A systematic review finds a possible reinforcing effect, but no clear winner among sealer categories
A common concern after root canal treatment is whether the tooth has become more vulnerable to fracture. The removal of dentin during access preparation and canal instrumentation can alter the mechanical behaviour of the tooth. This has led to growing interest in whether obturation materials can do more than seal the canal space—whether they can also help reinforce the remaining tooth structure.
Calcium silicate-based and bioceramic sealers are often discussed in this context because of their proposed bioactivity, dentinal interaction and ability to form mineral deposits at the sealer–dentin interface. But does the available evidence show that these materials strengthen endodontically treated teeth more effectively than conventional resin-based sealers?
A systematic review published in Frontiers in Dental Medicine evaluated this question by examining studies on the fracture resistance of endodontically treated teeth obturated with different root canal sealers and materials. The review included 24 studies in its qualitative synthesis. However, the evidence was predominantly laboratory-based: 22 studies were in vitro, one was an animal study and one was ex vivo.
What did the review find?
The review found that teeth obturated with root canal sealers generally showed greater fracture resistance than instrumented but unobturated teeth. This suggests that filling the prepared canal space may provide a degree of mechanical support.
However, the authors did not identify a specific sealer that could be considered clearly superior. Epoxy resin-based and calcium silicate-based sealers demonstrated broadly comparable performance overall. Zinc oxide eugenol-based sealers generally showed less reinforcing ability in the included studies.
The findings should not be interpreted as proof that obturation restores the original strength of a tooth. Endodontic treatment involves the removal of tooth structure, and the remaining dentin thickness, root morphology and extent of coronal destruction continue to influence fracture resistance.
The review also noted that the reported results varied considerably between studies. Some investigations found higher fracture resistance with calcium silicate-based or bioceramic sealers, while others reported comparable results between calcium silicate-based and epoxy resin-based materials.
Why are bioceramic sealers attracting attention?
Calcium silicate-based sealers have been proposed to reinforce dentin through several mechanisms. Their calcium ion release and potential to form hydroxyapatite-like deposits may improve the interaction between the sealer and the canal wall. These materials have also been investigated for their sealing ability and possible contribution to intratubular mineralisation.
Several studies included in the review reported higher fracture resistance values with bioceramic sealers compared with resin-based materials. In some comparisons, materials such as BioRoot RCS and other calcium silicate-based sealers performed better than epoxy resin-based sealers.
Nevertheless, the findings were not consistent across the entire evidence base. The review’s overall conclusion was that calcium silicate-based and resin-based sealers demonstrated generally comparable performance, and that the available evidence did not establish clear clinical superiority for any particular sealer category.
The review also observed that zinc oxide eugenol-based sealers generally showed limited reinforcement. The authors suggested that this may be related to their relatively higher solubility and limited adhesive interaction with dentin.
The sealer may not be the only important variable
One of the most important findings of the review was the considerable variation in the methods used by the included studies.
The investigations differed in:
Tooth type and root anatomy Canal preparation size Irrigation protocols Obturation technique Sealer thickness Loading direction Crosshead speed Periodontal ligament simulation Method of embedding the specimens
The studies used cold lateral compaction, single-cone obturation and warm vertical compaction. These techniques may influence the stresses placed on the root and the extent to which the sealer contributes to the final obturation mass.
For example, single-cone obturation relies more heavily on the sealer to occupy the space between the gutta-percha cone and the canal wall. In contrast, cold lateral compaction introduces condensation forces, while warm vertical compaction involves heat and compaction-related variables.
This makes it difficult to conclude that a higher fracture load observed in one laboratory experiment is solely due to the chemical composition of the sealer.
What does this mean for clinical practice?
The review provides support for the idea that obturation may contribute to the mechanical resistance of an endodontically treated tooth. However, it does not suggest that sealer selection should become the principal strategy for preventing root fracture.
The long-term prognosis of a root canal-treated tooth is influenced by several factors, including:
The amount of remaining dentin Conservative access preparation Avoidance of unnecessary removal of radicular tooth structure Root morphology The presence of a ferrule The quality and timing of the definitive restoration Occlusal loading and parafunctional activity Coronal leakage and recurrent caries
The authors specifically stated that preservation of tooth structure, ferrule design and appropriate restorative rehabilitation are likely to be more important determinants of long-term tooth survival than sealer selection alone.
Therefore, a bioceramic sealer should not be selected solely on the assumption that it will “strengthen” the root. Its biological properties, sealing ability, handling characteristics, moisture requirements, retreatability and compatibility with the obturation technique should also be considered.
Why the findings need to be interpreted cautiously
The major limitation of this review is the nature of the available evidence. Of the 24 included studies, 22 were conducted in vitro. Extracted teeth tested in a laboratory cannot fully reproduce the conditions present in the oral cavity, where teeth are exposed to repeated cyclic loading, thermal changes, moisture, periodontal support and long-term restorative stresses.
The methodological quality of the evidence was also a concern. Many studies did not provide adequate details about sample-size calculations, randomisation, allocation procedures or blinding. As a result, several studies were classified as having moderate or high risk of bias.
The absence of a meta-analysis is also important. Because of the differences in tooth selection, experimental conditions and fracture-testing protocols, the authors considered it inappropriate to combine the results statistically.
Future studies will need more standardised models, longer-term fatigue testing and, most importantly, clinical investigations that measure actual fracture incidence and tooth survival rather than only the force required to fracture extracted teeth.
The clinical takeaway
The current evidence suggests that root canal sealers may provide some reinforcement after obturation. Calcium silicate-based sealers show promising laboratory results, but they have not demonstrated clear clinical superiority over conventional resin-based sealers.
For the clinician, the practical message is not that one sealer can compensate for a weakened tooth. Instead, it is that sealer selection should be considered as one part of the overall treatment plan.
The more important questions remain:
How much sound tooth structure has been preserved? Is the remaining tooth adequately protected by the definitive restoration? Is there a functional ferrule? And have unnecessary stresses on the tooth been minimised?
Until stronger clinical evidence becomes available, root canal sealers should be selected primarily on the basis of their biological, physicochemical and handling properties—not on the assumption that they alone can prevent root fracture.