The amalgam restoration is regarded as the simplest and best method for the mass treatment of earlier carious lesions in pre-ventive dentistry but there are still some practical problems that remain unsolved.
More efficient technics is to be divised and also the suppresson of mercury absorption by the operators is the important point in such severe exposure to mercury.
This investigation was designed to improve the usual procedure by combining the use of an mechanical amalgamator and pre-prepared amalgam kept in a vacuum bottle containing dry ice.
The air turbine (Air Dent Unit) was also applied in full through this experiment to reduce the cutting time and the pain or uncomfortable feeling of the children.
1) The mechanical amalgamator which can mix mercury and alloy even at the weight ratio of 6 to 5 involed no need to sequeeze out mercury. Therefore, the time for restoration was markedly reduced to 71.5 sec.in comparison with 150 sec.in the routine manual procedure when the mixing time was set constant as 40 sec.in both methods.
2) Urinary mercury excretion of three mixing operators following constantly mixing amalgam far 50 min.showed on the average the increase of 80 μ g Hg per day in the usual procedure, while using amalgamator, it only increased by 15 μ g Hg per day.
3) After shaking with the amalgamator, the amalgam enough for three treatment was put in a small polyethylene tube and heat-sealed and instantly researved in a vacuum bottle containing dry ice.
On the next day after 24 hours, each small tube was pulled out and kept at room temperature for halt an minute to wait softening and then the amalgam was applied.
4) Physical properties of the reserved amalgam were tested with methods approved in J.I.S.(Japan Industrial Standards) and no significant differences were found.
5) The time required for treating one caries tooth was 10 min.in the routine procedure, whlie combining the use of Air Dent Unit and pre-prepared amalgam reserved in dry ice bottle, it was exceedingly shortened to 1 min.and 49.5 sec.
6) As a field experiment, 80 school children were successively treated by two dentists by this devised procedures in one day.The over-all time needed for the treatment of one children was 144.9 sec.on the average.
7) Thus the mass amalgam restoration in preventive dentistry might be applied with high efficiency by our devised procedures.

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