The Conversion of a Scope Cynic

A 20 year Retrospective

When the Endoexperience web site was first created in 2000, I originally had included a page that suggested that the use of a Surgical Operating Microscope (SOM) in endodontics was unnecessary and I questioned its routine use. I had been in specialty practice for 14 years, had a high degree of success and saw little need for this expensive piece of equipment. At the time I believed that the mandatory Postgraduate SOM certification was nothing more than a method to increase SOM sales. I also had some questions as to why this technology was so readily accepted without support from the literature. I also commented that the presence of a microscope could be used as leverage “against” the referring Generalist. The Endodontist could now say that optimal Endodontic treatment could only be delivered by using state of the art equipment, and that this included the SOM. I wrote that the subliminal message to “non SOM equipped dentists” was that they were second class, were ignorant, and that they just “didn’t get it”. It was a cynical attitude.

The reaction to this page was swift and dramatic. On the rxROOTS internet forum, several clinicians, (such as the father of Microscopic Endodontics Dr. Gary Carr) were very critical of the piece. They wrote that I could not treat what I could not see, that I had no concept of what a huge difference it made and that I could never reach my potential as an endodontist without one. There was much browbeating, name calling and at the same time very much encouragement from those on ROOTS. I finally saw the light, literally. After attending two scope courses at ROOTS Summits I and II, it became apparent to me that I was wrong. I made arrangements for immediate purchase of my first Global SOM with upgraded Starlite light source and I haven’t looked back.

I now believe that it is impossible to do the highest quality endodontic treatment without an SOM. It may be politically incorrect to say so but I believe that teeth such as molars should NOT be attempted by those who work without one. The difficulty with recommending that clinicians treat “easy” teeth and think about referring out the more difficult cases is the fact that many teeth that were initially thought to have been “easy” were actually much more difficult than anticipated. Rather than ledge the canal, break a file or make the case more difficult to treat prior to referral, perhaps it is best to decide whether you truly wish to perform the treatment yourself, rather than refer it out after the case has been made much more difficult to treat by these initial unsuccessful attempts .

For those that ARE willing to raise the bar of their practice ( Not just in Endodontics!) the SOM offers many advantages in visibility, magnification, light and ergonomics. Many of these attributes are not readily appreciated this device routinely. Then you will wonder how you worked without it!

Some initial impressions of a scope novice:

1. The light source is incredibly bright. My staff sometimes complain that they have difficulty seeing “away” from the field after they have been looking at the area for a few minutes. An assistant ocular would probably prevent this. Sunglasses are helpful if your assistants do not have their own ocular and work with the scope for long periods of time. A less expensive alternative to the assistant ocular is mounting a video camera on the scope and porting out the video to a monitor that is directly opposite to your assistant. This “Poor man’s Assistant Scope” is a way to allow your assistant to see what you are seeing, which is an important part of working together under scope magnification.

2. There is a tendency to go to “high power” immediately in order to “see better”. This is a mistake. Skills must be developed at lower magnifications. In many instances it is better to observe the field at lower magnifications to gain “perspective”. ( You also  have more light at lower magnifications). Then shift to higher magnification when close inspection of a specific area is required.

Staff have some major trepidation when confronted with this new technology. It requires a whole different set of assisting skills. Staff must be brought along slowly, as they regard the scope as a tool that will “slow us down” (i.e./ put more pressure on THEM) rather than as an augmentation to treatment.  The truth is that once you become proficient, the scope saves you a lot of tie.

3. Clinicians who are used to running multi-op practices (frequently filled with emergency toothaches) occasionally find themselves working alone while other ops are being prepared or patient’s seated. This breeds a bit of “laziness” in staff because the dentist sometimes reaches for instruments while he is alone in the operatory. When using a scope, this is not possible. The clinician’’s hands must be stationary in the operating field. Bur changes, file changes, suction and irrigation that may have been performed by the dentist alone in the past now cannot be done this way. Much greater staff discipline must be obtained and this takes time.

5. Scope Photography is a whole art by itself. It requires time to focus the image. After almost 20 years of scope use, I’m still struggling at times with deeper focus images and depth of field issues.

Although I had only been using the scope for a relatively short time when I first wrote this piece, its advantages are obvious. Visibility is greatly enhanced and I now saw much of what I missed earlier.

For example, I am noticing how “wet” prepared canals remain, even after attempting to dry them with paper points. (You need alcohol and Stropko syringes for proper drying!) Additional canals (such as MB2 and more!) are easier to find. Canals that looked “clean” superficially frequently have tissues, fins and canal branches deeper in the canals that can only be seen with a scope.   Most importantly, the SOM offers the ability to see changes in dentin coloration (as a clue to where orifices are). You can also see bubbling of NaOCl as it interacts with tissue, it is essenial for removal of broken instruments, etc. With specialized micromirrors the SOM allows for close examination of retropreparations at angles impossible to view with the unaided eye or with loupes. The list goes on and on.

