Long-term effects of simulated gastric juice alternated with brushing on hardness, substance loss, flexural strength and reliability of CAD-CAM monolithic materials.

OBJECTIVES: The purpose of this study is to evaluate, over a simulated 5-year period, the effect of simulated gastric juice alternated with brushing on CAD-CAM monolithic materials considering microhardness, substance loss, flexural strength, and reliability of the materials. METHODOLOGY: Blocks from Lava Ultimate (LU), Vita Enamic (VE), IPS Empress CAD (EMP), IPS e.max CAD (EMAX), and Vita Suprinity (VS) were milled into cylinders and sliced into disks. The EMAX and VS were crystallized, and all specimens were polished with silicon carbide papers and allocated as follows: 1) artificial saliva + brushing or 2) simulated gastric juice (0.113% hydrochloric acid (HCl) solution in deionized water, pH 1.2) + brushing, simulating 1, 3, and 5 years of clinical function. Each year of clinical function was simulated by three repetitions of immersion for 3 hours in artificial saliva or simulated gastric juice followed by 1,217 brushing cycles. The microhardness and substance loss were evaluated at baseline (T0) and at each year by using a Vickers hardness tester and an analytical balance. The biaxial flexural strength (BFS) test was performed in a mechanical testing machine at the end of the 5th year. Weibull modulus was calculated from the BFS data. RESULTS: The microhardness of the LU was not influenced by the treatment, whereas that of the other materials, in certain years, was significantly lower in the gastric juice + brushing groups in comparison with artificial saliva + brushing groups. In general, the materials did not present a significant change in microhardness over time, for either of the treatments. The LU alone showed greater substance loss in the gastric juice + brushing groups for every year. In both treatments, the LU, VE, and EMP exhibited a significant increase in the substance loss over time. The treatment did not affect the BFS of the materials. The gastric juice + brushing decreased the reliability of the VE. CONCLUSIONS: All materials were somehow impaired by the gastric juice + brushing in at least one of the evaluated parameters, except for the BFS. However, in a deeper analysis, the LU would be the least indicated materials, followed by VE, for patients with eating disorders.

Long-term effect of gastric juice alternating with brushing on the surface roughness, topography, and staining susceptibility of CAD-CAM monolithic materials.

STATEMENT OF PROBLEM: Studies on the behavior of computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials subjected to gastric juice alternating with brushing-as occurs in patients with bulimia nervosa-are lacking. PURPOSE: The purpose of this in vitro study was to evaluate, over a simulated 5-year period, the effect of gastric juice alternating with brushing on the roughness, topography, and staining susceptibility of CAD-CAM monolithic materials. MATERIAL AND METHODS: Disks of Lava Ultimate (LU), Vita Enamic (VE), IPS Empress CAD (EMP), IPS e.max CAD (EMAX), and Vita Suprinity (VS) were randomly allocated to artificial saliva+brushing or gastric juice+brushing groups, simulating 1, 3, and 5 years of clinical function. The roughness (Sa) and topography were evaluated at baseline (T0) and at each simulated year. For the staining susceptibility (ΔE00), the CIELab color coordinates were registered at baseline, and, at the end of the fifth simulated year, the specimens were immersed in deionized water, coffee, or cola before the second reading. Roughness data were submitted to mixed repeated-measures ANOVA and Bonferroni, and the staining susceptibility data were analyzed by 3-way ANOVA and the Games-Howell test (α=.05). RESULTS: The gastric juice+brushing led to higher roughness than artificial saliva+brushing only in the VE at T3 and T5 (P<.01). In both treatments, the LU and VE showed topography changes and an increase in roughness over time (P<.001), in addition to higher roughness than the other materials (P<.001). The staining susceptibility of the materials to each staining solution was not affected by the treatment (P>.05). The LU and VS groups were more stained by coffee (P<.001), while the VE and EMP groups were more stained by cola (P≤.016), except for the EMP in the gastric juice+brushing, where no significant difference was found between cola and coffee (P>.05). The EMAX was imperceptibly affected by the 3 solutions. CONCLUSIONS: Concerning roughness and topography, the LU and VE were the most affected by both treatments. The staining susceptibility of the materials was not affected by the treatment.

