Smear layer removal and sealer penetration with different tapers after using photon-initiated photoacoustic streaming technique.

Objective: To evaluate the effect of the photon-initiated photoacoustic streaming (PIPS) technique on irrigation performance with different instrumentation tapers in root canals regarding smear layer removal and subsequent sealer penetration.

Materials And Methods: One hundred twenty human mandibular molars were divided into three equal groups according to the apical preparation taper (25/4%, 25/6%, and 25/8%). Each group was divided into two equal subgroups, one received passive irrigation (PI) while the other received PIPS activation of 2.5% sodium hypochlorite and 17% EDTA. Half the samples were evaluated using electron microscope images to assess smear layer removal. The other half was obturated using gutta-percha and rhodamine B-labeled AH Plus sealer before being sectioned horizontally at different root levels (coronal, middle, and apical) to evaluate the percentage of sealer penetration using CLSM. Mann-Whitney U and Friedman tests were used to analyze smear layer scores, while sealer penetration data were analyzed using the three-way analysis of variance (ANOVA) and Tukey's post hoc test.

Results: Statistical analysis showed significantly better smear layer removal and better sealer penetration after PIPS activation when corresponding root thirds were compared (P<0.001). Only exception was sealer penetration in the apical third with root canal preparation of 25/4% where the difference between the irrigation methods was statistically insignificant (P>0.05).

Conclusions: The use of PIPS activation in the final irrigation protocol enhanced smear layer removal and sealer penetration into dentinal tubules if the taper of the prepared canal was at least 6%.

Clinical Relevance: Increasing apical preparation taper significantly enhances PIPS performance in terms of irrigation activation thus enhancing smear layer removal and subsequent sealer penetration in dentinal tubules.