SOMs are the future of dentistry for those clinicians who truly want to see what they are doing. Back in the days where amalgam was our only option and margins where checked with a dull explorer, it was easy to neglect things that we could not see. In the era of bonded restorations, precise margins, and high quality dentistry, this attitude IS passe. I believe that dentistry will eventually be divided into those who truly can/want to see and those who don’t.

One final question to ask yourself – Who would you rather have doing your restorations or Endo – someone who is or is not SOM equipped?

I owe much of my rethinking to the gang on the (now defunct) rxROOTS.com and to Dr. Gary Carr, and for that I will always be grateful.

One organization that has dedicated itself to the use of the SOM in Dentistry is  called AMED – The Academy of Microscope Enhanced Dentistry.  The clinicians in that organization are truly world class operators and if you have an interest in getting trained to use the SOM properly, that is a good place to start.
See AMED for further info.

July 2003:
It had been  almost a year since my first SOM was installed. I ran into a big problem: I realized that I couldn’t see as well in my other non-SOM equipped operatories. The difference was dramatic and obvious. On the occasions that I had to work in this 2nd op, I found myself cursing the fact that I simply couldn’t see what I needed to see to do a good job. That operatory was “handicapped” by the lack of the SOM. So on July 31st a second SOM (Seiler Revelation. My conversion as a “scope cynic” appeared to be complete.

May 2007
I subsequently purchased a Global G6 which has gone into my #1 operatory. It is a fabulous scope and by far the best of the 3 that I now own.  For more information about it please see the product section of this website. I am extremely happy with the G6 and wish I had one in each op! If you are considering an SOM, I strongly recommend that you do not “cheap out” and go with less expensive model.  These instruments are your “eyes'” and if you want to do the best endodontics possible, you need to make an investement that will allow you the best visibility possible. It truly is the LAST place you should be looking to save money. If you can’t see it….you can’t treat it.

2021 Update – Some 20 years has passed since I wrote that initial piece and  incorporated the SOM into my practice. Now, I cannot imagine practising without one. I eventually sold my Seiler scope ( I was never happy with the ergonomics and design of that Revelation model)  and purchased another G6. It has been flawless. Going “full Global” in all ops has solved all reliability and ergonomic problems.

One factor I have come to appreciate more that ever is the need for good seating and proper arm support. The Jed Med chairs ( See the product section of this website) are terrific. They are rugged, solidly built and have very comfortable over the past 20 years of use!

Ultimately, we each make decisions that define us and the way we practice.  Dentistry is both and art and a science. For those who wish to do their best work, it only seems logical that being able to see as well as possible will make you the best clinician you can be. The question we all have to ask ourselves is : How can I be my best?   The SOM will allow you to explore that possibility.

Mechanized Ni-Ti Rotary Endodontics  What Goes Around, Comes Around

Note: This article was originally published 20 years ago and discussed techniques being taught at the time – circa 2003 .  I have edited the article (with teal colored text)  to reflect what I am doing today – in 2021.

Mechanized Ni-Ti Instrumentation has taken Endodontics by storm. What is unusual about the rapid acceptance of this method of instrumentation is how most manufacturers and lecturers minimize the need to have a #15 file at working length before moving to this type of instrumentation. This is laughable. Virtually all instruction literature first states “Obtain a working length with a size #15 file.” Then move to the mechanized Ni-Ti Engine files.

Ask any Endodontist and they will tell you that the most difficult part of treatment is the location, and negotiation of small calcified or tortuous canals. It is not doing the bodywork of the canal. (Shaping the body may be the most “tedious” part of treatment but it certainly is not the most difficult.) Achieving apical patency in difficult canals can only be accomplished through the use of small hand instruments that allow transmission of the minute subtleties of canal system anatomy to the clinician. This “Endodontic Touch” is the essence of skilled endodontic treatment since these tiny probing file manipulations are the “eyes” of the clinician. Once the working length has been established with a size #15 file, the method used in shaping the body of a canal is really not that important, whether it is with hand files, reamers, rotary or sonic/ultrasonic instruments.

What HAS become generally recognized is that rotary motion is the most efficient way of shaping and enlarging the body of the canal; hence the popularity of rotary instruments, at the expense of the old “push pull step back filing” 1980s method. Oliet et al noted the efficiency of rotary instrumentation for canal enlargement as far back as 1970s. The advancements in Ni-Ti metallurgy have allowed for the creation of more flexible (albeit expensive) instruments. Unfortunately, pure rotary instrumentation does little to address the problems of irregularly shaped canals, canals with an isthmus and those canals with fins. These can only be cleaned with the use of irrigation and hand files used in a deliberate effort to clean these areas.

