Mineralized Cartilage and Bone-Like Tissues in Chondrichthyans Offer Potential Insights Into the Evolution and Development of Mineralized Tissues in the Vertebrate Endoskeleton

The impregnation of biominerals into the extracellular matrix of living organisms, a process termed biomineralization, gives rise to diverse mineralized (or calcified) tissues in vertebrates. Preservation of mineralized tissues in the fossil record has provided insights into the evolutionary history of vertebrates and their skeletons. However, current understanding of the vertebrate skeleton and of the processes underlying its formation is biased towards biomedical models such as the tetrapods mouse and chick. Chondrichthyans (sharks, skates, rays, and chimaeras) and osteichthyans are the only vertebrate groups with extant (living) representatives that have a mineralized skeleton, but the basal phylogenetic position of chondrichthyans could potentially offer unique insights into skeletal evolution. For example, bone is a vertebrate novelty, but the internal supporting skeleton (endoskeleton) of extant chondrichthyans is commonly described as lacking bone. The molecular and developmental basis for this assertion is yet to be tested. Subperichondral tissues in the endoskeleton of some chondrichthyans display mineralization patterns and histological and molecular features of bone, thereby challenging the notion that extant chondrichthyans lack endoskeletal bone. Additionally, the chondrichthyan endoskeleton demonstrates some unique features and others that are potentially homologous with other vertebrates, including a polygonal mineralization pattern, a trabecular mineralization pattern, and an unconstricted perichordal sheath. Because of the basal phylogenetic position of chondrichthyans among all other extant vertebrates with a mineralized skeleton, developmental and molecular studies of chondrichthyans are critical to flesh out the evolution of vertebrate skeletal tissues, but only a handful of such studies have been carried out to date. This review discusses morphological and molecular features of chondrichthyan endoskeletal tissues and cell types, ultimately emphasizing how comparative embryology and transcriptomics can reveal homology of mineralized skeletal tissues (and their cell types) between chondrichthyans and other vertebrates.

Application of collagen and mesenchymal stem cells in regenerative dentistry

: Collagen is an important macromolecule of extracellular matrix (ECM) in bones, teeth, and temporomandibular joints. Mesenchymal stem cells (MSCs) interact with the components of the ECM such as collagen, proteoglycans, glycosaminoglycans (GAGs), and several proteins on behalf of variable matrix elasticity and bioactive cues. Synthetic collagen-based biomaterials could be effective scaffolds for regenerative dentistry applications due to mimicking of host tissues’ ECM. These biomaterials are biocompatible, biodegradable, readily available, and non-toxic to cells whose capability promotes cellular response and wound healing in the craniofacial region. Collagen could incorporate other biomolecules to induce mineralization in calcified tissues such as bone and tooth. Moreover, the addition of these molecules or other polymers to collagen-based biomaterials could enhance mechanical properties, which is important in load-bearing areas such as the mandible. A literature review was performed via reliable internet database (mainly PubMed) based on MeSH keywords. This review first describes the properties of collagen as a key protein in the structure of hard tissues. Then, it introduces different types of collagens, the correlation between collagen and MSCs, and the methods used to modify collagen in regenerative dentistry including recent progression on the regeneration of periodontium, dentin-pulp complex, and temporomandibular joint by applying collagen. Besides, the prospects and challenges of collagen-based biomaterials in the craniofacial region pointes out.

Ossifying Fibroma of the Maxilla: A Case Report and Literature Update

Ossifying fibroma is a rare benign fibro-osseous neoplasm of the jaw characterized by the replacement of normal bone tissue by a combination of fibrous tissue and newly formed calcified tissues of bone and/or cementum-like material. Lesions often manifest at the 2nd to 4th decades of life with a predominant female predilection. The tumor is usually slow-growing and asymptomatic but can cause notable expansion of the jawbones. Definitive diagnosis of OF can be challenging and usually requires careful clinical, radiographic and histologic assessments. Treatment commonly depends on the size, location and aggressiveness of tumor and can accordingly vary from enucleation and curettage to resection and bone grafting. The prognosis is generally good when the lesion is completely removed, but recurrence is possible in some circumstances. The aim of this article is to present a case report of a recurrent ossifying fibroma in a 28-year-old female patient and to provide an update of the literature.

