Cavity Base Research Articles

Finite element simulation on MHD Free Convection in a Square Enclosure with Elliptical Shaped Obstacle

The study is focused on the magneto-hydrodynamic (MHD) free convection flow phenomenon with varied positions of elliptical obstacle in a square enclosure. Cavity's base wall is uniformly heated, and the enclosure has a cold top wall and insulated side walls. Three diverse positions of elliptical obstacle, such as, left-bottom elliptical obstacle (LBEO), right-bottom elliptical obstacle (RBEO) and right-top elliptical obstacle (RTEO) are deemed for the analysis inside the enclosure. Additionally, the elliptical barriers are evenly heated. The mathematical model was created using a few governing equations with boundary conditions, and the non-dimensional governing equations were then solved using a Galerkin finite element formulation. Various elliptical obstacles and the parametric research study for the wide range of Hartmann number (0≤Ha≤100), fixed Rayleigh number (Ra = 103) and Prandtl number (Pr = 0.7) have been used in this case. The results have been demonstrated for various positions of elliptical obstacle (LBEO, RBEO and RTEO) using the streamline phase, isotherms, and average Nusselt number in the cavity. The average Nusselt number was found to drop for the pattern of LBEO and RBEO when the Hartman number was raised, but increased for RTEO pattern.
 GANIT J. Bangladesh Math. Soc. 43.1 (2023) 063- 075

On the nonlinear thermal stress, thermal creep, and thermal edge flows in triangular cavities

Here, rarefied thermally driven flow is investigated in two-dimensional equilateral triangular cavities with different uniform wall temperatures. We used three different solvers, i.e., the direct simulation Monte Carlo solver, discrete unified gas kinetic scheme solver, and continuum set of equations of a slow non-isothermal flow solver. Two main cases were considered; in the first case, the cavity's base is considered hot, and the other sides were set cold. In the second case, the right half of the bottom wall was regarded as a diffuse reflector with high temperature, while the left half of the bottom border was set as a specular reflector. The adjacent side walls were set cold with diffuse reflector boundary conditions. The imposed temperature difference/wall boundary condition induces various vortices in the geometry. In case 1, we observe that principal vortices appearing in the triangle are due to nonlinear thermal stress effects, and the thermal creep effects cause other smaller, confined ones. In case 2, a thermal edge flow is set up from the specular wall on the way to the diffusive hot wall, creating a large vortex in the geometry. As the Knudsen number decreases, another small vortex appears near the left cold border.

Cavity Bases Revisited.

ObjectiveThe aim of this paper was to review the current literature on cavity bases while focusing on the role of zinc oxide eugenol (ZOE) and resin-modified glass ionomers (RMGI) as cavity bases.Materials and MethodsA thorough literature search between 1970 and 2020 was done using Scopus, PubMed, and Google Scholar databases. The keywords of the search strategy were as below: cavity liners and bases, pulp protection, zinc oxide eugenol, and resin-modified glass ionomer. No specific inclusion or exclusion criteria were applied as to what articles would be included in this review.ConclusionThis review emphasizes that the available literature provides very little evidence to support the routine use of a base under amalgam or composite restorations. This review favors the adoption of “no more lining or bases” in shallow and moderate cavity preparations. However, an exception might be a “protective base” of RMGI following the application of calcium hydroxide (CH) liners in deep cavities. Bonded RMGIs are suitable cavity base materials and should always replace zinc oxide eugenol bases in daily practice.

The tripartite architecture of the eukaryotic integral membrane protein zinc metalloprotease Ste24.