Attempting to “encompass” these areas with the rotary files would cause excessive enlargement and weakening, thinning or stripping of the root dentin. As much as we would all love a device (sonic/ultrasonic/rotary/laser/suction etc) that you could turn on and walk away from, negotiation and filing of irregularly shaped canals is still required.

(It remains to be seen whether “newer technologies” such as GentleWave, which claim to be able to do this, are as efficient as they claim. Unbiased, peer reviewed, non industry sponsored research is required for us to very these claims- Editor 2021)

The pitches of clinicians selling instruments of their own design must be examined. When claims of 75% reduction in treatment time are made, they must be scrutinized closely. In the real world of Endodontics, history has shown that most “time saving” devices/techniques are rarely supported with good results. When they fail, they often fail in the worst possible way, resulting in the need for protracted treatment times.

Ni-Ti rotary instrumentation is best used for shaping of the body of the canal after the initial working length and apical patency has been established. Attempting to use these instruments for “path finding” or “canal negotiating” can result in catastrophic instrument breakage, usually at the most complicated part of the canal. (junction of joined canals, sharp bends, dilacerations and apical deltas). (When this was written, heat treatment and ultraflexible files had not yet been invented and sold. Today, more flexible instruments (Pathfinders, for example) allow for instruments to reach the apex more easily and less need for “body work”. Also, there is more emphasis on conservation of dentin and decreased taper – “skinnier preps”. ) These fractured instruments can sometimes be removed or bypassed but at great cost in time and effort. (translated… $$$) In the worst-case scenario, when a fractured file is used in a “crown-down” fashion, a necrotic apical portion of the canal is left completely untouched. This virtually guarantees failure of the case or the need for surgical resection of the inaccessible portion.

The basic principles of Endodontics must always be adhered to:
(1) Establish a reliable working length (Electronically and/or via radiographic images)
(2) Maintain apical patency through recapitulation with smaller hand files
(3) Establish good canal taper to allow for better irrigation and obturation of the deeper apical portions of the canals
(4) Take a cbCT image BEFORE and DURING treatment if there is any question about the canal system anatomy. Maintain a “mental map” of the canal system in your head through the use of sensitive files and constant subtle tactile feedback.
(5) In Endodontics the axiom of “better, easier, cheaper…pick two” is the rule.

There is no magic bullet. Do not be fooled by those who wish to sell you an expensive chrome-plated revolver.

Access in Endodontics – Why is it so important?

DISCLAIMER – How well you “see” influences your access design.

HOW you access canals is directly proportional to your ability to see. Naked Eye Dentists (NEDs- as they are colloquially called) or  2-5 x Loupe based Dentists need accesses that allow the greatest amount of  light into the canals, so they can see.  (Dedicated Headlights or not) It is disingenuous and deceitful for those selling endodontic products to omit the concept that they would never use the products they are selling or lecturing about ….without a Surgical Operating Microscope.

The biggest criticism I have of those who advocate “ extreme dentin conservation” or the “Ninja Access” is not with the access itself. These clinicians are often very skilled and experienced and would NEVER think of trying to perform these procedures without an SOM. Where I object, is the idea that they can advocate or market these products or ideas to those who do NOT use an SOM and who do NOT have that level of experience.

But you will NEVER hear Endodontic speakers ( many of whom receive millions of dollars in patent revenues and from instrument sales) say “I’m sorry. If you are doing Endo and want to get the results I show ….you MUST use an SOM.” That would eliminate 95% of audience and their targeted sales, because few Generalists use one.

Endodontics can be difficult. In many cases, clinicians make it more difficult than necessary by not creating a proper access that allows them straight line approach to the canals. This is especially true for Mesiobuccal canals in both Mandibular and Maxillary molars. Before dealing specifically with molars, lets examine a few access concepts that will allow us to reach the apex more successfully.

Concept # 1 – Most Files can safely only “do” two curves at a time
Although the development of heat treated NiTi metals has improved instrument flexibility, it is important to understand one basic fact about endodontic instruments: In vivo, they can only be expected to consistently negotiate two curves at a time, especially files greater than a size # 15 or 20. Because canals are curved both in a mesio-distal and bucco-lingual directions, we must initially provide as straight line access as possible in order to allow maximum freedom for the instrument in the more confined, difficult apical sections. Most endodontic cases that are ledged occur because the clinician is attempting to guide the instrument through too many curves. The instrument is unable to negotiate the final curve, resists, and then a ledge is created. Limited purposeful straightening of the cervical portion of the canal is the key to negotiating the final apical curves. This was the reason for the popularity of the “Crown-Down” technique that ushered in a new era of canal instrumentation.

