In the treatment of endodontic infections, contemporary endodontic techniques focus on suppression of bacterial counts, through the use of mechanical shaping procedures to expose microbial niches combined with irrigation and medication with generic antimicrobial agents. In the following discussion, a review of contemporary disinfectants will be presented, with the recognition that most of these studies were performed in teeth with a mature apex, rather than on immature teeth, which are more relevant here.
The most effective agent available today appears to be sodium hypochlorite at 5.25-6% or 2.5-3% strengths (Siqueira et al., 1998
; Fouad and Barry, 2005
) (). However, several clinical trials have shown that this agent is effective in eliminating cultivable micro-organisms from infected root canals in only about 40-60% of cases (Byström and Sundqvist, 1985
; Shuping et al., 2000
). The small volume of hypochlorite available in the canal, its lack of permeation of anatomical recesses or dentinal tubules, or the buffering effect of dentin may contribute to this limited effectiveness of hypochlorite. When hypochlorite has been considered for regeneration procedures, concerns have been raised that it may interfere with the ability of the regenerated pulp tissue to re-attach to the dentin surface (Ring et al., 2008
), or denature proteins of the dentin matrix which may promote tissue regeneration (Casagrande et al., 2010
). Sodium hypochlorite may be toxic to highly proliferative cells in the apical tissues, which may play an important role in pulp regeneration, such as the stem cells of the apical papilla. Finally, sodium hypochlorite is a very unstable molecule, and does not have a lasting effect in the root canal environment, and so cannot be used to maintain an aseptic environment for regeneration to occur. For these reasons, it is not likely to be the most effective antimicrobial agent for pulp regeneration. Whether hypochlorite can be used initially because of its strong antimicrobial properties, then inactivated with 5% sodium thiosulphate, remains to be determined.
Figure 1. Comparison between common non-specific antimicrobials against 6 common endodontic pathogens: three Gram-positive and three Gram-negative bacteria. Bars show (in millimeters) inhibition zones in agar plates. Note increased efficacy among Gram-negative (more ...)
Chlorhexidine is another disinfectant commonly used in clinical endodontics. Clinical studies have shown that it is effective when used with 1% hypochlorite solution (Zamany et al., 2003
), and in vitro
studies have shown superiority compared with calcium hydroxide usage or controls (Cook et al., 2007
). However, other studies have not corroborated its absolute efficacy as an irrigant or a medicament between appointments (Manzur et al., 2007
; Paquette et al., 2007
; Tervit et al., 2009
). Chlorhexidine also interfered with cell attachment to dentinin vitro
, although not to the same extent as hypochlorite (Ring et al., 2008
Ethylene diamine tetraacetic acid (EDTA) is another agent used in contemporary clinical endodontics. As a chelating agent, EDTA in combination with hypochlorite is effective in removing the smear layer generated during root canal instrumentation procedures, which presumably results in better cleaning, and allows irrigants and medicaments to penetrate more deeply into dentinal tubules (Saif et al., 2008
). EDTA has weak antimicrobial properties by itself compared with hypochlorite or chlorhexidine (Siqueira et al., 1998
) (). However, perhaps more importantly in the context of pulp regeneration, is EDTA’s property of releasing bioactive growth factors that may be sequestered in dentin matrix, and which may aid in the proliferation of the regenerated pulp tissue (Graham et al., 2006
The topical use of antibiotics in endodontic infections is not novel; the reader is referred to Fouad (2002)
for a review on the subject. However, in recent years this practice has not been popular in endodontics treatment because of the availability of less costly alternatives, and the apparent success of treatment. A series of studies identified 3 effective antibiotics against root canal bacteria that did not include beta lactams, to which many patients are allergic or could become allergic (Sato et al., 1993
; Hoshino et al., 1996
). The so-called triple antibiotic mix, which consists of ciprofloxacin, minocycline, and metronidazole, has been used more recently in several reports in which pulp revascularization has been documented following pulp necrosis. The purported efficacy of this mix is related to the synergistic action of antibiotics with various spectra and efficacies to suppress endodontic flora.