Long-term effects of simulated gastric juice alternated with brushing on hardness, substance loss, flexural strength and reliability of CAD-CAM monolithic materials

Abstract Objectives: The purpose of this study is to evaluate, over a simulated 5-year period, the effect of simulated gastric juice alternated with brushing on CAD-CAM monolithic materials considering microhardness, substance loss, flexural strength, and reliability of the materials. Methodology: Blocks from Lava Ultimate (LU), Vita Enamic (VE), IPS Empress CAD (EMP), IPS e.max CAD (EMAX), and Vita Suprinity (VS) were milled into cylinders and sliced into disks. The EMAX and VS were crystallized, and all specimens were polished with silicon carbide papers and allocated as follows: 1) artificial saliva + brushing or 2) simulated gastric juice (0.113% hydrochloric acid (HCl) solution in deionized water, pH 1.2) + brushing, simulating 1, 3, and 5 years of clinical function. Each year of clinical function was simulated by three repetitions of immersion for 3 hours in artificial saliva or simulated gastric juice followed by 1,217 brushing cycles. The microhardness and substance loss were evaluated at baseline (T0) and at each year by using a Vickers hardness tester and an analytical balance. The biaxial flexural strength (BFS) test was performed in a mechanical testing machine at the end of the 5th year. Weibull modulus was calculated from the BFS data. Results: The microhardness of the LU was not influenced by the treatment, whereas that of the other materials, in certain years, was significantly lower in the gastric juice + brushing groups in comparison with artificial saliva + brushing groups. In general, the materials did not present a significant change in microhardness over time, for either of the treatments. The LU alone showed greater substance loss in the gastric juice + brushing groups for every year. In both treatments, the LU, VE, and EMP exhibited a significant increase in the substance loss over time. The treatment did not affect the BFS of the materials. The gastric juice + brushing decreased the reliability of the VE. Conclusions: All materials were somehow impaired by the gastric juice + brushing in at least one of the evaluated parameters, except for the BFS. However, in a deeper analysis, the LU would be the least indicated materials, followed by VE, for patients with eating disorders.

Does airborne-particle abrasion before, rather than after, zirconia sintering lead to higher mechanical strength even under aging challenge?

STATEMENT OF PROBLEM: Information concerning the effect of airborne-particle abrasion before zirconia sintering on its strength after aging is lacking. PURPOSE: The purpose of this in vitro study was to determine the influence of airborne-particle abrasion moment (before or after zirconia sintering), particle size, and aging on the mechanical strength of a yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic. MATERIAL AND METHODS: Four hundred presintered zirconia disks were allocated to nonabraded (control) and abraded groups with 50 µm or 120 µm Al2O3 particles before (50/BS or 120/BS) or after sintering (50/AS or 120/AS). The disks were aged by storing them in distilled water for 24 hours at 37 °C (24 h) (control); mechanical cycling (MC) (1×106 cycles; 2 Hz; 100 N); hydrothermal aging (HA) (134 °C; 0.2 MPa; 20 hours); or by both methods (MC+HA), totaling 20 groups (n=20). The specimens were subjected to biaxial flexural strength (BFS) testing. Fractographic analysis was performed to identify the fracture origin. Tetragonal to monoclinic transformation was determined by X-ray diffraction. The BFS data (MPa) were analyzed by 2-way ANOVA and the Games-Howell post hoc test (α=.05). Weibull statistics was also applied. RESULTS: The BFS and characteristic strength (σ0) of the 120/AS groups were significantly higher compared with the other abraded groups and statistically similar or higher compared with the respective nonabraded groups. In contrast, the 120/BS/24 h and all the 50/BS groups presented the lowest values. In all groups, the initial defect had its origin on the tensile stress side. Neither airborne-particle abrasion nor aging (except for the 50/AS/MC+HA) reduced the zirconia reliability compared with the respective controls. Abrading the zirconia in its presintered stage or after sintering increased the monoclinic phase content, and the sintering process eliminated this phase. CONCLUSIONS: Airborne-particle abrasion before zirconia sintering yields an inferior performance compared with that after sintering under aging challenges. The BFS and σ0 were strongly determined by the particle size and airborne-particle abrasion moment, while aging mainly acted in the nonabraded zirconia or when this material was abraded before sintering.

