Year : 2012 | Volume
: 15 | Issue : 3 | Page : 202--205
Endodontics - Current and future
Paul V Abbott
School of Dentistry, The University of Western Australia
Paul V Abbott
School of Dentistry, The University of Western Australia
|How to cite this article:|
Abbott PV. Endodontics - Current and future.J Conserv Dent 2012;15:202-205
|How to cite this URL:|
Abbott PV. Endodontics - Current and future. J Conserv Dent [serial online] 2012 [cited 2022 May 27 ];15:202-205
Available from: https://www.jcd.org.in/text.asp?2012/15/3/202/97935
The specialty discipline of Endodontics has progressed through many changes over the last 20 years. Most of these have been related to the technical aspects of root canal treatment with much emphasis on new designs for files and new devices for root canal fillings. Clinicians probably feel that they are technologically more advanced in what they are doing - but is this really the case and are we providing better treatment outcomes for our patients? Or, are we just using different instruments, devices, and perhaps materials that can achieve similar results? How do we know the answer to these questions? It is timely that the profession reviews these aspects and considers whether the current approaches are appropriate and the best for our patients.
Looking back over the last two decades from 1990 - 2010, there are 3 main areas of change in root canal treatment - in a broad sense, 2 are technological, and 1 is biological. The 2 technical areas are the increasing use of nickel-titanium rotary files and the use of magnification. The biological aspect centers around the use - or rather the non-use - of intracanal medicaments and the number of treatment visits. Many practitioners may have adopted all 3 of these changes into their practice, and therefore, it is impossible for researchers, let alone clinicians, to know what effect each individual aspect has on treatment outcome.
Although many papers that have been published about new files to be used in root canal treatment, most of these have been laboratory-based studies, and there is sadly no clinical evidence to show any improvements in treatment outcomes. Studies reviewing treatment outcomes have not shown improvement, and some have even shown a decrease in the rate of favorable outcomes in the 1990's and the 2000's compared to the 1970's and 1980's  when there was much research and evidence regarding the microbiological aspects of pulp and periapical diseases and their treatment. Is this decline in treatment outcome a direct result of the so-called technological advances, or are there other factors? The reality is that treatment outcome will always be multi-factorial, and so there is no simple answer to this question.
The focus of root canal treatment must be on the elimination of bacteria from the root canal system and from the tooth overall since pulp and periapical diseases are caused by bacteria. With this aim in mind, clinicians should question how this can be achieved and does the use of a different file help, does magnification help, and do medicaments help? An understanding of the structure and anatomy of teeth, along with an understanding of microbiology, should help clinicians answer these questions. Let's consider the biological aspect first and then return to the mechanics.
Bacteria are clever! They can enter a tooth via various pathways and then can establish colonies within the tooth structure. The pathway of entry is something that few dentists consider as part of their management of pulp and periapical diseases. Typically, dentists cut access cavities through existing restorations, yet these restorations may well be the reason for the pulpitis or the infected root canal system.  Restorations may look "clinically satisfactory," but how does a clinician determine whether there are marginal gaps under the restoration, which provide an entry pathway for the bacteria? How does a clinician know whether there is caries under the restoration, and how does a clinician know whether there are any cracks under the restoration, or indeed elsewhere in the tooth that provide entry pathways for the bacteria? Unfortunately, dentists seem to have forgotten that the first step in treating any disease is to remove the cause of that disease - in the case of pulp and periapical diseases, this means removing the pathway of entry for the bacteria as well as removing the bacteria themselves.  Old textbooks advocated removing restorations,  but somewhere in the last 50 years or so, this has been forgotten as dentists have focused on the technical aspects of root canal treatment. It is time all dentists reverted back to the basics and addressed this issue - then you will find more cases heal, and you will be able to select which cases are truly suitable for treatment.
Bacteria do not restrict their colonies to the root canal -there are many other parts of the tooth where they can establish colonies.  These include the dentine tubules, lateral canals, accessory canals, transverse anastomoses between canals, the isthmus, fins, "loops", etc.  Studies have demonstrated that bacteria colonize these areas and that instrumentation of the root canals does not remove these bacteria. Indeed, it is impossible to mechanically instrument and irrigate a root canal so that all micro-organisms have been removed from the canal, let alone from all these intricate and inaccessible areas of the root canal system.  Hence, clinicians should always remember that they are treating the "root canal system" and not the "root canal." The root canal is merely a pathway for clinicians to place anti-bacterial agents that can then diffuse through the remainder of the root canal system. In order to achieve this, we need to enlarge some canals and remove pulp tissue or other debris.
