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. 2023 Jun;27(6):2629-2639.
doi: 10.1007/s00784-022-04829-8. Epub 2023 Jan 5.

Effect of veneering material type and thickness ratio on flexural strength of bi-layered PEEK restorations before and after thermal cycling

Ahmed Gouda  1 , Ashraf Sherif  2 , Mennatallah Wahba  3 , Tarek Morsi  4   5
Affiliations

Effect of veneering material type and thickness ratio on flexural strength of bi-layered PEEK restorations before and after thermal cycling

Ahmed Gouda et al. Clin Oral Investig. 2023 Jun.

Abstract

Objective: The purpose of this study was evaluating the biaxial strength of bi-layered PEEK restorations before and after aging using different veneering materials in different thickness ratios.

Material and methods: Ninety specimens of thickness 1.5 mm were divided into three groups according to their veneering material. Group (CAD LD): BioHPP discs veneered with CAD milled lithium disilicate (n=30), group (CAD C): BioHPP discs veneered with CAD milled composite (n=30), and group (LC): BioHPP discs veneered with conventionally layered composite (n=30). Each group was subdivided into 3 subgroups (n=10) according to the different thickness ratios between the core and the veneering material (TC:TV). Subgroup 1: TC:TV=1:0.5, subgroup 2: TC:TV=0.7:0.8, and subgroup 3: TC:TV=0.5:1. Half of the specimens of each subgroup were subjected to thermocycling, and the bi-axial flexural strength of all specimens was tested before and after aging. Three-way ANOVA followed by Bonferroni's post hoc test were used for data analysis. The significance level was set at P ≤ 0.05.

Results: Material, thickness ratio, and aging all had a significant effect on biaxial flexural strength. (LC) group had the highest biaxial flexural strength. TC:TV=0.5:1 showed the lowest biaxial flexural strength. All groups showed significant decrease in biaxial flexural strength after aging.

Conclusions: Veneering material for PEEK together with the thickness ratio between the core and veneering material greatly affect the flexural strength of bi-layered restorations. Thermocycling negatively impacts the flexural strength of PEEK bi-layered restorations.

Clinical significance: According to the results of that study, PEEK cores are best veneered with conventionally layered composite with core to veneering thickness ratio being 1:0.5.

Keywords: Flexural strength; PEEK; Thermocycling; Veneering.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Digital microscopic assessment (×20) of TC:TV = 1:0.5 mm demonstrating: a IPS emax specimen before aging; b IPS emax specimen after aging; c HIPC specimen before aging; d HIPC specimen after aging; e Crea.lign specimen before aging; f Crea.lign specimen after aging
Fig. 2
Fig. 2
Digital microscopic assessment (×20) of TC:TV = 0.7:0.8 mm demonstrating: a IPS emax specimen before aging, b IPS emax specimen after aging, c HIPC specimen before aging, d HIPC specimen after aging, e Crea.lign specimen before aging, f Crea.lign specimen after aging
Fig. 3
Fig. 3
Digital microscopic assessment (×20) of TC:TV = 0.5:1 mm demonstrating: a IPS emax specimen before aging, b IPS emax specimen after aging, c HIPC specimen before aging, d HIPC specimen after aging, e Crea.lign specimen before aging, f Crea.lign specimen after aging
Fig. 4
Fig. 4
SEM fractograph for IPS emax CAD specimen: a low magnification showing debonding at the cement interface, b higher magnification demonstrating sharp fractures in the veneering material extending down to the BioHPP and exposing it
Fig. 5
Fig. 5
SEM fractograph for HIPC specimen demonstrated a fracture in the veneering material. a Low magnification showing a crack extending through the veneering HIPC itself and exposing the BioHPP core. b Higher magnification with the white arrow showing a debonding interface
Fig. 6
Fig. 6
SEM fractograph for Crea.lign specimen: a low magnification showing the interface area between the veneering material and BioHPP revealing good bonding and limited areas of debonding, b higher magnification demonstrating fracture in the veneering material extending down to the BioHPP core
See this image and copyright information in PMC

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