Effects Of Fiber Post Lengths And Simulated Periodontal Ligament On The Fracture Resistance Of Post-retained Restorations

Objective: To investigate the effects of different post lengths and simulated periodontal ligament on the fracture resistance after restoration in vitro study.Methods: Fifty-four mandibular first premolars which extracted for orthodontic reasons were collected and randomly divided into 6 groups of three different post insertion depths(A: 6mm,B: 9mm,C:12mm)and two simulated periodontal ligament states(with and without).All of them were restored by glass fiber posts with composite resin core and zirconia all-ceramic crown.The samples were loaded in a universal testing machine with a speed of 1 mm/min at 45° to the long axis of the tooth until tooth fracture occurred.The maximum load and failure mode were recorded.Results: Fiber post lengths and simulated periodontal ligament had no interaction effect on the fracture resistance(P>0.05)There was no significant difference in the mean value of fracture load between different post lengths(A1/B1/C1,A2/B2/C2)and two simulated periodontal ligament states(P>0.05).The fracture modes of teeth in each group were mostly repairable(P>0.05).conclusion: For the severely defected teeth,it is not necessary to increase the post length to improve the fracture resistance.In vitro study,the use of elastic impression materials to simulate the periodontal ligament had no significant effect to the results.The fracture of roots restored with fiber posts mostly happens in cervical third which is beneficial to the restoration.