Mini-review: Pathways of postural disturbances tracing to the stomatognathic system.

Postural alignment is strongly shaped by inborn anatomical and nonvolitional neural factors, whereas postural stability is dynamic in nature and driven by both automatic and volitional sensorimotor processes. The sensory and motor systems responsible for these functions are tightly integrated with the central nervous system, several vital structures of which are in close proximity to the stomatognathic system. Interventions in the oral cavity have therefore been stipulated to provide sensory feedback, which may then be translated into motor function. Since the early 90 s, numerous intervention studies have provided evidence of this correlation, with traditional views advocating that causative factors are mainly indirect. Dynamic postural responses were thus predominantly considered manifestations of head displacement, with most studies identifying potential connections along active and passive muscular interactions. The consideration however, that neuromuscular adaptations of whole-body dynamics might extend beyond biomechanical responses and involve direct pathways as well, has led to a recent paradigm shift, challenging conventional perspectives. Among the suggested pathways are central projections of trigeminal afferents, providing inputs for the oculomotor system, as well as active and passive muscular interactions. Further intervention studies indicate a sensory integration of the stomatognathic system to proprioception, likely through neural networks that work in concert with visual cues and the vestibular organs. Building on this accumulating pool of evidence, a timely perspective is provided on a critical yet underexplored aspect of neurophysiology: the intricate interplay between the cranio-cervico-mandibular system and the broader framework of body posture.

Clinical translation of polycaprolactone-based tissue engineering scaffolds, fabricated via additive manufacturing: A review of their craniofacial applications.

The craniofacial region is characterized by its intricate bony anatomy and exposure to heightened functional forces presenting a unique challenge for reconstruction. Additive manufacturing has revolutionized the creation of customized scaffolds with interconnected pores and biomimetic microarchitecture, offering precise adaptation to various craniofacial defects. Within this domain, medical-grade poly(ε-caprolactone) (PCL) has been extensively used for the fabrication of 3D printed scaffolds, specifically tailored for bone regeneration. Its adoption for load-bearing applications was driven mainly by its mechanical properties, adjustable biodegradation rates, and high biocompatibility. The present review aims to consolidating current insights into the clinical translation of PCL-based constructs designed for bone regeneration. It encompasses recent advances in enhancing the mechanical properties and augmenting biodegradation rates of PCL and PCL-based composite scaffolds. Moreover, it delves into various strategies improving cell proliferation and the osteogenic potential of PCL-based materials. These strategies provide insight into the refinement of scaffold microarchitecture, composition, and surface treatments or coatings, that include certain bioactive molecules such as growth factors, proteins, and ceramic nanoparticles. The review critically examines published data on the clinical applications of PCL scaffolds in both extraoral and intraoral craniofacial reconstructions. These applications include cranioplasty, nasal and orbital floor reconstruction, maxillofacial reconstruction, and intraoral bone regeneration. Patient demographics, surgical procedures, follow-up periods, complications and failures are thoroughly discussed. Although results from extraoral applications in the craniofacial region are encouraging, intraoral applications present a high frequency of complications and related failures. Moving forward, future studies should prioritize refining the clinical performance, particularly in the domain of intraoral applications, and providing comprehensive data on the long-term outcomes of PCL-based scaffolds in bone regeneration. Future perspective and limitations regarding the transition of such constructs from bench to bedside are also discussed.

Cellular biomechanics: Fluid-structure interaction or structural simulation?

The mechanisms by which cells respond to their changing mechanical environment and how this stimulus is decoded intracellularly from the tissue to the organ level, are widely considered as fundamental for most biological processes. Despite this, the underlying phenomena of mechanotransduction, are still not very well understood. Over the last years, numerical modeling has emerged as a cohesive element in the interpretation of biophysical and biochemical assays, concerning cellular mechanotransduction. We hypothesize that the consideration of continuum mechanics (studying all cellular entities as solids) is an inherent limitation of these models, and in part, responsible for their restricted application in cellular biomechanics. To evaluate this, a (verified and validated) 3D model of osteoblast is simulated through structural analysis, employing conventional Finite Element (FE) modelling and the results compared to a Fluid-Structure Interaction (FSI) analysis. Among the trend observed, FSI systematically leads to a higher stimulation of the nucleus (by up to 200%), while FE produced a more uniform stress field, resulting in the deformation of a notably larger portion of its volume. Although FE modelling captures a seemingly correct kinematic response of the cell when subjected to the simulated loading scenario, FSI represents a more realistic alternative. The equitable consideration of both, liquid- and solid-state material characteristics, in the latter analysis, revealed intra-cellular loading patterns that were more realistic from a biomechanical perspective. In conclusion, FSI can provide refined insight as to nuclear loading, thus serving as a far more accurate framework for decoding cellular mechanotransduction.

