Biofilm Removal by 6% Sodium Hypochlorite Activated by Different Irrigation Techniques

A comparison of irrigation methods reveals how activation technique impacts biofilm removal efficiency.

Objective

To compare the effectiveness of four different irrigation techniques for removing biofilm from a bovine root canal model using 6% sodium hypochlorite (NaOCl).

Materials and Methods

• Samples: Fifty dentine specimens (2 × 2 mm) infected with biofilm, placed in prepared cavities within bovine root canals.

• Irrigation protocol:

  • Each canal irrigated twice with 2 mL of 6% NaOCl for 2 minutes (total 4 minutes).

  • Four irrigation techniques applied for 60 seconds (3 × 20 s intervals):

    • Conventional needle irrigation

    • Endoactivator (sonic agitation)

    • Passive ultrasonic irrigation (PUI)

    • Laser-activated irrigation (photon-induced photoacoustic streaming, PIPS)

  • Controls: distilled water and conventional needle irrigation.

• Analysis:

  • Dentine samples analyzed by scanning electron microscopy (SEM).

  • Fifteen operative fields per block; images assessed by two calibrated evaluators using a four-degree scale.

  • Nonparametric statistical tests compared groups.

Key Results

• Laser-activated irrigation (PIPS): Achieved the most effective biofilm removal.

• Passive ultrasonic irrigation (PUI): Significantly more effective than Endoactivator and needle irrigation.

• Endoactivator vs. Needle irrigation: No significant difference.

• Controls: Showed the least biofilm removal.

Conclusions

Laser activation of 6% sodium hypochlorite (PIPS) significantly enhances biofilm removal from dentine, outperforming all other tested methods. Passive ultrasonic irrigation is the next most effective technique, while sonic and conventional needle irrigation are less effective and not significantly different from each other.

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