Photon-initiated photoacoustic streaming removes bacteria in root canals with small diameter, taper

The study is published in the BMC Oral Health Journal.

Cheng Wen and colleagues from the Department of Endodontics, Affiliated Stomatology Hospital of Guangzhou Medical University, Guangzhou Key Laboratory of Basic and Applied Research of Oral Regenerative Medical, Guangdong, China carried out the present study to compare the use of photon-initiated photoacoustic streaming (PIPS) and conventional needle irrigation (CNI) in conjunction with different concentrations of sodium hypochlorite (NaOCl) to remove Enterococcus faecalis (E. faecalis) suspended bacteria and biofilms from root canal systems with different diameters or tapers.

Artificial root canal samples (n = 480) were randomly divided into three groups (n = 160/group). The canals were prepared to fit file sizes #10/.02, #25/.02, or #25/.06. The size #10/.02 group was incubated for seven days.

The size #25/.02 or #25/.06 group was incubated for 2 days. A stable biological model of E. faecalis infection was established. The root canals were washed with distilled water or with 1%, 2%, or 5.25% NaOCl combined with CNI or PIPS.

Bacterial suspensions and biofilms were assessed using an ATP assay kit and fluorescence microscopy. Image-Pro Plus was used to analyse the average fluorescence intensity to determine the most suitable root canal irrigation solution.

The following findings were highlighted-

a. In the CNI and PIPS groups, the ATP value of the 5.25% NaOCl subgroup was the lowest, followed by that of the 2% and 1% NaOCl subgroups.

b. The ATP value of the distilled water subgroup was the highest (P < 0.05).

c. When the root canal taper was 0.02, the ATP value of the #10/.02 + PIPS group was significantly lower than that of the #25/.02 + CNI group (P < 0.05).

d. The average fluorescence intensity of the #10/.02 + PIPS group was lower than that of the #25/.02 + CNI group (P < 0.05).

e. When the apical diameter was #25, the ATP value of the 0.02 taper in the PIPS group was lower than that of the 0.06 taper in the CNI group (P < 0.05), and the average fluorescence intensity of the 0.02 taper + PIPS group was lower than that of the 0.06 taper + CNI group (P < 0.05).

f. PIPS combined with 2% and 5.25% NaOCl effectively improved the long-term antibacterial effect after irrigation and re-culture for 6 h.

Hence, the authors concluded that "compared with CNI, PIPS has greater ability to remove bacteria in root canals with a small preparation diameter and a small taper. PIPS with 2% and 5.25% NaOCl exhibited superior antibacterial and bacteriostatic effects."