Descriptive analysis (mean, standard deviation (SD), minimum, maximum) of the groups is presented in Table 4.

Group L-M exhibited the highest failure load values (2891.88 N ± 410.12 N), and the lowest values were observed in group ZL-M (1750.28 N ± 314.96 N). Two-way ANOVA indicated a statistically significant difference between materials and veneering technique (p = 0.00 < 0.05). Tukey’s test confirmed statistically significant differences observed between the groups ZL-V and ZL-M (p = 0.04 < 0.05) and L-V and L-M (p = 0.00 < 0.05). To compare the restoration design, monolithic design demonstrated a statistically significant difference between materials (p = 0.00 < 0.05; L-M > ZL-M). Although the veneering technique did not present a statistically significant difference between the materials (p = 0.87 > 0.05), this technique had opposite effects on two different ceramics that increased the failure load of ZLS ceramic and decreased it for LDS ceramic (Fig. 2).

Fracture analysis

No chipping or delamination was observed after the load-to-failure test since bulk fracture was observed in all groups. The fracture pattern was mostly the central groove direction in the veneered groups and the fissural direction with multiple fragments in the monolithic groups. Screw loosing was found in 5 specimens of groups L-M and ZL-V, 2 specimens of group L-V, and 1 specimen of group ZL-M.

Finite element analysis

The Pmax value of crown restoration of group L-M was 374.7 MPa, and the tensile stresses were concentrated in the load application site and the coronal part of the abutment (Fig. 3a). Von Mises stresses were also concentrated at the load application site and transferred to the coronal part of the abutment. The Pmax value of crown restoration of group ZL-M was 367.4 MPa, which was lower than other monolithic restoration (Fig. 3b). Tensile stress distribution and Von Mises stresses were similar to those in group L-M.

The tensile stresses in group L-V and group ZL-V were concentrated at the load application site on the veneering ceramic with relatively similar Pmax values (322.5–322.6 MPa; Fig. 3c, d) and also the occlusal part of the cores (34.7–31.5 MPa).

Von Mises stresses were relatively similar and concentrated at the coronal part of both implants (Fig. 4a–d) and abutments in all groups (Fig. 5a–d). All stresses such as tensile, compressive, and Von Mises stresses were concentrated in the cortical bone around the implant neck (Fig. 6a–d). The results of groups L-M and ZL-M were quite similar and considerably reduced all stresses.