Clinical Tips, Endodontic Preparation Techniques, Podcast

Podcast Episode 2 – Antonis Chaniotis on Managing Difficult Anatomy and Traveling the World

 

Antonis_Chaniotis

Antonis Chaniotis is an Endodontist practicing in Athens, Greece. He is one of the internet’s most famous dental educators and is passionate about teaching through the medium of video. He has a special interest in microsurgical endodontics, and the management of difficult endodontic anatomy. He gives us an insight into what it means to share your experience with devotees all over the world. 

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Show Notes and Links

Antonis’ Practice in Athens

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Hyflex EDM Files

Recent Research on Hyflex EDM Files

Clinical Tips, Endodontic Preparation Techniques

Deep Split Buccal Canals of Upper Second Molar

This case was referred as the dentist could only find two canals. The upper second molar will sometimes have the mesiobuccal and distobuccal canals very close, and sometimes the split will occur well below a a single, larger orifice.

Pre-operative Radiograph

Pre-operative Radiograph

The buccal canals split about 3mm below the orifice.

The buccal canals split about 3mm below the orifice.

page4

Palatal Canal

Amalgam Restoration

Amalgam Restoration

Post-Operative Radiograph

Post-Operative Radiograph

Pat Caldwell

Clinical Tips, Endodontic Preparation Techniques

Upper Pre-molars – The weakest Link?

Upper pre-molars present as a special case when they require endodontic treatment. They are skinny, weak teeth in their virgin form, and once a marginal ridge is lost, or endodontic access is performed, their resistance to fracture drops significantly.

My opinion on these teeth is that the restorative needs trump the endodontic needs in the majority of cases. Endodontists I know who have conducted long term follow ups of their cases find this tooth to be in the higher failure category, and the failure is most commonly fracture of the tooth. There’s many ways to skin a cat, but this is how I handled this case. The only dentine removed was directly over the pulp horns. I’m still recommending an onlay/crown. I’m interested to hear how you would restore this in your practice.

 

Pre-op. There is a recently placed deep distal restoration. The patient reports symptoms of irreversible pulpitis.

Copious irrigation is used to remove as much pulp tissue as possible.

Copious irrigation is used to remove as much pulp tissue as possible.

The only dentine removed was that directly over the pulp horn. Conservation of pericervical dentine and the dentine connecting the mesial and distal parts of the tooth assists in maintaining strength.

The only dentine removed was that directly over the pulp horn. Conservation of pericervical dentine and the dentine connecting the mesial and distal parts of the tooth assists in maintaining strength.

GP filling the pulp chamber.

GP filling the pulp chamber.

 

GP Filling

GP Filling

Bitewing view of root filling and composite core showing minimal preparation.

Bitewing view of root filling and composite core showing minimal preparation.

Composite Core

Composite Core

 

Post-Op Radiograph showing two canals merging apically.

Post-Op Radiograph showing two canals merging apically.

 

Clinical Tips, Endodontic Preparation Techniques, General Updates

The Lower Second Molar. Tricky in So Many Ways.

This case was referred as the treating dentist was astute enough to recognise that while some lower second molars only have two canals, the majority will have at least three. Only one orifice was visible mesially. The mesial roots of lower second (and third) molars are often challenging to treat for a number of reasons. Access can be difficult, there is often a double curve in the mesio-distal and bucco-lingual plane, and often we see a single orifice with two canals. This was one of those cases where only a single orifice was visible mesially.

Before attempting to tackle this case we took a CBVT. The CBVT presented a finding indicative of a second canal in the mesial root. This is good information to have, as if we suspect there are two canals, we know where to remove dentine in an attempt to locate the canal. If we suspect only one canal after viewing the CBVT, we don’t need to be needlessly removing further dentine in the all-important pericervical area.

 

The clinical picture is of one mesial orifice, but the CBVT indicates two canals.

The clinical picture is of one mesial orifice, but the CBVT indicates two canals.

The CBVT also tells us where to look – buccal or lingual of the orifice. In my experience, the classic situation for these canals is for the main canal to be the mesiobuccal, with the mesiolingual canal coming off the main canal a few millimetres below the orifice. The orifice to the second canal can be quite small, and as it comes off the main canal at a sharp, almost 90 degree angle, we have to be careful to open the canal coronally with some hand files before attempting to place a rotary file in it.

After removing about 2mm of dentin lingually to the existing orifice, the second canal was located.

