Marcella Reguzzoni

Mineralising avian tendon is a widely used experimental model for studying collagen-guided mineralisation. Yet, the three-dimensional organisation and topology of its internal canal system have never been quantitatively characterised. We combined high-resolution micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) to provide the first morphometric and topological analysis of the canalicular network in mineralised turkey gastrocnemius tendon. micro-CT revealed that unmineralised canals occupy approximately 34.6% of the mineralised tissue volume and form a single continuously connected network (99.8% of void volume), with a connectivity density of ~1.3 × 10² mm⁻³, a fractal dimension of 2.58, a degree of anisotropy DA = 0.87 [BoneJ convention, range 0–1], and a closed-loop topology. SEM revealed marked ultrastructural heterogeneity of the mineral phase across fascicle cross-sections, consistent with graded intrafibrillar-to-interfibrillar deposition. These findings establish the first quantitative morphometric framework for physiologically mineralising collagen tissue and support the use of turkey gastrocnemius tendon as a tractable model for studying mineralisation dynamics, enthesis biology, and the design of biomimetic scaffolds with controlled porosity and anisotropy.

The increase in the world population and consequent rise in food demand have led to the extensive use of chemical pesticides, causing environmental and health concerns. In response, biological control methods, particularly those involving microbial agents, have emerged as sustainable alternatives within integrated pest management. This study highlights the potential of Lysinibacillus fusiformis as a biocontrol agent against the dipteran Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), a pest responsible for damaging soft-skinned fruits. Experimental treatments using vegetative cells, spores, and secondary metabolites of L. fusiformis on D. suzukii larvae demonstrated significant larvicidal effects, accompanied by observable changes in gut morphology under microscopy. Moreover, preliminary immunological assays showed the interference of this bacterium with the host immune system. All the results indicate the suitability of L. fusiformis for its possible integration into sustainable agricultural practices, although additional research is required to understand its applicability in the field.

In the Chondrichthyes Raja asterias and Myliobatis aquila and in the Teleost Sparus aurata, the appendicular skeleton of the pectoral fins (including the calcified structures of the mouth in M. aquila) was investigated to find out how the specific skeletal segments were formed and stiffened over the course of evolution, not only with regard to the adaptation of the ontogenesis of the cartilage “anlagen” to the mechanical requirements of locomotion in the water column, but also to the specific feeding habits (durophagy) of M. aquila. The morphology of the pectoral fins of the three species showed a different layout, characterized by the geometry of the basic units (aligned tesserae and calcified radial columns), which provide varied flexibility of the pectoral fins, suggesting an adaptation to the “pelagic” and “benthic” locomotion patterns in the environment where the species live. The morphology of the calcified structures in the mouth of M. aquila showed the presence of two different masticatory systems: the first (external) with the rows of teeth resting on the maxillary and mandibular arches, and the second (internal, in the oral cavity) with the symphyseal plates specialized for durophagy. Chemical–physical analyses revealed that the calcified cartilage matrix of the Chondrichthyes fin rays, teeth and durophagy plates is stiffened by the same Ca₃(PO₄)₂ mineral phase deposed in the organic matrix of the Teleost S. aurata fins (with the characteristic SEM morphological texture of calcified bone matrix). The hitherto unknown presence of two different chewing systems in M. aquila documents an evolutionary adaptation to nutritional requirements that can be explained by two hypotheses: the coexistence of two functioning systems in current specimens, allowing for the ingestion of harder and softer prey (or plant food), or the persistence of a rudimentary dentition that is no longer used (vestigial dentition). Furthermore, the texture of the calcified matrix in teleost fishes, as observed by scanning electron microscopy, may indicate a bone-like organic matrix substrate, similar to that found in endochondral ossification.

