Fracture Resistance of Roots Obturated with Bioceramic or Resin-Based Sealers after Nanohydroxyapatite and Calcium Hydroxide Dressing

This study evaluated the effect of calcium-rich nanohydroxyapatite (nano-HA) as an intracanal medicament on root fracture resistance compared with calcium hydroxide (CH). Forty-eight caries-free maxillary central incisors were instrumented and randomly assigned to a two-factor design (two medicaments × two sealers), yielding four experimental groups ( n = 12/group): CH + resin-based sealer, CH + bioceramic-based sealer, nano-HA + resin-based sealer, and nano-HA + bioceramic-based sealer. The medicaments were applied and stored in simulated body fluid at 37 °C and 100% humidity for 10 days. After removal, the canals were obturated with heated gutta-percha using either a resin-based or a bioceramic-based sealer, and were then stored for an additional 28 days. Vertical fracture resistance was measured using an Instron Universal Testing Machine. Data were analyzed using two-way ANOVA ( p < 0.05). The nano-HA groups showed a higher mean fracture resistance (924.04 N) than the CH groups (818.54 N). The highest fracture resistance was observed in the nano-HA + bioceramic-based sealer group (1020.38 N), whereas the lowest was observed in the CH + resin-based sealer group (665.83 N). The main effect of sealer type was statistically significant ( p < 0.001), while no significant interaction between medicament and sealer type was detected. Within the limitations of this in vitro study using static vertical loading, sealer type had a large, statistically significant effect on fracture resistance, with the bioceramic-based sealer yielding higher values than the resin-based sealer. Although the nano-HA groups exhibited numerically higher fracture resistance than calcium hydroxide, the main effect of intracanal medicament did not reach statistical significance. These findings are limited to laboratory conditions and should not be directly extrapolated to long-term clinical performance.