A Contemporary Evaluation on Posterior Direct Restoration Teaching among Undergraduates in Dental Schools in Malaysia

There is a current trend to restore posterior teeth with composite resin due to increasing demands on natural tooth colour restoration and increased concern about the safety of amalgam restorations. The objective was to evaluate the current teaching of posterior direct restoration among restorative dental lecturers in Malaysia compared to available international literature. An online questionnaire, which sought information on the teaching of posterior restoration was developed and distributed to 13 dental schools in Malaysia. The response rate for the questionnaire was 53.8%. The most popular posterior restoration teaching methods among the respondents were lecture (95.7%), demonstration (87.0%) and problem-based learning (PBL) (73.9%), while continuous assessment and a practical competency test (82.6%) were the most popular assessment methods. Placing a hard setting calcium hydroxide and GIC base for deep cavity restored by composite restoration was taught in 79.2% of cases. The standard protocols for posterior composite restoration were incremental filling in deep cavity (87.5%), using circumferential metal bands with wooden wedge (91.7%), with a total etch system (95.8%), using a light emitting diode (LED) light curing unit (91.7%), finishing using water cooling (80%) and finishing with a disc (87.5%). Graduates from dental schools in Malaysia received similar theoretical, preclinical and clinical teaching on posterior restoration techniques, although there were variations in the delivery methods, techniques and assessments, pointing to a need for uniformity and consensus.

CONTRIBUTION OF DRIFT AND DIFFUSION TO WATER CAPACITY DEIONIZATION

Drift and diffusion of ions in a cavity having the shape of oblate ellipsoid of revolution are considered. The obtained approximate relationship, between the time of drift and diffusion filling of deep cavity with ions, contains the applied voltage and the ratio of cavity size to the distance between electrodes. It shows that in the performed experiments with the device for water capacitive deionization the filling of electrodes by ions was carried out, mainly, due to diffusion.

Investigation of Particle Loading On the Turbulent Flow Over a Deep Cavity

Turbulent particle-laden flows are of interest due to their presence in many industrial and natural flows. The effect that the particles have on the turbulence of the fluid is referred to as turbulence modulation. Experimental data is lacking at Reynolds numbers greater than 100,000, and at dense loadings (FV > 1%). In this work, turbulent particle-laden flow over a deep cavity with an aspect ratio of 1, was studied at Reynolds numbers of 11,500 and 115,000, and particle loadings of 0%, 1%, 3%, and 5% by weight/volume (solid-phase specific gravity = 1). Super absorbent particles were used to create an index-matched environment with water as the working fluid. Data were acquired using 2-D planar particle image velocimetry (PIV) along the center span of the geometry. Mean and root-mean-square (rms) velocities were calculated for the fluid phase. The flow structures were identified and located using the gamma criteria. The results showed that the particle loading changed the locations of the recirculation regions within the cavity. The mean velocities were nominally unaffected by loading for a respective Reynolds number case. Prior literature suggested that the particles would attenuate the turbulence, however, the current data showed no single trend. Turbulence modulation of the flow was found to be sensitive to the Reynolds number and location within the flow field. The changes in the turbulence appeared to be primarily due to the differences in the location in the flow structures.

Research on Sapphire Deep Cavity Corrosion and Mask Selection Technology

Aimed at the problem of the small wet etching depth in sapphire microstructure processing technology, a multilayer composite mask layer is proposed. The thickness of the mask layer is studied, combined with the corrosion rate of different materials on sapphire in the sapphire etching solution, different mask layers are selected for the corrosion test on the sapphire sheet, and then the corrosion experiment is carried out. The results show that at 250 °C, the choice is relatively high when PECVD (Plasma Enhanced Chemical Vapor Deposition) is used to make a double-layer composite film of silicon dioxide and silicon nitride. When the temperature rises to 300 °C, the selection ratio of the silicon dioxide layer grown by PECVD is much greater than that of the silicon nitride layer. Therefore, under high temperature conditions, a certain thickness of silicon dioxide can be used as a mask layer for deep cavity corrosion.