Reasons For Most Safe-Failure Separations

1. Advancing LSX too rapidly: Rapid advancement overstresses the instrument by engaging too much dentin too quickly. Use the recommended technique of always advancing the LSX with a VERY SLOW and gentle pushing motion when it is cutting dentin.

2. Blade enters a “fin”: A fin is a narrowed extension of the main canal. When this configuration is seen at the canal orifice, remove or minimize the fin through proper coronal flaring. Of course, this configuration may occur more apically and may not be visible. Even though you do not see the fin, you may feel it (tactile feedback). The LSX will begin to chatter and this will be your clue. The solution is simple, always use s-l-o-w apical advancement. Upon encountering chatter, hesitate for a moment (stop apical advancement) and then continue advancing very slowly.

3. Using the wrong handpiece: A slow RPM and low torque handpiece doesn’t provide enough power to cut dentin efficiently. This causes excessive stress on the instrument. The EndoMate (set at 2500 rpm) or the EndoPAL are the handpieces of choice.

4. Using too much force: Trying to advance the LSX with excessive force (when it doesn’t want to) may cause it to buckle because its non-cutting pilot (tip) is not designed to cut dentin. Rather than using force, irrigate and try again with very slow apical advancement. If unsuccessful, try a K-file to smooth out the curve. When feeling an apical stop at the end of the canal, resist the temptation to push the instrument against the stop even if you believe you are still slightly short of working length. Simply readjust to the new “corrected” working length. Insisting on getting that last 1/4 to 1/2 mm is a major cause of separation.

5. Other possible causes of failures: a) Using a gel (for example, RC Prep) instead of a liquid chelating agent (EDTA); b) Not making “straight-line access” to the mid root of the canal; and c) Using the LSX too many times. As with all instruments, the more uses the greater likelihood for separation. As the “last resort”, the spade (flat) blade of the LSX often provides ample room for bypassing should the separated fragment be impossible to remove. In these cases, bypass with hand instruments (never rotary instruments) and get as much sealer and filling material around the fragment. There are several studies that show success rates are no better or worse with a broken instrument left in the canal. This assumes, of course, a well obturated canal and a quality coronal restoration.

Learning a new technique takes a little practice and patience. One needs to become familiar with the behavior characteristics of any new instrument. You may experience a few “safe – failures” while learning. If you do, appreciate the fact that they were retrievable. Then, review the possible reasons (above) and determine how this might be prevented in the future.

EndoVac Demonstration With Dr. John Schoeffel (CDA Anaheim 2008)

You can check out Dr. Schoeffel’s demonstration of the EndoVac by visting DentalCompare:

 

http://www.dentalcompare.com/video_view.asp?videoid=241

Dr. Frank Allen on Apical Cleaning

Here is the link of the complete recording (audio and video) of Friday’s Webinar on apical cleaning. It runs 80 minutes, about 30 of which are Q&A.

 
http://www.discusdental.com/endo/webinar.php

Article: Micro-Computerized Tomographic Analysis of Radicular and Canal Morphology of Premolars with Long Oval Canals. Source: OOOOE, August 2008.

Objective: Measure root and canal diameters and ratios, canal tapers and wall thickness.

M&M: Thirty human premolars with single canals were selected. Specimens were scanned using Micro CT and cross-sections analyzed at the following levels: 1,2,3,4,5,7,9,11 and 13mm from the radiologic apex.

Take aways:
1) At all levels, the BL (bucccolingual) diameter of the canal was greater than the MD (mesiodistal) diameter. This means that the canal diameter the dentist typically sees on the x-ray (MD view) was always smaller than the size of the canal they don’t see (BL view). For example, the data shows that at 1mm from the apex, the canal diameter as seen by the dentist averaged 0.32mm. However, in the view they don’t see, the canal diameter was much larger, 0.45mm. If one prepares the canal with a size #35 instrument the canal would be under prepared at the 1mm level because in reality one would have to go two sizes larger to a size #45 to properly clean the canal, 3-dimensionally.

2) The canal’s taper, in the BL dimension is much greater than the MD dimension. So the taper you don’t see is much larger than the taper you do see. Measurements taken in the MD dimension showed tapers ranging from (0.03 to 0.06 mm/mm) but in the BL dimension they were significantly greater (0.13 to 0.27mm/mm)! If one prepares the canal to a common taper (let’s say .04 taper) it more often than not under prepared in BOTH dimensions, particularly in the BL dimension (.04 vs. 0.18 average).

This puts serious doubt as to the efficacy of tapered preparations in general. Can one expect to effectively clean canals, with 0.04 or 0.06 tapered instruments, when the canal’s dimensions (at a minimum) are 0.45mm diameter with a 0.13 taper?

Article: Micro-computerized tomographic analysis of radicular and canal morphology of premolars with long oval canals. OOOOE, August 2008.