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The present study aimed to determine the influence of adhesive luting on the fatigue mechanical properties of simplified lithium disilicate crowns luted to dentin analogues preparations, and to compare two different approaches of simulation of a non-adhesive luting procedure. To this end, 30 prosthetic preparations of glass fiber-filled epoxy resin used as dentin analogues were milled and lithium disilicate crowns were pressed (1.5 mm thickness), which were allocated into three different groups: resin cement (RC), resin cement isolated by paraffin oil (RCI) and zinc phosphate cement (ZP). For luting procedures, the ceramic crowns of the RC and RCI groups had their internal surface treated with 5% hydrofluoric acid and universal primer. Afterwards, a thin layer of paraffin oil was applied onto the ceramic crown intaglio surface in the RCI group. The dentin analogues were treated with 10% hydrofluoric acid, followed by primer application and luting as recommended by the manufacturer. No previous surface treatments were performed for the ZP group, and the cement was applied as recommended. The fatigue test was run under cyclic fatigue (load 400–2000 N, step-size 100 N, 15,000 cycles/step, frequency 20 Hz) until failure detection (radial crack) by transillumination. The fatigue failure load (FFL), number of cycles until failure (CFF), and survival rate in each testing step were recorded. The RC group presented a higher FFL, CFF and survival rate compared to the other groups (p < 0.001), which were statistically equal to each other (p > 0.05). Weibull analysis detected no difference between groups for the Weibull module. Therefore, loss of adhesion between the evaluated substrates induces a significant reduction in load-bearing capacity under fatigue of the lithium disilicate crowns, strengthening the strong-importance of long-lasting adhesion for crown's survival. In addition, different methods for the simulation of non-adhesive conditions induce the same performance in the explored outcomes, confirming that both are valid approaches for laboratory studies.

Objectives: To evaluate the effect of in-lab simulation of CAD/CAM grinding and intaglio surface treatments on the surface characteristics (topography and roughness) and fatigue behavior of adhesively luted 4YSZ simplified restorations. Methods: Ceramic discs (Ø = 10 mm, thickness = 1 mm) were randomly allocated into 6 groups considering: “In-lab simulation of CAD/CAM grinding” (ground or polished) and “intaglio surface treatments”: Ctrl (without surface treatment), AlOx (aluminum oxide air abrasion) or GLZ (glaze spray application). The surface roughness of all samples was measured, the treated discs received a ceramic primer, were luted with resin cement onto a dentin analogue material (woven glass-reinforced epoxy resin) and tested under a cyclic fatigue test (step-stress approach, n = 15; 1.4 Hz, 10,000 cycles/step, step-size of 100N starting at 200N until failure). A complementary analysis was performed to corroborate the findings in the fatigue test that the glaze fill defects increase the mechanical properties of the ceramic. To do so, bars (n= 10; 1.0 × 1.0 × 12 mm; considering the groups: N-ID: non-indented; ID: indented; ID-GLZ: indented plus glaze spray application) were indented in a vickers hardness tester to produce a crack pattern, treated with glaze or not, and then submitted to flexural strength tests (FS). Fractographic and topographic analysis were performed. Results: In-lab simulation of CAD/CAM grinding decreased the fatigue failure load of the 4YSZ ceramic when comparing polished and ground groups, regardless of surface treatment. GLZ induced better fatigue performance compared to the air abrasion, regardless of the grinding condition (ground or polished surface). The results of the flexural strength test corroborated the findings in the fatigue test, as the ID-GLZ group presented superior FS than the ID group, however both had inferior FS than N-ID. There is an inverse association between roughness and fatigue failure load, as the higher the surface roughness, the lower the fatigue failure load. Failures in the fatigue and flexural strength tests started from the face subjected to tensile stresses. Conclusion: In-lab simulation of CAD/CAM grinding had a detrimental effect on the fatigue behavior of 4YSZ and glaze spray induced better 4YSZ performance compared to the air abrasion. The intaglio surface treatments differently influenced the 4YSZ fatigue performance, however, only glaze spray can reverse the damage caused by the grinding.