Concept #2 – The access is complete when a DG 16 explorer can “stand” unaided in the canal.
How do we know when access is sufficient? I used to teach students to literally place a DG16 explorer in the canal and have it “stand up” (balanced in the canal orifice) without being held. That was for STUDENTS!  A conscious effort should me made to ensure that the explorer does not touch any other part of the access. When it “stands” on its own, access is sufficient. For less experienced clinicians or for clinicians who do endo less frequently, it is probably a good rule. For those advocating “minimalist” accesses, this concept is an anathema.

Concept #3. STRATEGIC  extension of the access
Strategic extension of the access is now the rule. By somtimes extending the access opening to “nontraditional areas” we allow for better direct line access to the deeper portions of the canal.  (For example in MB canals or madibular molars or MB2 in maxillary molars)

Concept #4. Creation of the “Glidepath”
General Dentists are often amazed at how quickly Endodontists treat their cases. Speed of treatment has very much to do with how easily and quickly instruments can consistently be placed in the canals. Dr. Ken Serota coined the term “Glidepath” with reference to how instruments are inserted into the canal orifice. The term describes the way that endodontic access is designed to

(a) allow for straight line access to the canal and

(b) allow the clinician to place instruments in the general vicinity of the orifice and have them passively led into the canal space as they are inserted.

i.e./ If the access is designed with the proper Glidepath, placing an instrument in “the vicinity” of the DB part of the access leads it directly into the DB orifice with no effort.

This dramatically decreases treatment time by :

(a) eliminating the need to “search” for the orifice with the file

(b) reduces the chance of acutely bent instruments that must be discarded

(c) allows for easier irrigation syringe insertion and better irrigation volume

Concept #5. Coronal tooth structure is not sacred
Endodontists who perform these type of accesses are occasionally criticized by Prosthodontists and Cosmetic dentists for being too aggressive in removal of sound coronal tooth structure. It is sometimes necessary to remind these clinicians that their restorative treatment depends on sound periapical health. (Both Endodontic and Periodontal) The best Prosthodontics is of absolutely no value in cases where the endodontic or periodontal treatment results are less than optimal. Straight line access is integral to successful endodontics. Having said that, excessive removal is not advocated.
My friend and colleague Dr. Terry Pannkuk put it perfectly when he coined the term “SEA – Strategically Extended Access”.  The SEA creates a balance between “Biomimetic” Dentistry (that may place undue emphasis on preserving tooth structure) and over-enlarging accesses to the point of weakening the tooth (simply because the clinician is unnecessarily destroying tooth structure to visualize the orifices or access) in their attempt to find or instrument canals.

If you ever  watch a skilled endodontist treat a case, you will invariably be impressed by the time invested in creation of the access cavity. Careful creation of smooth (unditched walls) and unhindered access to each canal pays handsome dividens later on when instruments, syringes, cones, heat carriers and pluggers are easily introduced into the tooth without the need to “finesse” them into the tooth.

Example Case 1- The Maxillary Lateral Incisor
Higher failure rates are associated with treatment of the maxillary lateral incisor. We know that the apical section of this root curves both distally and palatally in most cases. This is not a particularly difficult tooth to treat when proper access is made. However, when access is small and poorly designed, the final palatal curve is almost impossible to negotiate. The result is that these cases are often ledged, filled short or perforated at the final curve.  This happens less frequently with today’s more flexible Ni-Ti files.

Example Case 2- The Mandibular Incisor with 2 Canals
Buccal extension of the access is not a new concept. Some clinicians have even suggested that anterior teeth with two canals ( such and mandibular incisors and Cuspids) should actually be accessed from the buccal surface! They claim that this produces straighter line access to the often missed lingual canals and they are correct. These lingual canals are missed because most incisor accesses are made at the cingulum. The instrument must first be placed toward the buccal as it is negotiated into the buccal canal orifice. But with the lingual canal, It must immediately make a sharp transition toward the lingual to get into the lingual orifice. The classic endodontic access in the mandibular incisor often does not take this into account. That is why when an Endodontist opens a suspected two canal lower anterior tooth, you will often see the access is moved very far labially, In many cases it incorporates the lingual dentin and enamel all the way to the incisal edge. We may be criticized for the aesthetics of this type of access but it is the only way that these cases can be treated successfully by non-surgical means.

Example Case 3- MB canals of Mandibular Molars
We can also extend these principles to the molars. Mesiobuccal canals of mandibular molars have a particular characteristic that often is not noticed by clinicians performing endodontics. Whereas the the Mesiolingual orifice is centered under the mesiolingual cusp, the mesiobuccal canal orifice is often located much further buccally than anticipated. The “Classic” trapezoidal endodontic access preparation does not take this into consideration.

