Shear behavior of human skull bones

Finite element analysis of a new alveolar bone splitting technique in the mandibular posterior region

BACKGROUND

Finite element analysis was used to predict the risk of bone plate fracture and the expected bone augmentation effect of a new alveolar bone splitting technique in the mandibular posterior region for different alveolar crest widths, different alveolar bone densities, different root incision widths, and different insertion depths of bone expansion instrumentation.

METHODS

The jaw models of the mandibular posterior region were constructed by computer-aided software and surgical incisions and bone expansion instruments were prepared on the models, after which the alveolar bone splitting procedure was simulated by finite element analysis software, and the equivalent stress-strain distribution characteristics of the jaw models of each group, as well as the maximal force and the maximal displacement of the bone plate when it was fractured, were recorded.

RESULTS

The distribution of equivalent stress and strain was mainly concentrated in the cancellous bone area at the root incision and the lower 1/3 of the buccal cortical bone plate, and there was no significant difference in the stress-strain distribution characteristics of the jaw models of each group. The wider of the alveolar crest, the higher the force required to fracture the bone plate, but the smaller the maximum displacement; the plastic deformation capacity of type IV bone jaws was more excellent; the wider the width of the root incision, the shallower the depth of instrument insertion, and the larger the maximum displacement.

CONCLUSION

Finite element analysis can effectively simulate the surgical criticality index of the new alveolar bone splitting procedure. Alveolar crest width, alveolar bone density, root incision width, and instrument insertion depth had a clear correlation with the maximum displacement of the bone plate at fracture. The alveolar crest width and alveolar bone density also had a significant effect on the maximum force required to fracture the bone plate.

Guidelines derived from biomineralized tissues for design and construction of high-performance biomimetic materials: from weak to strong

Living organisms in nature have undergone continuous evolution over billions of years, resulting in the formation of high-performance fracture-resistant biomineralized tissues such as bones and teeth to fulfill mechanical and biological functions, despite the fact that most inorganic biominerals that constitute biomineralized tissues are weak and brittle. During the long-period evolution process, nature has evolved a number of highly effective and smart strategies to design chemical compositions and structures of biomineralized tissues to enable superior properties and to adapt to surrounding environments. Most biomineralized tissues have hierarchically ordered structures consisting of very small building blocks on the nanometer scale (nanoparticles, nanofibers or nanoflakes) to reduce the inherent weaknesses and brittleness of corresponding inorganic biominerals, to prevent crack initiation and propagation, and to allow high defect tolerance. The bioinspired principles derived from biomineralized tissues are indispensable for designing and constructing high-performance biomimetic materials. In recent years, a large number of high-performance biomimetic materials have been prepared based on these bioinspired principles with a large volume of literature covering this topic. Therefore, a timely and comprehensive review on this hot topic is highly important and contributes to the future development of this rapidly evolving research field. This review article aims to be comprehensive, authoritative, and critical with wide general interest to the science community, summarizing recent advances in revealing the formation processes, composition, and structures of biomineralized tissues, providing in-depth insights into guidelines derived from biomineralized tissues for the design and construction of high-performance biomimetic materials, and discussing recent progress, current research trends, key problems, future main research directions and challenges, and future perspectives in this exciting and rapidly evolving research field.

Mechanism and microstructure based concept to predict skull fracture using a hybrid-experimental-modeling-computational approach

Cellular and tissue-scale indent/impact thresholds for different mechanisms of functional impairments to the brain would be the preferred method to predict head injuries, but a comprehensive understanding of the dominant possible injury mechanisms under multiaxial stress-states and rates is currently not available. Until then, skull fracture could serve as an indication of head injury. Therefore the ability to predict the initiation of skull fracture through finite element simulation can serve as an in silico tool for assessing the effectiveness of various head protection scenarios. For this objective, skull fracture initiation was represented with a microstructurally-inspired, mechanism-based (MIMB) failure surface assuming three different dominant mechanisms of skull failure: each element, with deformation and failure properties selected based on its microstructure, was allowed to fail either in tension, compression, or shear, corresponding to clinical linear, depressed or penetrating shear-plug failure (fracture), respectively. Microstructure-inspired a priori values for the initiation threshold of each mechanism, obtained previously from uniaxial and simple-shear experiments, were iterated and optimized for the predicted load-displacement to represent that of the corresponding indentation experiment. Element-level failure enabled the visualization of the evolution of fracture by different mechanisms. The final crack pattern at the time of macroscopic (clinically-identifiable) injury was compared between the simulation and experiment obtained through 3D tomography. Even though the timing was slightly different, the simulated prediction represented remarkably well the experimental crack pattern before the appearance of the catastrophic unstable fast crack in the experiment, thus validating the implemented hybrid-experimental-modeling-computational (HEMC) concept as a tool to predict skull fracture initiation.