Direct restorative materials use in Australia in 2002

Background: This study aimed to determine the reasons for dentists' choice of materials, in particular amalgam and resin composite, in Australia. Method: A questionnaire was developed to elicit this information. The names and addresses of 1000 dentists in Australia were selected at random. The questionnaire was mailed to these dentists with an explanatory letter and reply-paid envelope. Results: A total of 560 replies were received. Regarding choice of material, 99 per cent of respondents cited clinical indication as an influencing factor, although patients' aesthetic demands (99 per cent), patients' financial situation (82 per cent), and lecturers' suggestions (72 per cent) were also reported to influence respondents' choice of materials. Twelve per cent of respondents used composite 'always', 29 per cent 'often', 32 per cent 'sometimes', 23 per cent 'seldom' and 4 per cent 'never' in extensive load-bearing cavities in molar teeth. For composite restorations in posterior teeth, 84 per cent 'always', 'often' or 'sometimes' used the total etch technique, 84 per cent used a thick glass-ionomer layer and 36 per cent never used rubber dam. Fifty-nine per cent of respondents reported a decreased use of amalgam over the previous five years. Sixty-eight per cent of respondents agreed with the statement 'discontinuation of amalgam restricts a dentist's ability to adequately treat patients'. Seventy-five per cent considered that the growth in the use of composites increased the total cost of oral health care. Conclusions: Of the respondents from Australia 73 per cent place large composite restorations in molar teeth and their choice of material is influenced greatly by clinical indications, and patients' aesthetic demands.

Quantum effects on adsorption and diffusion of hydrogen and deuterium in microporous materials

Monte Carlo and molecular dynamics simulations and neutron scattering experiments are used to study the adsorption and diffusion of hydrogen and deuterium in zeolite Rho in the temperature range of 30-150 K. In the molecular simulations, quantum effects are incorporated via the Feynman-Hibbs variational approach. We suggest a new set of potential parameters for hydrogen, which can be used when Feynman-Hibbs variational approach is used for quantum corrections. The dynamic properties obtained from molecular dynamics simulations are in excellent agreement with the experimental results and show significant quantum effects on the transport at very low temperature. The molecular dynamics simulation results show that the quantum effect is very sensitive to pore dimensions and under suitable conditions can lead to a reverse kinetic molecular sieving with deuterium diffusing faster than hydrogen.

Biodegradable starch-based nanocomposite packaging materials

Polymer processing experiments have been conducted with a twin screw extruder. Different formulations of starch-based nanocomposites are being tested in a pilot scale film blowing tower. The physical properties of different starch-based films have been examined with thermal and mechanical analysis and X-ray diffraction. The results show that the addition of organoclay significantly improves both the processing and tensile properties over the original starch blends. The mechanical and thermal properties of the blends are also sensitive to the scale the clay particles are dispersed.

Performance of some unbound roadbase materials from Queensland = Performance de certains matériaux granulaires de base du Queensland

This paper summarises recent investigations into characterisation and performance of unbound roadbase materials carried out by Main Roads, Queensland (QDMR), on road projects across the state. Performance based tests such as the Repeated Load Triaxial (RLT) and the Wheel Tracker (WT) are the primary tools which are increasingly used by QDMR to overcome the limitations of simple specification type tests. This paper shows the inadequacy of current specification tests to rank material performance. The performance based tests show that the properties of the coarse aggregate alone are inadequate for sound performance; enable the contribution to mechanical behaviour by plastic fines with high matric suction to be assessed,- further, and facilitates ranking of material behaviour. Simple shakedown analyses undertaken yield similar material rankings. Finally, some materials from the performance based characterisation are compared with Falling Weight Deflectometer (FWD) in-service pavement performance data.