Ste24 enzymes, a family of eukaryotic integral membrane proteins, are zinc metalloproteases (ZMPs) originally characterized as “CAAX proteases” targeting prenylated substrates, including a‐factor mating pheromone in yeast and prelamin A in humans. Recently, Ste24 was shown to also cleave nonprenylated substrates. Reduced activity of the human ortholog, HsSte24, is linked to multiple disease states (laminopathies), including progerias and lipid disorders. Ste24 possesses a unique “α‐barrel” structure consisting of seven transmembrane (TM) α‐helices encircling a large intramembranous cavity (~14 000 Å3). The catalytic zinc, coordinated via a HExxH…E/H motif characteristic of gluzincin ZMPs, is positioned at one of the cavity's bases. The interrelationship between Ste24 as a gluzincin, a long‐studied class of soluble ZMPs, and as a novel cavity‐containing integral membrane protein protease has been minimally explored to date. Informed by homology to well‐characterized soluble, gluzincin ZMPs, we develop a model of Ste24 that provides a conceptual framework for this enzyme family, suitable for development and interpretation of structure/function studies. The model consists of an interfacial, zinc‐containing “ZMP Core” module surrounded by a “ZMP Accessory” module, both capped by a TM helical “α‐barrel” module of as yet unknown function. Multiple sequence alignment of 58 Ste24 orthologs revealed 38 absolutely conserved residues, apportioned unequally among the ZMP Core (18), ZMP Accessory (13), and α‐barrel (7) modules. This Tripartite Architecture representation of Ste24 provides a unified image of this enzyme family.

Pulp response to the Er:YAG laser in the cavity preparation

Pulpal responses after cavity preparation and perforation by Er:YAG laser were examined by histopathological studies using adult dog teeth. In the experimental laser groups, 100 mJ/pulse–10 pps or 250 mJ/pulse–10 pps irradiations were performed for cavity preparation, and perforations were made at the cavity bases under the condition of 100 mJ/pulse–10 pps. As a control, an air-turbine group was employed. After cavity preparation, the restoration was made with composite resin and, on days 7 and 90, the histopathological specimens were prepared according to a conventional method, stained by hematoxylin and eosin double-staining, and observed. Pulpal responses after glass-ionomer cement restorations were also examined. The cavities were formed under irradiation conditions of 100 mJ/pulse–10 pps. Cavity preparation by Er:YAG laser caused no difference in the changes of pulp tissue compared with the cavity preparation by turbine. No differences were found between laser and turbine cavities restored by glass-ionomer cement. It was proved that, when a perforation to the pulp occurred during the laser application, calcium hydroxide treatment enabled the maintenance of healthy pulp tissue.

Temperature in the pulp chamber during polishing of amalgam restorations.

Temperature changes in the pulp chamber were determined by means of thermocouples during polishing procedures of Class V amalgam restorations. The dependence of the temperature elevation on the separation between cavity floor and thermocouple junction was determined. Temperatures obtained with rubber cups were higher than those with cup brushes. Intermittent polishing caused less heating, by about 30%, than continuous procedures. Cavity bases and liners, applied at a thickness of 0.2 to 0.3 mm, had little influence on the temperatures in the pulp chamber.

Pulpal response to four restorative materials

This study deals with pulpal response to four types of restorative material. Class V cavities were prepared in seventy-eight teeth of three miniature swine and were restored with zinc oxide and eugenol, a commercially available product called IRM, a mixture of ethoxybenzoic acid with fillers called EBA, and a mixture of isobutyl cyanoacrylate and zinc phosphate called CAZI. The animals were killed after 1, 2, and 3 weeks, and the teeth were examined microscopically. This study revealed the following: 1. 1. With the exception of one tooth, which showed a micro-abscess, irreversible pulp damage was not observed. 2. 2. All three of the restorative materials appear biologically acceptable to the dental pulp. 3. 3. Odontoblastic disruption and inflammatory infiltrate were not severe in any case. They were, however, least marked in the zinc oxide and eugenol restorations and most prominent in teeth restored with cyanoacrylate-containing restorative material. 4. 4. The layer of reparative dentine formed in response to the filling materials was proportional to the degree of odontoblastic disruption and the inflammator yinfiltrate. It was more prominent in those teeth which were restored with CAZI and EBA than in teeth filled with the other materials. 5. 5. It appears from this study that any of the three experimental materials tested could be used as filling materials. However, in cases in which the therapeutic aim is to acquire a thick layer of reparative dentine, a cavity base with either the EBA or CAZI would be preferable. On the other hand, where these materials are to be used as semipermanent restorations rather than as cavity bases, their physical properties and their resistance to the oral environment should be the decisive factors.