Effect of air inlet ring opening on sonic handpiece performance

This study investigated the effect of air inlet ring opening on the oscillatory pattern of the MM 1500 sonic handpiece and files. The oscillatory pattern of the driver head and files in air and under load was determined microscopically. The results showed that a critical opening of the air inlet ring was necessary to elicit oscillation of the driver head and sonic file. The driver oscillated in an elliptical manner, the displacement of which varied with air inlet ring opening. When operated in air the file exhibited an elliptical movement which was influenced by different design, length and thickness. This action was constrained under load and replaced by a longitudinal action of the same dimension for all files which appeared to have an efficient cutting action. This work shows that air inlet ring opening increases oscillation of the driver head once a critical opening has been reached and that clinical loading does not constrain the cutting action of the file.