Evaluating the Efficacy of Two Decalcifying Agents on Hard and Soft Tissues of Human Permanent Teeth

BACKGROUND Human teeth and bones consist of hard and soft tissues. Preparing calcified tissues for histological analysis by decalcification is a time-consuming procedure, and the quality of the sections thus obtained is dependent on the speed with which decalcification occurs, as well as the chemistry of the decalcification agent. The present study was intended to identify the method that combines the highest quality of stained sections with a short period of time. METHODS 50 extracted premolars were subjected to decalcification using 10 % Formic acid and 5 % Trichloroacetic acid (TCA). The efficacy of decalcifying agents was evaluated by recording the time taken by particular acid to decalcify the tooth completely. The preservation of morphological characteristics was assessed on the basis of ease of sectioning, uniformity of staining, damage to odontoblast layer, retraction of pulp and fraying of dentinal tubules. RESULTS Comparatively decalcification was faster with 5 % TCA than 10 % Formic acid. Whereas, 10 % formic acid was more considerate on soft tissues than 5 % TCA. All the results were statistically significant. CONCLUSIONS Samples decalcified with 10 % formic acid gave fairly good results, so it can be used in cases of diagnostic urgencies. KEY WORDS Teeth, Decalcification, Acids, Histopathology

Analysis of Mineral Density of Calcified Tissues in Children with X-Linked Hypophosphatemic Rickets and Hypophosphatasia Using Cone Beam Computed Tomography Data

The purpose of the present cohort study was a quantitative assessment of the enamel, dentin, and alveolar bone mineral density (BMD) using Cone Beam Computed Tomography (CBCT) scans in patients with X-linked hypophosphatemic rickets (HLHR) and hypophosphatasia (HPP) and a comparison with the data obtained from the control group. Methods and Results: The unrepresentative, non-random sample included 30 CBCT scans of children with genetically and biochemically confirmed XLHR (OMIM #307800) and HPP (OMIM: 146300, 241510, 241500, and 146300). X-ray examination and dental care were carried out in the Radiology Diagnostics Department and Pediatric Dentistry Department at Moscow State University of Medicine and Dentistry named after AI Evdokimov. The mineral density of calcified tissues (enamel, dentin, and alveolar bone) was evaluated using i-CAT Vision TM software options on reconstructed CBCT axial views. The images of all XLHR and HPP patients visualized large pulp chambers with prominent pulp horns extending to the dentin-enamel junction. The present study revealed poor alveolar bone mineralization in patients with HPP and XLHR. Analysis of CBCT scans showed a significant dentine hypodensity in XLHR patients, which may contribute to the emergence of multiple, spontaneous, periapical abscesses spreading rapidly in the jawbone. Conclusion: Data obtained could be used for planning dental treatment of patients with XLHR and HPP.

Histomorphometric Analysis of Osseointegrated Grade V Titanium Mini Transitional Implants in Edentulous Mandible by Backscattered Scanning Electron Microscopy (BS-SEM)

The purpose of this study is to assess the use of grade V titanium mini transitional implants (MTIs) immediately loaded by a temporary overdenture. For this, a histomorphometric analysis of the bone area fraction occupancy (BAFO) was performed by backscattered scanning electron microscopy (BS-SEM). Four female patients were submitted to surgery in which two MTIs were installed and immediately loaded with a temporary acrylic prosthesis. During the same surgery, two regular diameter implants were placed inside the bone and maintained without mechanical load. After 8 months, the MTIs were extracted using a trephine and processed for ultrastructural bone analysis by BS-SEM, and the regular-diameter implants were loaded with an overdenture device. A total of 243 BAFOs of MTIs were analyzed, of which 94 were mainly filled with cortical bone, while 149 were mainly filled with trabecular bone. Bone tissue analysis considering the total BAFOs with calcified tissues showed 72.13% lamellar bone, 26.04% woven bone, and 1.82% chondroid bone without significant differences between the samples. This study revealed that grade V titanium used in immediately loaded MTI was successfully osseointegrated by a mature and vascularized bone tissue as assessed from the BAFO.

Anatomical Distribution of Ochronotic Pigment in Alkaptonuric Mice is Associated with Calcified Cartilage Chondrocytes at Osteochondral Interfaces

Alkaptonuria (AKU) is characterised by increased circulating homogentisic acid and deposition of ochronotic pigment in collagen-rich connective tissues (ochronosis), stiffening the tissue. This process over many years leads to a painful and severe osteoarthropathy, particularly affecting the cartilage of the spine and large weight bearing joints. Evidence in human AKU tissue suggests that pigment binds to collagen. The exposed collagen hypothesis suggests that collagen is initially protected from ochronosis, and that ageing and mechanical loading causes loss of protective molecules, allowing pigment binding. Schmorl’s staining has previously demonstrated knee joint ochronosis in AKU mice. This study documents more comprehensively the anatomical distribution of ochronosis in two AKU mouse models (BALB/c Hgd−/−, Hgd tm1a−/−), using Schmorl’s staining. Progression of knee joint pigmentation with age in the two AKU mouse models was comparable. Within the knee, hip, shoulder, elbow and wrist joints, pigmentation was associated with chondrons of calcified cartilage. Pigmented chondrons were identified in calcified endplates of intervertebral discs and the calcified knee joint meniscus, suggesting that calcified tissues are more susceptible to pigmentation. There were significantly more pigmented chondrons in lumbar versus tail intervertebral disc endplates (p = 0.002) and clusters of pigmented chondrons were observed at the insertions of ligaments and tendons. These observations suggest that loading/strain may be associated with increased pigmentation but needs further experimental investigation. The calcified cartilage may be the first joint tissue to acquire matrix damage, most likely to collagen, through normal ageing and physiological loading, as it is the first to become susceptible to pigmentation.

