Heating Sodium Hypochlorite: "Peer-Reviewed Evidence Supporting the Heating of NaOCl"

I am frequently asked questions regarding sodium hypochlorite, disinfection, how to use active irrigation, which method, but today I’m going to focus on the question relating to what should be the ideal optimal temperature of sodium hypochlorite.  Do I believe in heating sodium hypochlorite to a higher temperature and what would be the rationale for that?  Is there any evidence to support this and what is the outcome if we did heat up our sodium hypochlorite?

Well, let’s take a look at this.  I was one of the first educators to advocate heating 6% concentrations of sodium hypochlorite to 60°C.  My idea arose from a well-known fact that virtually all laboratory reactions are accelerated in the presence of heat.  For your information, 60°C is about equivalent to the temperature of a cup of hot coffee and when warmed the irrigant is confined to the endodontic space which is surrounded by a non-conducting dentin so it is perfectly safe. 

I am oftentimes asked, well is this like a mainstream protocol that most clinicians in the United States use?  A lot of times international dentists want to know that, and I would have to characterize heating sodium hypochlorite as absolutely not mainstream.  In fact, even though I’ve taught it for 30 years, I would say there are some that do it, but most don’t. 

So, is there any evidence, has there been any research generated, to even support heating sodium hypochlorite up to 60°C?  In another blog I’ll talk about ways to heat it up and the actual clinical technical support on how that might happen.  Today, we’re just talking about should we heat it, should we not heat it. 

Well, I’ll give some papers because some of you are going to want to go back, obviously, to PubMed, punch in the key words, you know, such as sodium hypochlorite, heated, disinfection and things like that and authors names in journals and you can go find the very evidence that I’m going to now talk about that supports heating sodium hypochlorite up. 

My good friend, Elio Berutti, and Marini in 1996, in the Journal of Endodontics, I think it was 22(9), Volume 22, Number 9… They talked about the capabilities of sodium hypochlorite to de-bride pulp tissue at different temperatures.  This is a very interesting article and is really one of the groundwork articles in ’96 to support this.  Obviously it was reported much, much earlier.  Cunningham, you know, talked about the effects of temperature on collagen dissolving abilities of sodium hypochlorite.  He reported in the Triple O (currently Oral Surg Oral Med Oral Pathol Oral Radiol Endod), 49(2), 1980, that sodium hypochlorite was a potent adjunct to disinfection because it could sharply reduce digestion times.

You know, what we’re trying to do here is digest collagen.  It’s that sticky, collagenous mass that can be in a fin, a lateral canal, an apical bifidity, anastomoses… and it’s very difficult to get this tissue out in a reasonable amount of clinical time. 

Well, Gambarini, my friend from Rome… He talked about its stability because some people say, “OK, great, you can heat it up, but my god, if you heat it up, it might break down into its component salts, sodium and chloride.”  Well, this article by Gambarini talks about the stability of heated sodium hypochlorite for an endodontic irrigant and it was reported, in 1998, in the Journal of Endodontics, 24(6); always meaning Volume 24, Number 6… You can find out that if you mix your solutions fresh daily, you can heat sodium hypochlorite up without any degradation of the fluid or the reagent whatsoever.

Well, there’s more articles about stability.  Piskin, again in the Journal of Endodontics, 21(5), 1995, talked about the stability of various concentrations of sodium hypochlorite.  And, of course Brown, et al, and Carl Newton… They talk about, you know, how safe is it to use different temperature irrigations during endodontic canal preparation… 1995, Journal of Endodontics, 21(12).  And finally, I wrote about it myself in an international article.  I can’t even read it myself because it appeared in German, an article that Quintessence published in 1994 and it was again, Number 3.  What I talked about is just the efficacy from the clinical standpoint and how to use it, how to deliver it, and what we can expect.

So, certainly if you can Google and go to PubMed, you can definitely expand your knowledge of heating sodium hypochlorite, how you might do that, is there a logic for it and what is the rationale?  Again, in closing, the rationale for heating sodium hypochlorite is simply to more effectively digest pulpal tissue from the deep, lateral anatomy.  If we can do that, we’re going to have cleaner root canals, and if we have cleaner root canal systems, the opportunity to fill in three dimensions is definitely attainable.