Investigating the effect of the framework material, veneering technique and aging on flexural strength of core/veneered restorations

Abstract

Objective: To evaluate the flexural strength of different combinations of modified PEEK and 3-YTZP veneered restorations as well as the effect of aging on those combinations. Materials and Methods:Two core materials; partially sintered tetragonal monolithic zirconia and modified PEEK, and three veneering materials; lithium disilicate glass-ceramic, packable composite, and veneering porcelain were used. A total of sixty specimens were randomly divided into 3 groups (n=20). The specimens were constructed in the form of bilayered core/veneer disks of diameter12 mm and total thickness 1.5 mm. Half of the specimens of each group were tested for biaxial flexural strength using the piston-on-three-balls test. The other half of the specimens were subjected to artificial aging and then tested for biaxial flexural strength.Results: Two-way ANOVA showed there was a significant effect for the material of the bilayered restoration, aging, and the interaction between them on biaxial flexural strength. Unaged veneered Zirconia and Crea.lign veneered PEEK had significantly higher values (398.85±29.58) and (391.31±15.59) respectively than IPS e.maxCAD veneered PEEK (222.13±18.77). For the aged subgroups, veneered Zirconia (303.51±35.64) and Crea.lign veneered PEEK (277.10±13.37) also showed significantly higher values than IPS e.maxCAD veneered PEEK (198.10±6.57). For IPS e.max CAD veneered PEEK, there was no significant difference between unaged and aged sub-groups (p=0.100). However, for other materials, aging caused significant decrease in biaxial flexural strength values (p<0.001).Conclusions: Both Crea.lign veneered PEEK and porcelain veneered 3-YTZP could be used with the same efficiency, regarding flexural strength, as bi-layered restorations. Aging has a negative effect on both materials' combinations

Comparison of shear bond strength and color reproduction of two different high-performance polymers veneered with two different thicknesses of resin composite: an in-vitro study

“…All specimens in the present study were exposed to artificial aging in an attempt to simulate the oral conditions in agreement with previous studies which claim that thermal cycling did not affect the flexural strength or load-bearing capacity of PEEK [38]. However, other studies in the literature showed a significantly lower fracture resistance for the Crea.lign veneered PEEK cores after aging [34].…”

“…However, caution is advised when preparing 0.5-mm minimal thickness restorations [32,33]. Other studies showed that multiple factors are known to affect the entire strength of bi-layered restorations other than the thickness of the veneering material such as residual stress, interfacial bonding strength, the direction of loading, as well as the modulus of elasticity and fracture resistance of each layer [34].…”

“…Considering the effect of the material's modulus of elasticity, and the fact that materials having a more compatible modulus of elasticity are more likely to bend under load and distribute stresses more evenly [34], Crea.lign resin composite was used as a veneering material in the present study because it has an elastic modulus of 4.4 GPa which showed significantly high flexural strength values [35]. Additionally, the presence of 50% Nano ceramic fillers in the Crea.lign resin composite matrix played a role in improving its mechanical properties and contributing to the high flexural strength values [34]. All the specimens' surfaces are pretreated by air abrasion with 110 μm AL 2 O 3 particles followed by the application of Visio.link adhesive primer.…”