There is already a discussion on NaOCl and toxic effects, but the title is misleading/the original question was on another issue, but the discussion took a different direction.
https://www.researchgate.net/post/14_years_old_with_RR_upper_left_lateral_non-vital_oozing_pus_from_RC_Extraction_or_endo_ttt_with_apicectomy_retro-grade_filling
Sodium hypochlorite is degradating very quickly in body's temperature. Even if it is left in the root canal between the appointments, it reacts and turn into saline and short -lived radicals in few minutes. Toxic effect of NaOCl is only when it is extruded from the root canal. Another irrigant that can potetially interact with others is chlorhexidine. CHX with NaOCl reacts making very toxic and carcenogenous precypitate. CHX when overheated (for example by ultrasonics) turn into whitish precypitate that in porbably toxic, too. If u use CHX, it should be used at the end of irrigating protocol, after the reduction of NaOCl with short flush of citric acid and long flush of distilled water. EDTA is less strong inhibitor of NaOCl then citric acid. I'm in the big research project to establish "the perfect" irrigating protocol. Apart from its inhibitory effects, CHX can improve interaction between dentine and sealer.
I have nothing to add to Wojciech Wilkoński's comment. An important point is that CHX can't replace NaOCl because it doesn't have solving ability on organic tissues. So as you said, CHX can be used for a final flush before filling.
The "perfect"irrigating protocol depends on many parameters and we have to take care about the conclusions of in vitro study.
For exemple, the classic protocol NaOCL, EDTA for smear layer, removal then final flush with NaOCL has been critized by the Haapasalo's team. Indeed, they have pointed out that the use of NaOCl after EDTA generated dentin walls erosions which could be involved in future cracks. Very interesting observation...but what is the incidence in term of clinical relevance ??? We have used this protocol for a long while with a good reliability and we didn't observe a lot of problems.
Here are very interesting articles:
Tay et al. have published very interesting papers. Fo example file, that i added. In normal SEM u can't see real dentine's surface, because of dehydratation in alcohol. Tay modified preperation of specimens by adding silanization. He obtainen different images. It looks like we all were wrong: EDTA at the end made demineralization, but we didn't see it due to collapsed collagen. NaOCl after chelator simply just solve collagen and we seen "the real" dentine. Exposed collagen can't be hybridized by endodontic sealers, so the good idea is to solve it. It is good idea to rinse root canals with NaOCl after smear layer removal - better penetration to open dentine tubules.
Tay is one of my favorite author. Most of his papers is very usefull for researchers
Sorry for my mistakes, it should be: "obtained" not "obtainen", "see" not "seen" and "opened" not "open".
Tay and DeDeus are my personal favorites :-))) I am just finnishing the optical-microscope-based papers about smear layer removal with different approaches. When it will be ready, i will share (at least abstracts).
Mechanism of action of NaOCl as described by Estrella seems to somehow contradict
chemistry. Still searching for the full understanding of the above.
....and sorry if I don t share the enthusiasm in regards of the paper by Hülsmann and Hahn!
The use of laser in endodontics seems not to be superior than the agitation techniques (ultrasonic methods for instance) regarding irrigation efficiency. However, in vitro studies concerning photodynamic therapy are interesting even if it leads to a lot of technical questions in order to apply it in clinical activity.
And what do you mean about Saline ? Because you can't realize a root canal therapy without NaOCL.
Good point in regards of pad....we still are at the beginning....much research to come...
If this study is reliable and accurate why the authors didn't submit their work in the JOE or the IEJ ?
Yes, these questions are of interest, but there are a lot of reasons why they did not publish there. And the publication in these highly recognized journals does not guarantee a study which fulfills even most basic requirements of a scientific work. Compared to those this study is ways better...
I think this study is quite well designed, but it is suffering from the short observation period; this could be the explanation why there was no publication in one of the other journals.
