Biomechanical Performance Of PEEK Post-and-core

Objectives: This study aimed to evaluate the static and fatigue loading performance of endodontically treated mandibular premolars restored with polyetheretherketone(PEEK)post-and-core compared with three different post-and-core systems,including prefabricated quartz-fiber-reinforced composite(QFRC)post and composite core,polymer infiltrated ceramic(PIC),Cobalt Chromium(Co Cr)cast post-and-core.Methods: Eighty extracted mandibular premolars were decoronated 2 mm above the cemento-enamel junction,treated endodontically,embedded in acrylic resin and divided into four groups(n = 20):(A)prefabricated QFRC post and composite core,(B)PIC post-and-core,(C)Co Cr cast post-and-core,and(D)PEEK post-and-core.After appropriate surface treatment,the post-and-cores were cemented,restored with full Zirconia crown,and thermocycled.Each group was then divided to two subgroups(n = 10): static loading test and fatigue loading test.In the static loading test,the samples were subjected to a static load at an angle of 45 degrees at a crosshead speed of 0.5 mm/min until fracture.The static failure load(SFL)was recorded and analyzed by one-way analysis of variance(ANOVA)with least-significant difference(LSD)multiple comparison tests.The failure mode were recorded and analyzed by χ2 tests and Bonferroni adjustments.In the fatigue loading test,the samples were subjected to stepped-load cyclic fatigue loading at an angle of45 degrees.A warm-up load of 5×103 cycles was performed at the load ranged from10 to 100 N at a frequency of 5 Hz using sin-wave stress.A 100-N load increase was applied each 1.5×104 cycles.Samples were loaded until failure or to a maximum for cycles endured of 1000 N(1.4×106).The fatigue failure load(FFL)and cycles for failure(CFF)were recorded and analyzed by the Kaplan-Meier survival analysis(log-rank test and pairwise post-hoc comparisons).Differences between fatigue failure load and static failure load within each group were analyzed by Student’s t-test.The failure mode were recorded and analyzed by χ2 tests and Bonferroni adjustments.(P<0.05)Results: The static loading test indicated that the endodontically treated teeth restored with Co Cr post had the maximum fracture load(532.78±40.35 N),followed by PIC post(452.24±106.69 N),PEEK post(372.03±66.96 N),and QFRC post(305.46±45.57 N),which were statistically different.In the static loading test,Co Cr post restored teeth showed a more unfavorable fracture,while the other three groups showed a predominantly favorable fracture.In the fatigue loading test,all the specimens failed before 1.4×106 load cycles.The cycles for failure of Group Co Cr(28631.90±2912.10)were statistically higher than those of Group QFRC(19327.60±2620.08)and Group PIC(18492.70±3623.29),while there was no significant difference between Group Co Cr and Group PEEK(24329.10±3686.85).No significant difference of fatigue failure load was found between different post materials,and the fatigue failure load of each group was 290±17.95 N(Group QFRC),270±21.34 N(Group PIC),330±21.34 N(Group Co Cr),and 310±23.33 N(Group PEEK).In the fatigue loading test,Co Cr post restored teeth showed a more unfavorable fracture,while the other three groups showed a predominantly favorable fracture.The fatigue failure load of Group PIC and Group Co Cr were significantly lower than their static failure load,respectively,whereas,there was no significant difference in Group QFRC and Group PEEK.Conclusions: The static failure load of the endodontically treated mandibular premolars restored with PEEK post-and-core was higher than that corresponding to the normal occlusal load of an adult.PEEK post-and-core showed excellent fatigue resistance with high survival rate and a superior survival under the fatigue loading,which has the potential to be applied as post-and-core material.The incidence of irreparable failure of PEEK post-and-core was low whose failure mode was usually root fracture in the cervical third.