The SARS-CoV-2 virus has shaken the globe with an ongoing pandemic of COVID-19 and has set challenges to every corner of the modern health care setting. The oral mucosa and saliva are high risk sites for higher viral loads and dental health care professionals are considered a high risk group. COVID-19-induced oral lesions and loss of taste and smell are common clinical complaints in the dental health care setting. The SARS-CoV-2 virus has been found to cause a wide range of non-specific oral mucosal lesions, but the specific diagnosis of these mucocutaneous lesions as COVID-19 lesions will facilitate the prevention of SARS-CoV-2 in dental health care settings and aid in proper patient management. The reported loss of taste and smell needs further investigation at the receptor level as it will give new insights into SARS-CoV-2 pathogenicity. The high yield of virus in the salivary secretion is a common finding in this infection and ongoing research is focusing on developing saliva as a rapid diagnostic fluid in COVID-19. In this review, we discuss the significance of oral mucosa, saliva and the relevance of the COVID-19 pandemic in dentistry.

Human cleft lip and/or palate (CLP) are immediately recognizable congenital abnormalities of the face. Lip and palate develop from facial primordia through the coordinated activities of ectodermal epithelium and neural crest cells (NCCs) derived from ectomesenchyme tissue. Subtle changes in the regulatory mechanisms of NCC or ectodermal epithelial cells can result in CLP. Genetic and environmental contributions or a combination of both play a significant role in the progression of CLP. Model organisms provide us with a wealth of information in understanding the pathophysiology and genetic etiology of this complex disease. Small teleost, zebrafish (Danio rerio) is one of the popular model in craniofacial developmental biology. The short generation time and large number of optically transparent, easily manipulated embryos increase the value of zebrafish to identify novel candidate genes and gene regulatory networks underlying craniofacial development. In addition, it is widely used to identify the mechanisms of environmental teratogens and in therapeutic drug screening. Here, we discuss the value of zebrafish as a model to understand epithelial and NCC induced ectomesenchymal cell activities during early palate morphogenesis and robustness of the zebrafish in modern research on identifying the genetic and environmental etiological factors of CLP.

A small fresh water fish, the Mexican tetra (Astyanax mexicanus) is a novel animal model in evolutionary developmental biology. The existence of morphologically distinct surface and cave morphs of this species allows simultaneous comparative analysis of phenotypic changes at different life stages. The cavefish harbors many favorable constructive traits (i.e., large jaws with an increased number of teeth, neuromast cells, enlarged olfactory pits and excess storage of adipose tissues) and regressive traits (i.e., reduced eye structures and pigmentation) which are essential for cave adaptation. A wide spectrum of natural craniofacial morphologies can be observed among the different cave populations. Recently, the Mexican tetra has been identified as a human disease model. The fully sequenced genome along with modern genome editing tools has allowed researchers to generate transgenic and targeted gene knockouts with phenotypes that resemble human pathological conditions. This review will discuss the anatomy of the craniofacial skeleton of A. mexicanus with a focus on morphologically variable facial bones, jaws that house continuously replacing teeth and pharyngeal skeleton. Furthermore, the possible applications of this model animal in identifying human congenital and metabolic skeletal disorders is addressed. Developmental Dynamics 248:153‐161, 2019. © 2018 Wiley Periodicals, Inc.

The vertebrate bony skeleton is remodelled continuously by bone deposition and reabsorption, which is essential for normal development, growth, repair and for the mineral homeostasis. Remodelling of the skeleton usually involves the removal of the bone by osteoclasts and the subsequent formation of new bone by osteoblasts. These remodelling mechanisms can be found in the teleost fish skeleton with special adaptation to the aquatic life. Most of the fish species have teeth in their craniofacial region and replace their dentitions though out the life which lead to continuous bone remodelling activity in the tooth‐bearing bones. The Mexican tetra (Astyanax mexicanus), is a small teleost fish that exists as two morphs; sighted and blind cave form. The degeneration of the eyes, result in the characteristics craniofacial phenotype in cavefish. However, little is known about the cellular mechanisms underlying the remodelling activity of the skeleton of this species. This study was designed to identify the cellular interactions during the development of craniofacial skeleton of Mexican cavefish. Histological and whole mount analysis was performed to compare the development of the skeleton in these two morphs. The cavefish showed delayed eruption of teeth in tooth‐bearing bones but has large jaw bones compared to the surface larval fish. Sites of bone resorption in the bony skeleton will be investigated by RNA in situ hybridization and ultrastructural analysis. Live bone staining techniques will be used to identify the pattern of bone deposition. This study will provide insights into the evolution of osteoblastic and osteoclastic cell activity and will highlight the use of this species as a model in mammalian skeletal disorders.Support or Funding InformationThis research was funded by the University of Manitoba.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.