Intraradicular retainers. Retreatment of a tooth with a fiber retainer.
Teeth with fiber retainers are often challenging to retreat.
Patient, a dental surgeon, came to the clinic for retreatment of tooth 11 with fistula, treated 3 years ago and with a fiber pin inside the canal. Using a microscope and ultrasound tips, the retainer was bypassed and worn for endodontic retreatment of the canal.
In: Machado, Ricardo. Endodontics: Biological and Technical Principles. Available at: GEN Group, GEN Group, 2022.
Esthetic root retainers*
Ceramic root retainers are also considered esthetic. In the following, however, the term "esthetic" refers to fiber pins.
Esthetic pins have been increasingly used, mainly because they present a more favorable biomechanical behavior and superior esthetics, besides demanding less clinical time for fabrication and installation.51
Faced with the need for removal, the characteristics and the method of cementation are determinant for the success of the procedure, since resin cements are more difficult to remove due to their viscoelastic nature and resilience, which attenuate ultrasonic vibrations.
The most commonly used materials for the fabrication of esthetic pins are fiberglass, quartz and carbon with quartz. Because they are dark, carbon pins can be coated with quartz or glass fiber, which improves the aesthetics without compromising their positive properties. Fiberglass or quartz pins are cheaper than carbon fiber pins, and have a certain capacity for light transmission. However, for their cementation, an adhesive and a chemical or dual-cure cement are necessary, because the transmitted light does not reach the apical third.52
The protocols for cementing esthetic pins are based on the precepts of Adhesive Dentistry, in which a hybrid layer is formed inside the canal so that the pins are adhesively attached to the intradicular dentin. Thus, their removal can only be performed by grinding.
The grinding of cemented esthetic pins is considered a highly complex procedure, due to the eminent risk of embrittlement and root perforation, especially with the use of high rotation burs. Therefore, it is recommended that this procedure be performed with ultrasonic tips and "in the light of the operative microscopy".
Initial considerations for the removal of esthetic pins
Through the initial radiograph, the type and characteristics of the retainer (serrated, cylindrical, smooth, conical, with or without guide wire, etc.) must be identified. Generally, the colors of the pin and dentin are distinct, which contributes to the fact that only the pin is worn, preserving the root walls. The presence of a guide wire (metallic wire located in the center of the pin in all its length) favors the removal without excessive wear in the canal walls.
Another important factor that should be considered for the removal of esthetic pins is the length. The longer the length of the pin, the more difficult the removal is due to the narrowing of the root walls in the cervicoapical direction. In this context, the inclination of the tooth in the oral cavity should also be considered.
Selection of ultrasonic inserts for grinding
The most commonly used inserts for grinding and removing esthetic pins are diamond. However, smooth inserts can also be used, although they have a lower cutting ability and are therefore safer. The inserts should be long and thin to wear the entire retainer while preserving the canal walls. Irrigation during ultrasonic activation compromises visualization, which is why it should not be used. Thus, ultrasonic activation for 20 seconds, interspersed with conventional irrigation is recommended for cleaning the canal and cooling the root canal.
Removal of esthetic pins
1.Initial radiograph.
2.Analysis and identification of the following elements: pin, cement, tooth and resin.
Core wear and access to the retainer.
Start grinding the pin with a spherical diamond tip with a long shank and compatible size, considering the inclination of the tooth and the pin.
Further grinding of the pin with spherical diamond or smooth ultrasonic inserts (E9, E5, E4D and E2D - Helse Ultrasonic) with a power of 20 to 40%. Special attention must be paid to the color difference between dentin and pin in order to avoid wear on the root walls.
6.The diameter of the ultrasound tips should be compatible with that of the canal in each root third. Transoperative radiographs are strongly recommended.
Once the retentor is finished, the remaining cement is cleaned from the root walls with a smooth ultrasonic insert at minimum power.
8.Final radiography.
Intra-radicular retainer
