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Retreatment of Bioceramic Sealer-Obturated Canals

By Dr. Jianing (Jenny) He

Calcium silicate-based bioceramic sealers have been growing in popularity in the last 15 years. According to a recent survey, 49% of the AAE members and 27% of the ADA members reported using bioceramic sealers, which have surpassed resin-based sealers and become the most widely-used sealer type among endodontists 1. While many clinicians are attracted to the efficiency and simplicity of the bioceramic sealer-based single-cone technique, the wider acceptance of bioceramic sealers is also driven by the growing body of evidence demonstrating their favorable properties and clinical effectiveness. The reported success rates of cases obturated with bioceramic sealer-based single-cone technique range between 90 and 99% with no significant differences noted between this technique and warm vertical compaction technique using resin sealers 2-6.

Despite the high success rates reported in the literature, treatment failure inevitably occurs necessitating the need for retreament. Retreatability of bioceramic sealers is a perceived concern expressed by many clinicians because the materials are hard-setting and are not soluble in traditional solvents such as chloroform7. In vitro studies on the retreatability of these materials show inconsistencies and results seem to depend on the canal anatomy, whether gutta-percha is placed to length during the initial treatment, and whether a solvent is used. When gutta-percha is placed to length during the initial treatment, re-establishing working length and patency is possible in most cases especially in large, straight canals, and when chloroform is used 8-10. However, if there is a significant amount of set sealer present in the apical portion of a canal, it can be difficult to get through this blockage to achieve patency using traditional retreatment techniques (Figure 1) 9.

Efforts have been made to develop supplemental protocols to facilitate the removal of set bioceramic sealers. These protocols include the use of alternative solvents, mechanical removal, and the use of active irrigation. Various acids such as formic acid, hydrochloric acid, acetic acid, and citric acid have been tested on bioceramic sealers with mostly negative results 11,12. Although hydrochloric acid was reported to reduce the time needed to achieve patency, the difference is not clinically significant and its use is limited due to its highly corrosive nature 13. Citric acid has shown potential to cause surface changes and mass loss in certain bioceramic sealers which may facilitate their removal 14. However, an effective and clinically useful solvent for bioceramic sealers is not yet available. Therefore, mechanical means are necessary to remove the set sealer.

One of the mechanical means is the use of ultrasonic instruments activated directly on the set sealer, which is effective in breaking up the material when it is visible and accessible.  Clinical anecdotes also show that a stiff hand file such as C or C+ file can be used to penetrate the set sealer. In addition, mechanical enlargement of the canal space two sizes greater than the initial size has been shown to minimize the amount of residual sealer 15. However, additional dentin removed during this process may compromise the mechanical strength of the tooth.

Hydrodynamic forces generated by sonic, ultrasonic, or laser energy in active irrigation can disrupt and remove tissue debris, biofilms, as well as root filling materials including bioceramic sealers without the removal of dentin. Among the various active irrigation systems, ultrasonic activated and laser assisted irrigation with Photon-Induced Photoacoustic Streaming (PIPS) and Shock Wave Enhanced Emission Photoacoustic Streaming (SWEEPS) modes appear to be useful in removing additional bioceramic sealers (Figure 2) 16-21. XP-3D Finisher used with irrigants has shown similar or better efficacy as ultrasonic activation in sealer removal, though no system has proven superiority.

One consistent finding reported in all published studies on retreatment is that no root filling material can be completely removed despite the use of supplemental protocols regardless of the sealer type. It is particularly difficult to remove filling material from canal irregularities such as the isthmus, lateral canals, and deep in the dentin tubules 22. Although the impact of residual sealer on the success of retreatment has not been studied, it is unlikely that it will significantly compromise the treatment outcome if the primary etiology of the initial treatment failure has been addressed, which is the most important goal during retreatment. Locating and treating previously missed canals, correcting previous procedural errors and re-establishing working length are essential to the success of retreatment. Complete removal of existing root filling materials including the sealer is desirable to achieve thorough disinfection of the root canal space but not always possible. The selection of a sealer used in root canal obturation should be based on whether it possesses the properties to fulfil the functions of a sealer to optimize the chance of treatment success. Sealing ability, biocompatibility, dimensional stability, and antibacterial properties are more important considerations over retreatability.

In summary, concerns over the retreatability of bioceramic sealers do not seem to be substantiated by scientific or empirical evidence. Retreatment of canals obturated with bioceramic sealers is possible in most cases using traditional tools and techniques. Supplemental mechanical removal and active irrigation using ultrasonics, XP-Finisher and lasers help to maximize material removal.

Figure 1: SEM image showing an apical plug of set bioceramic sealer.

Figure 2: Reconstructed micro-CT images showing effective removal of bioceramic sealer with PIPS. a1, after obturation; a2, after mechanical retreatment; a3, after PIPS-assisted irrigation. (Yang et al., BMC Oral Health (2021) 21:275)


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