Effect of grinding and polishing on the roughness and fracture resistance of cemented CAD-CAM monolithic materials submitted to mechanical aging.

STATEMENT OF PROBLEM: The effect of clinical adjustments on the strength of cemented computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials under aging challenge is unclear. PURPOSE: The purpose of this in vitro study was to assess the surface roughness and fracture resistance (with or without mechanical aging) of cemented CAD-CAM monolithic materials submitted to grinding and polishing procedures. MATERIAL AND METHODS: Disks of Lava Ultimate, Vita Enamic, crystallized Vita Suprinity, and IPS e.max CAD were analyzed for roughness after polishing by using silicon carbide papers (Lava Ultimate and Vita Enamic) or glazing (IPS e.max CAD and Vita Suprinity) (control), after grinding by using 30-µm grit diamond rotary instruments, and after grinding and polishing by using a polishing kit. For fracture resistance, a simplified trilayer model consisting of a restorative disk, an epoxy resin disk, and a steel ring was used. The bonded trilayer disks received the same treatments described for the roughness analysis. Half of the specimens underwent mechanical aging for 1×106 cycles. All specimens were loaded until failure. The Weibull modulus was calculated. RESULTS: The IPS e.max CAD and Vita Suprinity showed the highest roughness after grinding and the lowest at baseline. For the Lava Ultimate and Vita Enamic, polishing provided lower roughness than at baseline. Grinding, followed or not by polishing, and mechanical aging did not adversely affect the fracture resistance or the reliability of the materials. CONCLUSIONS: Polishing did not recover the initial surface roughness of the glass-ceramic materials. Fracture resistance was not affected by grinding, followed or not by polishing, even after mechanical aging.

Fatigue resistance of monolithic lithium disilicate occlusal veneers: a pilot study.

The use of thin lithium disilicate (LD) occlusal veneers is an effective method to increase the vertical dimension of occlusion in cases of tooth wear. However, doubt remains regarding the threshold thickness to be used in this restoration class. This study aims to evaluate the effect of ceramic thickness on the survival rate and failure pattern of LD molar veneer restorations using a simplified fatigue testing machine. Sixty sound, freshly extracted human molars were used. Three groups (n = 20) were randomly created with different ceramic thicknesses (0.5, 0.8, and 1.2 mm), and 60 LD IPS e.max Press LT occlusal veneers were fabricated. The ceramic restorations were luted with a resin cement. The stainless-steel rotating drum of the ball mill contained 10 zirconia (Y-TZP) and 10 stainless steel spheres, in 500 mL of distilled water at 37 ± 1 °C. Crack growth in the LD restorations was evaluated under a stereomicroscope following each fatigue testing run (12 60-min runs). Progressive damage was observed as a function of cycling time. Survival was significantly influenced by the restoration thickness (p = 0.002, log-rank test), with thicker restorations exhibiting a higher survival rate. Thinner restorations (0.5 mm) showed significantly lower survival rate than 0.8- and 1.2-mm restorations (p < 0.016); no significant difference was observed between the 0.8- and 1.2-mm restorations. A threshold value of 0.8 mm may represent an acceptable compromise between fatigue resistance and tooth reduction.

Influence of Particle and Air-Abrasion Moment on Y-TZP Surface Characterization and Bond Strength.