Irrigants may help to some extent, but most of their action will be in the root canal proper since they are not typically left in the tooth for very long. There is little research to show how far irrigants can penetrate into the intricate and inaccessible (to files) parts of the root canal system.
If all of the bacteria cannot be removed from the root canal system of an infected tooth, then what can be done to achieve favorable treatment outcomes? The answer is simple and that is to destroy as many of the bacteria that remain after the instrumentation and irrigation procedures have been completed. Live bacteria are the problem rather than dead bacteria - and therefore, the use of medicaments with an adequate inter-appointment time interval not only seems logical and sensible, but essential. The choice of medicament then becomes the next question - to date, the most predictable medicament for anti-bacterial action remains calcium hydroxide.  Ideally, it needs to be in the tooth root for at least 3-4 weeks in order to diffuse throughout the root canal system and achieve as high a pH as possible since the basic environment it creates is not conducive to bacterial survival.  Calcium hydroxide also inactivates the lipopolysaccharide (LPS) endotoxins, so the remaining dead bacteria will not cause more apical periodontitis. 
Other medicaments can also be used, but the choice of which one to use should be dependent on the diagnosis of the presenting condition. In endodontics, the typical conditions being treated are either inflammation (pulpitis, apical periodontitis) or infection - and when there is an infection, there is also inflammation present. If treating an inflammatory condition, an anti-inflammatory agent should be used, whereas when treating an infection, an anti-bacterial agent can be used and this can also be combined with an anti-inflammatory agent. Corticosteroid-antibiotic compounds can, therefore, be used and these have been shown to be the best way to control post-operative pain.  However, the anti-bacterial spectrum of these compounds is not ideal  , and therefore, calcium hydroxide remains the medicament of choice to manage an infection - either as the sole dressing or as a subsequent dressing following the use of a corticosteroid-antibiotic compound as an initial dressing.
Now, back to the mechanics - there is no doubt that the technological advances in root canal treatment are favored by many practitioners, but we should ask for what reason, particularly in the light of them not being universally accepted by all practitioners. Root canal instrumentation techniques are now being "taught" - or is it really just "demonstrated" - by the manufacturers and the dental supply companies, and typically only on plastic models of root canals. The process looks very simple on these models, but experienced dentists will immediately know that a real tooth is a different proposition altogether because of the complex root canal anatomy that is inevitably present.
Many dentists have adopted new files for their root canal instrumentation. The choice of which file will be a personal one, and there may be many different reasons for choosing one system over another. The real question remains as to which system is the best, or even is there any system that is better than the others? However, there are no answers for these questions as it will depend on what criteria are used to evaluate them. Some dentists may choose cost as their criterion, others may choose availability whilst the more scientifically-minded will review the literature. Unfortunately, though, the literature is not very helpful as there are no standard testing methods, many studies have been done on plastic blocks, and almost every study has not addressed the key issue - that is, the effect on treatment outcome! Studies that compare prepared canal shapes are purely mechanical in nature - and the cynics amongst us should be asking whether the bacteria know the difference between a round, oval or irregular-shaped canal, do the bacteria know what a "centered canal preparation" is, or do the bacteria know whether a NiTi or a stainless steel file was used - indeed, do they know what a file is!! A round canal may be easier for practitioners to fill, but the root filling itself has little influence, if any, on the treatment outcome, and therefore, canal shape is not a relevant criterion for "better" root canal treatment. When only the best will do for our patients, the elimination of bacteria from the tooth and the subsequent treatment outcome need to be evaluated rather than a mechanical process.
The use of magnification is the third aspect mentioned above. Magnification can come in various forms - such as loupes and microscopes - and to varying degrees of magnification. Magnification may help clinicians to see some things more easily, but there is no evidence to demonstrate that the use of magnification has improved treatment outcomes.  Some practitioners will say that they can treat cases with a microscope that they could not treat before - that may be a good thing for the patient as long as the tooth was actually suitable for treatment, but it is still not evidence to justify having to use a microscope when very adequate and successful treatment can be, and is regularly done without magnification by many practitioners throughout the world.
Let's now consider what we need to do in the future to find out what really works, what factors really affect treatment outcome, and whether something new will improve the outcomes for our patients. If we use a hypothetical scenario as an example, we can see how difficult such research would be. Imagine that a new instrument has been developed. In order to investigate this instrument's effect on treatment outcome, we must first design a study to compare it with similar instruments that are currently in use. If this new instrument is a file for shaping root canals, then there are at least 6 types of hand files and upwards of about 30 rotary file systems that could be compared. Then, there are all the various techniques used for each file system - for example, a hand stainless steel Hedstrφm file could be used in the following techniques - step-back, step-down, crown-down, flared technique, circumferential filing, etc, etc. All these techniques apply to all hand file designs. Rotary files tend to have one recommended technique for each type of file, but practitioners often vary their techniques from that recommended by the manufacturer. Hence, when all the possible file systems are combined with all the possible techniques of use, there are likely to be thousands of possible permutations. And, do not forget that rotary files should only be used after hand files have been used - so, even more permutations! In order to fully assess the new file system, it should be compared to all of these possible permutations if the claim of "being better" is to be proven. It is simply not good enough to only pick a few files or techniques for comparison!