The calcified tissues of vertebrates are essentially represented by bone, cartilage, dentin and calcified tendons. In all these tissues a major hallmark of mineralization is the deposition of the inorganic phase on a pre-existing collagen template, but evident differences exist among these materials and the molecular details of the process are still incompletely understood. In this study, the ultrastructural aspects of the mineral phase of these tissues were investigated by means of high-resolution scanning electron microscopy (HR-SEM) after low-temperature thermal deproteination, a technique allowing a direct, unrestricted visualization of the mineral component. Each tissue showed distinctive features. In most cases, calcification proceeds in a discontinuous way through the formation of clumps or clusters of mineralized tissue; in all cases, except cartilage, the mineral phase shows an evident relationship with the layout and/or the D-period of the collagen fibrils. Our results highlight the peculiar aspect of the mineralization process in the cartilage with respect to the other tissues, all of them containing collagen type I instead of type II, and suggest that a different molecular mechanism may be at work. It is still unclear whether and how this may be related to the content, exclusive of cartilage, of collagen type II. The identification of the tissue-specific features exhibited by cartilage versus those shared by all the other three tissues, although from different species, requires further research on physiological calcification.

This study investigates the growth and calcification of the appendicular skeleton in Raja asterias (Delaroche, 1809), a member of the Batoidea, to explore the relationship between histomorphology and the mechanics of batoid locomotion within the water column. Although much prior research has focused on the “tessellated pattern” in these fishes, the variable structure of the appendicular skeleton provides fresh insights into the understudied interplay between skeletal histomorphology and the mechanical functions of Batoidea fins. The shape and initial growth of fin cartilage are influenced by the orientation of chondrocyte mitoses prior to mineral deposition, with subsequent calcification playing a pivotal role in shaping skeletal architecture. This study documents two distinct growth patterns: “crustal” and “catenated.” The crustal pattern is predominantly observed in larger skeletal elements, such as the central body structures (skull, rostrum, and jaws), girdles, pterygia, and compound radials, whereas fin radials follow the catenated growth pattern. Notably, early‐stage chondrichthyan cartilage shares similarities with mammalian metaphyseal growth plate cartilage, though in chondrichthyans, the calcified matrix is not resorbed or replaced by bone. Additionally, a previously unrecognized calcification pattern is identified in the pelvic‐fin radials of R. asterias, indicating that the mechanical demands of locomotion in the water column may have driven the evolution of variable fin flexibility in Batoidea. This flexibility is achieved through joint mobility (diarthroses and amphiarthroses), specialized fin structures, and the distinct calcification patterns of the pectoral and pelvic fins.

This study aimed to investigate the remineralization processes of dental enamel via scanning electron microscopy and observe the changes induced in the microstructure by oral hygiene products. More specifically, the effectiveness of Mentadent Professional Resilience was analyzed for its ability to demineralize erosion-affected enamel surfaces. This involved the sectioning of some teeth to preserve enamel integrity, followed by dehydration and preparation for SEM analysis. SEM observations were made at various magnifications to detect differences in enamel morphology after treatment with the product. These observations provide valuable insights into the mechanisms of action of dental care products and their potential to protect enamel. The study makes a contribution to our understanding of remineralization processes and describes the importance of microscopic analysis for evaluating and developing effective dental products.

The science of dental tissue grafting is evolving, with an increased understanding of factors influencing graft behavior. Despite the widespread clinical use of soft tissue grafts, the histological characteristics of different gingival harvesting sites are still underexplored. This study aimed to fill this gap by analyzing 50 tissue samples harvested from 25 patients across three sites: the hard palate, maxillary tuberosity, and palatal rugae. Each sample underwent thorough histological and histomorphometric analysis. Conventional statistical analysis was performed using SPSS, while predictive modeling was conducted with RapidMiner Studio. The study identified significant histological differences among the graft sites, with notable variations in total graft height, epithelial height, and interdigitation perimeter. These findings underscore the importance of donor site selection in influencing graft success. Pair plots and principal component analysis (PCA) further highlighted the distinct histological features of each tissue type. The random forest classifier identified total graft height, epithelial height, and perimeter as the most influential factors in predicting graft site behavior. This study offers valuable insights into the histological characteristics of soft tissue grafts, potentially leading to more predictable clinical outcomes.

