The influence of cavity configuration and irrigation activation on root canal smear removal-an in vitro study

Effective root canal therapy (RCT) depends on proper disinfection rather than complete sterilization of the root canal system. The smear layer created during instrumentation can inhibit disinfection, and its removal is crucial for successful treatment. Recently, various irrigant activation methods, including shock wave enhanced emission photoacoustic streaming (SWEEPS), passive ultrasonic irrigation (PUI), sonic activation (SA), and syringe irrigation (SI), have been developed to enhance cleaning efficacy. Sterilization of the root canal system is crucial for successful root canal therapy. Lasers have emerged as a popular choice for eliminating microorganisms from the root canal.

This in vitro study aimed to compare the effectiveness of different irrigant activation techniques-SWEEPS, PUI, SA, and SI-in removing the smear layer from root canals prepared with either a conventional access cavity (ConvAC) or an ultraincisal access cavity (UincAC) design. This study aimed to clarify and compare the effectiveness of various irrigant activation techniques in removing the smear layer from canals with conservative and conventional cavity designs.

Eighty extracted human maxillary incisors were prepared using a VDW 35/0.04 rotary system and randomly divided into eight groups (n = 10 per group), based on cavity configuration and activation technique: G1: SWEEPS-ConvAC, G2: SWEEPS-UincAC, G3: PUI-ConvAC, G4: PUI-UincAC, G5: SA-ConvAC, G6: SA-UincAC, G7: SI-ConvAC, G8: SI-UincAC. All samples were irrigated with 2.5% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA), followed by distilled water, and examined using scanning electron microscopy (SEM). Data were analyzed with Kruskal-Wallis and Bonferroni-adjusted Mann-Whitney U tests (α = 0.05).

No statistically significant difference was found in smear layer scores in the coronal and middle thirds among the groups. However, significant differences were observed in the apical third (p < 0.001). The SWEEPS-ConvAC group showed the least smear layer, while the SI-UincAC group exhibited the most. The effectiveness ranking was: SWEEPS, followed by PUI, SA, and SI.

While access cavity design alone did not significantly affect smear layer removal, SWEEPS was the most effective activation method. The combination of SWEEPS with conventional cavity design yielded the most effective smear layer removal in the apical third. These results emphasize the importance of selecting not only an effective irrigant but also an appropriate cavity design to optimize apical disinfection in clinical endodontics.