Once all the possible permutations have been identified, a sample size calculation needs to be done and then the subjects need to be recruited - it is likely that many thousands of cases will be required in order to statistically demonstrate a significant difference of even just 1%, given that most root canal treatment when performed well and when scientifically-based principles are followed, will achieve healing of the periapical tissues - but then consider, what does a 1% improvement in outcome really mean? Further to this, the typical attendance rate of patients for recall appointments is very low with most studies reporting around 40%. Hence, any power calculations of subject numbers needs to take this account as less than 1 in 2 people will return for their treatment outcome to be assessed - this means, the sample size needs to be at least double the many thousands suggested above!
Very specific criteria for inclusion will be needed and must be followed. If, for example, the elimination of bacteria and healing of periapical radiolucencies are the criteria for successful treatment, then only teeth with pulpless, infected root canal systems, and chronic apical periodontitis should be selected in order to standardize the disease being treated. Teeth with irreversible pulpitis, previous root canal fillings, acute apical abscesses, etc., should not be included as they are different disease conditions with different problems and different responses to treatment. A well-designed study should also eliminate all other possible confounding variables such as different operators, different tooth anatomy, different restorations on the teeth, different irrigants, different medicaments, etc. Time is a further factor to be considered since periapical healing takes anything from a few months up to 5 years to be evident on radiographs. The entire study would, therefore, be a very long drawn-out process of recruiting suitable patients, doing the treatment, following the patients for several years and then eventually analyzing the results and reporting them. In the meantime, another file system - or perhaps many more - will have been developed and will ideally need the same research and testing. Hence, such a study, whilst being the ideal and also what is required, is unlikely to ever be started let alone finished - it is simply too hard, too costly, and will not be timely enough.
There is then a further consideration that complicates such a study even more. Periapical radiolucencies are not always apical periodontitis as a result of an infected root canal system.  The periapical tissue responses can vary, and assessment of a persistent radiolucency can be difficult unless a biopsy is performed, but this cannot be recommended for most cases on ethical grounds. A radiolucency that persists following root canal treatment may be due to the root canal system still being infected, an extra-radicular infection, a periapical true cyst or a periapical scar.  The true incidence of these conditions in the population is unknown. Reports of biopsy studies suggest that these conditions are not common, but such studies are only reporting the relative incidence of each condition in the sample examined and not within the population in general. However, despite this shortcoming, these studies still tell us that some periapical radiolucencies will not show healing after root canal treatment because the periapical condition is no longer just a sign of an infected root canal system. It is a sequel to an infected root canal system, but it has progressed to become a self-sustaining entity that will require more treatment - such as re-treatment of the root canal system, periapical surgery or simply regular review and reassessment in the case of a scar. Hence, there is an upper limit to the number of cases that will show radiographic signs of healing following root canal treatment, even with the best treatment or technique. This may well mean that the new file that was being tested will not show any significant difference in treatment outcome if the existing files and techniques are adequate - which they likely are!
So, where do we go from here? I suggest we go backwards - that is, back to the basics! We should concentrate on the biological aspects of the diseases we are treating. This must include the development of a better understanding of the diseases, better diagnostic processes, identification of the cause of the diseases, removing the causes, better case selection, better ways to disinfect the root canal system, and more reliable ways to assess the healing responses following treatment. If our research focuses on these aspects, then our patients will benefit from all of our efforts. The mechanical processes are excellent aids to help achieve good outcomes for patients, but we must not lose sight of the biology of what we are treating and what we are aiming to achieve.
Remember, we are diagnosing and treating a very complex tissue system - that is, the tooth-pulp-peri-radicular complex - and within the tooth, we have a very complicated root canal system….not just a root canal! We are also dealing with very clever micro-organisms that have the incredible ability to colonize parts of the tooth that we cannot see (even with magnification!) or treat mechanically. These micro-organisms can also adapt to changes in the environment and survive within the root canal system despite our best efforts at times. Our aim must be to eliminate them and create an unfavorable environment in which they cannot survive. The mechanics and technology may help, but they are not the sole answers - the biology must never be forgotten!
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