Case 1.
Apical surgery #14.
Pre-op
Pre-op Angulated
Pre-op Photo
MTA
MB1-MB2 isthmus, DB MTA
Calcium Sulfate Barrier
Five interrupted and one vertical matress sling
Post-op
Case 2.
RCT #15
Pre-op
MB1-MB2 obturated
Post-op
Pre-op
Access
Post-op
Pre-op
Post-op
RCT #15
Pre-op
Post-op
Case 6.
Pre-op
Pre-op (buccal IRM)
Post op
The normal anatomy of the mandibular first premolar is well documented in dental literature and text books. However, there are variations in the number of roots, canals and foramenas. A literature review by Cleghorn and Christie in JOE 2007, combining all cited studies with over 6700 teeth revealed the following with regards to the number of canals in the first mandibular premolar:
Single canal – 76% of teeth
Two or more canals – 24% of teeth
Angulated radiographs and their careful interpretation can give us a clue as to the complexity of the root canal space. Specifically, a sudden disappearance of a canal space in the middle third of the root radiographically is a strong sign of multiple canals. In addition, the use of the microscope and symmetry laws are especially helpful when unexpected or unusual anatomy is present. In some cases, a cone beam image may be taken to get a better understanding of a root canal anatomy of a particular tooth.
I saw a 35 year old white male yesterday with irreversible pulpitis on tooth #21. His general dentist referred him for a root canal and noted the unusual anatomy of the pulp space.
Angulated pre-op radiograph reveals presence of more than one canal.
Pre-op tooth #21
Upon endodontic access and microscopic examination, four distinct canals were located and treated. A glass ionomer barrier was placed over the root filling material to augment the seal.
Post-op tooth #21
I often use images taken with the camera attached to the microscope as part of documentation, communication with the referring dentist or patient education.
In this post, lets pay attention to photographs illustrating the use of a concept of liquid surface tension and cappilary adhesion. I call it a “water bending” or a “prism” effect.
Water, or any liquid for that matter exhibits surface tension which is related to the cohesive properties of water (molecules “stick” to each other), and capillary action which in turn is related to adhesive properties of water (molecules “stick” to the surface of an object).
Case 1
Pre op
Access opening
Note, the image above of an access opening: cant see the canals well unless the walls of the prep would be flared quite a bit.
The image below is taken of the same exact access opening but with a little hypochloride liquid in the access. Due to surface tension and capillary adhesion, the liquid bends inside the prep and with proper illumination we can see all four canals nicely.
Same access with liquid in it
Post op
Case 2
Pre op
Due to a “water bending effect” we can clearly see four canals through a very conservative access opening.
Access, "water bending effect"
Post op
The “water bending effect” has limited clinical applications. Occasionally during apical surgery, I use it to view/detect lingual canals and to see where the ultrasonic tip should go with out changing the position/angle of the microcsope.
Case 3
Image below shows an osteotomy for an apical surgery tooth #14.
Note minimally angled resection of the MB root (I try to get as close to 90 degrees resection as possible to minimize the number of exposed dentinal tubules), cant see the canals unless we look at this resection from a slightly different angle.
MB root of #14 resected
Next image was taken from the same angle as the first one but with a little saline in the surgical crypt. Now we can see gutta percha/sealer due to a water bending effect, and the ultrasonic instrumentation can immediately start with out repositioning of the microscope.
Water bending effect
MTA in MB1-MB2 with isthmus and DB
Although its clinical implications are minimal, the “water bending” or a ”prism” effect is really cool and can be used in dental photography as an educational tool.
So, why do root canal files break?
1. Operator errors
- pushing rotary files, no glyde path, instrumenting dry, overusing files
2. File defect
- It is extremely unlikely that a file has a manufacturing defect, however it can have defects and/or fatigue from multiple use.
3. Root canal anatomy
- Canals are generally not round. They can be bunch of different shapes: tear drop, figure eight, oval… There are also fins and isthmuses where a file may get caught and inevidably break.