Unless accommodation is made, the file shaft often is quite close to the MB cavosurface margin of the access or orifice and may be deflected by it. The file must first “negotiate” this curve as it enters the orifice. This happens even before it again must curve toward the lingual aspect of the tooth where it sometimes joins the mesiolingual canal on its way to the apical foramen. In most cases the file is able to negotiate two of these turns but as the final curve occurs either mesially or distally, there is so much tension on the instrument that, as in the maxillary lateral incisor, the canal often ledges. The clinician becomes frustrated and the case is filled short of the apical foramen.

The best way to prevent this is by modification of the access by buccal extension. This is done by again extending the principles of “Triangle1 and 2” by removing the cusp tip of the mesiobuccal cusp. In some cases where CL V buccal restorations have been placed, the orifice may be even further down the root than anticipated. In that case a “slot” is actually cut in the MB cusp that allows for straight line placement of the file into the orifice. You will notice immediately that the “first curve” that you negotiate is no longer high up in the area of the orifice,it is further down the canal. This allows you instrument to negotiate the two turns that are required to reach the terminus, the lingual curve and the M-D curve ( depending on the root curvature).

Example Case 4 – MB1 canals of Maxillary Molars
Good direct visibility is paramount. This may include removal of the ENTIRE MB cusp in molars. The Buccal canals are often tucked far to the buccal and you will NEVER see them if you don’t do this. They also often have multiple curves ( bucco-lingual and Mesio distal) You’ll never negotiate those unless you get as straight line access to the orifice as you can. I sometimes even use a “slot” type access that moves the opening very far buccally. Cameras or scopes won’t help you if this is not done correctly. (2) The creation of a “Glide Path” is essential to smooth shaping. You really should be able to place instruments into the canals WITHOUT LOOKING. If you are constantly picking up your mirror to get an instrument into the canal, you are wasting time and causing much unnecessary stress. The problem in that case is that the access is gouged or ledged and the instruments to not naturally glide down the prepared access walls right into the canal. i.e./ place the instrument “somewhere” in the MB of the orifice, and it goes directly down the canal. Same for DB, palatal etc. This may seem like an obvious concept but the access cavity is much like a crown prep in that it has to be refined and contoured properly to be effective.

Example Case – MB2 canals of Maxillary Molars
The MB2 of maxillary molars is most often very small. Recent studies have shown that at least 90 % of first molars have these canals. Fortunately, many of them are joined to MB1. In those cases it may be possible to just treat MB1 without even knowing about MB2 because sealing the common formen is often enough. But do we want to take that chance in a necrotic molar ?

Location of MB2 is a whole topic in itself and I will address that in another area of the web site. Having found MB2, it is important to get direct line access in this canal because of the minimal diameter of the canal and the tendency for their to be a “proximal lip” that covers the canal from the mesial aspect. If this mesial “lip” is not removed, the file will be deflected distal upon initial insertion. Just like the other canals mentioned above, this initial bend will make it difficult to negotiate the file as it moves buccally to join MB1 and then distally as the root curves. Creation of a proper Glidepath for this canal also solves the problem of repeated inadvertent entrance to MB1 when what you to do is insert the instrument into MB2.

Exceptional or Unusual Anatomy
In the case of bayonet or dilacerated canals, there may be another curve that can be very challenging even with adherence to the above principles. I believe that these cases should be radiographically anticipated before treatment and referred before the clinician ledges the case or breaks an instrument. cbCT imaging has been extremely helpful in determining and assessing anatomy previously impossible to image with 2D conventional radiography.

The End is Near!  How near?  
Well, I’m Not Exactly Sure

Where to “End” a root canal filling?
For a long time, clinicians performing endodontic treatment were deathly afraid of “overfilling” canals.  Many of these cases were associated with failure and exacerbation of symptoms.  It wasn’t until the real difference between “Overfilling/Underfilling” and ” Overextension/Underextension” of endodontic fillings was understood that a rational discussion of the topic could commence.  With the advent of the warm gutta percha technique, canals routinely became filled in three dimensions. As pressure was applied in a warm vertical manner, “buttons” of gutta percha, sealer or a combination became visible at multiple foramina.  This was commonly known as the “Boston or Schilder Puff”.

What immediately became apparent was that (regardless of those who opposed the intentional placement of this “foreign” material beyond the apex) these cases healed predictably. As long as the canal was sealed in three dimensions, this “Overfilling” was not of consequence. Yet today, there still remain segments of the Endodontic academia and research that disdain this technique because of the “puff”. They are rapidly becoming an anachronism as Dentists ” warm” to the idea of use of softened gutta percha with controlled heat and vertical pressure.

