Biomechanical performance of post-and-cores of polyetheretherketone and its composites

Abstract

Background: Polyetheretherketone (PEEK) and its fiber-reinforced composites have been indicated as ideal post-and-cores materials due to its mechanical properties. However, the laboratory evidences of post-and-cores restored with fiber-reinforced PEEK are lacking.

Materials and methods: A total of 120 extracted mandibular premolars were treated endodontically and divided into six groups restored with different post-and-core materials (N = 20): (1) prefabricated quartz fiber-reinforced composite (QFRC), (2) polymer-infiltrated ceramic (PIC), (3) cobalt chromium (CoCr), (4) PEEK, (5) 30% glass fiber-reinforced PEEK (GFR-PEEK), and (6) 30% carbon fiber-reinforced PEEK (CFR-PEEK). Stress distribution was analyzed by finite element analysis (FEA). Then, each group was then divided into two subgroups (n = 10): static loading test and fatigue loading test. The static failure load (SFL) was analyzed by one-way analysis of variance (ANOVA) with least-significant difference (LSD) multiple comparison tests. The fatigue failure load (FFL) and cycles for failure (CFF) were evaluated by Kaplan-Meier survival analysis (P < 0.05).

Results: Groups PEEK, GFR-PEEK, and CFR-PEEK exhibited lower maximum peak principal stress and better stress distribution than Group CoCr. The SFL of Groups PEEK and QFRC did not differ from each other, and both were lower than those of Groups CoCr, GFR-PEEK, and CFR-PEEK. In the fatigue loading test, Group CoCr exhibited the best survival; however, with the progression of fatigue, the survival probabilities of Groups PEEK and its composites were close to that of Group CoCr. In all groups apart from Group CoCr, the rate of repairable failure modes was higher than that of irreparable ones.

Conclusions: Customized post-and-cores manufactured with PEEK and its fiber-reinforced composites showed superior biomechanical performance, making them potential alternatives for the restoration of massive tooth defects.

Clinical relevance: This study provides a theoretical basis for clinicians to select post-and-core materials for different root canal morphology residual roots and helps to reduce the occurrence of complications such as root fracture and post core debonding.

Keywords: Dental material; Esthetic dentistry; Polyetheretherketone; Polymer; Post-and-core.

Fig. 1

Specimen preparation and specimen on testing machine. (A) Schematic illustration and the dimensions of the post-and-core and crown (mm). (B) Different post-and-cores. (B-I) QFRC post. (B-II) PIC post-and-core. (B-III) CoCr post-and-core. (B-IV) PEEK post-and-core. (B-V) GFR-PEEK post-and-core. (B-VI) GFR-PEEK post-and-core. (C) The specimen was set in the fatigue testing machine

Fig. 2

Finite element analysis. (A) Peak maximum principal stress in Group 1 to Group 6 with restored tooth components: root, post-core, and cement layer p. (B) Distribution of maximum principal stress in each group within restored tooth components: root, post-core, and cement layer p

Fig. 3

Static loading test. (A) Static failure load of different post-and-cores [different lower-case letters indicate significant differences, P < 0.05; one-way analysis of variance (ANOVA) with least-significant difference (LSD) multiple comparison tests]. Box-and-whisker diagram of static failure loads presenting the median (bold black horizontal line), minimum and maximum values (vertical “t” lines or whiskers) of different post-and-core materials. (B) Failure mode analysis of different post-and-core materials regarding the static loading test. (C) The representative failure mode of each material in the static loading test; the arrow points out the fracture area. (C-I) Root fracture in the cervical third was shown in Group QFRC. (C-II) Root fracture in the cervical third was shown in Group PIC, and the fracture line was closer to the crown margin. (C-III) Vertical root fracture was shown in Group CoCr. (C-IV) Root fracture in the cervical third was shown in Group PEEK. (C-V) Root fracture in the cervical third was shown in Group GFR-PEEK. (C-VI) Root fracture in the cervical third was shown in Group CFR-PEEK

Fig. 4

Fatigue loading test. (A) Kaplan-Meier fatigue resistance survival curves in terms of cycles for failure. (B) Mean survived cycles and standard errors of cycles for failure (P < 0.05, Kaplan-Meier test followed by post hoc log-rank test). (C) Kaplan-Meier fatigue resistance survival curves in terms of fatigue failure load. (D) Failure mode analysis of different post-and-core materials regarding the fatigue loading test. (E) The representative failure mode of each material in the fatigue loading test; the arrow points out the fracture area. (E-I) Root fracture in the cervical third was shown in Group QFRC. (E-II) Root fracture in the cervical third was shown in Group PIC, and the fracture line was closer to the crown margin. (E-III) Vertical root fracture concomitant with cervical-third fracture was shown in Group CoCr. (E-IV) Root fracture in the cervical third was shown in Group PEEK. (E-V) Root fracture in the cervical third was shown in Group GFR-PEEK. (E-VI) Root fracture in the cervical third was shown in Group CFR-PEEK