The important thing is if a procedural error happens, and most of these occur during intra-operative stage as we saw from the last post, a prudent clinician should evaluate why the error occured to minimize such things in the future.
Had a very humbling experience yesterday…
I broke a file in a seemingly straight-forward case!
Had a patient that came in for a root canal #30. This tooth is asymptomatic, perio probings are 5mm or less, no response to cold, WNL to percussion and palpation, periradicular area radiographically. Tooth #31 is planned to be extracted due to extensive endo-perio involvement and loss of furcal bone due to a fracture.
pre-op #30
I believe that my yellow protaper got caught in a fin, but this doesn’t make me feel any better. The reason I think it was a fin is because during instrumentation, my instrument was “grabbed” as it was rotating (so it started screwing into the canal actively) and it snapped in the ML canal before my foot was off the pedal. Now, this canal had a glyde path, patency, instrument had a lubricant on it, and a previous instrument in a Protaper series (white protaper) was to the apex with out problems.
mid-op #30, broken file ML canal
Once the file broke, I continued with instrumentation of three other canals and an x-ray was taken with master cones. This film shows that the ML canal is fairly straight, root walls are rather thick and the access to the instrument in the apical 1/3 is possible. The file was then removed using the microscope and ultrasonic instruments in the following order: buc1, cpr#4, cpr#5 and finally cpr#6.
Instrumentation was then completed and canals were obturated using Resilon obturation material in a warm vertical fashion and a thin layer of glass ionomer resin was placed over each orifis as a barrier. This patient was then scheduled for a routine 6 months follow-up.
post-op1 #30, instrument removed
post-op#2, instrument removed
These types of cases remind us that the root canal system is a network of very complex and delicate structures and we must treat it with the utmost care and respect!
Maxillary molar with four distinct roots is a rarity!
The overall incidence of four-rooted maxillary molars has been reported to be less than 0.4%. Nevertheless, dentists should be aware of such variation.
When examining the pre-operative periapical radiographs of maxillary molars, if the outlines of the roots are unclear, the root canals show sharp density changes, or the apices cannot be well defined, then extra roots can be suspected! Horizontally angulated radiographs can also be helpful to distinguish the multiple root morphology of maxillary molars. Most definitive means however is visualizing the “road map” on the pulp chamber floor.
The following two cases had pulp chambers shaped like a quadrangle with one orifice in each corner.
Case 1: Tooth #14 (palatal roots length: 23mm on both)
Pre-op
Post-op
Case 2: Tooth #15 (palatal roots length: 25mm MP and 24mm DP )
Pre-op
Post-op
In both cases canals were instrumented with a combination of hand files and Protaper rotary instruments and sealed with Resilon cones and sealer using warm vertical condensation.
It is often challenging to clean and shape curved canals. Most, if not all dentists who perform root canal treatment are familiar with this ugly feeling of breaking an instrument in the canal. I get a jolt down my spine and “butterflies” in my stomach when it happens.
To avoid these types of errors, I come up with a “game plan” and think through every case from the beginning to the end before I actually do it . It takes only a minute….
When I get a curved case, these are some of the things that go through my mind:
1. Slow down!!!!!!!!!!
2. Straight line access to make those curves gentler.
3. Lots of lubricant (RC Prep, Glyde, etc.) and irrigation (NaOCl, EDTA)
4. Use hand instruments more. (I may finish the apical third by hand, pre-curving stainless steel files or using Ni-Ti hand files)
5. Check patency more often with #6, 8 or 10.
6. Instrument in a “crown down” fashion.
7. I typically use Protaper files for rotary instrumentation, but in curved cases I will use those for coronal shaping and may choose Profile instruments (since they are landed and tend to stay centered in the canal and zip less) to finish the apical third.
8. Choose rotary files with the lesser taper as well, like .02 rather than .04 or .06.
9. Do not “push” rotary files, they will break!
10. Be more conservative with apical enlargement.
Case 1: Tooth #32
Pre-op
Post-op
Case 2: Tooth #4
Pre-op
Post-op
