Background: Durable bonding between resin composite luting agents (CLA) and zirconia is still a matter of controversy. The purpose of this study was to evaluate the effect of water storage on hardness and interfacial strength of three CLA, a non-adhesive (Multilink Automix/ML), an adhesive (Panavia F 2.0/PF) and a self-adhesive (PermaCem 2.0/PC), bonded to polished (CL) and grit-blasted (AL: 50 μm alumina, SJ: Sil-Jet + Monobond Plus silane) monolithic zirconia surfaces. Methods: CLA specimens (n = 5/cement, condition) were prepared, stored under dry conditions or immersed in water, and Vickers hardness (VH) measurements were obtained at 1 h, 24 h, 1 week and 3 weeks intervals. Optical profilometry was used to determine the roughness parameters (Sa, Sz, Sdr, Sci) of zirconia surfaces (n = 5/treatment). A shear strength test (SBS, n = 10 × 2/cement) was performed to assess the strength and fractography of the cements bonded to zirconia after isothermal water storage and thermal-cycling (TC). Results: PF demonstrated significantly lower VHN after water storage at all time intervals, PC at 1 w, 3 w and ML at 3 w. SJ and AL showed significantly higher values from CL in all roughness parameters. Weibull analysis revealed the following significance in σ_ο ranking within the same material: AL, SJ, ALTC > SJTC, CL > CLTC (PF); SJ, SJTC, AL, ALTC > CL, CLTC (PC) and SJ, SJTC > AL > ALTC > CL, CLTC (ML). Within the same surface treatment subgroups, the significance in σ_o ranking was PC, ML > PF (before/after TC) for SJ; PC > PF > ML (before TC), PC, PF > ML (after TC) for AL, and PC > PF > ML (before/after TC) for CL. For the m ranking, the only significant difference within each material group was found in PC (AL > ALTC) and for the same surface treatment in AL (PC > ML). Conclusion: There are significant differences in the water plasticization susceptibility of the CLA tested; the materials with adhesive monomers were the most affected. Tribo-chemical silica coating combined with a silane coupling agent was the most efficient bonding treatment for the non-adhesive and the self-adhesive materials. The adhesive CLA performed better on alumina-blasted than on tribo-chemically coated surfaces.

Advancements in Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) have promoted the development of novel dental materials for several types of definitive restorations. The aim of this study was to evaluate the surface characteristics of resin-based CAD/CAM restorative materials, fabricated using both subtractive and additive manufacturing techniques. The materials tested included Filtek Z550 (FZ), Vita Enamic (VE), Shofu HC (SH), and VarseoSmile TriniQ (TQ). For each material, 24 specimens were prepared; half were manually polished following the manufacturer’s recommendations, while the other half underwent standardized metallographic polishing. The surface roughness, wettability, and molecular composition were assessed. A statistical analysis was performed using IBM SPSS 29.0 at a 95% confidence level (α = 0.05). Statistically significant differences in surface properties were observed between direct and indirect restoratives following manual polishing, with SH performing favorably in terms of surface roughness. The polishing method significantly influenced the surface characteristics of each material, except for certain roughness parameters in SH. Both surface roughness and wettability were dependent on the material and the polishing technique, highlighting the need for improved material-specific polishing protocols.

Light attenuation and excess handling of light-cured luting agents create problems in bonding veneer restorations. The aim of the present study was to assess the curing capacity of light-cured veneer luting agents (VLA) [Choice 2 (CH2), G-Cem Veneer (GCV), Panavia LC Veneer (PNV), PermaCem LC Veneer (PMS), and Variolink Esthetic LC (VEV)] under lithium disilicate veneers, in the presence or absence of touch-cure primers (Adhese Universal Bond DC for VEV, G Premio Bond + DCA Activator for GCV, and V5 Tooth Primer V5 for PNV) and to evaluate material setting under two tack-curing irradiation modes (contact, distant). The methods used were ATR–FTIR spectroscopy and Vickers hardness (VHN) tests (n = 5/product and test). According to the results, all materials cured under the ceramic demonstrated significantly lower DC% from the controls, with a ranking of VEV, CH2 > GCV, PMS, PNV. The primers improved DC% by 4–13% only in the veneer groups. Tack-curing in contact mode demonstrated conversion and hardness values ranging from 37% to 78% and 31% to 57% of the controls respectively, corresponding to a vitreous state. For the distant mode, very low conversion values were found (0–7% of the controls), with untraceable indentations. It can be concluded that low translucency veneers reduce conversion of VLAs, which can be improved by using touch-cure activators. Tack-curing, as instructed, creates vitrified materials, resulting in difficult removal of set excess, which implies the need for better standardization of the procedure.

