Ceramic strengthening by tuning the elastic moduli of resin-based luting agents

Resin-based luting agents (RBLAs) with tuned elastic moduli (E) were prepared and their influence on the strengthening, reliability, and mode of failure of luted feldspar ceramic was investigated.

RBLAs with low E (2.6GPa), intermediate E (6.6GPa), and high E (13.3GPa) were prepared and used to coat acid-etched ceramic disks. Positive (untreated ceramic) and negative (acid-etched ceramic) control groups were tested. The response variables (n=30) were biaxial flexural strength (σ_bf, MPa), characteristic strength (σ₀, MPa), and Weibull modulus at the ceramic surface (z=0) and luting agent surface (z=-t₂). A 3D finite element analysis simulated the biaxial flexural test. Fractographic analysis and morphology of the bonded interfaces were analyzed using scanning electron microscopy.

The RBLAs improved σ_bf and σ₀ at z=0, particularly those with intermediate and high E, whereas the mechanical reliability was only affected in the negative control. At z=-t₂, differences between all RBLAs were observed but the structural reliability was independent of the RBLA tested. Increasing E of the RBLA was associated with increased stress concentration at the RBLA and reduced stresses reaching the ceramic. Failures originated on the ceramic surface at the ceramic-cement interface. In the high E group, failure sometimes originated from the RBLA free surface. All RBLAs completely filled the ceramic irregularities.

Increased E of the RBLA reduced the variability of strength, the stress reaching the ceramic structure, and sometimes altered the origin of failure. The use of high E RBLAs seems beneficial for luting feldspar ceramics.