Biomechanics of Rehabilitating
the Perioprosthetic Patient
77
Testing the biomechanical performance of the connectors related to their dimensions in
clinical studies is not easy because it is difficult to standardize the dimensions of the
connectors. [113, 114] Therefore, the analysis of the biomechanics of the connectors has been
studied primarily using theoretical methods. [81, 109, 110, 113, 115-126]This emphasizes the
importance of proper
insilico
studies. The most sophisticated theoretical method for
simulating clinical reality is Finite Element Analysis (FEA), [20] an
in silico
numerical tool
predicting biomechanical response. [21]This has the advantage over clinical studies of
reducing the number of uncontrolled variables influencing the final outcome. [20]Finite
element analysis (FEA) may solve such complicated design problems, [127-129] using the
principles of engineering and material science. [130, 131] However, few FEA studies are
available, [124, 126] and the authors identified no studies pertaining to the optimal dimension
of the connectors proximal to the retaining abutment of cross-arch FDPs, extended as
cantilever segments, with minimal osseous support. Consequently, in research activity of the
Department of Fixed Prosthesis and Implant Prosthodontics, Aristotle University of
Thessaloniki,
in silico
studies have been conducted using Finite Element Analysis Software in
order to investigate and optimize the biomechanics of the metal-framework regarding to
technical and biological integrity of cross-arch FPDs in the perioprosthetic patient.
The methodology followed was based on the evaluation of digital parametric anatomic
models, derived from a 3-D basic one. All the structures were either obtained from a
Computed Tomography (CT) image processing system (MIMICS: Materialise Interactive
Medical Image Control System; Materialise N.V., Leuven, Belgium) or developed in 3-D
Computer-Aided Design (CAD) (Solidworks 2006; Solidworks Corp, Concord, Mass) and
Reverse Engineering (RE) (Geomagic Studio; Geomagic Inc, North Carolina) environments.
The original model simulated a human adult mandible, dentate bilaterally to the second
premolars, with a normal height of alveolar bone (Figure 3, A and B).
A.
B.
Figure 3. Original Model. A. Mandible, B. Teeth.
Petros
Koidis and Manda Marianthi
78
Figure 4. Connectors
proximal to the end-abutment, adjacent to cantilever segment. 3, 4, 5 mm-
connectors in vertical dimension.
Figure 5. Models. NC3: No-cantilever FPD, 1UC3: 1-unit cantilever FPD, 3mm-connector, 2UC3: 2-
unit cantilever FPD, 3mm-connector, 1UC4: 1-unit-cantilever FPD, 4mm-connector, 2UC4: 2-unit
cantilever FPD, 4mm-connector, 1UC5: 1-unit cantilever FPD, 5mm-connector, 2UC5: 2-unit
cantilever FPD, 5mm-connector.
The original model was modified to form parametric models restored with a cross-arch
FPD: a. not extended-without cantilevers and b. extended bilaterally as 1- or 2- unit
cantilevers. The VD of the connectors proximal to retaining abutment of the extended FPDs
was investigated for the values 3 (conventional), 4 and 5 mm, while their HD remained stable
at 2,5mm (Figure 4). [132]
Each type of restoration was investigated at 50% of reduced bone support. [7]The
resulting models and their symbols are shown in Figure 5.
Biomechanics of Rehabilitating the Perioprosthetic Patient
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