Effect of ultrasonic-assisted iRoot SP single-cone technique on root canal filling efficacy: an in vitro study

Abstract

Objective: To evaluate and compare the sealing efficacy of three root canal filling techniques: AH plus with warm vertical compaction (WVC), iRoot SP with the single-cone technique, and ultrasonic-assisted iRoot SP single-cone technique.

Methods: Ninety premolars extracted for orthodontic purposes at Dalian Stomatological Hospital between March 2022 and March 2024 were collected. After standardized root canal preparation, specimens were randomly assigned to three groups: AH plus group (WVC technique + AH plus), iRoot SP group (single-cone + iRoot SP), and US-iRoot SP group (ultrasonic-assisted single-cone + iRoot SP). Apical microleakage was assessed using dye leakage tests. Sealer penetration at 3 mm, 5 mm, and 8 mm from the apex was evaluated using optical microscopy and confocal laser scanning microscopy (CLSM). Stereomicroscopy and scanning electron microscopy (SEM) were used to analyze sealer distribution within the root canal.

Results: The US-iRoot SP group exhibited significantly less apical microleakage than the AH plus and iRoot SP groups (P<0.05). CLSM analysis revealed significantly greater average and maximum sealer penetration depths in the US-iRoot SP group at all evaluated levels (P<0.05). Stereomicroscopy showed the smallest gap between sealer and gutta-percha in the US-iRoot SP group. SEM confirmed improved adaptation of the sealer to the dentin wall and deeper penetration into dentinal tubules.

Conclusion: The ultrasonic-assisted iRoot SP single-cone technique significantly enhances root canal obturation quality compared to both the conventional iRoot SP single-cone technique and the AH plus with WVC technique.

Keywords: AH plus; Ultrasonic activation; bioceramic sealer; iRoot SP; root canal filling; warm vertical compaction.

Figure 1

Root canal preparation. A: Establishing root canal patency; B: Root canal irrigation; C: Root canal drying.

Figure 2

Results of the dye leakage test (20×). A: AH plus group; B: iRoot SP group; C: US-iRoot SP group; D: microleakage length. *P<0.05; ***P<0.001.

Figure 3

Representative SEM image of the microstructure at 3 mm from the root apex. A: AH plus group; B: iRoot SP group; C: US-iRoot SP group. SEM: Scanning electron microscopy. The yellow arrows denote the interface between the sealer and the dentin wall, whereas the red arrows highlight the penetration of the sealer into the dentinal tubules.

Figure 4

Microstructural observation results at 3 mm from the root apex (5×). A: AH plus group; B: iRoot SP group; C: US-iRoot SP group; D: The average penetration depth; E: The maximum penetration depth. *P<0.05; **P<0.01.

Figure 5

Microstructural observation results at 5 mm from the root apex (5×). A: AH plus group; B: iRoot SP group; C: US-iRoot SP group; D: The average penetration depth; E: The maximum penetration depth. ****P<0.0001.

Figure 6

Microstructural observation results at 8 mm from the root apex (5×). A: AH plus group; B: iRoot SP group; C: US-iRoot SP group; D: The average penetration depth; E: The maximum penetration depth. ***P<0.001; ****P<0.0001.

Figure 7

Representative stereomicroscopic images (20×). A: AH plus group; B: iRoot SP group; C: US-iRoot SP group.

Figure 8

CLSM analysis of sealer penetration depth (5×). (A) Representative CLSM images showing sealer penetration (20×). (B, C) Average (B) and maximum (C) penetration depths at 3 mm from the apex. (D, E) Average (D) and maximum (E) penetration depths at 5 mm from the apex. (F, G) Average (F) and maximum (G) penetration depths at 8 mm from the apex. CLSM: Confocal laser scanning microscopy. *P<0.05, **P<0.01, **P<0.001.