Mustafa Hayati Atala

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.

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.

Aim: The aim of this study is to determine the cytotoxic effects of Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) blocks produced by different companies on human peripheral blood lymphocytes by MTT assay. Methods: Six different CAD/CAM materials were investigated: feldspar ceramic VM (Vitablocks Mark II ), resin nano-ceramic LU (Lava Ultimate), hybrid ceramic C (Cerasmart), leucite-reinforced ceramic LRF (GC LRF), zirconia-reinforced lithium silicate ceramic VS (Vita Suprinity), polymer-infiltrated ceramic-network VE (Vita Enamic). A total of 36 disc-shaped samples (Ø: 5 mm; h: 2 mm) were prepared from commercial blanks and blocks. Cell proliferation and cytotoxicity were assessed at 24h and 48h using MTT assay. The data were statistically evaluated with the Two-way ANOVA test (p < 0.05). Results: MTT viability data at 24 h showed that group VM and LU blocks were mildly cytotoxic, but there was no statistically significant difference when compared with other groups (p>0.05). It was determined that all blocks caused cell proliferation after 48 hours of exposure (p>0.05). It has been shown that all blocks whose cytotoxic effects were investigated did not cause any toxic effects (except VM and LU for 24 h) at different application times (24 h and 48 h). Conclusion: Based on the results obtained and the limitations of the current in vitro study, the tested materials were not cytotoxic. Only VM and LU caused negligible cytotoxicity at 24-hour exposure.

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.

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.

Objective While the radiopacity of restorative material affects the radiographic diagnosis of the teeth, there is no data about the radiopacity of current restorative computer‐aided design (CAD)/computer‐aided manufacturing (CAM) materials. Therefore, the present study compared the radiopacity values of current restorative CAD/CAM blocks to facilitate the material choice within such a wide variety of materials. Materials and Methods Specimens were prepared from 13 different restorative CAD/CAM blocks to compare with enamel and dentin. The specimens placed on the occlusal phosphor plate were imaged with aluminum step wedge and tooth section. The radiopacity values were calculated using the Image J program. The radiopacity values of the specimens were converted to mmAl values with the Curve Expert 1.4 program. Results The difference between the radiopacity values of dentin and e.max CAD was not significant, however, they exhibited a significant difference from the other 14 groups (P < .05). Enamel and Obsidien, Suprinity, and Celtra Duo had greater radiopacity values with significant differences from the other 12 materials whereas the difference within these groups was not significant (P > .05). Conclusions The evaluated restorative CAD/CAM materials have significantly different radiopacity values. Among these permanent restoration blocks, the highest radiopacity value was observed in Celtra Duo, the lowest in Block HC. Clinical Significance Cerasmart, Lava Ultimate, Obsidian, Vita Suprinity, Celtra Duo Blocks have adequate radiopacity for inlay, onlay and crown restorations, however, the use of Vita Enamic, Vita Mark II, GC LRF blocks and the others which have lower radiopacity value than dentin for the same kind of restorations depend on the radiopacity of the luting cement for the purpose of recurrent caries detection.