Managing endodontic cases of differing complexity

General guideline of RCT:

1. Analysis of the specific anatomy of the case
2. Canal scouting
3. Coronal modifications
4. Negotiation to patency
5. Determination of working length
6. Glide path preparation
7. Root canal shaping to desired size
8. Gauging the foramen, apical adjustment 

Pay attention to the following steps with these difficulties

Cases with relatively low complexity:

Step 1: Analysis of the specific anatomy of the caseStep 4: Negotiation to patencyStep 5: Determination of working lengthSimple cases probably have larger pretreatment canals. Consider using larger files for working length determination with an apex locater. The better the adaptation of the tip of the instrument to the foramen, the more accurate the length determination.Step 6: Glide path preparationStep 7: Root canal shaping to desired sizeThe more recently advocated simplification of using a single-file, single-length technique may work well in this anatomy, where a single rotary or reciprocating instrument may perform the whole shaping procedure. However, it is especially important to check the amount of debris accumulated in the last millimeters of the file. The absence of dentin indicates that the foramen is larger than the tip of the file and a larger file may be needed to complete the shaping procedure.
Step 8: Gauging the foramen, apical adjustmentIt is more difficult to perform this step correctly in a canal with a large apical third compared to a small-diameter one. A gauging .02-tapered K-file with the same diameter of an inadequate master apical file could bind short of WL due to a lack of a continuous taper increasing progressively from the apical to the coronal third in a large canal. This mistake can impede the improper selection of the
apical file size and therefore can create problems during vertical compaction of gutta-percha.

Case with moderate complexity:

Step 4: Negotiation to patencyCareful precurving any negotiation file may be needed to ensure patency without creating procedural errors during this stage.
Step 7: Root canal shaping to desired size 
A single-file technique is typically not appropriate in molar cases of moderate difficulty. The fact that there will be wide variations in the anatomical complexity does not allow reducing the number of preprogrammed apical size to 1 or 2. Consider adapting the tools to the anatomy of the specific canal system, rather than adapting the canal to the tool. 

Step 8: Gauging the foramen, apical adjustment 

Cases with high complexity including challending S curves:

Step 3: Coronal modificationsWhen shaping very difficult canals with significant and multiplanar curvatures, shaping procedures can be simplified by dividing the entire root canal in two different root canals or shaping stages. Procedural accidents in the apical third during negotiation can be avoided when the coronal two thirds of the root canal are preenlarged before the negotiation of the apical third. Preenlargement procedures may be done as if the root canal were two different canals. After scouting the canal with a #08 or #10 file, first shape the straight coronal portion (first part of the curvature or first stage) as an easy canal and this will allow a better negotiation of a shorter difficult apical third and an easier shaping of this third alone after removing the restrictive dentin in the coronal and middle third. Generally speaking, the overall length of a molar ranges from 19 to 25 mm, with around 10 mm the length of the clinical crown and the rest (9–15 mm) the length of the root. If this 9–15 mm is divided between the three-thirds of a root canal, it makes a total of 3–5 mm for the coronal, middle, and apical root third, respectively. 

When shaping a difficult root canal, the most challenging anatomy is often located in the apical third of the root canal. If we break down the root canal in the three segments described above and prepare the two coronal thirds before even trying to scout the apical third with a small file, procedural accidents are predictably avoided and preparation of the most delicate area is facilitated. With the coronal two-thirds optimally prepared, we can then scout the rest of the canal with small instruments, reach the working length with precurved files, confirm apical patency, and decide if the apical third can be shaped with rotary techniques (if a glide path is achieved) or manual instrumentation.

Step 4: Negotiation to patencyApart from the strategies for negotiation mentioned above, the following can be of great help when working with extreme anatomies: Files with large soft handles help reduce fingers fatigue (Senseus, Dentsply, Maillefer, Ballaigues, Switzerland) during the arduous task of negotiating the
most difficult curvatures, for example # 08 and # 10 K-files with silicon handles. In difficult canals it is desirable to use also #08 files. If negotiation with a #08 or #10 file is not possible due to an impediment, place a short curvature at the last mm of the file and look for the passive way to length when a “sticky” feel is noticed with the curved portion in order to bypass the impediment. Once
bypassed, use a #10 file with the same bend and push pull to reduce the impediment. Many times, the actual problem in difficult canals is that the apical foramen is 90° from the main canal.

Keep the canal patent throughout the procedure. The more difficult the canal, the more important it is maintaining apical patency to avoid blocking the apical foramen and posterior accidents when trying to reach the appropriate length again.
Step 6: Glide path preparationAfter sizes #8 and #10, different strategies have been suggested to get a #15 file to WL and achieve a glide path. There is a big jump between #10 and #15 when   shaping difficult canals. The use of a Golden Mediums instrument (Dentsply Maillefer) with a half size 0.12 will help the #15 file to reach working length. Step back with #20 and #25 files with balanced force techniques to remove the resistance coronal to the WL that is not allowing the #15 instrument to reach the full length.

Creating a glide path with rotary instruments as Pathfile #1 and #2 (Dentsply Tulsa Dental) after reaching the working length with a #10 file helps to manage the difficulties avoiding the transportation of the apical foramen in these extreme cases.Step 7: Root canal shaping to desired sizeSelecting flexible and resistant rotary instruments is very important not to deform the apical third of these more complicated canals after achieving a glide path. Thoroughly follow the instructions recommended in the step “root canal preparation” to avoid flexural fatigue of the instruments when shaping extreme curvatures.
Different rotary systems have manual instrument sets (ProTaper, GT, both Dentsply Tulsa Dental) with the same characteristics, tapers, and diameters than corresponding rotaries that provide the same shape as the rotary instruments. This reduces the risk of instrument fracture when no predictable glide path was created. If manual instrumentation is performed with such hand instruments rather than the classic ISO files, the resistance form along the root canal is maintained.

Step 8: Gauging the foramen, apical adjustment