After removing about 2mm of dentin lingually to the existing orifice, the second canal was located.

The final root filling with composite closing the access.

The final root filling with composite closing the access.

So there you have it. One more little gem in your bag of tricks for treating difficult anatomy. Have you had experience in cases such as this? Share your comments below.

Pat

Conservation of tooth structure
Clinical Tips, Endodontic Preparation Techniques, General Updates

Endodontic Access for Conservationists. A How To Guide.

 

There are a huge number of factors that can affect the outcome of endodontic therapy. Attempting to isolate these individual factors and determine the relative importance of each is something that has proven difficult or impossible in endodontic scientific literature.

Ultimately, our primary aim is to allow our patients to keep their teeth for the rest of their lives. The evidence we have available points to the majority of endodontically treated teeth surviving for long periods of time. (1) Those that are extracted most commonly fail due to non-endodontic reasons. The most common cause of extraction of root filled teeth is crown fracture and periodontal disease.(2)

In terms of crown (and root) fracture, I believe that the conservation of dentine in the crown and in the region a couple of mm just above and below the cervical area is essential to providing ongoing resistance to fracture. In order to have as strong a tooth as possible, we need maximum thickness of tooth structure in this area.

In terms of this, I see that using strategies to limit the amount of tooth structure loss during endodontic access as one of the most important measures that can be taken to ensure the greatest longevity for root filled teeth. Of course, we still need to achieve the aims of endodontic treatment, but this shouldn’t come at the cost of doing irreversible damage to the crown of the tooth that may compromise the tooth’s long term survival.

Poor endodontic access

Endodontic access has been performed which gives good access to the canal orifices. But imagine the thickness of dentine that will remain mesially and distally if a crown was prepared for this tooth. The endodontics can be perfectly performed, but the tooth is compromised due to the excessive loss of tooth structure during access.

This is why we aim to keep access limited and you will sometimes see what appears to be incomplete opening of the pulp chamber. This is by design and allows important tooth structure to be maintained that contributes to the strength and durability of the tooth. Strategies for conserving tooth structure during endodontic access include removing restorations and caries and utilising this space for endodontic access. A good discussion of these strategies, along with examples can be found in articles by Clark and Khademi. (3) (4)

Conservative endodontic access in lower molar

Maintaining the dentine in the peri-cervical region whilst achieving the goals of endodontics give this tooth the best possible chance of survival. Ultrasonics and copious irrigation allow the cleaning of the pulp chamber space and canal spaces without the need for excessive removal of tooth structure.

Maintaining dentine for endodontic access

The restricted access still give good straight line access to the canal orifices. But see how much solid tooth structure remains? It does, however make the job of performing high quality endodontics more difficult. But what’s more important? Us having an easy time of it, or giving the patient the best possible long term outcome?

Limiting tooth destruction becomes a greater challenge when attempting to treat teeth with calcified pulp chambers or canals. When attempting to work through pulp chamber calcification or locate these difficult to find canals it can be easy to remove vitally important dentine.  Assessing the degree of calcification prior to attempting treatment is the key to preventing this iatrogenic damage to teeth. Additionally, if upon access the location of all canals is difficult, it may be better to consider referring at that early stage, rather than to damage the tooth’s long term prognosis in an attempt to locate a difficult to find and prepare canal.

One important aspect of learning to limit the removal of healthy tooth structure for access is that it actually makes endodontic procedures much more difficult (especially in second and third molars) and increases the chances of missing canals, so you need to balance these potential issues with benefits of doing so.

1.    Salehrabi R, Rotstein I. Endodontic treatment outcomes in a large patient population in the USA: An epidemiological study. J Endod. 2004;30(12):846-50.
2.    Vire D. Failure of endodontically treated teeth: classification and evaluation. J Endod. 1991;17:338-42.
3.    Clark D, Khademi J. Modern molar endodontic access and directed dentin conservation. Dent Clin North Am. 2010 Apr;54(2):249-73.
4.    Clark D, Khademi JA. Case studies in modern molar endodontic access and directed dentin conservation. Dent Clin North Am. 2010 Apr;54(2):275-89.

Clinical Tips, Endodontic Preparation Techniques, General Updates, Irrigation

The Squid. A Study in Persistence and Access Design

I know it’s been a long time since I’ve posted so I thought I’d show a case that caused me some trouble recently. The owner of this tooth had suffered a significant facial swelling and ended up in hospital. Fortunately, the swelling had subsided by the time I saw him and he was keen to save the tooth.

