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Abstract

Background/purpose:

Residual apical biofilm often persists despite sodium hypochlorite (NaOCl) irrigation with sonic or ultrasonic activation. Submicron diamond particles (SMD) have shown promise as a particle-assisted adjunct for root canal cleaning, but their effects on mature intracanal biofilm remain unclear. This study evaluated whether 500-nm SMD particles (10 mg/mL) improve the antibacterial and antibiofilm efficacy of saline or NaOCl irrigation against mature Enterococcus faecalis (E. faecalis) biofilms.

Materials and methods:

One hundred single-rooted human premolars infected with E. faecalis for 21 days were randomly allocated to ten irrigation protocols (n = 10). Antibacterial efficacy was assessed by colony-forming units (CFU), biofilm-forming capacity by crystal violet assay (OD590), and residual biofilm by scanning electron microscopy in the coronal, middle, and apical thirds. Data were analyzed using Kruskal–Wallis, pairwise Mann–Whitney U tests, and Bonferroni correction.

Results:

All outcomes differed significantly among protocols (P < 0.001). NaOCl protocols significantly reduced CFU counts versus the no-irrigation and saline controls (P ≤ 0.008), but SMD produced no statistically significant additional CFU reduction. In contrast, NaOCl + SMD protocols showed lower biofilm-forming capacity than NaOCl activation without SMD (P = 0.008) and the lowest apical residual biofilm scores (median 1.0; most specimens < 5% coverage), significantly lower than all other protocols (P ≤ 0.002).

Conclusion:

SMD improved apical biofilm removal, whereas no statistically significant additional reduction in CFU counts was demonstrated, indicating a region-specific mechanical adjunctive role rather than a general improvement.

Publication Date

2026

Received Date

July 9 2026

Accepted Date

July 27 2026

Final Revision Date

July 26 2026

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