The use of 0.5% or 3% NaOCl for irrigation during root canal treatment results in similar clinical outcome: A 6-year follow-up of a quasi-randomized clinical trial.

Aim: To evaluate the 6-year outcome of root canal treatment irrigated with 0.5% or 3% sodium hypochlorite (NaOCl).

Methodology: The baseline trial was designed as a quasi-randomized clinical trial. Patients referred for root canal treatment to an endodontic specialist clinic were recruited to the study (n = 298). The concentration of NaOCl was allocated quasi-randomized to 271 subjects (0.5% [n = 139], 3% [n = 132]). Bacterial sampling was performed immediately before root canal filling. Samples were cultured and evaluated as growth or no growth. Patients were invited to a clinical and radiological follow-up >5 years postoperatively. The clinical outcome measurements were tooth survival, cumulative incidence of endodontic retreatments, patients' assessment of pain, clinical findings and radiological signs of apical periodontitis (AP).

Results: Tooth survival was 85.6% in the 0.5% NaOCl group and 81.1% in the 3% NaOCl group (p = .45). There was no record of retreatment in 94.4% in the 0.5% NaOCl group and in 92.2% in the 3% NaOCl group (p = .76). The percentage of asymptomatic cases were 87.8% in the 0.5% group and 85.3% in the 3% NaOCl group (p = .81). Absence of clinical signs of AP was seen in 86.6% in the 0.5% NaOCl group and in 83.6% in the 3% NaOCl group (p = .80). Absence of radiological signs of AP was seen in 74.0% in the 0.5% NaOCl group and 64.1% in the 3% NaOCl group (p = .20). Subjects with positive culture before root filling reported subjective pain with a significantly higher frequency as compared to negative-culture subjects (p = .014).

Conclusions: The use of 0.5% or 3% NaOCl for irrigation during root canal treatment resulted in similar clinical outcomes 5-7 years postoperatively. Persisting bacteria immediately before root filling may predict future episodes of subjective pain.