Lower Premolar with unusual anatomy

A Wide Canal That Narrows Suddenly is an Indication of a Splitting Canal.

Lower premolar AP 2
Apical Periodontitis is Apparent. Note the Bulbous Shape of The Root.

The thing to note about this pre-op xray are that the canal appears to split at the mid root level. Even if you can’t see the split, the fact that the canal narrows suddenly is an indication of a split in the canal system. The second telling point that we are dealing with something complex is the bulbous shape of the root, when compared to the first premolar. This alone would tell us that we should be looking for anatomy other than a single canal.

I was able to locate two canals, and confirm that these canals joined apically, but I wasn’t happy with the position of the files in the radiograph. As you can see, the lingual canal was quite centred in the root, while the distobuccal canal is shifted to the distal. It doesn’t look right does it? There must be another canal.

Lower Premolar with unusual anatomy showing working length

Note the Off-Centre Location of the Second File

So…. I know to look for a third canal, but no matter how hard I looked, I just couldn’t find it. The canal were prepared and obturated, with the result below.

Initial Obturation Unusual Premolar

After Preparation and Obturation a Small Squirt of Sealer to the Mesial Confirms the Missed Anataomy

So you can see the squirt of sealer to the mesial at the mid-root point. There is no doubt that some anatomy has not been properly cleaned, and would likely be full of infected tissue. Back in we go. The GP was removed and the access expanded to allow location of the canal to be identified and confirmed with a file.

Unusual Anatomy in Premolar

There it is!

The third canal was then prepared. It too joined the other canals apically. The key to cleaning this sort of anatomy is passive ultrasonic irrigation, which I have discussed previously. The only way to then obturate is with a warm technique such as continuous wave or warm vertical. The tooth, of course needs a crown. In this case persistance paid off and the outcome can be much more certain now that the full anatomy has been cleaned and obturated. In hindsight, a cone beam CT scan may have assisted in locating the full anatomy.

Pat

Premolar with unusual anatomy

I Call This Tooth “The Squid”

Unusual Anatomy of Premolar After Obturation

The Arrow Shows the Spot Where the Missing Canal Was Located

C-shaped Canals
Clinical Tips, Endodontic Preparation Techniques, General Updates

Endospot Cases of Note. Case 1. C-Shaped Canal.

Welcome to the first Endospot Case of Note. This case is of a C-Shaped lower molar and I’ve tried my best to highlight the interesting aspects of the case, explain what can be seen using our diagnostic tools, and also how to treat these cases. As usual, I would love to hear your thoughts and you can leave a comment below.

If you want to review the anatomical variations of C-shaped canals, I recommending reading the following references:

Fan B, Cheung GS, Fan M, Gutmann JL, Bian Z (2004). C-shaped canal system in mandibular second molars: Part 1 Anatomical features. Journal of Endodontics 30(899-903.
Fan B, Cheung GS, Gutmann JL, Fan W (2004). C-shaped canal system in mandibular second molars: Part II Radiographic features. Journal of Endodontics 30(904-8.

This video can be watched in HD on Youtube. Please enjoy!

httpv://www.youtube.com/watch?v=dF3JUsY_k8I

The SAF Pump
Endodontic Preparation Techniques, General Updates, Irrigation

First Impressions of the Self Adjusting File

I had the opportunity during the Australian Dental Association Congress to get my hands on the new Self Adjusting File. It’s not yet available for purchase in Australia, but will be in a couple of months. The SAF comes in 21, 25, 31mm lengths and two widths.

The Self Adjusting File

The three lengths of the Self Adjusting File

To be honest, there is a lot of cynicism out there amongst Endodontists regarding this instrument, mainly because of the manufacturer’s claim that you only require one SAF file to prepare the canal. I think some of the cynicism is driven by the fact that both Dentsply and VDW have recently released their own single file reciprocating systems. The cynicism of Endodontists regarding single file systems is warranted in my opinion. Realistically no one single round file is going to be adequately able to clean and shape the complex anatomy that we are faced with in root canals. They may also force the heavily infected contents of the coronal part of the canals apically and they may not give sufficient time and bulk of irrigant to allow cleansing. When you read the fine print. even the manufacturers will admit that certain canals with particular anatomy preclude the use of the reciprocating files.

In the case of the SAF, the manufacturer told me that they were not selling the system as something that will make preparation easier, cheaper or faster, but rather increase the quality of the preparation. This is probably a good line to take if you want acceptance by the Endodontic community.

