Letter to the editor regarding study comparing chlorine dioxide oral rinse to chlorhexidine
The editors of Surgical-Restorative Resource recently received a letter from Bill Landers, president of OraTec, regarding the article, “An in vitro study comparing a two-part activated chlorine dioxide oral rinse to chlorhexidine” by Richard D. Downs, DDS, Jeffrey A. Banas, PhD, and Min Zhu, DDS, PhD. Landers objected to some of the wording in the article. The authors responded to his comments here.
Bill Landers: [In the sentence] “The in vitro potential demonstrated for the Oracare rinse supports the hypothesis that it may be particularly efficacious for the reduction of oral malodor and to treat and maintain periodontal health,” note the conditional “may be.” Reading the entire article, it's clear that it might be effective only if note the conditional “may be.” Reading the entire article, and it's clear that the condition under which that might be true was if the peak didn't begin degrading immediately on mixing. The authors further state that their assumption that the product would remain effective 30 seconds after mixing was wrong.
Response from by Richard D. Downs, DDS, Jeffrey A. Banas, PhD, and Min Zhu, DDS, PhD: This is not what we said. What we said was that the reaction to continue to build higher levels of chlorine dioxide was stopped after dilution. Earlier in the paper we said the degradation was about an hour. What we found out was that contrary to what we thought, after dilution reactions slowed so much, that it was for all intents stopped. When the product was diluted after 30 seconds, it still had chlorine dioxide in it that would last more than an hour. It does not degrade immediately after mixing. It actually grows in concentration for at least four minutes and then gradually begins to degrade. We recommend use of the product for patients after mixing 30 to 60 seconds. At 30 seconds, there is a concentration of about 14 ppm, and at 60 seconds there is a concentration of about 30 ppm, so a patient can use this rinse at two to three times the strength tested in this in vitro study.
Landers: Concentration — At the supplied concentration, the product was markedly less effective than CHX. For most species, CHX was effective at dilutions of 1:256, whereas the maximum effective dilution of the product tested was only 1:2 for most species.
Response from the authors: Yes, at the clinical uses recommended, CHX is effective at higher dilutions. We believe any product should be used at the lowest possible concentration of effectiveness. Also, we mentioned that because Oracare gases out after about an hour, an MIC is not a good way to compare it to a rinse that stays active for the whole 18 to 24 hours that CHX can do. No one rinses for 18 hours straight. We also mentioned that the rinse most likely killed all the microbes instead of just inhibiting them as might be the case with a rinse that stays active the whole time. We did not say so, but if chlorine dioxide could be active for the whole 18 to 24 hours of an MIC, it most likely could have even lower concentrations of inhibiting or killing activity, but that is speculation, and we cannot test for that due to the nature of the rinse. The fact is that both rinses killed or inhibited all microbes tested in concentrations of at least one half their strength, and the second part of the study on VSCs showed no activity of CHX against those toxins. The point of this parts-per-million concentration comparison is to speak to the issue of toxicity. All rinses have some hypersensitivity reactions and CHX has many; that was mentioned as a concern at the start of the article. Rinses made at concentrations as low as possible and yet effective are a goal that should be striven for. Oracare can get to as high a concentration of about 90 ppm. The company recommends using at that concentration when the rinse can then be diluted 10 to 1 and placed in an irrigation system for subgingival use.
Landers: The authors attempted to obscure that shortcoming by saying that the two products approached equal efficacy at equal parts per million. But, they're not sold that way. Clearly, if CHX was effective at 1:256, it would also be effective at 1:2, but the point is that CHX is effective at far greater dilutions (as occurs in vivo given saliva and crevicular fluids).
Response from the authors: I can see where some may interpret it as an attempt to sidestep the straight-up comparison. But importantly, we did not hide the data. We presented the actual MICs, not just the ppm comparison. So the reader is fully informed.
Landers: In summary, the authors only said that IF Oracare could be supplied at a higher concentration and IF it didn't degrade so rapidly, it MIGHT be an effective agent. But that's not the case.
Response from the authors: As was mentioned in this response, Oracare can be mixed at higher concentrations. It does not degrade that rapidly and is effective as this study does clearly demonstrate.