Author name: Noor Hayati Azami1, Nora Sakina Mohd Noor1, AfafAl-Haddad2, Rana Diab1, Fauzi Majid3 & Zeti Adura Che Ab Aziz1
Journal reference: Azami, N.H., Sakina, N., Afaf Al-Haddad, Diab, R., Majid, F. and Che, A. (2025). Adhesive performance and failure modes of hydroxyapatite coated gutta percha with different root canal sealers. Scientific Reports, [online] 15(1), pp.38933–38933. doi:https://doi.org/10.1038/s41598-025-22842-1
In root canal treatment, gutta percha (GP) is the most widely used core filling material, often combined with a sealer to achieve a hermetic seal between the filling material and the root canal dentine. However, conventional GP does not bond to either dentine or sealer meaning the success of the seal depends almost entirely on the sealer’s ability to adhere and keep the filling securely in place. To overcome this limitation, researchers have developed hydroxyapatite-coated gutta-percha (HAGP), in which GP cones are coated with hydroxyapatite, a calcium phosphate mineral that closely resembles the composition of dentine, to establish a more bondable interface with both the sealer and dentine. The purpose of this study was to evaluate the adhesive performance of HAGP when used with different root canal sealers and to analyse the modes of failure, comparing these outcomes with those of conventional GP paired with a standard sealer.
In this in-vitro investigation, 80 extracted single-rooted human teeth were instrumented using standardised preparation techniques and divided into four groups. The control group was obturated using conventional GP with the resin-based sealer AH Plus, while the experimental groups used HAGP paired with one of three sealers: AH Plus, the bioceramic sealer iRoot SP, or the calcium-silicate-containing material GuttaFlow Bioseal. All teeth were filled using a single-cone obturation method, and after 30 days of storage, the roots were sectioned at the mid-root level for push-out bond strength testing.
The results showed that all HAGP groups demonstrated significantly higher push-out bond strength than the conventional GP control group. Among the experimental groups, HAGP used with the bioceramic sealer iRoot SP produced the highest mean bond strength; however, no statistically significant differences existed among the three HAGP-sealer combinations. This suggests that the hydroxyapatite coating itself, rather than sealer chemistry, is the primary factor enhancing adhesion. In contrast, the conventional GP group showed the lowest bond strength values, reflecting its known lack of bonding capability.
Failure mode analysis revealed that none of the HAGP groups exhibited adhesive failures at the sealer–dentine or sealer–GP interface. Instead, failures were predominantly mixed or cohesive, indicating that the interface created with HAGP was strong and remained intact during stress. The absence of adhesive failures reinforces the conclusion that hydroxyapatite coating improves interfacial integrity
Overall, the study concludes that hydroxyapatite-coated GP significantly enhances adhesion between obturation materials and root dentine, regardless of the sealer used. While the findings are promising, further research is needed to assess long-term performance, behaviour in complex canal anatomies, bonding mechanisms, and retreatability before clinical use. Nonetheless, HAGP emerges as a potentially valuable advancement for improving the durability and sealing quality of root canal fillings.
Research Summary Written By: Warshika Gopikrishna, University of Manchester – BDS 4