Background: Present study compared the failure load of CAD/CAM-manufactured implant-supported crowns and the stress distribution on the prosthesis-implant-bone complex with different restoration techniques. Methods: The materials were divided into four groups: group L-M: lithium disilicate ceramic (LDS, monolithic), group L-V: LDS ceramic (veneering), group ZL-M: zirconia-reinforced lithium silicate ceramic (ZLS, monolithic), group ZL-V: ZLS ceramic (veneering). Crown restorations were subjected to load-to-failure test (0.5 mm/min). Failure loads of each group were statistically analyzed (two-way ANOVA, post hoc Tukey HSD, α = 0.05). Finite element analysis (FEA) was used to compare the stress distribution of crown restorations. Results: Group L-M had the highest failure load (2891.88 ± 410.12 N) with a significant difference from other groups (p < 0.05). Although there was a significant difference between group ZL-M (1750.28 ± 314.96 N) and ZL-V (2202.55 ± 503.14 N), there was no significant difference from group L-V in both groups (2077.37 ± 356.59 N) (p > 0.05). Conclusions: The veneer application had opposite effects on ceramics, increased the failure load of ZLS and reduced it for LDS without a statistically significant difference. Both materials are suitable for implant-supported crowns. Different restorative materials did not influence the stress distribution, but monolithic restorations reduced the stress concentration on the implant and bone.

It was aimed to evaluate the effects of conventional surface treatment techniques and femtosecond (FS) laser on shear bond strength (SBS) between zirconia and resin cement. 84 zirconia blocks (2 × 10 × 10 mm) (Zirkonzahn, Zirkonzahn USA Inc, USA) were divided into six groups (n = 14): group FS, FS laser application; group SB-FS, sandblasting followed by FS laser treatment; group FS-SB, FS laser treatment followed by sandblasting, group PS, plasma sputtering; group R, tribochemical silica coating; group SB, sandblasting with 110 µm Al₂O₃. The resin cement (Panavia F 2.0, Kuraray Medical Inc., Tokyo, Japan) was applied to the samples and polymerized with a LED curing light. SBS test was performed on 72 samples (12 samples from each group) with a universal testing machine. The other two samples of each group were analyzed with SEM and profilometer. For statistical analysis, ANOVA and Tukey HSD tests were used. Although, there were no significant differences between the group SB (7.66 ± 2.04 MPa), group PS (7.39 ± 2.98 MPa) and group R (5.62 ± 1.39 MPa) (p > 0.05), the SBS values of the group FS (13.35 ± 2.48 MPa), group SB + FS (13.23 ± 1.84 MPa) and group FS + SB (11.31 ± 2.07 MPa) were higher than them with a statistically significant difference (p < 0.05). SEM images showed differences in surface morphology among the groups. According to the 3-D profilometer images, the Ra values of Group SB, Group R, Group PS, Group FS, Group FS-SB and Group SB-FS were 0.93, 0.98, 0.16, 6.40, 10.70 and 9.11, respectively. The FS laser surface treatment provided a significantly higher bond strength than the conventional techniques. It is not recommended to combine FS laser treatment with sandblasting.

The long-term esthetic performance of indirect restorations is closely related to the color stability and surface integrity of the restorative materials used. With the increasing use of CAD/CAM technologies, a wide range of ceramic- and resin-based materials have been developed for indirect restorative applications. These include feldspathic ceramics (VITA Mark II, VITA Zahnfabrik), hybrid ceramics (VITA Enamic, VITA Zahnfabrik), resin nanoceramic CAD/CAM blocks (Lava Ultimate, 3M), and indirect microhybrid resin composites (GC Posterior, GC Corporation). However, these materials are continuously exposed to chemical and mechanical challenges in the oral environment, such as staining from beverages and daily toothbrushing, which may compromise their optical and surface properties over time. The purpose of this in vitro study was to evaluate and compare the color change (ΔE) and surface roughness (Ra) of these materials after repeated coffee immersion and simulated toothbrushing. A total of 240 disk-shaped specimens were fabricated and subjected to three aging cycles consisting of storage in coffee or distilled water, followed by simulated toothbrushing with or without toothpaste. The color parameters were measured using a spectrophotometer according to the CIE Lab* system, surface roughness was assessed using a contact profilometer, and surface topography was qualitatively analyzed by atomic force microscopy. The results demonstrated that coffee immersion significantly increased both color change and surface roughness for all tested materials, with more pronounced effects observed in resin-based materials. Ceramic-based CAD/CAM materials (VITA Mark II and VITA Enamic) showed greater resistance to discoloration and surface degradation, whereas the resin nanoceramic material (Lava Ultimate) and the microhybrid resin composite (GC Posterior) exhibited clinically perceptible color changes and higher roughness values, particularly after toothbrushing with toothpaste.

Background: The aim of this study was to compare the failure loads and stress distribution of two different CAD-on systems used for implant-supported crowns. Methods: Implant-supported crowns were designed with CAD/CAM software (Cerec InLab V15.0) and fabricated using the CAD-on technique ( n = 12 per group): Group ZF (zirconia core veneered with feldspathic ceramic) and Group ZL (zirconia core veneered with lithium disilicate ceramic). Following cementation onto titanium abutments, the restorations were subjected to failure load testing using a universal testing machine. Simultaneously, 3D models of FEA were generated to evaluate Von Mises, Maximum Principal, and Minimum Principal stress distributions across the restoration, implant, abutment, and supporting bone. The mean failure loads were compared using the independent samples t-test ( p < 0.05). Results: Group ZL exhibited significantly higher failure loads (4649.22 ± 733.42 N) compared to Group ZF (2085.91 ± 555.61 N) ( p < 0.001). While stress concentrations were primarily located at the implant neck in both groups, the distribution on the abutments differed significantly. In Group ZF, delamination was the primary failure mode (100%), whereas Group ZL presented bulk fractures and abutment deformation. Conclusion: While the Group ZL exhibited significantly superior failure load, the veneer delamination observed in Group ZF could act as a protective failure mode. Although the FEA revealed that different veneer ceramics did not alter the stress distribution across the implant and the bone, the selection of restorative system should ideally balance high fracture resistance with the biomechanical safety of the implant components.