Before calcification begins, the early embryonic and fetal skeletal development of both mammalian Homo sapiens and the chondrichthyan fish Raja asterias consists exclusively of cartilage. This cartilage is formed and shaped through processes involving tissue segmentation and the frequency, distribution, and orientation of chondrocyte mitoses. In the subsequent developmental phase, mineral deposition in the cartilage matrix conditions the development further. The stiffness and structural layout of the mineralized cartilage have a significant impact on the shape of the anlagen (early formative structure of a tissue, a scaffold on which the new bone is formed) and the mechanical properties of the skeletal segments. The fundamental difference between the two studied species lies in how calcified cartilage serves as a scaffold for osteoblasts to deposit bone matrix, which is then remodeled. In contrast, chondrichthyans retain the calcified cartilage as the definitive skeletal structure. This study documents the distinct mineral deposition pattern in the cartilage of the chondrichthyan R. asterias, in which calcification progresses with the formation of focal calcification nuclei or “tesserae”. These are arranged on the flat surface of the endo-skeleton (crustal pattern) or aligned in columns (catenated pattern) in the radials of the appendicular skeleton. This anatomical structure is well adapted to meet the mechanical requirements of locomotion in the water column. Conversely, in terrestrial mammals, endochondral ossification (associated with the remodeling of the calcified matrix) provides limb bones with the necessary stiffness to withstand the strong bending and twisting stresses of terrestrial locomotion. In this study, radiographs of marine mammals (reproduced from previously published studies) document how the endochondral ossification in dolphin flippers adapts to the mechanical demands of aquatic locomotion. This adaptation includes the reduction in the length of the stylopodium and zeugopodium and an increase in the number of elements in the autopodium’s central rays.

Before calcification begins, the early embryonic and fetal skeletal development of both mammalian Homo sapiens and the chondrichthyan fish Raja asterias consists exclusively of cartilage. This cartilage is formed and shaped through processes involving tissue segmentation and the frequency, distribution, and orientation of chondrocyte mitoses. In the subsequent developmental phase, mineral deposition in the cartilage matrix conditions the development further. The stiffness and structural layout of the mineralized cartilage have a significant impact on the shape of the anlagen (early formative structures of organs or tissues) and the mechanical properties of the skeletal segments. The fundamental difference between the two studied species lies in how calcified cartilage serves as a scaffold for osteoblasts to deposit bone matrix, which is then remodeled. In contrast, chondrichthyans retain the calcified cartilage as the definitive skeletal structure. This study documents the distinct mineral deposition pattern in the cartilage of the chondrichthyan R. asterias, in which calcification progresses with the formation of focal calcification nuclei or “tesserae”. These are arranged on the flat surface of the endo-skeleton (crustal pattern) or aligned in columns (catenated pattern) in the radials of the appendicular skeleton. This anatomical structure is well adapted to meet the mechanical requirements of locomotion in the water column. Conversely, in terrestrial mammals, endochondral ossification (associated with the remodeling of the calcified matrix) provides limb bones with the necessary stiffness to withstand the strong bending and twisting stresses of terrestrial locomotion. In this study, X-rays of marine mammals (reproduced from previously published studies) document how the endochondral ossification in dolphin’s flipper adapts to the mechanical demands of aquatic locomotion. This adaptation includes the reduction in the length of the stylopodium and zeugopodium and an increase in the number of elements in the autopodium’s central rays.

This study presents a scanning electron microscopy analysis of a failed PEEK retainer in an orthodontic patient. After 15 months of use, the patient reported a gap opening between teeth 41 and 42. The PEEK retainer was removed and sent for electron microscope analysis. To investigate the failure, scanning electron microscopy was employed to assess the microstructure and composition of the retainer at various magnifications. These findings suggest that the failure of the PEEK retainer was multifaceted, implicating factors such as material defects, manufacturing flaws, inadequate design, environmental factors, and patient-related factors. In conclusion, this scanning electron microscopy analysis offers valuable insights into the failure mechanisms of PEEK retainers in orthodontic applications. Further research is necessary to explore preventive strategies and optimize the design and fabrication of PEEK retainers, minimizing the occurrence of failures in orthodontic practice.