Influence Of Different Ferrule Designs And The Posts On The Fracture Resistance Of Teeth

Objective: The aim of this study was to evaluate the influence of different ferrule designs and posts on the fracture resistance of endodontically treated mandibular premolars.Methods: Sixty-four mandibular premolars were collected for the reason of orthodontic treatments within 3 months and were divided into eight groups A1-D1 ? A2-D2 according to a table of random number.Samples were sectioned 2.0 mm coronal to the buccal CEJ.Following canal preparation,eight restorative treatments were performed: Group 1 is fiber post,group 2 is casting post.The group 1 and 2 were divided into 4 groups,each with eight samples.Group A: teeth with 2mm circumferential ferrule.Group B: teeth with 2mm ferrule only in the buccal region.Group C: teeth with 2mm ferrule only in the lingual region.Group D: teeth with 2mm ferrule in the buccal and lingual region.A1-D1,A2-D2 groups were used with fiber posts and casting posts before restored with Co-Cr metal crown.All experimental teeth were subjected to thermal cycling(5?-55?,5000times)and then were loaded till failure by the electrical universal machine.The maximum loading value and failure mode were recorded.SPSS21.0 statistical software was performed to determine whether there were significant differences in fracture resistance and failure mode among groups.One-way ANOVA and t-test were used to determine the significance of the failure resistance loads.A nonparametric chi-square test was conducted for statistical evaluation of the mode of fracture(?=0.05).Results:1 The difference of the length and the size of teeth is not statistically significant(P>0.1).2 The fracture resistance of group A1 and group A2 were higher than other three groups respectively(P<0.05).The difference in remaining groups is not statistically significant(P>0.1).3 The loading force of group 2 is higher than group 1(P<0.05),exceptgroup C1 and C2 group.4 The fracture mode of repair-type of group 1 is more than group 2(P<0.05).Conclusions:1 Try to save the healthy tooth as much as possible can improve the fracture resistance in the clinic and the different ferrule designs may not have an influence on the fracture resistance of the teeth.2 The casting posts have a higher loading force.Considering the unfavorable fracture mode,we preferred to the fiber posts which can also meet the clinical demand.