This study aimed to investigate the effect of surface roughness (polished vs. CAD/CAM milling simulation) on impact strength of five dental ceramics for manufacturing CAD/CAM monolithic restorations. Specimens of five ceramics (FC- feldspathic glass-ceramic; PICN- polymer-infiltrated ceramic-network; ZLS- zirconia-reinforced lithium silicate glass-ceramic; LD- lithium disilicate glass-ceramic; YZ- yttria-stabilized tetragonal zirconia polycrystal ceramic) to be tested under impact (15×10×2mm3; n= 15) were divided into two groups, according to surface treatment: polishing (pol) and grinding (gri) as CAD/CAM milling simulation. Impact strength was tested using the Dynstat method. Roughness, topographic, fractographic and finite element analyses were performed. The impact strength data were analyzed by Weibull, and Pearson correlation was used to correlate roughness and impact strength data. The CAD/CAM milling simulation led to significantly (p

Objective: To evaluate the fatigue behavior of lithium disilicate crowns with a simplified anatomy against progressive cement/ceramic debonding scenarios. Materials and methods: Lithium disilicate crowns were fabricated via CAD/CAM and luted onto a dentin analogue material using resin cement following the manufacturer's instructions. Then, the different crown regions were isolated with paraffin oil for the absence of chemical adhesion according to four experimental groups (n = 15): Shoulder; Shoulder + Axial; Fully isolated; and Control (no insulation/fully bonded). Load to failure tests (n = 3) were run to determine cyclic fatigue parameters, and the specimens were subsequently submitted to a cyclic fatigue test (n = 12) (initial load 200 N for 5000 cycles, step 100 N, 15,000 cycles/step, frequency 20 Hz) until cracks were observed, and later fracture. The data were analyzed by Kaplan-Meier + Mantel-Cox post-hoc tests for both outcomes (cracks and fracture). Fractographic, cross-sectional surface, and finite element (FEA) analyzes were performed. Results: When it comes to crack occurrence when the chemical adhesion to the occlusal surface is compromised, there is worsening (p < 0.05) in fatigue behavior compared to groups where the occlusal portion of the crown is still bonded. Considering fracture occurrence, there was no difference (p > 0.05) among the tested groups. All cracks occurred in the occlusal portion, first as a radial crack at the ceramic intaglio surface, and posteriorly unleashing a Hertzian cone crack at the top surface, resulting in fractures on the frontal walls. The interface analysis showed no interference of the insulating agent. FEA showed that as the isolated areas increased, there was also an increase in both tensile and shear stresses concentration in the crown and in the cement layer. Conclusion: The chemical adhesion between cement and ceramic is essential for better fatigue behavior of lithium disilicate crowns with a simplified anatomy, especially in the occlusal portion, but the restoration performance is impaired when such adhesion is compromised. There is an increase in crown and cement stress concentration with the progressive loss of chemical bonding of the crown's walls.

The aim of the study was to evaluate whether the region (internal or external) of the CAD/CAM block influences the mechanical performance of restorative materials. Blocks of different CAD/CAM materials (Composites: KAV – Katana Avencia; LULT – LULT Ultimate; Ceramics: ENAM – Vita Enamic; NICE - N!CE; EMP – IPS Empress CAD; VMII – Vita Mark II; EMAX – IPS e.max CAD) were selected, and direct resin composite blocks (APX - Clearfil AP-X; FSUP - Filtek Supreme) were built using the incremental technique on a mold from one of the CAD/CAM blocks. All blocks were sectioned into bar-shaped specimens (1 × 1 × 14 mm), which were separated into two groups according to the region of the block (inside or outside). 3-point bending tests were performed following ISO 6872:2015 and flexural strength data were analyzed using one-way ANOVA and Bonferroni post-hoc tests (p < 0.05). Weibull module and characteristic strength were also calculated. In general, the mean flexural strength values were not statistically different (p > 0.05) between the inside and outside regions of each material, except for LULT (inside > outside) and EMAX (outside > inside). Comparing the materials, a similar strength (only discrete variations) was observed for inside, outside or merged (inside and outside data assembled together) regions: EMAX > KAV = LULT > NICE = APX > EMP = ENAM = VMII ≥ FSUP (merged condition). Characteristic strength at 63.2% failure probability and at 5% failure probability generally corroborates such observations. There were no statistical differences for Weibull module data (inside, outside, or merged), except for KAV and NICE (outside > inside). Thus, the region from where the restoration is milled within the CAD/CAM block generally does not influence the mechanical performance hereof (flexural strength, failure probability, risk of premature failures, and mechanical reliability) of the material, except for LULT and EMAX.

