The Role of Aragonite in Producing the Microstructural Diversity of Serpulid Skeletons

Aragonite plays an important role in the biomineralization of serpulid polychaetes. Aragonitic structures are present in a wide range of serpulid species, but they mostly belong to one clade. Aragonitic structures are present in a wide range of marine environments, including the deep ocean. Aragonitic tube microstructures were studied using a scanning electron microscope. X-ray powder diffraction was used to identify the aragonite. Aragonite is used to build five different types of microstructures in serpulid tubes. The most common aragonitic irregularly oriented prismatic structure (AIOP) is also, evolutionarily, the most primitive. Some aragonitic microstructures, such as the spherulitic prismatic (SPHP) structure, have likely evolved from the AIOP structure. Aragonitic microstructures in serpulids are far less numerous than calcitic microstructures, and they lack the complexity of advanced calcitic microstructures. The reason why aragonitic microstructures have remained less evolvable than calcitic microstructures is currently unknown, considering their fit with the current aragonite sea conditions (Paleogene–recent).

Biomineralization in Polychaete Annelids: A Review

Polychaete annelids are a very important group of calcifiers in the modern oceans. They can produce calcite, aragonite, and amorphous phosphates. Serpulids possess very diverse tube ultra-structures, several unique to them. Serpulid tubes are composed of aragonite or calcite or a mixture of both polymorphs. The serpulid tubes with complex oriented microstructures, such as lamello fibrillar, are exclusively calcitic, whereas tubes with prismatic structures can be composed either of calcite or aragonite. In serpulids, the calcareous opercula also have complex microstructures. Evolutionarily, calcitic serpulid taxa belong to one clade and the aragonitic taxa belong to another clade. Modern ocean acidification affects serpulid biomineralization. Serpulids are capable of biomineralization in extreme environments, such as the deepest part (hadal zone) of the ocean. The tubes of calcareous sabellids are aragonitic and have two layers, the inner irregular spherulitic prismatic layer and the outer spherulitic layer. The tube wall of cirratulids is composed of aragonitic lamellae with a spherulitic prismatic structure. In some other polychaetes, biominerals are formed in different parts of the animal body, such as chaetae or body shields, or occur within the body as granule-shaped or rod-shaped inclusions.

Quantitative analysis of Protective Role of salivary protein on demineralization of enamel

Objective: The aim of this study was to analyze the effect of salivary proteins (statherin and histatin-1) on demineralized enamel surface and to study changes in texture, magnitude and direction of crystallites and changes in prismatic structure of enamel respectively. Material & Methods: Synchrotron x-ray diffraction technique to determine the variation in degree of crystal orientation (texture). Incisors were demineralized and sectioned to 300-500 microns, rinsed with salivary protein solutions of statherin and histatin separately and in combination with short and full-lengths. A beam spot size of 20μm × 20μm was used to obtain 2D diffraction patterns to distinguish orientation of crystallites. Results: The contour maps as well as the SEM analysis present similar surface properties of the sample treated with STN-21 and the controlled PBS sample. Therefore, STN-21 was found potent in preventing demineralization and restoring surface enamel texture followed by STN-21+HTN-21 and STN43+HTN38. HTN-21 and HTN-38 showed similar demineralization pattern as the controlled demineralized sample. Conclusion: Ranking of demineralization among samples was found to be controlled demineralized > HTN-21 = HTN-38 > STN-43+HTN-38 > STN-21+HTN-21 > STN-21. Developing STN-21 as a therapeutic against dental caries and erosion. Keywords: Enamel, Demineralization, salivary proteins.

Effects of Composite Resin on the Enamel after Debonding: An In Vitro Study—Metal Brackets vs. Ceramic Brackets

