But since so many people still have them, I leave this here for it's historical value and for the tidbits of information that you might glean from it and the fact that the Fine-Cut Endo Handpiece does exactly the same motion as the STS but without all the drawbacks. Among which are:

  1. STS In Operating Position.

    (Notice Finger Positions)

    The plain truth is that the STS is a modified toothbrush.

    It is larger than a typical handpiece, and heavier, and more awkward to use.

    The main advantage it has is that it is the fastest, most efficient, safest way to prepare canals.

    No rotating instruments.

    Minimal possibility of breakage.

    AND IT IS FAST.

    Most canals can be enlarged from 15-50 in less than two minutes, most of the time with only four and sometimes only ONE file.
Linear Oscillator-Sonic Adapter Special Products takes the toothbrush as it comes from Sonicaire and remanufactures it by removing the brush and brush guard and threading the metal tang that held the toothbrush to hold the Fine-Cut Sonic Adapter which in turn holds the Fine-Cut Sonic Files.

The Permanent Magnet What makes this such an efficient cutting tool is the linear movement created when a circuit board in the handle take the 1.5 volt current from the rechargeable batteries and sends it into two electromagnets changing the polarity 250 times per second.

These magnets inside the handle create a magnetic field that affects two permanent magnets in the tooth brush (now endodontic) assembly, moving them back and forth or in the case of endo, in and out.
Side View of the permanent magnets
Another View
Alignment Rib This alignment rib assures that the assembly cannot be inserted incorrectly into the handle.
Water Port(Vestigial) We call this a vestigial water port because the same adapter that is used in the STS is in a slightly altered version, used for sonics and ultrasonics. No water can be put through the port since the STS uses a 4-48 female thread instead of a male thread.
Sliding Safety Sheath covers the head of the Fine-Cut Sonic file and keeps it in proper operating position.
Since the head is so small, Fine-Cut files are the only ones that will fit.
File Insertion Slot where files are inserted can be seen here
Inserting File with the sliding safety sheath back. Notice how the shaft of the file is inserted first.
Another View
File Partway in Insertion Slot Ready to drop file downward. After the shaft of the file is in place, move the file downward until the head is entirely inside the file well.
Correct Insertion After the sheath has been allowed to snap back into position the STS is ready to use.
Sliding Safety Sheath Back to remove a file. Simply lift the file upward and reverse the motion of insertion.

It is generally a good idea to adjust the position of the rubber stop after the file is in place to avoid moving it while handling the file.
Checking File Size by Color Coded Dot Each file has a small color coded heat resistant colored dot on the top of the file indicating files size. The standard color code is used
Close up view of color coded dot
Proper Finger Position for Normal Operation
Fourth Finger Stabilization Technique When inserting the file into the tooth, the STS can already be running.

To stabilize the file, simply slide your fourth finger forward. There is too little movement to injure the finger or to cut through the rubber glove.
Operation Position
More Linear Movement.

Notice Water Spout Position If the amount of linear movement is too small and the free-floating self-aligning feature of the Fine-Cut Sonic Adapter is not needed for some reasong, it is possible to insert the file up-side-down.

The file will be held much more rigidly in place and the amplitude of the stroke will be greater.

This might be used to remove set cement.
To insert the file Up-Side-Down File Insertion
Up-Side-Down Insertion
Ordinary Plier to Loosen Lock Nut To remove the Fine-Cut Sonic Adapter for sterilization, turn the lock nut about a quarter turn clockwise looking at it from the end.

Then simply screw the adapter off, screw the lock nut off, sterilize and reverse the process to reassemble.

Note: This is not necessary with the Fine-Cut Endo Handpiece as the head is permanently attached and is sterilized with the whole handpiece.
Tightening Lock Nut Once the lock nut has been replaced and screwed down about 8 mm or so, screw the adapter back on.

Align it properly and holding it in place, turn the lock nut counter-clockwise until tight against the adapter.

Small adjustments for proper alignment can be made by turning the adapter itself after the lock nut has been tightened.
Correct Alignment After Installing You can purchase replacement adapters or modified toothbrushes separately.

The modified toothbrushes will wear out before the Fine-Cut Sonic adapter.

If you are mechanically inclined and want to save a few dollars, you can even make your own modifications of the toothbrush.

It would probalby not be productive but it is simple to do.

We suggest that you buy your first one so you can be sure it will be done correctly and then copy it after that.
Fine-Cut Sonic files are available in sizes 15,20,25,30,35, and 40 but you will find that only sizes 15-30 are effective in the STS.

They are available in lengths 22, 25 and 29mm.

If you are a pedodontist you may need 22mm but no one else will. The overall size of an adapter including a 25mm file is about 28mm which makes it shorter than most handpieces with a 21 mm file.