This study compared the flexural strength under monotonic (static - sσ) and cyclic load application (fatigue - fσ), hardness (H) and fracture toughness (KIC) of different layers of a multi-layered zirconia (IPS e.max ZirCAD MT Multi, Ivoclar). Each layer was sectioned, classified into three groups according to yttria content (4-YSZ, 4/5-YSZ and 5-YSZ), and shaped on samples for flexural strength and fracture toughness tests (bars: 1.0 × 1.0 × 11 mm); and Vickers hardness test (plates: 1.5 × 4.0 × 5.0 mm). Flexural strength under monotonic load application (sσ; n = 10) was obtained through two different devices (three-point-bending and ball-in-hole device) and fatigue flexural strength (fσ; n = 15; initial load: 10 N; step-size: 5 N; 10,000 cycles/step) was assessed using a ball-in-hole device under cyclic load application. Vickers hardness test (n = 5), fracture toughness test (n = 10), and additional analyzes (Finite Element Analysis - FEA, Energy-dispersive X-ray spectroscopy - EDS and Scanning Electron Microscopy - SEM) were also performed. No differences were found between the different devices in the monotonic flexural strength test, and FEA showed similar tensile stress distribution for the two devices. 4-YSZ showed higher values of flexural strength under monotonic and cyclic load application modes (sσ = 1114.73 MPa; fσ = 798.84 MPa), and fracture toughness (KIC = 3.90 MPa√m). 4/5-YSZ had an intermediate sσ; however, fσ was similar to 5-YSZ (404.00–429.36 MPa) and KIC similar to 4-YSZ (KIC = 3.66 MPa√m). No statistical differences were found for hardness and Weibull modulus for fatigue flexural strength data. The amount of yttria in the layer compositions increased from 4-YSZ to 5-YSZ, and larger zirconia crystals were observed in the topographic images of 5-YSZ. Failures in the flexural strength and toughness tests started from the face subjected to tensile stress. Different layers of the multi-layered zirconia blank presented distinct mechanical properties. 4-YSZ (cervical layer) presented the highest flexural strength under monotonic and cyclic loads (fatigue), and higher fracture toughness even similar to the transition layer (4/5-YSZ). Hardness was similar between the layers. The ball-in-hole device performed similarly to the three-point bending device and can be used as an alternative to the traditional method.

Objective: To characterize the effect of pigmentation techniques on the fatigue behavior of a 4YSZ ceramic adhesively luted onto dentin analog (glass fiber-reinforced epoxy resin). Methods: 4YSZ ceramic discs (Ø= 10 mm, 1 mm thickness) were allocated into 5 groups: Ctrl – unshaded (IPS e.max ZirCAD MT BL); Manuf – shaded by the manufacturer (IPS e.max ZirCAD MT A2); Brush – unshaded pigmented, pre-sintering, using a brush; Stain – unshaded pigmented, post-sintering, during glaze application; Brush+Stain – combination of both techniques. Color assessments ensured the same perceived color (Vita Classical A2). Dentin analog discs (Ø= 10 mm, 2.5 mm thickness) were obtained, paired with the 4YSZ discs, and adhesively luted using a resin cement. Cyclic fatigue testing (n = 15) was run (20 Hz; 10,000 cycles/step, initial load 200 N; step-size 100 N up to 700 N; then 50 N until specimen failure). Fractographic, roughness and topography analyses were performed. Results: No statistical (p > 0.05) detrimental influence were observed for fatigue outcomes (Ctrl = Manuf = Brush = Stain = Brush+Stain). However, the Brush+Stain technique induced inferior statistical (p < 0.05) fatigue performance compared to Stain. All failures were radial cracks with origin at the ceramic intaglio surface. The staining technique triggered statistically higher roughness (p < 0.05). Uniformly sized zirconia crystals were seen in the Ctrl, Manuf and Brush groups, and a smooth vitreous surface with encrusted pigments in the Stain and Brush+Stain groups. Significance: Pigmentation techniques (Vita Classical A2 shade) have no detrimental effect on the mechanical fatigue properties of 4YSZ ceramic adhesively luted onto dentin analog.