OK, on to the SAF. Basically, the file is made of a NiTi mesh with a coating that is designed to “sandpaper” the walls of the canal. The mesh compresses to fit the shape of the canal. I admit I thought the engineering concept behind the file was pretty cool. The manufacturer told me that the designer was involved in the production of cardiac stents and utilised the basic design concept of these. I made the short video below to give you an idea of how the file behaves.

httpv://www.youtube.com/watch?v=UGZZP6_vtN0

On using the file, my first impression is that I’m not going to be out of a job as an Endodontist due to the release of the SAF. You still need to find the canals and prepare to a size 20 at the apex before using it. If you don’t prepare a path, then you’ll end up blocking the canal with debris, just like can be done with rotary files. That said, the ability of the file to prepare these irregular plastic shaped blocks was impressive. The block has an oval shaped canal with fins in it and a fine red coating on the inside. In a one minute session, the file pretty much cleaned all the red stuff off the inside.

I took one of these blocks back to my surgery to see how well I could clean it using traditional methods and after about four minutes of using rotary Ni Ti, hand files, and ultrasonic files, I still couldn’t get the block as clean as I did with the SAF. I’m not sure how well the apical part of the preparation was phycially cleaned by the SAF. If I was using the SAF, I think I’d probably end up gauging the apical portion after using SAF and maybe finishing off with rotary files to enlarge it if required.

Self Adjusting File Compared to Rotary

Plastic block prepared by rotary NiTi on the right and SAF on the left. I took this image from the manufacturer's online powerpoint presentation, but it mirrors the experience I had.

There are two aspects to the SAF system. The first is the ability of the file to clean, and the second is the fact that it is constantly pumping fresh NaOCl through the centre of the file. It may well be that this is the most useful/best aspect of the system. Often in our literature and certainly by manufacturers an improperly greater emphasis is placed on the mechanical preparation of root canals systems compared to our efforts to actually clean the canals of tissue and microorganisms. In a previous post I’ve mentioned the benefits of passive ultrasonic irrigation, and I think the continual deposition of fresh NaOCl into the canal during preparation has great potential.

There isn’t really much research available on the SAF. I could find seven papers in pubmed, all bench top studies (see the end of this post for a complete list). The general outcome of these is that the SAF does a reasonably good job of debriding most areas of the canals under the conditions of the studies, and some nice microCT images were produced. One study (remember these are in vitro, not in actual clinical situations) found the SAF was significantly better at disinfecting canals infected with e. faecalis than rotary NiTi (Siquiera Jr et al. 2010). I guess we need to see more research and time will tell if the SAF is able to disinfect canals better than what we currently have available. My feeling is that it’s a possibility.

httpv://www.youtube.com/watch?v=bWhd8Mgbtmw&NR=1

Above is the manufacturer’s description of the irrigation function of the SAF

The irrigation part of the SAF system is also the biggest downside. In order to use it as described, you have to buy the electronic pump that goes with it. The pump has a timer to make sure you use the file for the full minute, so I guess that’s a good thing. However, I believe that the pump will be susceptible to failure as you manage to spill the NaOCl over it as you repeatedly fill the reservoir. The manufacturer admitted this fact and impressed that the correct funnel needed to be used.

The pump is also another contraption that we have to plug in and put on our benchtops (along with our endo motor, ultrasonic unit, pulp tester, apex locator, system B, obtura etc etc), not to mention another foot pedal on the floor. To be honest, having to buy the pump might stop me from buying the whole unit. We did question the manufacturer on whether we could just use a a syringe filled with NaOCl attached to the tubing which connects to the file, and although he obviously wants us to buy the pump, I think the answer is yes. This would be a much neater and more acceptable to me than having the pump on the bench.

The SAF Pump

The SAF pump. Another machine to clog up our benchtops.

One of the big concerns with rotary NiTi files is obviously the issue of fracture. My friends and I tried very hard to break the SAF and were successful. It did take a while though, and to it’s credit, when the file broke, it was just one of the arms that breaks, leaving the whole file retrievable. I do stand to be proven wrong, but I think that it would be quite unlikely that a separate portion of the file would break and lodge in a canal requiring removal.

SAAF breakage

Mode of failure of the SAF. This image was taken from manufacturer's powerpoint presentation, but is exactly what I saw during the trial.