The Effect of Body Mass on the Shoe-Athlete Interaction.

Long-distance running is known to induce joint overloading and elevate cytokine levels, which are the hallmarks for a variety of running-related injuries. To address this, footwear systems incorporate cushioning midsoles to mitigate injurious mechanical loading. The aim of this study was to evaluate the effect of athlete body mass on the cushioning capacity of technical footwear. An artificial heel was prototyped to fit the impact pattern of a heel-strike runner and used to measure shock attenuation by an automated drop test. Impact mass and velocity were modulated to simulate runners of various body mass and speeds. The investigation provided refined insight on running-induced impact transmission to the human body. The examined midsole system was optimized around anthropometric data corresponding to an average (normal) body mass. The results suggest that although modern footwear is capable of attenuating the shock waves occurring during foot strike, improper shoe selection could expose an athlete to high levels of peak stress that could provoke an abnormal cartilage response. The selection of a weight-specific cushioning system could provide optimum protection and could thus prolong the duration of physical exercise beneficial to maintaining a simulated immune system.

The effect of osteoarthritis on the regional anatomical variation of subchondral trabecular bone in the femoral head.

BACKGROUND: The subchondral trabecular bone is located deep inside the articular cartilage, with the subcapital region carrying up to 70% of the diurnal loads occurring in the hip joint. This leads to severe regional anatomical variations of subchondral trabecular bone in the femoral head and the purpose of this study was to examine whether osteoarthritis affects these topographic characteristics. METHODS: 60 femoral heads were harvested during hip replacement and studied by osteopenetration at 8 pre-defined angles, at a penetration rate of 1mm/s. Twenty-eight of the donors underwent surgery due to osteoarthritis, whereas the remaining were trauma patients with hip fractures. To correlate these measurements to non-invasive data, all specimens were scanned by micro Computed Tomography (µCT) prior to experimentation. A cross-sectional area, perpendicular to the needle penetration pathway, was analyzed and the deviations compared to the recorded osteopenetration energy. FINDINGS: The experiments revealed significant topographical deviations in the trabeculae. These were more pronounced in the osteoarthritic samples which also required overall higher osteopenetration energy. A notable dependency of the directional bone strength to its cross-sectional characteristics was observed. Although the effect of "gender" on osteopenetration energy was proven to be significant, gender was not considered an independent variable in a regression model correlating osteopenetration energy to 2D trabecular bone density as this did not improve the value of the adjusted R(2). INTERPRETATION: The investigation provided refined insight into femoral head load-bearing capacity of patients suffering from osteoarthritis, as a comparison of osteoarthritic to healthy samples illustrated that subchondral trabecular bone in the femoral head region is subjected to increased remodeling and demineralization, reflected in higher osteopenetration values.

A FEM based endosteal implant simulation to determine the effect of peri-implant bone resorption on stress induced implant failure.

Although dental implants exhibit only limited failure rates, their fracture is associated to major modifications of the prosthetic treatment and complex surgery for the removal of the remaining embedded implant part. This investigation aims to assess the developing stress fields in the bone-implant interface during mastication and asses the failure modes of oral implants.In order to achieve this, a FEM model of an implant was reverse engineered and virtually loaded at the top of the crown for a force spectrum ranging from 75-225 N in a vertical, horizontal and oblique occlusal direction. The calculated stress fields were compared with clinically retrieved fractured implants with identical geometrical characteristics and the fracture modes of both cases were correlated. The developing stress patterns facilitated the interpretation of the implant failure as the maximum stresses, indicated critical values in both, lingual and buccal sides of the implant-bone interface at a certain critical level of bone resorption, in which failure occurs.