This study aimed to evaluate the influence of ceramic surface treatments, resin cement viscosities, and storage regimens on the fatigue performance of bonded glass-ceramics (lithium disilicate, LD; feldspathic, FEL). Ceramic discs (Ø = 10 mm; thickness = 1.5 mm) were allocated into eight groups per ceramic (n = 15), considering three factors: “ceramic surface treatment” in two levels – 5% hydrofluoric acid etching and silane-based coupling agent application (HF), or self-etching ceramic primer (E&P); “resin cement viscosity” in two levels – in high or low viscosity; and “storage regimen” in two levels – baseline, 24 h to 5 days; or aging, 180 days + 25,000 thermal cycles. Adhesive luting was performed onto glass fiber-reinforced epoxy resin discs (Ø = 10 mm; thickness = 2 mm) and the bonded assemblies were subjected to cyclic fatigue tests: initial load = 200 N; step-size = 25 N (FEL) and 50 N (LD); 10,000 cycles/step; 20 Hz. Scanning electron microscopy (SEM) inspections were performed. Regarding the LD ceramic, the fatigue behavior was reduced after aging for HF_HIGH and E&P_LOW conditions, while stable performance was observed for HF_LOW and E&P_HIGH. Regarding the FEL results, aging negatively affected HF_HIGH, E&P_HIGH, and E&P_LOW, being that only the HF_LOW condition presented a stable behavior. The failure initiated from defects on the etched surface of the ceramics, where the cross-sectional analysis commonly revealed unfilled areas. Long-term aging might induce a decrease in mechanical behavior. The ‘ceramic microstructure/surface conditioning/resin cement viscosity relationships’ modulate the fatigue performance of lithium disilicate and feldspathic glass-ceramics.

Made available in DSpace on 2022-04-29T08:41:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-07-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The present study aimed to investigate the bond strength between resin cement and different glass-ceramics manufactured in different processing systems using two different microtensile bond strength test (μTBs) assemblies (ceramic-ceramic or ceramic-dentin). For this, ceramic blocks were fabricated with adhesive surface area of 5 × 5 mm to test the different possibilities combining the two different glass-ceramic compositions (feldspathic – FEL and lithium disilicate - LD), the three manufacturing-processes (CAD/CAM, heat-pressed or layered for FEL; CAD/CAM or heat-pressed for LD) and the two μTBS assemblies (ceramic-ceramic or ceramic-dentin). Half of the samples of each ceramic evaluated were made by cementing the ceramic blocks in another ceramic block and the other half by cementing the ceramic blocks in ground molars with exposed dentin, using resin cement (Rely X ARC, 3 M ESPE). The samples were stored for 24 h in distilled water at 37 °C and then sectioned into microbars (±1 mm2, n = 30). These specimens were submitted to the μTBS and the data were analyzed by specific statistical tests (α = 0.05). The fractured surfaces were examined under a stereomicroscope and the failure mode was classified. In addition, finite element analysis (FEA) was performed to observe the maximum tensile stress in the resin cement when a μTBS load was applied (10 N) and during the resin cement polymerization shrinkage. The CAD/CAM glass-ceramics have better bond strength than the other evaluated manufacturing processes, the LD groups had higher μTBS values than the FEL groups in ceramic-ceramic assembly; dentin as a substrate (ceramic-dentin assembly) had a negative influence on the results for all evaluated materials. Regarding the FEA results, the maximum tensile stress in ceramic-ceramic groups was 16.1–16.5 MPa (when 10 N load was simulated), and 50.8–51.2 MPa (during the resin cement polymerization shrinkage). For the ceramic-dentin groups, the maximum tensile stress was 16.9 and 17.1 MPa on the ceramic side and 17.6 and 17.8 MPa on the dentin side (10 N load simulation); 49.8 and 49.4 MPa on the ceramic side and 49.7 and 49.4 MPa on the dentin side (resin cement polymerization shrinkage). Different glass-ceramic compositions and manufacturing processes induced distinct bond strength values (LD had better results). Moreover, the μTBS assembly interferes with the results obtained, having the ceramic-ceramic set-up inducing higher bond results than the ceramic-dentin arrangement. Department of Dental Materials and Prosthodontics São Paulo State University, São José Dos Campos Faculty of Odontology Federal University of Santa Maria, Rio Grande do Sul Department of Dental Materials Science Academic Centre for Dentistry Amsterdam (ACTA) Universiteit van Amsterdam and Vrije Universiteit Department of Dental Materials and Prosthodontics São Paulo State University, São José Dos Campos CAPES: 001 FAPESP: 2010/07237-8