PRE-BENDING Small Instruments to Negotiate to the Apices of Curved Canals

NEGOTIATING TO THE APEX in order to gain  working length is not always an easy task.  In some instances, the canals are blocked with calcium, but most of the time the canal makes a sharp turn that makes it impossible for a straight instrument to get around or past that bend in the root. 

The answer is always the same: pre-bend the endodontic instrument (8 0r 10 size k file). A bent instrument will never get you into trouble. 

A straight instrument in a curved canal can lead to several iatrogenic problems. 

If the instrument has a bend at the apical tip, the instrument circumscribes a circle at the tip when you rotate it. As you rotate the circle around the canal wall, it will eventually drop into the curved part of the canal. You will then be able to go to the apex of the canal. If the instrument is straight, it will circumscribe a point at the apical tip when you turn it to find the bend in the canal. The point will not find or fall into a curved canal. In fact, if you work the instrument enough it will make a ledge in the canal. Ledge formation is iatrogenic and makes instrumentation harder to do.

The best way to avoid creating a ledge in the canal and to find the curved canal itself is to place a 45-degree bend in the endodontic instrument. As you place the endodontic instrument into the canal and rotate, it will eventually fall into the canal .

                                    

One of the greatest challenges in performing root canal therapy is instrumenting an S-curve or a reverse curve.The most important thing is to maintain patency.  Patency is the key to a successful navigation of the curves.Once you have blocked the canal in a case like this, you can forget about trying to unblock it.  Just fill it to that point and call it a day.  The worst thing you can do is to use a crown-down technique to open up the canal.  Doing so can pack debris down the canal, resulting in a roadblock.  The following is a step-by-step process that I used in cleaning the two molars seen in the x-rays.  

1. The first step is to get the #6 or #8 reamer down to the apex, using an apex locator.
2. Once the apex has been reached, fill the chamber with sodium hypochlorite.  The sodium hypochlorite will lubricate the canals during instrumentation and aid in the removal of debris.
3. After using each reamer in the sequence of increasing sizes, I would go back in with the #8 reamer to make sure that it did not block .
4. Once reached the apex with the #25 reamer, take a #2 Gates Glidden down the canals with a light pecking motion.  Do not force it.  Just let it ease into the canal.  If you force it, you will block yourself out or ledge the canal.
5.  Irrigate the canals and go back in with the #8 reamer to keep it patent.
6.  Next take #2 Peeso reamer down the canals with the same light pecking motion.  Always remember to irrigate and re-instrument the canals after each step to prevent blockage.
7. After the Peeso,  instrument the canals up to a #30 reamer.  I then took the 30/.04 NiTi (orange) down to the apex.  This is a great instrument for removing debris along the walls of the canals at the apical end.
8. finish the instrumentation with the 25/.08 NiTi (brown).

 Use a fine gutta percha cone to coat the canals with the cement.  It will break the bi-directional spiral in curved canals like these.  I used a single cone to fill each of the canals with cement.  The x-rays that follow show the beautiful results that can be obtained with the SafeSiders® technique in dealing with curved roots.