The business end of all these things are how much they cost. If you buy in bulk, the cost of one of these files in Australia is going to be about AU$70. That’s about US$73 at today’s rates. So, they are quite expensive, especially if you plan to use additional rotary files to further prepare the apical area, you break one before you finish the tooth or you need to use both the larger and smaller width files to complete multiple canals in one tooth. You also need to buy a special handpiece or handpiece head, plus the irrigation system if you go by the manufacturer’s instructions. This might scare a few people away and into the arms of the single file reciprocating systems. I’ve previously stated that the reciprocating files may become a part of our armamentarium for particular cases, and it may be that the SAF fits into this category.

My overall impression of the SAF, despite being cynical to begin with was a positive one and I think that this system has potential to do more for us than the reciprocating files. Stephen Cohen, author of Pathways of the Pulp will be in Australia in June running workshops on the system, so we’ll get another look at it then. The SAF is certainly no panacea for endodontically infected teeth, and preparing canals that are already opened to a size 20 file is actually the easiest part of an Endodontist’s day. That said, if further evidence comes through indicating that the SAF system does in fact kill more bacteria in the root canal than our current systems, then I guess we’ll all want one.

Pat Caldwell

References: Hof R, Perevalov V, Eltanani M, Zary R, Metzger Z. The self-adjusting file (SAF). Part 2: mechanical analysis. J Endod. 2010 Apr;36(4):691-6.

Metzger Z, Teperovich E, Cohen R, Zary R, Paqué F, Hülsmann M. The self-adjusting file (SAF). Part 3: removal of debris and smear layer-A scanning electron microscope study. J Endod. 2010 Apr;36(4):697-702.

Metzger Z, Teperovich E, Zary R, Cohen R, Hof R. The self-adjusting file (SAF). Part 1: respecting the root canal anatomy–a new concept of endodontic files and its implementation. J Endod. 2010 Apr;36(4):679-90.

Paqué F, Peters OA. Micro-computed Tomography Evaluation of the Preparation of Long Oval Root Canals in Mandibular Molars with the Self-adjusting File. J Endod. 2011 Apr;37(4):517-21.

Peters OA, Boessler C, Paqué F. Root canal preparation with a novel nickel-titanium instrument evaluated with micro-computed tomography: canal surface preparation over time. J Endod. 2010 Jun;36(6):1068-72. Epub 2010 Apr 10.

Peters OA, Paqué F. Root canal preparation of maxillary molars with the self-adjusting file: a micro-computed tomography study. J Endod. 2011 Jan;37(1):53-7. Epub 2010 Oct 8.

Siqueira JF Jr, Alves FR, Almeida BM, de Oliveira JC, Rôças IN. Ability of chemomechanical preparation with either rotary instruments or self-adjusting file to disinfect oval-shaped root canals. J Endod. 2010 Nov;36(11):1860-5. Epub 2010 Sep 16.

Endodontic Microorganisms
Clinical Tips, Endodontic Preparation Techniques, Irrigation

1 Minute to Bacteria Free Canals. Here’s How.

Endodontic Microorganisms

Endodontic Microbes. Who needs them?

OK so a patient has come to see you complaining of toothache. It’s root canal time. You open up the lower right first molar and find a necrotic pulp. You’ve isolated well and done a nice endodontic preparation. Length is good and you’re happy with the sizes of your apical preps. You’ve been irrigating with plenty of sodium hypochlorite and used a final rinse of EDTA. Job done right?

Think again. In the vast majority of teeth, canals are not round, and as such there are going to be vast areas that are still harbouring debris and microbes. Just take a look at some of the microCT produced by Paque et al after preparation with rotary Ni Ti (Paque at al. 2010). It’s quite clear in these images that a good proportion of the original canal space remains untouched by our instruments.

So, hopefully, our irrigant is managing to get into these nooks and crannies? Well it will, but even after irrigation, there is still going to be significant debris from preparation (mushed up dentine, bacteria, necrotic pulp remnants) hiding away in fins, apical delta and especially in isthmuses.

I recommend you check out the work by Burleson and colleagues for some nice images on what can be left behind (Burleson et al. 2007). These guys conducted a randomised controlled trial (nice and high on the level of evidence) and compared preparation and irrigation alone, or with the addition of 1min of passive ultrasonic irrigation (PUI). They used the mesial roots of infected lower molars and then extracted the teeth to examine how much debris was left behind. Check out the table below to see the results on cleanliness of the canals at various levels from the apex. The isthmus especially is full of debris without PUI.

