Atomic force microscopy studies of enamel, inner enamel, dentin, and cementum in canine teeth

Gradient Magnesium Content Affects Nanomechanics via Decreasing the Size and Crystallinity of Nanoparticles of Pseudoosteodentine of the Pacific Cutlassfish, Trichiurus lepturus Teeth

The formation of biomaterials such as enamel, dentin, and bone is important for many organisms, and the mechanical properties of biomaterials are affected by a wide range of structural and chemical factors. Special dentins exist in extant aquatic gnathostomes, and many more are present in fossils. When a layer of compact orthodentine surrounds the porous osteodentine core in the crown, the composite dentin is called pseudoosteodentine. Using various high-resolution analytical techniques, including micro-computed tomography (micro-CT), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and nanoindentation, we analyzed the micro- and nanostructures, chemical composition, and mechanical properties of pseudoosteodentine in the Pacific cutlassfish, Trichiurus lepturus teeth. Nanoscale oval-shaped hydroxyapatite (HA) crystals were distributed in a disordered manner in the pseudoosteodentine, and a cross-sectional analysis showed that the mineral crystallinity and crystalline particle size of the outer orthodentine were greater than those of middle and inner osteodentine. Moreover, the outer orthodentine comprised a mixture of smaller crystals and larger, more mature crystals. The nano-hardness and nano-stiffness of outer orthodentine were significantly higher than those of middle and inner osteodentine along a radical direction. The hardness and stiffness of pseudoosteodentine were inversely proportional to its magnesium (Mg) content. These data are consistent with the concept that Mg delays crystal maturation. The crystal size, crystallinity, nano-hardness, and nano-stiffness of pseudoosteodentine all decreased commensurately with the increase of its Mg concentration. The pseudoosteodentine of T. lepturus also can be regarded as a functional gradient material (FGM) because its mechanical properties are closely related to its chemical composition and nanostructure. Special pseudoosteodentine may therefore serve as a design standard for biomimetic synthetic mineral composites.

Tooth Wear and Tribological Investigations in Dentistry

Dental or tooth wear is a physiological process in the life cycle of teeth. Loss of the occlusal surface may cause excessive tooth wear. Several factors may contribute to tooth wear with different intensities and duration in the oral cavity. The oral cavity is generally compared to a tribological system to determine the various types of wear between teeth and restorative materials and assess the amount of dental wear. However, it is challenging to investigate in vitro and in vivo wear owing to the complexity of tooth wear; thus, a clear correlation between in vitro and in vivo data could not be established. This review is aimed at providing an insight into the etiology of tooth wear and tribological investigations in dentistry.

Surface and Structural Studies of Age-Related Changes in Dental Enamel: An Animal Model

In the animal kingdom, continuously erupting incisors provided an attractive model for studying the enamel matrix and mineral composition of teeth during development. Enamel, the hardest mineral tissue in the vertebrates, is a tissue sensitive to external conditions, reflecting various disturbances in its structure. The developing dental enamel was monitored in a series of incisor samples extending the first four weeks of postnatal life in the spiny mouse. The age-dependent changes in enamel surface morphology in the micrometre and nanometre-scale and a qualitative assessment of its mechanical features were examined by applying scanning electron microscopy (SEM) and atomic force microscopy (AFM). At the same time, structural studies using XRD and vibrational spectroscopy made it possible to assess crystallinity and carbonate content in enamel mineral composition. Finally, a model for predicting the maturation based on chemical composition and structural factors was constructed using artificial neural networks (ANNs). The research presented here can extend the existing knowledge by proposing a pattern of enamel development that could be used as a comparative material in environmental, nutritional, and pharmaceutical research.

Applications of scanning electron microscopy and focused ion beam milling in dental research

The abilities of scanning electron microscopy (SEM) and focused ion beam (FIB) milling for obtaining high-resolution images from top surfaces, cross-sectional surfaces, and even in three dimensions, are becoming increasingly important for imaging and analyzing tooth structures such as enamel and dentin. FIB was originally developed for material research in the semiconductor industry. However, use of SEM/FIB has been growing recently in dental research due to the versatility of dual platform instruments that can be used as a milling device to obtain low-artifact cross-sections of samples combined with high-resolution images. The advent of the SEM/FIB system and accessories may offer access to previously inaccessible length scales for characterizing tooth structures for dental research, opening exciting opportunities to address many central questions in dental research. New discoveries and fundamental breakthroughs in understanding are likely to follow. This review covers the applications, key findings, and future direction of SEM/FIB in dental research in morphology imaging, specimen preparation for transmission electron microscopy (TEM) analysis, and three-dimensional volume imaging using SEM/FIB tomography.

The electrophoretic deposition of TiB2 nanoparticles produced by pulsed laser ablation: Case study on microstructural features and micromorphology properties

In the last decade, laser Ablation technique (Nd:YAG) has been considered as a perfect method for producing nanostructures with high purity. In the present study, Titanium diboride nanoparticles (TiB₂ NPs) have been deposited on Aluminum (Al) and their micromorphology and microstructural properties have been investigated. The synthesis of TiB₂ NPs has been carried out by the Laser Ablation technique (Nd:YAG) which has not been reported so far. Moreover, the effects of laser energy on improving the synthesis of TiB₂ NPs have been examined. In this regard, five samples of TiB₂ NPs were prepared by Laser Ablation method in different values of laser fluency in the range of 0.4-1.2 J/cm² . The structural properties of prepared nanoparticles were detected by grazing incidence X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The morphology of samples was also investigated by field effect scanning electron microscopy. The results demonstrate the formation of spherical nanoparticles in all samples. Based on the results of the GIXRD patterns, pulsed laser energy is an effective parameter for the size of ablated nanoparticles. As can be seen, increasing the energy of laser beam decreases the average size of nanoparticles from 79.41 to 4 nm. As the next step, the as-prepared nanoparticles were deposited on Aluminum substrate with electrophoretic deposition technique at constant applied voltage (30 Volt) and constant deposition time (30 min). The X-ray diffraction pattern of TiB₂ NPs deposited onto Al substrate confirmed the formation of the TiB₂ thin films on all Al substrates. Also, the roughness and average particle size of deposited films were measured by atomic force microscopy images and MountainsMap® Premium software. Increasing the fluency of laser beam made the surface more irregular and the maximum value of fractal dimension and hence, the most irregular topography has been observed in the sample produced by maximum laser fluency. RESEARCH HIGHLIGHTS: Titanium diboride nanoparticles have been synthesized by the laser ablation technique. The effects of laser energy on improving the synthesis of TiB₂ NPs have been investigated. The micromorphology of samples have been investigated by analyzing AFM and SEM images.