The causes of subcutaneous emphysema of relevance to dental practitioners?

Data sources An electronic search was conducted using EMBASE, LILACS, PubMed, SciELO, Scopus, Web of Science, and two grey literature data sources. All issues of nine dentistry journals and relevant chapters in four endodontic textbooks were manually searched.Study selection Abstracts of all the studies that were identified during the electronic and manual searches were obtained and screened independently by two reviewers in order to select clinical studies, case series, or case reports describing subcutaneous emphysema that occurred in adult patients during or immediately after root canal treatment.Data extraction and synthesis Predetermined data were extracted from each study independently by two reviewers and organised into data tables. All disagreements were resolved through discussion with a third reviewer. The data obtained were combined through a narrative synthesis.Results Following full-text evaluation according to the inclusion criteria, 51 articles that described 65 cases of subcutaneous emphysema were included. There were 36 case reports and 15 case series. The condition was mainly reported in female patients and maxillary teeth. While the age of the patients ranged from 18 to 63 years, this demographic information was missing from a few studies. Details on the involved tooth and diagnosis were also missing from several articles. In most of the cases, subcutaneous emphysema developed during initial root canal treatment. The diagnosis was mainly based on intraoral, plain facial, neck, or chest radiographs, while computed tomography (CT) scans were obtained in fewer cases. The majority of the patients were referred to a different practice, a hospital or university clinic for the management of the condition by more specialised healthcare practitioners. In addition to drying root canals using air pressure, irrigation with hydrogen peroxide, and the air-water spray produced by handpieces, it was reported that laser-produced spray and ozone gas infiltration may also be the culprits of subcutaneous emphysema. The signs and symptoms resolve within 17 days. Its management mostly remains empirical and involves the use of antibiotics, analgesics, local application of cold or hot compresses, or administration of oxygen and hospitalisation, among other methods.Conclusions The systematic review showed that subcutaneous emphysema can occur during both surgical and nonsurgical endodontic treatment. Air streams or air-water sprays should not be directed toward the root canals or areas with mucosal discontinuity. None of the management approaches were clearly associated with a faster recovery. The review asked for developing guidelines in order to avoid unnecessary or potentially harmful interventions.

Degenerative and regenerative morphological aspects in peri-implantitis.

The purpose of this study was to describe the tissues surrounding two early failed dental implants morphologically and ultrastructurally. In the first case, the implant's surface was analyzed by scanning electron microscopy (SEM) using an environmental scanning electron microscope and the surrounding tissues were analyzed by light microscopy (LM) and transmission electron microscopy. In the second case we used only LM. By SEM analysis, very thin connective tissue was seen at the implant's apex; in the middle part, highly vascularized connective tissue and poorly mineralized areas were found, and there were fewer mineralized areas at the implant's base. Histologically and ultrastructurally, we identified a heterogeneous cellular population including fibroblast-like cells and osteoblasts with abundant amorphous extracellular matrix, as well as a number of inflammatory cells, predominantly neutrophils. In a small area around the implant, microorganisms classified as Actinomyces were identified. In this case, degenerative aspects were predominantly caused by infection. In the second case, our observations focused on recruitment of mesenchymal stem cells, their proliferation and differentiation into epithelial cells with keratinocyte phenotype, and formation of de novo capillaries from mesenchymal progenitors of endothelial cells. These regenerative events were accompanied by multiple areas of mineralization, culminating in bone formation around the implant. Correlative microscopic observations are necessary to conduct in future studies, in various clinical conditions and post-operative stages, to better define the cellular events involved in healing and osseointegration; our observations clearly depict significant regenerative aspects despite the degenerative ones.

Methamphetamine-induced neuronal necrosis: the role of electrographic seizure discharges.

We have evidence that methamphetamine (METH)-induced neuronal death is morphologically necrotic, not apoptotic, as is currently believed, and that electrographic seizures may be responsible. We administered 40mg/kg i.p. to 12 male C57BL/6 mice and monitored EEGs continuously and rectal temperatures every 15min, keeping rectal temperatures <41.0°C. Seven of the 12 mice had repetitive electrographic seizure discharges (RESDs) and 5 did not. The RESDs were often not accompanied by behavioral signs of seizures-i.e., they were often not accompanied by clonic forelimb movements. The 7 mice with RESDs had acidophilic neurons (the H&E light-microscopic equivalent of necrotic neurons by ultrastructural examination) in all of 7 brain regions (hippocampal CA1, CA2, CA3 and hilus, amygdala, piriform cortex and entorhinal cortex), the same brain regions damaged following generalized seizures, 24h after METH administration. The 5 mice without RESDs had a few acidophilic neurons in 4 of the 7 brain regions, but those with RESDs had significantly more in 6 of the 7 brain regions. Maximum rectal temperatures were comparable in mice with and without RESDs, so that cannot explain the difference between the two groups with respect to METH-induced neuronal death. Our data show that METH-induced neuronal death is morphologically necrotic, that EEGs must be recorded to detect electrographic seizure activity in rodents without behavioral evidence of seizures, and that RESDs may be responsible for METH-induced neuronal death.