The need to establish the position of the apical foramen

The most critical piece of endodontic treatment information remains the size and location of the apical foramen.  Until the invention of reliable electronic location techniques, Endodontists had little to go on other than the Radiographic Terminus (RT) and tactile sensation. (Something that CANNOT be easily perceived with the use of engine driven rotary instruments) Study after study was used to discount the radiographic technique because of the obvious difference between the actual foramen position and its perceived radiographic location. In some cases, (Palatal roots of Maxillary Molars and Maxillary Lateral Incisors for example) the distance can be quite significant.

Just like the concept of Centric Relation in Prosthodontics, the RT is an artificial measurement, used ONLY because of its relative reproducibility.  (Even still, this can be “fudged”. Anyone who performs endodontic treatment knows how foreshortening of a film can make a short filled case look less “short”!) With reliable EALs, clinicians now have several methods (EAL, X Ray Image and tactile sensation) that, when combined, can produce very accurate results. It is still necessary to have radiographic confirmation because EALs (although very accurate) are not 100 % accurate in all cases. However, when combined with new cbCT 3D inmaging techniques, the question of “wher the canal ends” has become much easier to solve.

Working to the radiographic terminus

For many years, working to the RT produced excellent results, even though it was technically “long”. Why is this?  Mostly it was because although the instruments were “long”, the entire length of the canal space was adequately cleaned and shaped.  This allowed for better irrigation and filling of the apical third. In contrast, those who were afraid of “tearing the apex” or removing the “apical constriction” found that their cases were often filled short of the RT. These cases were associated with a higher rate of failure, mainly because it is these last few millimeters of the canal that are the most important for cleanliness and seal.

Experienced clinicians will confirm that filling “short” (especially in necrotic cases) invariably causes more concern for long-term success than overextending a case (as long as it is filled completely).  The importance of working to the RT has diminished with better EALs and cbCTs  but the concept of cleaning the entire length of the canal remains a staple of good endodontic technique. In Endodontics, it is always better to have “been there” than to “never have been there”.

Working to the “Apical Constriction” and apical patency

I have always been amused at those who use the concept of working to the “Apical Constriction”. Experienced clinicians know that this concept is a myth.  This because:

(1) It is almost impossible to locate the actual position of the constriction during measurement of initial working length. Its position depends on a myriad of factors (Root and canal curvature, dentin thickness, cementum thickness, apical resorption etc.) Often the true position of the constriction is only apparent AFTER the tooth extracted, sectioned and evaluated under a microscope.

(2) Curved canals become shorter as they are straightened. Failing to compensate for loss of canal length during treatment can often lose the initial “constriction”.

(3) It only takes one or two pushes of a size 25 or 30 file to remove any  “Constriction”. In many cases, poor access due to limited patient opening, patient movement or lack of length control can remove what little “constriction” there is in matter of a few seconds.

(4) It is much more difficult to achieve adequate apical patency when you are forever concerned about not placing instruments past the “constriction” lest the “constriction” be removed. Apical Patency is the key to maintaining an unblocked canal.

(5) In the vast majority of chronic periapically involved necrotic cases, there is some remodelling of the root apex due to the effects of chronic periapical inflammation. In many cases there is NO constriction left. How do Apical Constriction advocates handle those cases? If they fill them to the RT with success, why is a constriction necessary in ANY case, regardless of whether it is resorbed or not?

One additional adjunct to determining foramen location in such resorbed cases is the “Rosenberg Paper Point WL Determining Technique” which uses a paper point placed in the canal to assist in determining WL. See Another article in this section that describes it in detail.

Similarly, retreatment cases are often “reamed out” and do not have a constriction. However, they too can be reliably re-treated by routine filling to the radiographic terminus (perhaps technically “long”). If these cases can also be treated successfully without the presence of a constriction, is one really necessary at all?

Summary

The end is near and it is often closer than we think. Determining exactly where to end a root canal obturation must use  all available tools as well as tactile sense and experience will result in success. The keys to successful management of the end of the canal are:

(1) Maintaining the apical foramen in its original 3 dimensional relationship to the root

(2) Maintain apical patency through the use of small files. Irrigate frequently.

(3) Keep the foramen size as small as is practical to achieve good seal

(4) Use the EAL to check the working length before, during and after the canal has been cleaned and shaped.

 Sonics and Ultrasonics in Endo

As an Endodontic specialist of almost 40 years practice, I have seen products and techniques come and go. Hydron, the magic hydrophilic filling material of the 80s is no more. Resilon, the “Monobloc endo resin of the future” is no longer being sold. Friction driven filling devices (McSpadden Compactor) have fallen out of favor as the endodontic community has generally “warmed” to the concept of pushing gutta-percha vertically under the influence of heat.

