Bacterial Biofilm Removal Using Static and Passive Ultrasonic Irrigation

The aim of the present study was to evaluate the efficiency of two irrigating techniques - static and dynamic (passive ultrasonic instrumentation) irrigation in the elimination of bacterial biofilm.

Forty extracted human permanent maxillary central incisors teeth with straight roots and single canals, were randomly allocated to two groups for static irrigation and passive ultrasonic irrigation (PUI). The root canal irrigant used was 2.5 % sodium hypochlorite. The root canals were prepared to tip sizes (20, 40) and tapers (0.04, 0.08). Using system GT instruments (Dentsply Malliefer, Switerzland). The teeth were split longitudinally into two, stained collagen was applied to the canal surfaces and the tooth reassembled for static and PUI. Digital images of the canal surface were taken before and after irrigation with 9, 18, 27 and 37 mL solution. The digital images were analyzed using ImageJ software (National Institute of Health, USA) to quantify residual canal coverage by the stained collagen. The data were analyzed using linear regression models and subjected to statistical analysis.

The mean percentage of canal surface with residual collagen increased with the coronal level of canal, decrease in apical size and taper of canal preparation and decrease in the volume of the irrigant. There was less residual collagen after PUI compared with static irrigation. The canal surface facing the open side port of the needle had less residual collagen after irrigation than the opposing surface.

The stained collagen biomolecular film could not be removed completely either by passive ultrasonic instrumentation or static irrigation. The PUI was found to be more effective in the removal of collagen, especially in the apical part of the root canal.