Fixed orthodontic therapies include several procedures that can affect the enamel surface. The aim of this study was to assess the action of composite resin on the surface of the tooth through variation of enamel changes after debonding metal and ceramic brackets, by means of scanning electron microscopy. An in vitro study was conducted on 48 human premolar specimens, which were extracted within a period of two months for orthodontic purposes. On half of them, metal brackets were bonded, and on the other half, ceramic brackets (Al2O3) were bonded, using light cure adhesive paste and a two-step, etch-and-bonding technique. The brackets were debonded after 24 h using a straight debonding plier. The adhesive remnant index (ARI) was determined by visual observation of the specimen. Post-debonding scans were aligned with the baseline, and the surfaces’ changes were quantified. A quantitative analysis was made on the debonded brackets to determine the presence or absence of enamel on the base pad. Evaluation of pre-bonded and post-clean-up enamel surface revealed no crack and increased roughness in both ceramic and metal brackets, which was higher for the ceramic ones. The enameled band (perikymata), artificial caries, or the superficial fissures revealed in the pretreatment stage were replaced with the loss of the prismatic structure and the presence of remnant adhesive. No enamel substance was found on the base pad. The ARI tooth was higher for metallic brackets than for ceramic ones. Metallic brackets and ceramic brackets have undergone mechanical changes by showing fractures in their structure. According to our present investigation, we can conclude that the adhesive composite resin is safe for use on both metal and ceramic brackets in orthodontic treatments, with no iatrogenic enamel damages.

Case Report: Crown Resorption in a Patient With Junctional Epidermolysis Bullosa and Amelogenesis Imperfecta With LAMB3 Gene Mutations

Background: Epidermolysis bullosa (EB) corresponds to a series of conditions characterized by extreme fragility of the skin and/or mucous membranes. Of the four main types of EB, junctional EB (JEB) is the most associated with alterations in the teeth. The purposes of this study were to determine the clinical, histopathological, and ultrastructural characteristics of teeth with amelogenesis imperfecta (AI) in a patient with JEB, and compare them with control teeth, and correlate the findings with the mutations present in the patient.Case Report: The study was conducted on a 10-year-old patient with JEB carrier of two recessive mutations in the LAMB3 gene and absence of the laminin-332 protein (LM-332), determined by immunofluorescence on a skin biopsy. The patient presents hypoplastic AI with very thin and yellow-brown colored enamel. Extraction of two permanent molars was performed due to pain and soft tissue covering the crown, resembling pulp polyp or hyperplastic gingiva. Light and scanning electron microscopy (SEM) revealed very thin enamel varying from complete absence to 60 μm, absence of normal prismatic structure, and presence of a cross-banding with a laminated appearance. The histopathological study revealed granulation tissue causing external crown resorption.Conclusion: Although coronary resorption has been reported in patients with syndromic and non-syndromic AI, this is the first clinicopathological report of coronary resorption in partially erupted teeth in patients with JEB with mutations in the LAMB3 gene and hypoplastic AI. In patients with this condition, the presence of partially erupted teeth with soft tissue covering part of the crown, without a periodontal pocket, and with a radiographic image of partial coronal radiolucency should lead to suspicion of external coronary resorption.

Post Decentralization Corruption: A study on perpetual corruption at the local level in West Lombok

The current article aims to explore corruption at the local level. There are two main discourses that set the background for this study. First, corruption is considered a result of decentralization, which opened up the local political structure. Second, corruption happened as a result of a societal shift along the prismatic continuum. These two main discourses serve as the theoretical background in research to find the meanings behind the reality of perpetual corruption occurring at the local level. The research employed the theory of decentralization and a prismatic society approach as analytical tools along with a phenomenological approach. The study found linkages in decentralization as a new reason for the growth and development of corruption at the local level on account of the prismatic structure empowering elite rulers to replicate corrupt practices.

A Comparative Evaluation of Nanohydroxyapatite-Enriched Hydrogen Peroxide Home Bleaching System on Color, Hardness and Microstructure of Dental Enamel

This study aimed to evaluate two hydrogen peroxide (HP)-based at-home bleaching systems in order to analyze whether nano-hydroxyapatite (nHA) addition may represent a reliable and safe solution for tooth whitening without altering dental microstructure and hardness. Human third molars (N = 15) were treated with two bleaching agents, one containing 6%HP (6HP) and the other 6% HP nHA-enriched (6HP-nHA) with average particle diameter ranging from 5–20 nm. Their effects on enamel were assessed using a spectrophotometer, Vickers microhardness (VMH) test and Scanning Electron Microscopy (SEM), comparing the treated groups with the non-treated control group (CTR). Color analysis revealed improvement in whiteness in both groups compared to CTR. VMH test results showed no differences among the groups. SEM analysis highlighted no evident changes in the enamel microstructure of tested groups compared to CTR. At high magnification, in 6HP group, a slight increase in irregularities of enamel surface morphology was observed, while 6HP-nHA group displayed removal of the aprismatic layer but preservation of the intact prismatic structure. These results suggest that the 6HP-nHA agent may be recommended to provide reliable whitening treatment, without damaging the enamel micromorphology and hardness.