Ultrasonics, the converted Cavitron touted in the mid 80s by Cunningham and Martin as the “Vegematic” of Endodontics (it cleans, shapes, sterilizes, implodes, produces less extrusion of debris etc etc) has been relegated to “electronic swizzle stick” status. Once research is performed by those not financially affiliated with the device or technique, the published results are inevitably less favorable than originally claimed.

The initial positive effects of endosonic/ultrasonic instrumentation were predicated on the free movement of the energized file in the canal. Once it was understood that contact of the file with the canal wall dampened and reduced the sonic vibration, the  in vivo effects were less clinically relevant or not as reproducible than the results from in vitro studies. Furthermore, as canal shapes become more narrow (with increasingly flexible files and the move toward more conservative canal preparation shapes), there will inevitably be less volume of irrigant to activate and ever greater chance that any sonic or ultrasonic instrument movement will be dampened by these more conservative shapes. Most of the initial studies in the late 80s studies began to show that in vivo cases were not shaped more quickly than conventional treatment. It was also noted that the tip of the instrument had the most amplitude and the body of the file the least. This is opposite to the desired endodontic result, minimal enlargement of the deepest portions of the canal and more enlargement in the body and cervical portions.

Some research suggests that both sonic and ultrasonics are equally effective in activating irrigation solutions once canals have been cleaned and shaped. The recommended time for activation of these canals is three minutes per canal (it varies according to study). Therefore in maxillary molars, ultrasonics will increase the canal preparation time for most teeth by 12 minutes. Since the ultrasonically activated files must not contact the canal walls, they must be held in position manually. (Should Dentists choose to delegate this duty to assistant, there will no doubt be legal ramifications since in most states/provinces assistants are not allowed to perform this type of “treatment”. Also, if a file breaks in the hands of an assistant, it is doubtful that the dentist’s malpractice coverage would cover the consequences of this scenario.) It is also uncertain whether  clinicians will comply with an extra 12 minutes of instrumentation time per molar, especially when some Endodontic clinicians are claiming to clean and shape an entire tooth in only a few minutes with Ni-Ti engine driven rotary files.

There is no question that the use of sonics/ultrasonics in conjunction with endodontic irrigation can produce cleaner canals in many cases. Whether this technique is useful in teeth with cases with difficult access or extremely curved canals, whether the increase in time and necessity for maintaining files in free space by hand are justified remains to be proven by unbiased research.  Most recently, the GentleWave device has been heavily marketed as the new Endodontic wonder-machine that most effectively cleans canals. Unfortunately, almost all the research published has been sponsored by the manufacturers sponsors or paid consultants of the device.  Until this is verified, the claims of manufacturers and their paid advocates/lecturers should be viewed with the appropriate skepticism.

The Broach- An Underutilized Time Saver

One of the most critical skills that need to be developed is that of broach size selection. In many cases, you only get one or two tries before the pulp is severed into pieces. It is important to select a broach that is smaller than the diameter of the canal but not too small that it merely punctures the pulp and does not engage it. If that happens, go to a larger size and repeat the procedure. If the broach is too large, generally it will not fit very far into the canal without resistance. Forcing the broach at this point risks loss of the barbs or fracture of the instrument. Broaches are notoriously difficult to remove in deeper sections of the canal because of their barbs. If you are unsure, always select a smaller size. You can always move up a size if the pulp does not engage.

 The Controversy of the Lateral Canal

Why don’t you get all those wonderful accessories in your cases?

We all have been there. You sit in on a lecture by a famous Endodontist using a warm gutta percha technique and marvel at all the wonderful accessory canals that are filled. You may even take a course or two (usually given at their expensively equipped ultra-modern laboratories) and work on extracted teeth. In most of those cases your results are spectacular but when you return to your practice you are discouraged by the lack of similar results, especially in vital cases. Why is there such a difference? Why can’t you achieve the same results?The answer is quite simple. Most lecturers use necrotic cases when they show examples of treated cases. Many of these have impressive bifidities, spectacular lateral and accessory canals that are quite impressive when blown up on a screen. They invariably have large lesions of endodontic origin that heal perfectly when such high quality treatment is rendered. We also have to remember that these few cases have been chosen out of the many thousands that may have been treated by the lecturer.

Remember to ask the lecturer a few simple questions:

(1) Lets see some examples of vital cases with such spectacular anatomy.
(2) How long did treatment take?
(3) How long did the case sit with irrigation in the canal?
(4) Was treatment performed in a single or multiple appointments?

