Octavio Alejandro Mastache-Miranda

The mechanical compatibility between dental restorative materials and the natural tooth structure is a relevant factor for long-term clinical performance. Although zirconia (yttria-stabilized tetragonal zirconia polycrystal, Y-TZP) and lithium disilicate are widely used for full-coverage crowns, their biomechanical interaction with the underlying dentin and pulp under functional loading remains insufficiently characterized. This study reports a comparative finite element analysis (FEA) of a mandibular first molar under vertical (200 N, axial) and oblique (200 N, 30°) loading, evaluating three configurations: an intact healthy tooth, a zirconia Y-TZP full-coverage crown, and a lithium disilicate full-coverage crown. The three-dimensional geometry was obtained from a cone-beam computed tomography (CBCT) study of a caries-free mandibular first molar, previously described and verified by the present group, and was analyzed in ANSYS Workbench (Static Structural). Von Mises equivalent stress, maximum principal stress and total deformation were obtained for enamel or restoration, dentin, and pulp in each configuration. Zirconia produced the highest stress concentrations in the coronal restoration (88.4 MPa vertical; 174.5 MPa oblique), exceeding the healthy enamel baseline by 57.6% and 89.7%, respectively. Both restorative materials reduced dentin stress relative to the healthy tooth, consistent with the stress-shielding effect driven by elastic-modulus mismatch. Under oblique loading, the maximum principal stress in healthy enamel reached 61.7 MPa, approaching or exceeding the upper bound of the reported tensile strength range (~10–40 MPa) and identifying oblique loading as the more demanding of the two conditions analyzed. Within the limitations of the present finite element model, lithium disilicate demonstrated a more favorable stress distribution, with dentin stress values closer to the intact-tooth baseline. The model does not include a luting cement layer, a periodontal ligament, the dentin–enamel junction, anisotropic tissue behavior or cyclic loading, and no experimental validation was performed; the results are therefore presented as a controlled numerical comparison between three configurations under the specific conditions simulated, and not as direct clinical selection criteria.

Computational biomechanics has grown substantially alongside imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI), which together enable high-fidelity biomodels of both hard and soft tissues. Most such biomodels, however, are represented as continuous homogeneous solids, limiting their capacity to reproduce the internal architecture of living tissues. Micro-finite element (μFE) analysis has addressed this limitation for bone at sub-millimetric scales using micro-CT data, but its adoption remains constrained by scanner availability, computational cost, and workflow complexity. This work proposes a methodological framework, termed intrabiofidelity, as a taxonomic descriptor complementary to biofidelity that characterizes the degree to which a biomodel reproduces the internal morphology and morphometry of a tissue. A reproducible pipeline based on ScanIP^® segmentation of MRI-derived DICOM data, SolidWorks^® solidification, and ANSYS^® Workbench finite element analysis is presented, through which a macro-scale trabecular representation is extracted from the distal femoral cancellous bone and integrated into a knee biomodel. Two numerical analyses were performed under an equivalent bipodal-standing load with orthotropic material properties for cortical and trabecular bone: one with external biofidelity only (Case 1), and one incorporating macro-scale intrabiofidelity in the trabecular bone (Case 2). The introduction of intrabiofidelity produced a substantial redistribution of peak von Mises stress between compartments. Trabecular peak stress increased from 2.66 to 12.10 MPa (a 4.5-fold elevation), while cortical peak stress decreased from 56.25 to 45.97 MPa (an 18.3% reduction), whereas the volume-averaged stress remained essentially unchanged in both tissues, indicating that intrabiofidelity primarily affects local concentrations rather than the bulk stress state. Principal stress data further revealed that the trabecular region transitions from a low-stress, predominantly compressive state in Case 1 to one in which substantial local tensile and compressive concentrations of comparable magnitude coexist in Case 2. The proposed methodology provides an accessible workflow for macro-scale integration of internal bone architecture using routinely available MRI data and commercial FEA software, and introduces intrabiofidelity as a terminological complement useful for teaching and for systematically documenting the fidelity of computational biomodels.