The aim of this study was to compare the load-to-failure resistance and optical properties of nano-lithium disilicate (NLD) with lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) in different aging processes. Thirty crowns were milled from NLD, LDS, and ZLS (n = 10). All crowns were subjected to thermomechanical aging and loaded until catastrophic failure. Ten specimens from each material were prepared in two different thicknesses (0.7 mm and 1.5 mm, n = 5), and color coordinates were measured before and after coffee thermocycling. Color differences (ΔE00) and relative translucency parameter (RTP) were calculated. Data were analyzed by using ANOVA and Bonferroni-corrected t-tests (α = 0.05). ZLS had the highest load-to-failure resistance (p ≤ 0.002), while the difference between LDS and NLD was nonsignificant (p = 0.776). The interaction between material type and thickness affected ΔE00 (p < 0.001). Among the 0.7 mm thick specimens, ZLS had the lowest ΔE00 (p < 0.001). Furthermore, 1.5 mm thick ZLS had lower ΔE00 than that of 1.5 mm thick LDS (p = 0.036). Other than ZLS (p = 0.078), 0.7 mm thick specimens had higher ΔE00 (p < 0.001). The interaction between material type, thickness, and thermocycling affected RTP (p < 0.001). Thinner specimens presented higher RTP (p < 0.001). NLD and LDS had higher RTP than ZLS (p ≤ 0.036). However, 0.7 mm thick specimens had similar RTP after coffee thermocycling (p ≥ 0.265). Coffee thermocycling reduced the RTP values of 0.7 mm thick NLD (p = 0.032) and LDS (p = 0.008). NLD may endure the occlusal forces present in the posterior region. However, long-term coffee consumption may impair the esthetics of restorations particularly when thin NLD is used.

Purpose To evaluate the fracture resistance and fracture patterns of single implant‐supported crowns with different prosthetic designs and materials. Materials and Methods One hundred and forty‐four identical crowns were fabricated from zirconia‐reinforced lithium silicate (ZLS), leucite‐based (LGC), and lithium disilicate (LDS) glass‐ceramics, reinforced composite (RC), translucent zirconia (ZR), and ceramic‐reinforced polyetheretherketone (P). These crowns were divided into 3 subgroups according to restoration design: cementable crowns on a prefabricated titanium abutment, cement‐retained crown on a zirconia‐titanium base abutment, and screw‐cement crown (n = 8). After adhesive cementation, restorations were subjected to thermal‐cycling and loaded until fracture. The fracture patterns were evaluated under a stereomicroscope. Statistical analysis was performed by using 2‐way ANOVA/Bonferroni multiple comparison post hoc test (α = 0.05). Results For each prosthetic design, ZR presented the highest fracture resistance (p ≤ 0.005). Other than the differences with ZLS and RC for screw‐cement crowns (p > 0.05) and RC for crowns on zirconia‐titanium base abutments (p > 0.05), LGC showed the lowest fracture resistance. P endured higher loads than LDS (p < 0.001), except for the crowns on zirconia‐titanium base abutments (p > 0.05). Cementable crowns presented the highest fracture resistance (p < 0.001), other than LGC and LDS. The differences between LGC crowns (p > 0.05) or LDS crowns on prefabricated titanium and zirconia‐titanium abutments were nonsignificant (p = 0.133). Fragmented crown fracture was predominant in most of the restorations. Screw and abutment fractures were observed in ZR screw‐cement crowns, and all P crowns were separated from the abutments. Conclusions Restorative material and restoration design affect the fracture resistance and fracture pattern of implant‐supported single‐unit restorations. Clinicians may restore single‐unit implants in premolar sites with the materials and prosthetic designs tested in the present study.

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