Challenges
Curved root canals present several significant difficulties, including challenges in instrumentation, insufficient cleaning, and complications during the filling process (16). According to Călin et al.’s systematic review, continuous rotary systems appear to be preferable to reciprocating systems in managing the extracted teeth root canal instrumentation with moderate and severe curvatures (17). Ultrasonic activation of irrigation has been proven to enhance the effectiveness of disinfection in the apical third, which is usually unreachable due to canal curvature (16, 17). The single-cone, warm vertical compaction, and lateral condensation techniques, which are common obturation methods, have significantly different efficacy and suitability for curved root canals (18). The single-cone method, although simple and time-efficient, often fails to achieve the desired level of canal adaptation and has a high tendency to form voids, especially in irregularly shaped and curved canals (19, 20). Lateral condensation enhances obturation quality through mechanical compaction but has less ability to fill complex anatomical spaces well due to its reliance on lateral pressure (21). on the other hand, the warm vertical compaction technique demonstrates superior adaptability and sealing ability in curved canals by using thermoplasticized gutta-percha, which flows to conform to the canal’s intricate morphology, including isthmuses and lateral canals. This not only significantly reduces microleakage and voids but also enhances long-term results (21). While much of the previous studies utilized single-cone and lateral condensation techniques, the authors propose warm vertical compaction as a more favorable option in complicated cases and consider the application of other methods limited to simpler cases (22, 23).
S-shaped root canals present even greater difficulties due to their double curvatures in opposite directions, which makes it harder to navigate the instruments (9, 24). In this case report, we demonstrated precise instrumentation to treat three double-curved root canals with severe curve angles based on the Schneider approach (25). Previous cases have not highlighted severe S-shaped teeth as seen in our study.