Cleaning and Shaping
General Workflow
Phase I: Preparation
Initial canal exploration and assessment of canal size, shape, and anatomy. Radiographs are helpful for this step and provide information on estimated working length
Armamentarium
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Overview of Techniques
Hand Instrumentation
There are a number of hand instrumentation techniques. We recommend the Watch Winding method as a first choice in the pre-clinical setting
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Watch Winding: alternate between clockwise (180˚) and counterclockwise (180˚) rotation of the hand file. Grasping the file between the thumb and forefinger, use light apical pressure and frequently remove the file partially out of the canal to remove dentin and debris
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Reaming: the hand file is gently placed into the canal until contact is felt on all sides of the instrument. Rotate the file clockwise 180-360˚ without pushing down apically and withdraw
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Filing: place the hand file into the canal and make light contact with the wall while withdrawing along the path of insertion
Watch Winding
Video Demonstration
Procedure
Before you begin:
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Ensure that there is straight line access to the orifice openings using the endo explorer
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Ensure that the tooth is properly isolated with a rubber dam
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Inspect the files so that separation can be identified if it occurs during the procedure
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In the preclinical setting, if you can’t take a radiograph, you may measure the root length outside of your typodont to obtain an estimated working length
Instrument options: Endo explorer
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Straight Line Access
Clinical Notes:
Pre-treatment radiographs should be made to estimate the working length and determine an apical point of termination. This will determine the file length (e.g. 21 mm, 25 mm, etc.) that you use
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Traditional radiographs showing the apex (the working length is 1 mm from the radiographic apex)
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Cone-beam computed tomography (CBCT) scans
Canal anatomy should also be assessed radiographically to identify sharp curvatures, dilacerations, or accessory canals
Hand Filing:
Using a #10 stainless steel K-file suitable for working length, navigate toward the estimated termination point
Instrument options: Size #10 Stainless Steel K-file (length should be slightly longer than estimated working length)
Adjust the rubber stopper on the file so that it is perpendicular to an anatomical reference point
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Anatomical reference points are reproducible locations (e.g. a cusp tip) at the more coronal extent of the tooth. They are used to ensure that the file is not going beyond working length
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Optional: Remove the tooth from the typodont and assess the location of the file in relation to the apex
Measure the working length using the ruler on your Endo Ring
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Ensure that you are no more than 3 mm away from the anatomic apex
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Clinical Note: Obtain a radiograph to determine the working length, which should be approximately 1 mm from the radiographic apex. Taking multiple angled radiographs is necessary to identify early exit foramina
Irrigate the canal:
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Gently insert the syringe tip into the canal space until light contact with canal walls is achieved. Withdraw approximately 1-2 mm
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Never go beyond ⅔ of the length of the canal. While gently flushing the canal space with 1-2 mL of irrigant, slowly move the syringe tip up and down within the canal space, being careful not to move beyond the working length
Irrigant options: NaOCl
Clinical Note: Irrigants (including NaOCl) are frequently toxic to host cells and therefore caution should be taken to avoid extruding any solution beyond the canal space. High speed surgical suction should be used at the entrance to the canal space
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In the pre-clinical lab setting, it may be appropriate to use water as a placeholder for irrigant
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Always check which materials are appropriate for use with your typodont and mannequin
Irrigant options: NaOCl
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Progress to the next hand file in the series (e.g. size 15), which should have a slightly larger diameter, and file to working length.
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Optional: A small amount of lubricant may be used to coat the file prior to instrumentation
Begin with the smallest diameter file reaching the full working length and then increase the file size
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Adjust the rubber stopper on each file using the ruler on your Endo Ring to make sure you do not go past the working length
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Use the sponge on your Endo Ring to clean debris off your file periodically
Instrument options: NiTi hand files, Stainless Steel hand files, Carbon Steel hand files
Lubricant options: Glycerin, RC Prep
Repeat the process of hand filing, irrigating, recapitulating, irrigating, and hand filing with a larger file size until the desired diameter is achieved
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We recommend using a hand file up to a size 20 or 25 for most scenarios in the pre-clinical setting
Rotary Instrumentation:
Once the canal has been shaped with hand instruments, a rotary instrument can be used. The file progression will depend on the instrument used and the canal anatomy, so it is advisable to follow manufacturer’s guidelines. When using any rotary instrument, vertical movements should follow a continuous in-and-out pattern, should be used with only very light apical pressure, and should not be used for longer than 10-15 seconds at a time
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NiTi rotaries should always follow hand instrumentation. Follow the glide path created by hand instruments and do not apply apical force that risks bending the rotary file
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Based on the previous working length measurement, utilize the rubber stopper and coronal reference point to minimize the risk of perforation
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Continue to irrigate between filings
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You can lubricate files prior to use. Extrude some lubricant on a mixing pad and gently coat the file with a thin layer. A little will go a long way
Instrument options: NiTi Rotary Instrument
Lubricant options: Glycerin, RC Prep
Irrigant options: NaOCl
Sample file size progression for rotary instrumentation:
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ProTaper Gold NiTi Shaping and Finishing files: Sx → S1 → S2 → F1 → F2 (→ F3)
Clinical Notes:
The location of the working length can be confirmed using an electronic apex locator
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Connect the apex locator to the desired file
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Place a metal grounding component in the patient’s cheek
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Advance the file until it reaches signal scale 0, indicating that the interface between the apical foramen and PDL has been reached
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Withdraw the file until the signal is back to 0.5
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Place the rubber file stopper at the predetermined anatomical reference point
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Remove the file
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Measure the working length using your Endo Ring ruler
Note: Care should be taken to avoid short-circuiting the current (e.g. through contact with decay or metal restorations). Instructions should be reviewed prior to using any electronic apex locator
Instrument options: apex locator
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Checklist
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Smooth walls that are free of ledges or shoulders
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Canal is clear of debris and irrigant
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Original shape of canal maintained and widened in a tapered manner
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Dimensions:
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Distance from apex
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CDCA Recommendation: Canal extends no more than 3 mm coronally from the anatomic apex
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Clinical Note: Canal should extend to approximately 1 mm from the radiographic apex
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F2 (0.25) or F3 (0.3) file at the apex
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File does not extend through or beyond the apex
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Apical foramen in original position and apical opening is as small as possible
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Inspect files and confirm that there has been no separation