Fluoride and Functionalized β-tricalcium Phosphate (fTCP) Fluoride Toothpaste Affect the Primary Dentin Caries Surface: A Comparison by Estimation Statistics

This study aims to compare the effect of fTCP-contained toothpaste in combination with 950 ppm fluoride on primary dentin caries surface to ordinary 1100 ppm fluoride toothpaste by using estimation statistics. Dental caries with deep lesion and dentin exposure from nine primary teeth were cut into two equal parts and randomly divided into two groups in a before-after study. Each group was brushed with one type of toothpaste two times per day for 28 days and rested in artificial saliva. SEM images of cavity bottom surfaces and energy-dispersive X-ray spectrometry (EDX) were used to determine the percentage of calcium (Ca), phosphorus (P), fluoride (F) and oxygen (O) at six continuous measured areas from the surface of the cavity bottom into 45 µm depth before and after brushing. About 95% confidence interval of the mean difference was calculated by performing bootstrap resampling with 5000 resamples followed by comparison analysis. The percentage of Ca, P, F, O was shifted after treatment. There was no difference between the two groups. The SEM images reflected a similar illustration of EDX data. The combination of fTCP and 950 ppm fluoride in toothpaste showed equivalent effectiveness to the 1100 ppm fluoride toothpaste in primary dentin caries.

OPEN PERFORATION OF MAXILLA ALVEOLAR SPROUT, PERFORATION OF THE TOOTH CAVITY BOTTOM AT ENDODONTIC TREATMENT OF THE FIRST MOLAR ON MAXILLA (CLINICAL CASE)

The paper presents a clinical issue of multiple doctor’s errors when he/she performs endodontic treatment. Injection needle defects that caused perforation in the bone tissue of the alveolar process, partial preparation of the tooth cavity, loss of the cheek, medial root canal, perforation of the bottom of the tooth cavity were revealed. As a result, errors caused complications. A corresponding medical-prophylactic complex was completed with a successful result.

Study of Starting Problem of Axisymmetric Divergent Dual Throat Nozzle

Compared to the conventional axisymmetric dual throat nozzle, the axisymmetric divergent dual throat nozzle (ADDTN) can offer larger thrust vector angles. However, the starting problem maybe exists in the ADDTN and results in a huge thrust loss. In this paper, the ADDTN starting problem has been studied by steady and unsteady numerical simulations. The effects of nozzle geometric parameters on internal nozzle performance have been discussed in detail, including cavity divergence angle, cavity convergence angle, cavity length, expansion ratio, rounding radius at the nozzle throat, and rounding radius at the cavity bottom. And, the shock oscillation phenomenon is found inside the recessed cavity in some high-expansion ratio configurations. In addition, a bypass is proposed in this study to solve the ADDTN starting problem. The main numerical simulation results show that the expansion ratio is the most sensitive parameter affecting the starting characteristic of ADDTN, followed by the cavity divergence angle and the cavity length. And, among these parameters, the parameters of cavity convergence angle and rounding radius at the cavity bottom contribute the least to the starting problem. Besides, the ADDTN configurations of large rounding radius at the nozzle throat tend to start.

Turbulent heat transfer for impinging jet flowing inside a cylindrical hot cavity

Convective heat transfer from an isothermal hot cylindrical cavity due to a turbulent round jet impingement is investigated numerically. Three-dimensional turbulent flow is considered in this work. The Reynolds stress second order turbulence model with wall standard treatment is used for the turbulence predictions the problem parameters are the jet exit Reynolds number, ranging from 2x104 to 105and the normalized impinging distance to the cavity bottom and the jet exit Lf, ranging from 4 to 35. The computed flow patterns and isotherms for various combinations of these parameters are analyzed in order to understand the effect of the cavity confinement on the heat transfer phenomena. The flow in the cavity is divided into three parts, the area of free jet, and the area of the jet interaction with the reverse flow and the semi-quiescent flow in the region of the cavity bottom. The distribution of the local and mean Nusselt numbers along the cavity walls for above combinations of the flow parameters are detailed. Results are compared against to corresponding cases for impinging jet on a plate for the case of the bottom wall. The analysis reveals that the average Nusselt number increases considerably with the jet exit Reynolds number. Finally, it was found that the average Nusselt number at the stagnation point could be correlated by a relationship in the form Nu=f(Lf,Re).

On Energy Harvesting Characteristics of Cymbal Transducer

The energy-generating capability of a cymbal transducer was studied in order to supply the power of low-consumption electric products. An analytical model of the cymbal transducer was established by the hydrostatic piezoelectric constant method. The relation between the material of metal cap as well as the structure of transducer and energy generation were analyzed by numerical simulation. The simulation validation was done by the element software ANSYS. The results of the study show that, in the same force, the materials of metal cap, the radius of cavity bottom, and the thickness of metal cap have bigger influence on the voltage outputted, the radius of cavity top have less influence on the voltage outputted.