The first dinosaur egg remains a mystery

A recent study by Norell et al. (2020) described new egg specimens for two dinosaur species, identified as the first soft-shelled dinosaur eggs. The authors used phylogenetic comparative methods to reconstruct eggshell type in a sample of reptiles, and identified the eggs of dinosaurs and archosaurs as ancestrally soft-shelled, with three independent acquisitions of a hard eggshell among dinosaurs. This result contradicts previous hypotheses of hard-shelled eggs as ancestral to archosaurs and dinosaurs. Here we estimate the ancestral condition for dinosaur and archosaur eggs by reanalyzing the original data from Norell et al. and that from a recent study on reptile eggshells (Legendre et al., 2020) with the addition of these new dinosaur specimens. We show that the recovery of dinosaur eggs as ancestrally soft-shelled is conditioned by the discretization of a continuous character (eggshell thickness), the exclusion of turtle outgroups from the original sample, and a lack of branch length information. When using a larger sample, calibrated trees, and a definition of hard-shelled eggs referencing their unique prismatic structure, we recover dinosaur and archosaur eggs as either hard-shelled or uncertain (i.e. equal probability for hard- and soft-shelled). This remaining ambiguity is due to uncertainty in the assessment of eggshell type in two dinosaur species, i.e. ∼1% of the total sample. We conclude that more reptile egg specimens and a strict comparative framework are necessary to decipher the evolution of dinosaur eggs in a phylogenetic context.

Temperature Dependent Structural Evolution of WSe2: A Synchrotron X-ray Diffraction Study

A thorough investigation of the structural parameters of micromechanically exfoliated multilayer WSe2 flakes was undertaken between 400 K to 110 K. Crystal structure of WSe2 remains in the trigonal prismatic structure in this temperature range, however, with a clear difference in the temperature dependence of the in-plane a, and the out-of-plane c, lattice parameters. The linear coefficients of thermal expansion of a and c are 5.132 × 10−6/K and 8.105 × 10−6/K, respectively. The temperature dependence of the unit-cell volume is analyzed using zero-pressure equation-of-state which yielded the Debye temperature of the WSe2 to be 160 K. Following the temperature dependence of the W-Se and W-W bond distances, a nonlinear behavior is observed in the former in contrast to a rather regular behavior of the later. This significant difference in the temperature dependence of the a and c lattice parameters can have consequences in the macroscopic physical properties of the system. A good correlation between the temperature dependence of the W-Se bond distance and Raman E2g1 mode has been observed.

Future Perspectives of Biomimetics in Restorative Dentistry

The main goal of tooth restoration aims at achieving mineralization of initial enamel and dentinal lesions in native form. Most of the restorative materials and remineralization adjuvants for enamel and dentin mineralization are evidenced in the literature. Although commercially available restorative materials exhibit superior esthetics, mechanical properties and cost effectiveness, durability of the restoration threatened by the occurrence of inadequate strength, long-term solubility, and weaker adhesion to tooth and accelerated degradation after being bonded to tooth structure. Recently, the role of biomimetic science in restorative dentistry aims at creating a restoration that can be highly compatible with the structural, functional and biologic properties of dental tissues to reproduce and emulate the original performance of the intact tooth with high durability. In order to recover the prismatic structure in mineral-depleted enamel and to achieve interfibrillar mineralization in dentin, non-collagenous protein analogues have been proposed as templates for apatite deposition. Biomimetic analogues must be necessary to achieve functional mineralization and to recover the dynamic mechanical properties of teeth. The use of these analogues associated with ion-releasing materials seems to be a promising approach for both enamel and dentin remineralization. This review enlightens the current and future perspectives of biomimetic analogues used for enamel and dentin remineralization as the clinical translation of this biomimetic research can be considered as the boon to restorative dentistry.