Intercellular communication by extracellular vesicles with emphasis on the roles of cordocytes in the human brain. An ultrastructural study.

We describe in this work the presence of extracellular vesicles (EVs) along different cell types, especially cordocytes, in various clinical conditions of the human brain (atherothrombotic disease, cerebral tumors, hygroma durae matris, intracerebral cysts, Moyamoya disease and parenchymatous hematoma) using transmission electron microscopy (TEM). EVs, illustrated as exosomes and microvesicles, were causally related to cell-to-cell communication, and other vital functions of resident cells around the brain parenchyma, either around the cortical vessels or into the subarachnoid space and the reticular arachnoid. Our direct demonstration by TEM of these information transporters in all locations and situations where the cordocytes play coordinating and regulating roles, producing and delivering a significant number of EVs to their targets, remains to be better documented in future studies. This first study on this topic showed clearly that EVs can be important modulators of cell functions with roles in cell activation, differentiation, phenotypic change, cancer progression, from precursor/stem cells to tumoral phenotypes, because EVs are released en masse during key interactions and certain moments.

Cordocytes-stem cells cooperation in the human brain with emphasis on pivotal role of cordocytes in perivascular areas of broken and thrombosed vessels.

This study is based on data analysis by light and transmission electron microscopy of the surgical cases in cerebral tumors, cerebrovascular malformations, thromboses in the carotid system, and other injuries such as perivascular hemorrhage. We examined cortical arteries and veins, perivascular areas with old hematic masses, vasculogenic foci, and broken large vessels. We identified, characterized, and compared both undifferentiated cells and well-differentiated cordocytes within periadventitial areas where these cells cooperate very well with precursor/stem cells to perform vital functions for cerebral vasculature with immediate effect on brain parenchyma. This useful cellular cooperation was observed by serial sections pointing out the main role of cordocytes during the entire process of collateral vessel formation after thrombosis and, respectively, in vascular wall repair after ruptures. This is the first cytohistopathological study which illustrates and explains some facets of cordocytes-stem cells cooperation around the vessels of human brain with emphasis on the fundamental role of cordocytes in response to vascular injuries. Our pioneering study will be completed for both basic science and modern medical care by further studies.

Ultrastructural patterns of the activated cell death programs in the human brain.

The authors analyzed by transmission electron microscopy (TEM) neurosurgical samples obtained from patients with cerebral tumors, neurotrauma, cerebral ischemia, Moyamoya disease, encephalitis, etc. Their observations concern a variety of dying cell types by different programmed death pathways, including apoptosis, paraptosis, autophagy, autoschizis, programmed necrosis, as well as combined and coexisting forms. This ample work pointed out not only the role of TEM in cell death diagnosis, but the biological differences in cell behavior and beneficial or detrimental effects of suicides for homeostasis, survival, or normal functioning of a tissue, like the integrated vascular tissue and brain parenchyma.

From pluripotent stem cells to multifunctional cordocytic phenotypes in the human brain: an ultrastructural study.

Light microscopy and transmission electron microscopy were used to investigate surgical cases in a variety of pathological conditions (thromboses, tumors, cerebrovascular malformations, Moyamoya disease) to identify and characterize different phenotypes belonging to a new interstitial cell recently described ultrastructurally in the brain and here named "cordocyte." Also, this work is an attempt to identify and characterize precursor/stem cells for cordocytic lineage in the perivascular areas, within perivascular nerves and pia mater (now considered a cordocytic-vascular tissue). Unexpected relationships and functions emerge from observations concerning these phenotypes, almost ubiquitous, but not yet fully studied in the brain.

A comparative ultrastructural study of a new type of autoschizis versus a survival cellular mechanism that involves cell membranes of cerebral arteries in humans.

The authors analyzed by transmission electron microscopy the modifications of plasmalemma and nuclear envelope in the cerebral arterial wall in humans. Their ultrastructural observations are performed on the tunica media and endothelium. During autoschizis, some smooth muscle cells showed deep invaginations of the nuclear envelope with multiple craters that disintegrate the nucleus, whereas in the endothelium repetitive invaginations of plasmalemma lead to cell demise by cytoplasmic self-excisions. During survival mechanism, a perinuclear constriction of plasmalemma occurs, which conserves nucleus and cytoskeleton, and only a segregated cytoplasmic area, without organelles, is removed in lumen.