Step 4 – Pulp extirpation
This is only necessary for vital teeth. Remove the pulp using a barbed broach – if the canal is curved, a #10 file may be used. A barbed broach is contraindicated in severely curved or calcified canals.
Step 5 – Pre-Enlargement of Coronal Two-thirds (aka “Coronal Flaring”)
Remember to always irrigate canals with bleach while passively irrigating up and down and use ProLube (for hand files only). Never introduce an instrument into dry canals; you should also recapitulate and reconfirm patency frequently.
Clinic Tip: When irrigating the canals with bleach, make sure to have suction ready and place on tooth structure.
If the canals are large, you may start by using your Gates Glidden burs to open the most coronal portion of the canal. You should sequence through the GG's by increasing or decreasing in size. (Ex. use the #2 GG followed by the #3 or use #3 in the coronal 2mm followed by #2 for 2 additional mm). Confirm with the endodontist if they want you to use GGs and which ones they recommend. Remember that the Gates Glidden burs are used in a pull stroke only. Passively insert the file into the canal without rotation, then step on the rheostat full throttle and pull the file out (and away from the furcation). Alternatively you may use the WaveOne primary for coronal flaring. Before you are able to move on, you must open the canals with hand files. If your canals already fit a #20 file, you may start finding your working length. Otherwise, you should cycle through #10-15-20 hand files in the coronal 2/3rds using a watch wind and balanced forces technique. Remember to always irrigate in between files and use ProLube. These steps will allow the early measurement of the canal and facilitate the establishment of the glide path. NEVER prepare with hand files larger than size #20 if you want to use WaveOne.
Step 6 – Establish Working Lengths
Now that you have opened up access to the canals, you must determine your working length. The quickest way to do this is to use an apex locator, which is available from the clinic window.
Clinic Tip: When using the apex locator, remember to turn on the machine before plugging in the probe. Also, the canals must be moist but the pulp chamber should not be overflowing; you should use the largest file possible.
Remember to have the curved end on the patient's cheek and probe touching only the file. Use a radiograph as your guide to get an estimate of canal length. Make sure that you pre-curve all files before introducing them into curved roots. The curve of the file must be within the last 1-2 mm of the file. Work a small file (8 or 10) down to the estimated length and take an X-RAY. Make the appropriate adjustments to your working length based on this picture.
Clinic Tip: The rubber stopper has a black line on it. Line the black mark line up with the curve that you have created. Often times the apical opening of the canal does not exit straight out of the root, but instead it deviates to one direction. You can determine which direction it exits based on the location of the black line after you are at patency.
Step 7 – Shaping the Canals Using Rotary Files (Wave One Files)
The rotary files must be provided by the clinic dispensary. Fill out a slip for them to sign out for you. When you are ready to use the rotary files ask the endodontist to sign for them and have your assistant get them for you. Most often the endodontist will tell you to take the files down to full working length. Use your endo motor to operate the files in a reciprocating motion. In the vast majority of roots after you have completed your glide path to a size #20 file, the Primary Wave One file, which is a 25/.08 size and taper, will be sufficient. You may have to repeat the use of the Primary file more than once. Remember that you only enter the canals until you meet resistance and then you pull out, clean the rotary file with a moistened sterile gauze and then continue to advance. Be sure to mark your working lengths with the rubber stopper and never let off the rheostat when using them until you stop making forward progress. Make sure that you only use passive pressure and do not push too hard apically to prevent possible damage to the canals or breaking off the file in the canals. Also, don’t forget to irrigate well and confirm patency when finished with the rotary file.
Clinic Tip: Watch out for the flute loading. This is when the dentin "mud" gets into the flutes of the rotary files. The "mud" should only be present in the upper 1/2 of the file. The file should never be fully loaded as this causes too much stress/torque on the file and can lead to separation of the file due to maximum stress on the file.
Clinic Tip: Electric handpiece motors must be checked out from dispensary. They are important because they keep a defined reciprocating motion while you are instrumenting the canals.
Step 8 – Apical Preparation-Step-Back
If you find using your predetermined working length that the canal is larger than the WaveOne primary you may enlarge the apical portion of a straight root canal beyond the apical diameter of the with a large Wave One 40/.08. If necessary, the root canal may be further enlarged by taking larger hand files to working length using the Balanced Force Technique (remember to engage the file by twisting ½ turn clockwise then apply apical pressure and up to a full turn counterclockwise to cut the dentin, then remove the file while turning ½ turn clockwise) to achieve circumferential preparation and minimize the chance of creating ledges. A master file is typically about 3 file sizes larger than the original apical file size (The initial apical file is the first file that cuts when introduced to working length). Typical sizes in molars are #25-30 for buccal or mesial canals and #40-45 for palatal canals.
Step 9 – Recapitulation
This is the process of removing any debris from the canal using the master file (for example a size #25 K-file if you used WaveOne Primary to WL). Introduce the master file gently to working length and remove it turning clockwise to load the flutes with the debris and dentin chips remaining in the canal. Don’t forget to check for patency with a #10 file past working length.