PURPOSE: To evaluate the influence of particle and air-abrasion on the surface characterization and shear bond strength (SBS) of a Y-TZP ceramic with a resin cement. MATERIALS AND METHODS: Y-TZP specimens were air-abraded with 50 µm alumina particles; 120 µm alumina particles; 30 µm silica-coated alumina particles (Rocatec Soft); 110 µm silica-coated alumina particles (Rocatec Plus). Air-abrasion was performed before (BS); after (AS); before and after (BAS) zirconia sintering. Surface characterization included roughness (n = 10), wettability (n = 10), morphology (n = 2), and elemental composition (n = 2). For SBS (n = 11), composite resin discs were bonded to the air-abraded and silane-treated zirconia surface, with the resin cement RelyX ARC. Failure mode was determined. Roughness, wettability, and SBS data were analyzed by two-way ANOVA with pairwise interaction and Tukey's test (α = 0.05). RESULTS: Air-abrasion performed with coarser particles at BS and BAS moments provided the highest roughness values, while the lowest roughness values were observed with particles combined with AS moment (p < 0.01). Rocatec Plus provided lower contact angle than the 120 µm alumina particles (p = 0.013), and BAS exhibited lower contact angle than BS (p = 0.002). The combinations 120 µm/BS and the silica-coated alumina particles/AS and /BAS showed the highest SBS (p < 0.05). The combination of each particle/BAS was statistically similar to the same particle/AS. Failure mode was 100% adhesive for all groups. The interaction particle size/air-abrasion moment determined the morphological pattern. Silicon was observed only in the Rocatec groups. CONCLUSIONS: Roughness was influenced by the particle size and was higher when the zirconia was air-abraded in its green stage. The particle composition played an important role in the wettability and both studied air-abrasion moments provided similar wettability than the one in which air-abrasion is usually performed. The highest SBS values were observed in the three moments, by using certain particles for each moment.

Marginal Fit of Metal-Ceramic Copings: Effect of Luting Cements and Tooth Preparation Design.

PURPOSE: To evaluate the effect of the triad finish line design, axial wall convergence angle, and luting cement on the marginal fit of metal copings used in metal-ceramic crowns. MATERIALS AND METHODS: Schematic dies and their respective copings were cast in NiCr alloy. The dies exhibited the following finish line/convergence angle combinations: sloping shoulder/6°, sloping shoulder/20°, shoulder/6°, shoulder/20°. Marginal fit was evaluated under a stereomicroscope, before and after cementation. Copings were air-abraded with 50 µm Al2 O3 particles and cemented with Cimento de Zinco, RelyX U100, or Panavia F cements (n = 10/group). Data were square-root transformed and analyzed by 3-way factorial random effect model and Tukey's post hoc test (α = 0.05). RESULTS: Statistical analysis showed significance for the interactions finish line and convergence angle (p < 0.05), convergence angle and time (p < 0.001), and luting cement and time (p < 0.001). Sloping shoulder/20° provided the highest marginal discrepancy when compared to the other finish line/convergence angle combinations, which were statistically similar among each other. For both convergence angles and for all luting cements, the marginal discrepancy was significantly higher after cementation. Before and after cementation, 6° provided better marginal fit than 20°. After cementation, Panavia F provided higher marginal discrepancy than Cimento de Zinco. CONCLUSION: Lower convergence angle combined with shoulder and a low-consistency luting cement is preferable to cement metal copings.

Effect of zirconia substructure thickness on the mechanical properties and adhesion of veneering porcelain

Aim: This study investigated the influence of yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP) thickness on fracture load of porcelain-veneered crowns (FL), fracture toughness of porcelain (FT), and the shear bond strength zirconia/porcelain (SBS). Methods: Artificial first molar was prepared for full crown (N=45) with different occlusal reduction. Y-TZP cores were made with different thickness at the occlusal face (1mm, 2mm and 3mm) (n=15). The cores were veneered with VM9 ­ Vita porcelain with 1.0 mm layer. For FL testing, axial load was applied to the mesiolingual cusp of the crowns. For FT testing, flat Y-TZP plates (5X5 mm) with 1, 2 or 3 mm thickness were veneered with 1.0 mm porcelain layer (n=10). FT by indentation fracture technique was measured close to the interface and at the top surface. For SBS by knife-edge shearing rod, cylindrical porcelain with 5 mm in diameter and 3 mm was applied on flat Y-TZP plates (1, 2 and 3 mm thickness) (n = 10). Results: Data analyzed by 1-Way ANOVA for FL of crowns and SBS between Y-TZP and porcelain were not significant. Two-way ANOVA for FT was significant for zirconia thickness and measurement area. The post-hoc test showed higher values for the groups with 2 and 3mm, and higher values at the interface, irrespectively of Y-TZP thickness. Conclusion: The zirconia thickness did not affect the FL of veneered crowns and the SBS between the ceramics, but FT of porcelain was lower in thinner zirconia substructure and close to the interface Y-TZP/Porcelain

