Effects of different apical preparation sizes and root canal sealers on the fracture resistance of roots aged for 12 months endodontically retreated mandibular premolars

Objective This study evaluated the effect on fracture resistance of different apical preparation sizes and root canal sealers. Materials and methods One hundred mandibular premolars were collected, 60 were prepared up to 25/0.04, obturated with AH Plus, and stored for 1 month, after which ProTaper Universal Retreatment System instruments were used to remove the root canal filling materials. The 100 root segments were randomly divided into 10 experimental groups (𝑛 = 10 roots/group) with as follows: positive control Group 1 (intact tooth group), negative control Group 2 (25/0.04 preparation, without obturation), negative control Group 3 (30/0.04 preparation, without obturation), negative control Group 4 (40/0.04 preparation, without obturation), Group 5A (30/0.04, AH Plus), Group 5B (40/0.04, AH Plus), Group 6A (30/0.04, NeoSealer Flo), Group 6B (40/0.04, NeoSealer Flo), Group 7A (30/0.04, MTA Bioseal), Group 7B (40/0.04, MTA Bioseal). All the experimental groups were incubated at 37°C for 12 months in 100% humidity. A universal testing machine measured the fracture resistance of each segment, and the results were recorded in Newtons. Results There were no significant differences between the sealers and apical preparation sizes. The root segments obturated with AH-Plus, NeoSealer Flo, and MTA Bioseal yield values significantly higher than those in the positive control groups. Conclusions All types of sealer (AH Plus, NeoSealer Flo, MTA Bioseal) exhibited nearly the same fracture resistance in retreated root segments aged 12 months. Clinical relevance Obturation with AH Plus, NeoSealer Flo and MTA Bioseal using the single cone technique enhanced the fracture resistance of retreated roots.