Effect of different luting cements on fracture resistance in endodontically treated teeth

The aim of the present study was to evaluate the effect of three types of luting cements used for post cementation on the fracture resistance of endodontically treated maxillary premolars، restored with resin composite. One hundred intact single-rooted human maxillary premolars were randomly divided into 5 groups of 20 each. In groups 2-5، post spaces were prepared after root canal treatment and clinical crown reduction up to 1. 5 mm above the CEJ. Teeth were divided in groups as follows: Group 1: intact teeth، Group 2: active prefabricated metallic posts (PMP)، Group 3: PMP cemented with zinc phosphate luting cement، Group 4: PMP cemented with glass ionomer luting cement and Group 5: PMP cemented with resin luting cement. In groups 2-5 the teeth were restored with resin composite. Following thermocycling، the palatal cusp of each specimen was loaded to compression at an angle of 150˚ to its longitudinal axis at a strain rate of 2 mm/min until fracture occurred. Data were analyzed using one-way ANOVA and a post hoc Tukey test. Chi-square test was used for comparison of failure mode. There were significant differences in fracture resistance between the test groups (P<0. 001). The differences between group 2 with groups 1، 4 and 5 were statistically significant (P<0. 05); whereas there were no significant differences in fracture resistance between the two other groups (P>0. 05). Furthermore، there were no significant differences in the mode of failure between the 5 groups (P>0. 05). Zinc phosphate، glass ionomer and resin luting cements showed similar behaviors and achieved fracture resistance comparable to intact teeth. However، the use of active post (without cement) adversely affected the fracture resistance of root canal treated teeth.