_terms: D000069343:Bone-Implant Interface; D015921:Dental Implants; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D006801:Humans; D019904:Polymethyl Methacrylate; D019736:Prostheses and Implants; D012886:Skull; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants; D019904:Polymethyl Methacrylate
keywords: 3D printing; Cranial trauma; Osteotomy; Patient-specific modelling; Rehabilitation