Biomechanical performance of an immature maxillary central incisor after revitalization: a finite element analysis.

AIM: To investigate the stress distribution in an immature maxillary incisor and the same tooth after simulated revitalization with deposition of tubular dentine or cementum by finite element analysis (FEA). METHODOLOGY: A finite element model of a maxillary central incisor was developed on the basis of a µCT scan. The tooth was segmented in two parts: a part that represented a tooth in an immature state and an apical part that represented the tissue formed after revitalization. The apical part was given the mechanical properties of dentine or cementum. The immature tooth and the same tooth reinforced by either dentine or cementum underwent simulation of biting, trauma and orthodontic movement. Von Mises stress values were compared between the scenarios and tooth segments. RESULTS: Maximum stress in the immature incisor developed apically; however, dentine- and cementum-reinforced teeth revealed the greatest stress in the external portion of the root decreasing towards the apex. Greatest mechanical stress was caused by dental trauma perpendicular to the long axis of the root followed by biting and orthodontic movement. Stress peaks were lower in the dentine-reinforced tooth compared with the cementum-reinforced tooth in all scenarios; however, median stress in the immature part was reduced irrespective of dentine or cementum deposition. Dentine reinforcement caused greater stress values in the apical segment due to absorbance of the applied force, whereas stress was not transferred towards deposited cementum. CONCLUSIONS: Apposition of simulated hard tissue in a maxillary central incisor after revitalization reduced mechanical stress in the immature tooth. Formation of dentine was advantageous because, unlike cementum, it facilitated an even stress distribution throughout the root resulting in lower stress values.

Computational modeling of electromechanical propagation in the helical ventricular anatomy of the heart.

The classical interpretation of myocardial activation assumes that the myocardium is homogeneous and that the electrical propagation is radial. However, anatomical studies have described a layered anatomical structure resulting from a continuous anatomical helical disposition of the myocardial fibers. To further investigate the sequence of electromechanical propagation based on the helical architecture of the heart, a simplified computational model was designed. This model was then used to test four activation patterns, which were generated by propagating the action potential along the myocardial band from different activation sites.

Temnospondyli bite club: ecomorphological patterns of the most diverse group of early tetrapods.

Temnospondyls were a successful group of early tetrapods that lived during the Palaeozoic and Mesozoic periods. Different ecomorphotypes were present (terrestrial, amphibious and fully aquatic) with a wide range of lifestyles. Herein, we analysed several clades of temnospondyls using geometric morphometrics, Finite Element Analysis, and comparative phylogenetic analysis. Some temnospondyli clades were 'crocodilomorph' feeding analogues. The skull analysis reveals a concordance between form and feeding function, in amphibious and fully aquatic feeders. The form of terrestrial feeders could be consequences of adaptative or phylogenetical constraints. Basal temnospondyls, as edopoids, were able to leave the water and feed on land. Eryopids continued as terrestrial feeders, although some members showed a shift to increased aquatic feeding. The aquatic environment was especially occupied by archegosaurs during the Permian. After the Permo-Triassic extinction, trematosaurs and capitosaurs returned to the aquatic environment and their members were amphibious and fully aquatic feeders until their disappearance.