Root Canal Irrigation: Solutions and Techniques

Why no mechanical shaping alone is enough to disinfect a root canal, and how sodium hypochlorite, EDTA and chlorhexidine work together — never mixed — to remove biofilm and smear layer.

Mechanical instrumentation of the root canal alone, however thorough, can never physically contact every surface of the endodontic system: isthmuses, lateral canals and anatomical irregularities inevitably remain out of reach of rotary instruments. This is where chemical irrigation comes in, with a dual goal: reducing bacterial load, often organized into a resistant biofilm that adheres to dentinal walls and colonizes mechanically unreachable spaces, and removing the smear layer, the dentinal mud made of organic and inorganic debris produced by the cutting action of the instruments.

Sodium hypochlorite (NaOCl), typically used at concentrations between 5% and 6%, is considered the irrigant of choice thanks to a unique combination of properties: it effectively dissolves residual organic tissue, including necrotic pulp fragments, and exerts broad-spectrum antibacterial action against bacteria, viruses and even spores. Its main limitation is its inability to remove the inorganic component of the smear layer, which is why the standard protocol involves alternating it with 17% EDTA (ethylenediaminetetraacetic acid), a chelating agent that acts specifically on the mineral component, applied for no more than a few minutes to avoid excessive demineralization of the canal walls.

Chlorhexidine (CHX), used at concentrations between 0.1% and 2%, represents an alternative or complement to hypochlorite thanks to its substantivity — prolonged antibacterial action after application, particularly useful in retreatments against resistant bacteria like Enterococcus faecalis. A point on which the literature is categorical: sodium hypochlorite and chlorhexidine should never be mixed or applied in direct sequence without an intermediate rinse with saline solution, because their chemical reaction produces para-chloroaniline, a compound whose toxicity and potential carcinogenicity are well documented.

Since no single irrigating solution fully solves the cleaning problem on its own — complete removal of the smear layer in the apical third of the canal has never been definitively demonstrated, even with the most aggressive protocols — in recent years activation systems have emerged that increase irrigant effectiveness without changing their chemical formulation: passive ultrasonic irrigation (PUI), in which a non-cutting ultrasonic tip vibrates freely in the already-shaped canal generating acoustic cavitation, remains the gold standard against which more recent technologies, including sonic and negative-pressure systems, are compared.

On Oralzon you'll find endodontic irrigating solutions — sodium hypochlorite, EDTA in gel and liquid form, chlorhexidine — along with ultrasonic and sonic activation systems to enhance their clinical effectiveness.