Health Benefits and Application of Stevia rebaudiana Bertoni in Dentistry

A wide range of artificial and synthetic products have been replaced by the natural products for daily use. The natural products are believed to have more advantages and less adverse effects. The plant products such as stem, flower, fruit, seed, leaves, etc have been experimented. Stevia rebaudiana Bertoni, a perennial shrub which is a native of South America. During World War II, England used it as a sweetener as sugar was not available. By 1970, it was used as a sweetener in Japan. In 1994, US approved steviol glycosides as functional ingredient in dietary supplements. It is non-caloric sweetener which is 200-300 times sweeter than table sugar. Its use as a sweetener was approved by FDA in 2011. There is growing evidence supporting the use of stevia in diabetes, hypertension, weight loss, etc. Dental caries is an infectious microbiologic disease of the tooth that results in localized dissolution and destruction of calcified tissues. There has been an increased interest on antimicrobial and anti-plaque activity of stevia mouth rinse and chewing gums. Researches on the aqueous and alcoholic extracts of stevia have also been conducted to evaluate its potential advantages in the dental field. This review describes in detail the health benefits and application of stevia in dentistry. Keywords: Stevia, Dental, Medical

Dental Caries assessment of Rural Population of Sindh by DMFT (Decayed missing and filled teeth) Index.

Dental caries is known as an infectious disease of microbiologic origin. Streptococcus mutans is established to be the main causative agent, which leads to localized dissolution and destruction of the calcified tissues. It is the most prevalent oral disease which shows an inevitable geographic dissimilarity, socioeconomic patterns and severity around the globe. The role of Fluoride in Caries prevention is extremely imperative as it is substance which relates strongly in the caries process and favours remineralisation of the affected tooth after the bacterial attack has ceased. Objectives: The objective of this study was to record dental caries experience in rural population of district Matiari Sindh. Study Design: Descriptive Cross Sectional. Setting: Camp of Taluka Hospital Matiari. Period: From the period of one year from Jan-Dec 2018. Material & Methods: A total of 102 visitants of camp were included in the study with caries evaluation of around 2569 teeth. Dental Caries status was checked by using DMFT index as recommended by WHO for oral health surveys. Results: Mean DMFT was found to be 0.07±. 146 (5.75%) teeth were found decayed, 43 (1.7%) were found missing due to caries, No tooth was found restored while 2378 (92.6%) were found to be in sound condition. Conclusion: Access to Oral and Dental healthcare services found to be minimal may be due to inadequate Dental facilities and lack of Dental professionals in rural areas of Sindh province.

Development of an in vitro model of calcified cerebral emboli in acute ischemic stroke for mechanical thrombectomy evaluation

​BackgroundCalcified cerebral emboli (CCEs) are a rare cause of acute ischemic stroke (AIS) and are frequently associated with poor outcomes. The presence of dense calcified material enables reliable identification of CCEs using non-contrast CT. However, recanalization rates with the available mechanical thrombectomy (MT) devices remain low.ObjectiveTo recreate a large vessel occlusion involving a CCE using an in vitro silicone model of the intracranial vessels and to demonstrate the feasability of this model to test different endovascular strategies to recanalize an occlusion of the M1 segment of the middle cerebral artery (MCA).​MethodsAn in vitro model was developed to evaluate different endovascular treatment approaches using contemporary devices in the M1 segment of the MCA. The in vitro model consisted of a CCE analog placed in a silicone neurovascular model. Development of an appropriate CCE analog was based on characterization of human calcified tissues that represent likely sources of CCEs. Feasibility of the model was demonstrated in a small number of MT devices using four common procedural techniques.​ResultsCCE analogs were developed with similar mechanical behavior to that of ex vivo calcified material. The in vitro model was evaluated with various MT techniques and devices to show feasibility of the model. In this limited evaluation, the most successful retrieval approach was performed with a stent retriever combined with local aspiration through a distal access catheter, and importantly, with flow arrest and dual aspiration using a balloon guide catheter.​ConclusionCharacterization of calcified tissues, which are likely sources of CCEs, has shown that CCEs are considerably stiffer than thrombus. This highlights the need for a different in vitro AIS model for CCEs than those used for thromboemboli. Consequentially, an in vitro AIS model representative of a CCE occlusion in the M1 segment of the MCA has been developed.