Experimental investigation and finite element analysis on the durability of root-filled teeth treated with multisonic irrigation

Objective: This study compared the fracture load, stress distribution, and survival probability under cyclic loading of extensively restored teeth treated with multisonic irrigation with those treated with conventional instrumentation, with or without a post. Methods: Mesial-occlusal-distal cavities were prepared in 30 human mandibular premolars. The teeth were randomly divided into 3 groups of 10 based on the endodontic and restorative procedures: (1) Root canal treatment (RCT) followed by resin composite restoration (control group), (2) RCT followed by a glass fiber post restoration (conventional group), and (3) minimal instrumentation plus multisonic irrigation followed by resin composite restoration (GW group). All groups were restored with full-coverage crowns. The samples were subjected to step-stress cyclic loading until fracture and then scanned using micro-CT to identify the fracture modes. FEA was conducted to evaluate the failure-causing stresses. Results: The mean fracture loads for the control, conventional, and GW groups were 1700 ± 176 N, 1760 ± 97 N, and 1760 ± 70 N, respectively. The respective numbers of cycles to failure were 39461 ± 6634, 41261 ± 3965, and 40151 ± 3127. There was no significant difference in the fracture load or number of cycles to failure among the groups (p > 0.05). This was supported by the FEA results which showed similar critical stress values in the three groups. Significance: The multisonic irrigation system led to a comparable fracture load and durability in extensively restored premolars as conventional RCT with or without a fiber post.