But it opens an interesting option. And we have to consider that they are simply right. From a theoretical standpoint there seems to be no reason why the results should be different. Using Ca-hydroxide, they have a disinfection; and it is really the question whether a short exposure against some more aggressive solutions would add any additional effect: In these narrow canals, you can't even guarantee that your solutions reach the most apical parts of the canal. Or the apical ramifications. Or the dentinal tubules. I always had problems with the idea that these problematic zones can be reached sufficiently: These little canals are not only very complex, they are also not empty waiting for our irrigants, they are already completely "filled up". Just try to replace the water in a cup with a different solution, and then imagine that you should do that in a tube which is some hundred times longer than wide...
Recently, a friend of mine, Prof. Ebeleseder, from University of Graz, trauma and endo freak, made a nice comparison. He used the Stephansdom in Vienna (height: 137m) as a tooth analogon - the bacteria would then have the size of a raisin. Very nice, gives us a much better idea of the problems we have in endodontology.
I have quite a good feeling with this publication. The observation time must be increased. But I think it is justified to redo it elsewhere. Especially if I look on the toxic alternatives...
The penetration depth of root canal irrigant is a big and interesting issue in endodontics. This is the reason why many authors try to find several ways to improve the fluid circulation within the root canal system especially in the noninstrumented areas. Due to its proteolytic and antiseptic action, NaOCl must be systematically required from my point of view. There are no other irrigants which have the solving ability on pulp tissues and it is a crucial point because the entire endodontic anatomy is plenty of pulp ! There is a wide consensus about this allegation. However, there are many possibilities in order to enhance root canal irrigation depending on many technical parameters:
- root canal preparation (taper and diameter),
- penetration depth of the needle tip and type of needle (open-end or side opening...),
- irrigation techniques (seringe, activation techniques such as sonic or ultrasonic agitation, master cone agitation...)
- volume and renewal of a fresh NaOCl solution (between 1 and 5.25 %)
- modifications of irrigants properties: wettability, surface tension, viscosity...
One of the main problem is probably the gaz bubbles formation in the apical part (vapor lock effect) which stops the irrigant penetration around 1.5 mm beyond the needle tip. Therefore it is crucial to use a patency file and an agitation technique in order to allow a deep penetration of the irrigant in the last 2mm of the root. The way NaOCl spreads onto the canal and reaches the non-instrumented areas is of primary importance in endodontics. In term of fluid dynamics, irrigants circulation is better when root canals have been prepared...To summarize we have to use and combine these several means in order to improve irrigant efficiency. I'm sorry not to agree with the use of saline solution even if this article opens a lot of astonishing questions.
I only add to Frederic's answer: Passive ultrasonic agitation is the most effective. Gas bubbles can be evacuated by ultrasonics or Machtou's master cone agitation. After the removal of the smear layer, NaOCl agitated with ultrasonics can reach the very end of the dentinal tubules. Even the sealer can penetrate to 0,5-1mm into tubules. I totally agree with Frederic about NaOCl. It kills bacteria in biofilm (5,25%) and it can solve it. To put it in another way: NaOCl i the killer that gets rid of the dead bodies ;-) Very important role of NaOCl is solving ability of organic compounds. Apart from pulp tissue remnants, exposed collagen (due to smear layer removal with chealtors) and also predentin (of unprepared areas) should be also solved.
Well, I am so lucky, since at the moment I don't do (conventional) endodontic therapy in patients, that I can afford to have no conviction. I'm also not an endo-specialist.
If I do endo - in avulsed teeth - I do it before the microorganisms can enter the canal - prevention is always the best choice.
In the end everything must be used clinically what theory and experiments - at the lab or in animals - told us - or we thought told us.
Thus, I just suggested to redo that study from Nepal. I consider that justified, despite (or becausew of?) the missing effects on the tissues. But if their results are true, they set quite a good mark...
Is there ANY other study which compared saline and other irrigants?
Yes you have Orstavik and Bystrom's studies but i have to retrieve the references.
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