SHAPING ROOT CANALS

The four (4) Mechanical Objectives of cleaning and shaping are:

1. Continuous tapering preparation
2. Original anatomy maintained
3. Position of the foramen maintained
4. Foramen as small as practical

The ideal working length should be to the most apical foramen or foramina. To consistently meet this clinical objective, small, flexible hand files are carried to the radiographic terminus to encourage the mechanical objectives of cleaning and shaping.

To maintain patency during shaping procedures, irrigate with sodium hypochlorite (NaOCl) and fill the pulp chamber brimful with either NaOCl or a viscous chelator. Then passively slide a small, most flexible hand file to the radiographic terminus. When at length, gently and repeatedly move the file in short 0.5 mm amplitude strokes to break up debris, move debris into solution and maintain patency.

When you can fit a "trimmed" nonstandard fine-medium (FM) or medium (M) gutta percha cone to length. Canals that have been shaped to receive FM or M gutta percha importantly hold a sufficient volume of irrigant, that over adequate time, will clean into all aspects of the root canal system. The rate of taper of the gutta percha must be less than the rate of taper of the canal preparation, which would ensure apical tugback. Confirm radiographically.

In regards to recommending a rotary file system, I am very excited about the ProTaper line. The development of ProTaper represented a collaborative effort from Drs. Ben Johnson, Pierre Machtou, John West and myself, along with the Dentsply Maillefer engineers. The ProTaper system is carried by Dentsply Tulsa Dental. There are eight (8) instruments in the set - 3 Shapers and 5 Finishers - so it is a very simple system to learn and use. Tulsa has a CD that comes with the introductory package and I also have published various articles on ProTaper (download articles). Additionally, my DVD is available through Advanced Endodontics and features all aspects of conventional treatment with emphasis on the ProTaper rotary files for shaping root canals. For your reference, some ProTaper advantages:

1. More efficient cutting edges as these files do not have radial lands.
2. Progressive changing tapers on each shaping file reduces the contact zone between the file and the dentin which improves efficiency and decreases breakage.
3. More flexible than a fixed tapered instrument the same size due to its progressively tapered design.
4. Continuously changing pitch and helical angle reduces the screw effect.

I prefer the ProTaper rotary file series. There are only eight (8) instruments in the set - 3 Shapers and 5 Finishers - so it is a very simple system to learn and use. The ProTaper S1 and S2 file are especially useful for managing the coronal two-thirds of virtually any canal you are flaring. Specifically, the S1 is used first followed by the S2. Each are used in the same manner as GG's (i.e. brush cutting on the outstroke). Although there are many different rotary file lines that can achieve the coronal shape required to clean and pack, it will require more time and more instruments compared to two ProTaper files or 4 gates gliddens.

As a general rule, you precurve only stainless steel hand files -- not nickel titanium, regardless of hand or rotary. One exception would be precurving NiTi ProTaper hand files in nonsurgical retreatment to bypass a ledge, which is shown in the Ruddle on Retreatment DVD entitled "Management of: Blocks, Ledges, Transportations & Perforations". These instruments can be easily precurved, if necessary, and effectively used in many clinical situations.