Sir, sodium hypochlorite (NaClO) is an effective intracanal irrigant used widely in restorative and paediatric dentistry which although generally considered safe, has cytotoxic effects that can result in soft tissue necrosis if extruded beyond the root canal system.1 Whilst the consequence of extrusion is well recognised, there is limited literature surrounding hypochlorite accidents in teeth with open apices, particularly regarding the effect of concentration on the incidence of injury.

The majority of hypochlorite accidents can be attributed to incorrect working length, the presence of perforations and excessive force during irrigation.2 Although immature root development has been associated with an increased risk of extrusion, endodontic treatment can be carried out safely with careful pre-operative assessment, determination of working length and appropriate use of side-vented irrigation needles.3,4 Taking these measures prior to commencing treatment is therefore essential and clinicians should be competent in the appropriate management of hypochlorite injury.

Anecdotally, clinicians typically err on the side of caution for paediatric patients by using low concentrations of hypochlorite, with the aim to reduce the risk of injury through extrusion or perforation. However, the evidence base to support this is limited and there is lack of a protocol for endodontic treatment in teeth with immature apices. Whilst high strengths may increase tissue irritation, concentrations of 5.25% have been shown to demonstrate greater antibacterial activity in comparison to 2.5%, and when diluted, result in a significantly impaired ability to dissolve necrotic tissue.5 Furthermore, the effectiveness time of hypochlorite is significantly reduced when using 5.25% compared to 2.5%, allowing greater antimicrobial action within a more efficient timeframe.5

The nature of patients managed within paediatric dentistry may necessitate a limited treatment duration. The use of higher concentrations of NaClO may permit superior antimicrobial activity during the restricted timeframe that often accompanies endodontic treatment for paediatric patients. Whilst the optimal concentration is open for discussion, the specialty should consider the viability of safely using 5.25% NaClO for endodontic treatment on teeth with both complete and incomplete root development. When used alongside a protocol to reduce risk of extrusion and guidelines for the management of potential injury, could higher concentrations be adopted to improve treatment outcomes for root canal treatment in children?