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In a recent article authored by Mari-Lou Rowley and published on the University of British Columbia Dental School’s website, the research of M Haapasalo on root canal treatment and dental endodontic biofilm, bacteria, and fluid dynamics is highlighted. Dr Haapasalo is a UBC dentistry professor. http://www.dentistry.ubc.ca/features/documents/battling_biofilms_inovations_in_endodontics.pdf

Dr Haapasalo has authored or co-authored over 100 articles in peer reviewed journals on a variety of aspects of root canal treatment including numerous articles related to bacteria associated with persistent periapical infection. His most recent work focuses on irrigating solutions and fluid dynamics that are the most effective in cleaning mechanically debrided canals.

As he states “there have been remarkable changes in the field of endodontics in the past 10 years, resulting in a shift away from mechanically focused treatment to a more biological approach”

In patients with root canal infections it is now accepted that systemic antibiotics are not effective treatment. This is because once the bacteria are introduced into the interior of a tooth, the pulpal blood supply is altered to such an extent that it is impossible for the antibiotic to reach the region of infection. In addition, the growth rate of bacteria in biofilm also reduces the efficacy of antibiotics.

Another aspect of biologic debridement of the root canal is fluid dynamics. As the article on Dr Haapasalo states, knowing he physics of irrigation should help to improve its effectiveness. To this end, Dr Haapasalo is said to be developing the first flexible ultrasound needle tip for root canal irrigation. The introduction into the marketplace of such an instrument should improve irrigation of contorted canals and maximize the spread of the irrigant solution using ultrasound vibration.

Dr Haapsalo and others have contributed to a substantial literature addressing the efficacy of various irrigation solutions, particularly in the last 10 years. Multiple articles are cited on PubMed with one review and several studies referenced in 2011.

Among those recently published include a recent study by P Baca and colleagues from the School of Dentistry, University of Granada, Spain. The authors of this study sought to test a variety of irrigating solutions used separately or in combination for their effectiveness in eradicating Enterococcus feacalis biofiolm (J Endod, 2011, 37(3):353-6)(http://www.ncbi.nim.nih.gov/pubmed).

To perform the study the authors prepared dentin blocks after three weeks of biofilm formation that included Enterococcus feacalis that had formed on the blocks. The applied solutions were then assessed for their ability to inhibit biofilm formation and kill the bacteria. They included: 1. 2.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 0.2% cetrimide (alkyltrimethylammonium bromide) (CTR), 17% ethylendiaminetetraacetic (EDTA), 7% maleic acid (MA), and a variety of regimens that combined 2.5% NaOCl with 17% EDTA or 7% MA and 0.2% CTR or 2% CHX.

What was found was that cetrimide used alone or in combination with 2% chlorhexidine demonstrated the greatest antimicrobial activity. Sodium hypochlorite at 2.5 % showed the lowest residual activity. The irrigant containing thylendiaminetetraacetic was the least effective of the solutions studied.

In a review published in Bratisl Lek Listy, 2011; 112(7):410-415, authors J Kovac and D Kovac discuss the effect of irrigating solutions in endodontic therapy. As they note “highly pathogenic bacteria appear in the root canal only after passed infection and after complete or non-complete enclosure” of an open apex. They note that among the many bacteria playing a role in apical periodontitis, Enterococcus faecalis may be the most resistant to antimicrobial therapy. Thus the killing of this bacterium is the gold standard for assessing the efficacy of irrigating solutions.

The authors also review the history of the various disinfecting agents used in endodontics over the years and note that sodium hypochlorite is the most frequently used irrigant. Of significance, they report that concentrations of this chemical greater than 1% are not likely to provide a greater antibacterial effect than that achieved by the use of 1% but the higher the concentration, the less time needed to achieve a 100% inhibition of growth. They state that “it takes less than 30 seconds if 5.25% solution is used” and site BPFA Gomes, et al (Int Endod J, 2001;34(6):424-428) as the source of this information based on their in vitro studies of concentrations.

Kovac notes that NaOCl irritagion in the presence of ultrasound appears to be even more effective in cleaning the canal and reducing bacteria counts per the results of a study by JFSiqaueira, et al, published in the International Endodontics Journal in 1997 (30(4):227-293).

The author also reviews chlorhexidine and reports that it has bacteriostatic and bactericidal attributes and a wide spectrum of effectiveness against gram-negative and gram-positive microorganisms. Its effect may be the longest lasting and it also appears to inhibit the formation of biofilm. However, as they suggest, it is not used routinely in endodontics.

Also reviewed are hydrogen peroxide and chloramines which also have antimicrobial effects.

This review and the presented research suggest NaOCl has significant antibacterial properties but that other irrigating solutions such as 0.2% cetrimide (alkyltrimethylammonium bromide) used alone or in combination with a 2% chlorhexidine solution also demonstrates significant promise as irrigating solutions for use in root canal treatment.

Submitted by Jeff Burgess DDS MSD