Resistance to vertical fracture of MTA ‐filled roots

Aim To investigate the effect of MTA root canal fillings on the resistance to vertical root fracture ( VRF ) over different time intervals. Material and methods Freshly extracted anterior human teeth with single canals and minimal curvatures were decoronated, instrumented to size 50/.05 P ro T aper file, irrigated with 1% N a OC l and randomly allocated to one of three groups ( n  = 36): (i) filled with MTA , (ii) filled with gutta‐percha and sealer and (iii) unfilled roots used as a negative control. Each group was subdivided into three subgroups ( n  = 12) according to the storage time of 48 h, 1 and 6 months at 37°C in synthetic tissue fluid ( STF ). Following the storage periods, filled roots were mounted in acrylic supports, and the periodontal ligament was simulated using elastomeric impression material. Vertical loading was carried out with a ball‐ended steel cylinder fitted on a universal testing machine at 1 mm/min crosshead speed. The maximum force at fracture ( F ‐max) and the fracture mode were recorded for each root. Results Data were statistically analysed using two‐way anova and B onferroni post hoc tests. The mean F ‐max was significantly higher in the MTA subgroups after 1 and 6 months compared with all other subgroups. Two modes of fracture were identified: split and comminuted. The mean F ‐max values recorded with the latter were significantly higher compared with the former ( P  < 0.001). In all groups, split fracture was the most dominant mode apart from the MTA /1 month and MTA /6 month groups. Conclusion MTA increases the resistance to VRF of endodontically treated teeth and influences the mode of fracture after 1 and 6 month of storage in STF compared with gutta‐percha and sealer.