# Development of Novel Root Canal Obturation Techniques Using Prototype Obturators in Conjunction With a Resin-Based Hybrid Root SEAL (MetaSEAL) Soft Paste Sealer

## TL;DR

A new root canal filling tool and sealer combination was tested and showed better sealing and fewer voids compared to existing methods.

## Contribution

A prototype obturator combined with a resin-based sealer was developed and shown to improve root canal sealing.

## Key findings

- The prototype obturator reduced air voids and dye leakage in plastic and bovine dentin models.
- Smaller canals (0.25 and 0.35 mm) showed better sealing performance than larger ones (0.45 mm).
- The prototype outperformed NT condenser and JIZAI in sealing ability in bovine dentin models.

## Abstract

Background: Sealer-dependent single-cone root canal filling methods have recently been widely applied clinically. With the advancement of sealers and obturating instruments, the sealer-only root canal filling method may be established and shifted in the future. In this study, we evaluated the sealing effect of the prototype obturator on various sizes of plastic models and bovine dentin root canal models using only a hybrid root seal without using a core material.

Methods: The study assessed the sealing efficacy of a prototype obturator in plastic models of varying sizes and bovine dentin root canal models. Plastic models (apical diameters: 0.25, 0.35, and 0.45 mm; taper: 0.07; length: 18.5 mm) were filled with MetaSEAL Soft Paste (Sun Medical, Shiga, Japan) and obturated using the prototype obturator, NT condenser (US trade name: Microseal condenser, Kerr Corp., Orange, CA), and JIZAI (MANI INC., Utsunomiya, Japan). Each device was inserted to a depth of 17.0 mm and rotated forward at 500 rpm, but only JIZAI used reverse rotation. After obturation, the models were sectioned into apical, middle, and coronal parts. Void formation and apical leakage were analyzed using a stereoscopic microscope and the image analysis software (n = 14 each, SigmaScan Pro 5.0, Hulinks, Tokyo, Japan). Then, bovine dentin models were prepared with nickel-titanium files, and apical leakage was assessed (n = 24). Statistical analysis used the Kruskal-Wallis test with Dunn's post hoc test (α = 0.05), ensuring 80% power.

Results: The prototype obturator consistently exhibited fewer air voids and reduced dye leakage compared to the NT condenser and JIZAI. In 0.25- and 0.35-mm plastic models, it showed significantly fewer voids and less dye penetration (p < 0.01-0.05). Smaller canals (0.25 and 0.35 mm) had superior sealing performance over 0.45 mm (p < 0.01). In bovine dentin, the prototype obturator demonstrated the best sealing ability, with significantly lower dye leakage than the NT condenser (p < 0.01) and JIZAI (p < 0.05).

Conclusions: These results highlight the prototype obturator's superior sealing and void reduction. Canal size influenced sealing efficacy, emphasizing the need for appropriate instrument size selection. Further studies should assess performance in complex root anatomies and human teeth.