Experimental study of the effect of one-wall ferrule in different location and heights on fracture resistance of tooth roots

Objective To evaluate the effect of one-wall ferrule in different location and heights on fracture resistance of tooth roots.Methods Thirty-five intact extracted mandibular first premolars were randomly divided into seven groups: Group 1 to Group 3: teeth with 1 mm ferrule only in the buccal,lingual or proximal region separately;Group 4 to Group 6: teeth with 2 mm ferrule only in the buccal,lingual or proximal region separately;Group 7: teeth with no ferrule.All the extracted teeth were restored with fiber posts,composite cores and metal full crowns.Each specimen was subjected to an increasing compressive force at buccal spire at 135 degrees from the long axis in a universal testing machine with a crosshead speed of 1.0 mm/min until fracture.Fracture resistance was analyzed statistically.Results The fracture resistance of teeth was significantly affected by the location of ferrule(P0.025),and the mean failure strength of the buccal group was significantly higher than that of the lingual group(P0.025).Group 4 demonstrated the highest mean failure strength value among all groups,and the value was significantly higher than that of group 2,group 3,group 5,and group 7(P0.025).The remaining groups showed no statistical difference.All the fracture modes of specimens were repairable.Conclusions The fracture strength is higher when the dentin wall of ferrule was closer to the side loading force.Compared with teeth with no ferrule,to provide a one-wall ferrule at least 2 mm high on the main loading force side can improve the fracture strength of teeth.