Effect Of Incomplete Partial Ferrule Location On Fracture Resistance Of Post-and-core Crown

Objective: The purpose of this in vitro test and finite element analysis was to evaluate the fracture resistance of post and crowned maxillary premolar with various ferrule configurations.Methods: According to the partial ferrule location,maxillary premolar after endodontical treatment were assigned to four groups: Group A: with a circumferential ferrule;Group B: with a palatal ferrule;Group C: with a buccal ferrule;Group D: with a proximal ferrule.All specimens were reconstructed with fiber posts,resin cores,and metal crowns,then specimens were mounted and loaded in a universal testing machine to evaluate the anti-fracture ability.Meanwhile,Cone-beam CT scan and finite element analysis software were employed to reconstruct five models of post and core crowned maxillary premolar with different residual ferrule location:Group A :teeth with a circumferential ferrule;Group B: teeth with a palatal ferrule;Group C: teeth with a buccal ferrule;Group D: teeth with a mesial ferrule;Group E: teeth with a distal ferrule.The Von Mises Stress and the maximum principal stress of each group were analyzed Results: The vitro test showed significant difference existed between those groups,and the anti-fracture ability of group A was significant higher than other groups(p<0.05,p=0.037,p=0.001,p= 0.004).No significant differences were found between the other three groups(p>0.05).According to the results of finite element analysis,The Von Mises Stress in group C was the highest,which was 64.53 MPa,while the minimum Von Mises Stress in group A,which was 50.87 MPa.The maximum principal stresses in group C was highest(47.34Mpa),while the lowest maximum principal Stress was founded in group A(43.04 MPa)Conclusion: A complete ferrule could significantly enhance fracture resistance of the maxillary premolar reconstructed with post and cored crown.While the residual dentinal tissue is not enough,more palatal dentinal tissue may enhance the fracture resistance of the maxillary premolar Post and cored crown by protecting the integrity of the adhesive layer between the dentin and resin.