PUI Bacteria

Cleanliness of Canals at various levels from the apex. Pay special attention to the number in the isthmus.

Interesting right? It’s even better when you see the images in their article and realise just how much is being left behind when you only rely on irrigation.

I know what you’re thinking though. It’s bacteria that we’re concerned about, not debris. Well, Burleson’s colleagues thought of this, and conducted a separate study, I assume on the same teeth, using microbiological sampling to see what they could find (Carver et al. 2010). They concluded that PUI resulted in a significant reduction in colony forming units and positive cultures. In fact PUI was, “7 times more likely to yield a negative culture”.

So, it seems that PUI is something worth doing, and it’s certainly part of my routine. If you haven’t heard of it, I’ll explain what it is. PUI is simply the placement of an ultrasonically activated file into the canal filled with irrigant. There is some debate over how it works exactly, but acoustic streaming seems to be the key. This basically means moving the solution around so that fresh sodium hypochlorite gets into areas that needles won’t push it. The important point here is that the ultasonic file has to be loose in the canal. Touch the canal wall and acoustic streaming stops.

Personally, I use the Irrisafe from VDW because it’s easy. Just screw it on to your US unit and place it in the canal. The irrisafe is “smooth” i.e. it doesn’t have the sharp cutting edges that files do, so it is safer in the canal (Hence the name – smart huh). Here are my three keys to PUI:

1.     Use a low power setting as recommended by the manufacturer. You risk fracturing the ultrasonic file otherwise;

2.     Keep the file loose in the canal and don’t push it too deep;

3.     Replenish your sodium hypochlorite as you go.

Irrisafe

The Irrisafe. Attach it to your ultrasonic and kill more bugs.

Acoustic Streaming Endodontic

Acoustic Streaming in Action

I generally have my DA using a syringe to supply sodium hypochlorite and suction while I run the ultrasonic in the canals. If you don’t have a stand alone ultrasonic unit where you can easily control the power, then I wouldn’t risk using an ultrasonic file. You can achieve the same result by just holding a normal scalar tip against a size 10 stainless steel file. This is obviously much cheaper as well. Just be careful not to put the file too deep into the canal or you might actually damage the canal walls and ruin your nice preparation.

There are other methods for activating irrigant such as the Endoactivator and the Endovac. These work slightly differently. The Endoactivator is a sonic machine and has disposible polymer inserts. It seems very safe to me, but there isn’t much in the literature indicating that it is better at killing bugs than other methods (Huffaker at al. 2010), and it is not as effective as PUI at removing calcium hydroxide from canals (Wiseman et al. 2010).

Endodontic Endovac

This is just part of the Endovac system

The Endovac shows promise. It relies on a vacuum to remove irrigant that is being supplied by a needle deep in the canal. That means there is no positive pressure. One clinical trial showed that post-op pain was reduced after using the Endovac compared to needle irrigation (Gondim et al 2010). It is a bit of a contraption though and I have enough machines clogging up my surgery. I am waiting to see some studies comparing PUI directly to Endovac and Endoactivator before I give up my proven method of cleaning the canals.

Next time you finish a prep, grab your ultrasonic and give the canal a bit of a shake up. It’s impressive to see how much more debris you can get out when you irrigate again.

References:

BURLESON A, NUSSTEIN J, READER A, BECK M. 2007. The in vivo evaluation of hand/rotary/ultrasound instrumentation in necrotic, human mandibular molars. J Endod. 33: 782-787

GONDIM E, SETZER F, BERTELLI C, KIM S. 2010. Postoperative Pain after the Application of Two Different Irrigation Devices in a Prospective Randomized Clinical Trial. J Endod. 36:1295–1301

HUFFAKER S, SAFAVI K, SPANGBERG L, KAUFMAN B. 2010. Influence of a Passive Sonic Irrigation System on the Elimination of Bacteria from Root Canal Systems: A Clinical Study. J Endod. 36:1315–1318

PAQUE F, BALMER M, ATTIN T, PETERS OA. 2010. Preparation of oval-shaped root canals in mandibular molars using nickel-titanium rotary instruments: a micro-computed tomography study. J Endod. 36(4): 703-7

WISEMAN A, COX C, PARANJPE A, FLAKE N, COHENCA N, JOHNSON J. 2011.  Efficacy of Sonic and Ultrasonic Activation for Removal of Calcium Hydroxide from Mesial Canals. J Endod. 37:235– 238