The most frequently used primary obturating substance in root canal therapy is gutta-percha.

- During root canal treatment, the aim is to completely fill and seal the cleaned and shaped root canal system to prevent reinfection.
- Gutta-percha is widely preferred because of its biocompatibility, dimensional stability, and ease of manipulation.
- It can be compacted effectively within the canal to create a fluid-tight seal when used with an appropriate sealer.

- Other materials listed, such as Resilon, are alternatives but have not achieved the same level of consistent clinical success and long-term reliability as gutta-percha.
- Calcium hydroxide is generally used as an intracanal medicament, not as a permanent obturating material.
- Zinc oxide eugenol cements are often used as sealers rather than the core filling material.

Thus, gutta-percha remains the gold standard for root canal obturation due to its versatility and proven effectiveness in clinical endodontics.