Intraradicular retainer. Removal of a fiber pin in a patient with acute abscess.
Patient came to the clinic complaining of pain and swelling in the left lower region. On clinical examination, swelling in the apical gingival region of the left mandibular prongs and presence of a retainer. Radiographic examination revealed the presence of a fiber retainer and unsatisfactory endodontic treatment on tooth 34, as well as the presence of a diffuse periapical radiolucent image on said tooth.
We then proceeded to grind the retainer from its center with a diamond tip to the gutta-percha and then to remove it with a Gates bur and rotary files.
Case conducted by student Bruna Regiani, from the endodontics specialization course at APCD Bragança Paulista.
Machado, Ricardo. Endodontics: Biological and Technical Principles. Available at: GEN Group, GEN Group, 2022:
Removal of retainers or intraradicular pins
Retainers or intraradicular pins are usually indicated for the rehabilitation of teeth affected by significant loss of coronary structure. Their use should be preceded by endodontic treatment, although the opposite is inexplicably observed. There is no justification for cementing intraradicular retainers in non-endodontically treated canals.
After the cementation of an intracanal pin, the endodontic retreatment can only be performed by removing it. The difficulties in performing this procedure depend mainly on the characteristics of the retainer.
Intraradicular retainers are classified as cast and prefabricated. The former are made from cast metal alloy and, due to this process, normally adapt well to the walls of the root canal. Prefabricated intraradicular pins, on the other hand, can be metallic and non-metallic. The metallic ones are made of stainless steel or titanium and, according to their geometric shape, are classified as cylindrical or conical. As to their surface finishing, they are divided into smooth, knurled, and threaded. Non-metallic pins are made of carbon fiber, epoxy resin, ceramics (zirconium dioxide and yttrium oxide) or glass fibers embedded in a filled resin matrix.
Intraradicular retainers can be removed by traction, wear, ultrasonic vibration or a combination of these techniques, according to their type. The degree of difficulty of the procedure depends mainly on their morphological characteristics, their adaptation to the canal walls and the cementation process. Short, conical and smooth pins are more easily removed than long, cylindrical and serrated ones.
Fused metal intraradicular retainers
The use of traction methods for the removal of fused metal pins should be very well evaluated, since the application of eccentric traction forces can cause cracks and root fractures. These retainers can also be worn, preferably with spherical diamond or carbide burs at high rotation, despite the eminent risk of embrittlement and root perforation. Even with the use of the operating microscope, visualization of the working field is impaired due to the size of the pen and the length of the burs.
Ultrasonic vibration is the safest and most effective method for removing cast intraradicular metal retainers. The transmitted energy promotes cement degradation and displacement of the pin. The simultaneous use of two ultrasonic devices has been recommended to enhance the intensity of the vibration and decrease the clinical time required to perform the procedure.
Regardless of the technique, the removal of intraradicular retainers must be properly planned and executed in order to avoid errors and accidents. Abbott, in 2002,44 removed pins from 1600 teeth and only one root fracture was observed. Garrido et al., (2009) 45 evaluated the impacts of core diameter and length, and the motion applied to the ultrasonic insert on the ease of removal of intraradicular retainers. The results of the study demonstrated that when the diameter of the core was similar to that of the intracanal portion, ease of removal was appreciably greater than when the cores were more calibrous than the pin in 47% of the specimens. When the diameter and height of the cores were smaller than those of the pin, the force required to remove the prosthetic piece was reduced by up to 70%.
Zinc phosphate-cemented pins are more easily removed compared to those fixed with resin cements, which attenuate vibrations and absorb ultrasonic energy.46,47 The ultrasonic vibration of pins fixed with glass ionomer and zinc phosphate cements should be cooled, as it facilitates displacement. In the case of resin cements, the absence of cooling interferes with adhesion and favors debonding. However, the increase in temperature may damage the periodontium. Ultrasound can be used for 1 minute at maximum power under cooling - a period described in previous studies as effective in reducing the traction force required for removing the retainer and preventing excessive heating of the root surface.
The positioning of the tip of the insert can also influence the time and force required to dislodge the retainer. The ultrasonic vibration, when applied with the tip positioned in the cervical region of the core, favors the removal. Moreover, when it is alternated on all surfaces, it is more effective than when applied on a single surface, because the alternating vibration reduces the friction between the ultrasonic tip and the metal, minimizing heat release without losing efficiency.
Several ultrasonic inserts can be used to remove intraradicular retainers, depending on the brand of equipment used by the professional. The most used are:
-Inserts with blunt, calibrated tips specifically developed for removing retainers, used at full power (90 to 100%)
-Periodontal inserts with thinner tips, used at medium power (50 to 80%).
-Endodontic inserts with narrower and finer tips, diamond or smooth, of various sizes and calibers, used at low power (10 to 40%) to promote cement fragmentation.
After the core is worn, ultrasonic vibration is applied to its different faces using a blunt-tipped insert. In some cases, periodontal tips can be used for their smaller dimensions. The ultrasonic vibration should be applied at the most cervical portion of the core and with cooling to avoid overheating of the pin and root surface, which can damage the periodontium.
https://www.youtube.com/watch?v=QNxKwMPwuEc
https://ferrariendodontia.com.br/retentores-intrarradiculares-2/
