Most all sonic scalers and their descendents, the sonic endo systems produce a motion that is known as waggling.
Waggling means a back and forth motion such as a pendulum makes.
Technically, I suppose, waggling is a form of oscillation which simple means repeating the same motion and returning to the same point repeatedly.
Usually however oscillation does not include waggling.
This is important because when a file waggles it moves the tip back and forth which of course can do no cutting unless the flutes are parallel to the long axis of the file.
In order for common files to cut, the oscillation must be linear, that is, along the long axis of the file blade.
This is the common motion used in circumferential filing, i.e. in and out of the canal.
In a file where the blades are more or less at right angles to the long axis of the file, this type of motion produces the cutting.
In the case of piezo-electric scalers, there is a crystal that distorts when electricity is applied and pops back to shape when the current is removed.
These crystals are mounted at right angles to the long axis of the handpiece.
Thus when they distort, the motion of the crystal and anything attached to it is along the long axis of the handpiece.
If a file is attached to the handpiece at a right angle to the long axis, the file moves bodily in a waggling motion which means that it too moves at right angles to the handpiece.
Since the file is flexible, the tip moves in a waggling motion also, like the tip of a fishing rod when the fisherman is casting.
In some of the sonic and in the magneto-strictive scalers the motion of the file can have a small orbital component but not enough to move the file enough to do any cutting.
In order for a file to cut, the amplitude of the linear oscillation must be at least one inter-flute distance and in these systems the amplitude is in the +-0.001mm range and the interflute distance is ofter over 1mm.
The upshot of this is that YOU must do the linear oscillation, because the file does not.
You move the file in and out of the canal.
This adds to the work load as well as introducing depth of penetration errors.