The aim of this study was to evaluate (a) the degree of conversion (DC%), (b) film thickness, and (c) the effect of film thickness on DC% in modern light-cured resin composite restoratives [Filtek Universal (F), Clearfil Majesty ES 2 Universal (M), Tetric EvoCeram (T) and Viscalor (V)] used for luting composite onlays before/after preheating. For (a), the luting composites placed at 150 μm film thickness under the onlays (4 mm thickness, 2.9% transmittance) were light-cured for 120 s (3 × 40 s top, buccal, lingual sites) before and after preheating (54 °C/5 min-F,M,T and 65 °C/30 s-V). The DC% was measured at central, middle and side locations along the median in-length axis by ATR-FTIR spectroscopy. Specimens polymerized without onlays (40 s, top) served as controls. For (b), film thickness was measured employing a modified ISO 4049 standard (37 °C plate temperature, 5 N load) before and after preheating, using a dual-cured resin luting agent as control. For (c), onlays were luted with preheated T at 150 and 350 μm film thickness and light-cured for 2 × (3 × 40) s and 3 × (3 × 40) s, employing directly irradiated specimens (60 s, 120 s) as controls. For (a), significant differences were found in F and T before and after preheating. Before preheating, significant differences were registered between F–T, F–M, F–V and V–T, whereas after they were registered between F–M, F–T and F–V. All these values were significantly lower than the controls. For (b), significantly lower film thickness was recorded after preheating (−16.1–−33.3%, highest in V), with a ranking of F, M > V > T (before) and F, M > T, V (after). All values were significantly higher than the control. For (c), increased exposure improved DC% in the greater spacer group, with the controls providing superior values. It can be concluded that the use of modern highly filled composites as luting agents for low translucency onlays may result in suboptimal polymerization and film thickness, warranting caution.

The aim of the study was to evaluate changes in the degree of C=C conversion (DC%), chemical structure, optical properties and roughness of one-shade composites before/after photoaging. Τhe one-shade materials tested were Charisma Topaz One (CHT), Clearfil Majesty ES-2 Universal (MES), Essentia Universal (ESU) and Omnichroma (OMN), with G-aenial Anterior (CNA) serving as control. Specimens (2 mm thickness) were prepared and tested for DC% and chemical structure (ATR–FTIR spectroscopy), optical properties (L*a*b*–ΔΕ, translucency parameter–TP, opalescence parameter–OP, contrast ratio–CR and total transmittance–TT by UV–Vis spectroscopy) and roughness (Sa, Sz, Sdr, Sds and Sc by optical profilometry) before and after photoaging (Xe-arc weatherometer). Significant differences were found in DC% between top–bottom surfaces (ESU, OMN before; ESU, CNA after). Photoaging improved DC%, reduced ester peaks implying photodegradation, reduced L* (CHT, OMN, CNA), a* (CHT, CNA), b* (OMN, CNA), TP (all, except for MES), OP (only MES), CR (only MES, but an increase in CNA) and TT (CHT, OMN). OMN, CNA and MES demonstrated ΔΕ > 3.3. Photoaging significantly increased all roughness parameters in all materials, except for MES (Sz, Sdr, Sc) and OMN (Sdr). Although listed in the same group, significant differences were found in one-shade composites before and after photoaging. Several products were strongly affected by photoaging, demonstrating evidence of photodegradation, an increased roughness and color changes exceeding the clinically acceptable levels.

Advancements in Computer Aided Design/Computer Aided Manufacturing (CAD/CAM), promoted the development of novel dental materials for several types of definitive restorations. The aim of this study was to evaluate the surface characteristics of resin-based CAD/CAM restorative materials, fabricated using both subtractive and additive manufacturing techniques. The materials tested included Filtek Z550 (FZ), Vita Enamic (VE), Shofu HC (SH), and VarseoSmile TriniQ (TQ). For each material, 24 specimens were prepared; half were manually polished following manufacturer’s recommendations, while the other half underwent standardized metallographic polishing. Surface roughness, wettability, and molecular composition were assessed. Statistical analysis was performed using IBM SPSS 29.0 at a 95% confidence level (α = 0.05). Statis-tically significant differences in surface properties were observed between direct and indirect restoratives following manual polishing, with SH performing favorably in terms of surface roughness. The polishing method significantly influenced surface characteristics within each material, except for certain roughness parameters in SH. Both surface roughness and wettability were dependent on the material and the polishing technique, highlighting the need for improved material-specific polishing protocols.material-specific polishing protocols.