A predictable method for retrieval of silver cones using ultrasonics

Case report

A 53-year-old female patient was referred to the Department of Endodontics for the management of the lower incisors (LL1, LL2 and LR1). She gave a history of RCT carried out several years previously and oral examination revealed tenderness to percussion of these teeth. The radiographs showed silver cone obturations (Figure 1) and periapical radiolucencies were present around the roots apices of LL1 and LL2. Based on the clinical and radiographic assessment, a differential diagnosis of chronic periapical granuloma/chronic peripical abcess was established and it was decided to re-treat LL1, LL2 and LR1 with the patient's consent.

The re-treatment of the teeth was planned using the Dental Operating Microscope (Sieler IQ, USA) and Ultrasonic Tips (BUC and CPR Tips, Obtura Spartan Endodontics USA) to keep the procedure minimally invasive. The steps planned for removal of the silver cones were as follows:

The above steps were followed in all three teeth. The silver cones, which were firmly stuck to the walls of the root canal, were successfully retrieved in their entirety. This was confirmed with radiographs. Chemomechanical preparation was done by Crown Down technique with a combination of hand files and ProTaper engine-driven Rotary Nickel–Titanium files (Dentsply Maillefer, Ballaigues, Switzerland) following the manufacturer's instruction. Irrigation was performed with 2.5% sodium hypochlorite and saline after each instrument. Apical enlargement was done with a Protaper F3 file. The root canals were subsequently cleaned and dried, followed by placement of intracanal medicament dressing (Calcium hydroxide – Calcicur, VOCO Germany) and temporized. The intracanal medicament was repeatedly flushed out and replaced over the next four appointments until the teeth were asymptomatic to percussion. The time interval between each appointment was one week⁵ and, finally, obturation was carried out with gutta-percha using a lateral compaction technique; this was then followed by coronal restoration with composite resin direct restorations (Figure 3).

Discussion

The American Association of Endodontics issued a position statement against the use of silver cones in 2013.⁶ Often, silver cones may come out trouble-free and fast as the small cones do not fit well in the wide canals. In easy cases, where the cone is loosely bound, heavy irrigation and the use of forceps, like Stieglitz forceps, Mosquito hemostat, Splinter forceps and Gold foil plier, along with hand instruments like Spoon excavators, may help in removal of the cones from the canal. If space is available between the silver cone and canal walls, negotiation with hand files can enable cone retrieval.⁴

In moderately difficult cases, where the cone is securely bound, indirect application of ultrasonics can be applied to loosen it. The silver point is engaged with the forceps, and the ultrasonic tip is applied to the forceps. If silver point exposure in the pulp chamber is less, a Caulfield elevator tip can be helpful. Some authors advocate the use of the ‘Multiple-File’ or ‘Braiding’ technique, where Hedstrom files will be kept beside the silver cones and then twisting is done around the cone.⁷

Several different methods and devices have been described for the retrieval of silver cones in difficult cases where they are tightly bound, such as the Tube and Hedstrom file technique and the Wire-Loop-and-Tube technique. In the Tube and Hedstrom file technique, a short piece of stainless steel tubing is pushed over the exposed silver cone and subsequently a smaller Hedstrom file is inserted between the tube and end of the cone; slow clockwise motion of the file produces binding between the silver cone and the internal part of the tube. The entire unit is then pulled coronally.⁸ In the Wire-Loop-and-Tube technique, a larger diameter tube, such as an injection needle, and a thin steel wire ligature are utilized. The two ends of the ligature wire are passed from one end of the needle until they slide from the other end, creating a wire loop on the first end. The loop is passed around the silver cone, a small hemostat is used to pull the wire loop up and tighten it around the silver cone and the entire unit is then taken out from the canal.⁹ Another effective technique is the use of extraction devices like Endo Extractors which use Cyanoacrylate adhesives. In this technique, a hollow tube with the adhesive is inserted around the silver cone to overlap it and 5–10 minutes of time is allowed for the Cyanoacrylate to set; later, pulling of the tube permits removal of the cone due to the bond created by the Cyanoacrylate. Instrument retrieval systems, such as the Masserann Kits (Micromega, Besancon, France), have also been suggested for the removal of intracanal metallic objects, such as broken files, silver cones and posts. Finally, surgery or extraction is always an option if the silver cones cannot be bypassed or removed from the root canals.¹⁰

The application of ultrasonics is much more effective under an operating microscope as the visibility is enhanced and there is a constant view of the tooth material that is being removed. Use of dental microscopes along with ultrasonic devices makes the removal of any foreign body from the canal much easier for the reasons mentioned above.¹¹

Conclusion

In the present case, retrieval of silver cones was possible with magnification using ultrasonics. A constant view of the silver cones under magnification makes the procedure more predictable. The magnification offered by the microscope allows for very precise application of the ultrasonics, reducing the unnecessary loss of the peripheral dentine and also reducing the time of the procedure.