The truth is that the attainment of spectacular anatomy depends mostly on the tissue solvent ability of the Sodium hypochlorite. NaOCl works far better on necrotic tissue than on vital tissue. The solvent ability of the irrigant is dependent on basically two factors:

(1) The concentration of the irrigant
(2) The time in contact with tissue (preferably necrotic)

Other factors can increase the solvent ability of the irrigant such as heating the solution or the addition of surface-active agents (Surfactants) such as Tween 80, Sodium Laurel Sulfate or Zephiran.

Vital cases (by nature) tend to have less spectacularly filled anatomy because of the lack of penetration of the irrigation. In years past this was countered by the fact that multiple appointment endodontics used to be the norm. After two or three appointments, any tissue that may have originally been vital was made non-vital by file manipulation or contact with Ca(OH)2. This is also why for many years (aside from the outdated and inaccurate culturing techniques), single appointment or “one shots” were officially discouraged by many leading endodontists and institutions.

Because we worked much more slowly, multiple appointment cases had solution in contact with the canal walls for as much as two or three times the duration of the single appointment case. With the advent of the Ni-Ti rotary system, treatment times have been cut even further (some claim by as much as 75%). Unless there is a conscious effort made by the clinician to have these prepared cases “soak”, the contact time of the NaOCl with the canal will be even less. Unless the canals are cleaned very efficiently with these instruments, the lesser irrigation times may be detrimental to the case. This is especially critical in cases with fins and isthmuses. Rotary instruments, used in a circular motion are not able to clean these areas, meaning that contact time with tissue solvents is even more critical than in hand files cases.

So we can see that the attainment of beautiful filled anatomy (with warm gutta percha) in extracted teeth can often be more a function of the fact that they are extracted (and the necrotic tissue remaining readily responds to NaOCl) rather than that of any special technique.

Cleaning and shaping will continue to be the primary method of ensuring canal cleanliness and ultimately, endodontic success. Irrigation is an essential part of cleaning and shaping. Cleaning facilitates shaping by removing pulp remnants. Shaping facilitates cleaning by allowing penetration of tissue solvents into the deeper portions of the canal, giving rise to the spaces that are ultimately sealed by the warmed gutta percha, sealer or a combination of the two.

Proper protection for non-vital bleach cases – A Case Study

The increase in the demand for cosmetic services has resulted in more bleaching treatments being performed by General Practitioners. In the case of the Endodontically treated tooth, internal bleaching techniques such as the Walking Bleach Technique are often used to improve the cosmetic appearance. Proper use of these caustic bleaching solutions can have real benefit. However, when used improperly and with inadequate protection of the root canal filling material, they can cause catastrophic external resorption.

I came upon an example recently. Discolored #21 (US #8) had a history of traumatic episode and 8 year successful NSRCT. The patient requested Cosmetic improvement. One year previously, the tooth had an internal bleach attempt (Superoxol)  with no protection of the gutta percha filling. Percolation of the bleach into the unprotected dentinal tubules resulted in circumferential external resorption to the level of gutta percha.  Periodontal findings indicated circumferential acute gingival inflammation and generalized loss of attachment to the level of the gutta percha. The prognosis was grim. Compounding the situation was the presence of virgin proximal teeth. I very much wished to avoid having the referring Dentist prepare these perfect proximal virgin teeth for a 3 unit fixed bridge. The patient had insurance benefits to the end only to the endo of the month. When I explained the situation and options, the patient became very upset, mostly because his insurance would NOT cover the cost of the omplant.

This scenario placed me (the Endodontist) in the precarious position of having to explain why the referral’s apparently successful 8-year-old endodontic treatment had suddenly become symptomatic after the tooth was bleached.  The patient  elected to extract and place a single tooth implant. Unfortunately, I lost a good referral because I was forced to truthfully explain to the patient what had happened.

All of this could have easily been avoided by:
(1) Avoiding the use of strong Peroxide solutions INSIDE the access of previously endodontically treated teeth.  Adequate protection of the gutta percha and underlying dentin is required before application of the bleaching agent. Protection is best provided by the use of a well sealing glass ionomer or composite restoration of 3-4mm minimum thickness. This can be removed and replaced after the bleach, if necessary. You must also get FULLY informed consent (includeing ALL possibilities such as tooth loss) before proceeding with internal bleach.

(2) Dr. Ilan Rothstein’s papers have shown  that Using Sodium Perborate alone ( without Superoxol – High concentration Hydrogen Peroxide ) can give equally good results without the resorption risk.  The color change may be slower and it may require more applications over time, but results can be equally as good.

Summary

Clinicians performing internal bleach techniques must be aware of the potential adverse effects of these caustic agents. In the case of traumatized teeth, patients must always be informed of the potential risks of any treatment. Failure to provide adequate protection of the root canal filling material can lead to embarrassing loss of teeth with apparently successful endodontic treatment.