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Case Profile: Single File, Double Curve by Dr. Gianluca Gambarini

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Categories: Endodontics;
Case Profile: Single File, Double Curve 

by Dr. Gianluca Gambarini

Editor's Note: This article was originally submitted using the European product name, EdgeOne R. In the United States, the same product is marketed as EdgeOne Blaze. References to EdgeOne R in this article refer to EdgeOne Blaze for the U.S. market.
This case illustrates the value of newer reciprocating systems in addressing anatomical variations that often compromise primary endodontic success.

A 62-year-old female patient was referred to my practice because of persistent discomfort during mastication localized to the maxillary left first molar. Clinical examination revealed mild percussion sensitivity. The referring clinician had provided a periapical radiograph showing prior endodontic therapy involving three canals (Fig. 1). However, the two-dimensional imaging did not clarify the etiology of the persistent symptoms.
Single File, Double Curve
Fig. 1

Because of the diagnostic limitations of conventional radiographs, a CBCT scan was obtained, which confirmed a previously untreated second mesiobuccal (MB2) canal and a periapical lesion associated with the MB root (Fig. 2). Based on these findings, non-surgical orthograde retreatment was deemed the appropriate course of action.

It is well established in the endodontic literature that missed MB2 canals are a leading cause of treatment failure. Their detection is challenging, and even when located, their intricate morphology—including narrow diameters and abrupt curvatures—makes them susceptible to procedural complications such as ledging, zipping, or instrument separation. Traditional rotary NiTi systems are particularly strained under such anatomical demands because of the constant rotational load they impose.

Over the years, I have adopted reciprocating single-file techniques in my practice, which offer enhanced safety profiles in these scenarios. The reciprocating motion reduces continuous torsional stress, improves resistance to cyclic fatigue, and preserves canal anatomy. Instruments like Reciproc Blue have proven effective, especially in complex and retreatment cases.

In this case, Reciproc Blue size 40 was used in the palatal canal and size 25 in the MB, MB2, and DB canals. However, despite my extensive experience with this system, I was unable to negotiate the working length in the MB2 canal. The canal’s double curvature and severely narrowed lumen impeded progress. These challenges often arise when the initial file tip size and taper are too large, limiting penetration in severely constricted spaces. At this point, many clinicians might opt to abandon the single-file philosophy in favor of glide path enlargement.

Instead, I opted to evaluate a newer single-file reciprocating instrument, the EdgeOne-R Utopia R20, specifically designed for tight, calcified, or highly curved canals (Fig. 3). The R20 shares a similar S-shaped cross-section with Reciproc Blue, ensuring cutting efficacy and fatigue resistance, but it benefits from a proprietary heat treatment that enhances both torsional strength and flexibility, essential attributes for navigating high-curvature, narrow canals.
Single File, Double Curve
Fig. 2: CBCT confirming untreated MB2 canal and periapical lesion
Single File, Double Curve
Fig. 3: EdgeOne-R Utopia R20 instrument

The instrument’s reduced tip size and overall dimensions allowed smoother apical progression, and its pilot tip facilitated safe negotiation without canal transportation or iatrogenic errors. Using the same motor settings as with Reciproc Blue, the R20 instrument easily reached working length, maintained canal integrity, and exhibited no signs of deformation post-operatively.

The case was completed using standard irrigation protocols, followed by single cone obturation with EdgeOne R gutta percha points (Fig. 4) and EdgeBioCeramic Sealer (Fig. 5), ensuring a biocompatible and hermetic seal. Post-operative radiographs confirmed a well-centered fill and adequate canal debridement (Fig. 6). The patient reported no significant post-operative discomfort and was asymptomatic within days.
Single File, Double Curve
Fig. 4: EdgeOne R Utopia Gutta Percha Points
Single File, Double Curve
Fig. 5: EdgeBioCeramic Sealer
Single File, Double Curve
Fig. 6: Post-operative radiographs confirming well-centered fill and adequate canal debridement

Takeaways
  1. EdgeOne-R Utopia R20 successfully negotiated a narrow, double-curved MB2 canal without the need for glide path preparation or multi-instrument techniques.
  2. R20’s proprietary heat treatment improves torsional resistance and flexibility, allowing safer navigation in highly curved or calcified canals.
  3. R20 maintained working length and canal integrity, minimizing risk of ledging, transportation, or instrument separation.
  4. The case was completed using a true single-file technique, reducing chair time and preserving conservative canal shaping.
This content is sponsored by EdgeEndo.
For more information, visit edgeendo.com.
To request a product sample for evaluation, visit edgeendo.com/product-evaluation.
Author Bio
Dr. Gianluca Gambarini Gianluca Gambarini, DDS, is a professor and head of endodontics and restorative dentistry at La Sapienza University of Rome, where he directs the master’s program in endodontics. An internationally recognized lecturer and researcher, he has authored more than 500 publications and delivered more than 600 presentations worldwide. Gambarini is president-elect of the European Society of Endodontology and maintains a private endodontic practice in Rome, Italy.
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