Wear resistance and abrasiveness of CAD-CAM monolithic materials.

STATEMENT OF PROBLEM: Computer-aided design and computer-aided manufacturing (CAD-CAM) restorations are in contact with the antagonist tooth, either a natural tooth or a restoration. Therefore, clinicians should be aware of the wear resistance of CAD-CAM materials and the wear behavior of the antagonist. PURPOSE: The purpose of this in vitro study was to evaluate the wear resistance and abrasiveness of CAD-CAM materials. MATERIAL AND METHODS: In a 2-body wear test, the materials IPS e.max CAD (Ivoclar Vivadent AG), Vita Suprinity (Vita Zahnfabrik), Lava Ultimate (3M ESPE), Vita Enamic (Vita Zahnfabrik), and Lava Plus (3M ESPE) acted as abraders and, together with bovine enamel, also as antagonists. Each antagonist wheel ran against each abrader wheel for 200000 cycles, with a spring force of 15 N, and at a rotational speed of 1 Hz in distilled water. The wear rate was determined with a surface profilometer. The surfaces were observed with scanning electron microscopy, and their hardness, coefficient of friction, and roughness were evaluated. RESULTS: Lava Plus and IPS e.max CAD exhibited the highest potential for wear of Lava Ultimate. These 2 materials, together with Vita Suprinity, provided the highest wear of enamel and Vita Enamic. Vita Suprinity and IPS e.max CAD had higher wear than Lava Plus, and the inverse was also true. Vita Enamic and Lava Ultimate were among the materials that caused the lowest wear of enamel and all other evaluated materials. Scanning electron microscopy images revealed that except for Lava Ultimate, all other materials damaged enamel, in which Vita Suprinity and IPS e.max CAD were more aggressive when sliding against the materials. Lava Plus had the greatest hardness, followed by Vita Suprinity and IPS e.max CAD, Vita Enamic, and then Lava Ultimate. The coefficient of friction varied from 0.42 to 0.53. The Vita Enamic and Lava Ultimate showed the highest surface roughness. CONCLUSIONS: The nanofilled composite resin and polymer-infiltrated ceramic were more antagonist-friendly (whether enamel or CAD-CAM material) than glass-ceramics and zirconia. Care should be taken when selecting the material that will contact mainly with glass-ceramics. Hardness should also be considered when selecting a material.

Effect of surface treatments on repair with composite resin of a partially monoclinic phase transformed yttrium-stabilized tetragonal zirconia.

STATEMENT OF PROBLEM: Studies of composite resin repairs of yttrium-tetragonal zirconia polycrystal (Y-TZP) are usually performed in its tetragonal phase, but it may be partially transformed into a monoclinic phase in a clinical fracture. PURPOSE: The purpose of this in vitro study was to evaluate the effect of airborne-particle abrasion (APA) and a bonding agent on the shear bond strength (SBS) between a composite resin and hydrothermally aged Y-TZP. MATERIAL AND METHODS: Specimens (7.0×7.0×1.7 mm, N=112) of Y-TZP Lava were obtained, and 50% were aged in an autoclave at 134°C at 300 kPa for 8 hours. The surfaces were treated with APA 50-µm Al2O3 particles (ALU) or Rocatec Soft (30 µm) (ROC) followed by Clearfil SE Bond Primer (10-methacryloyloxydecyl dihydrogen phosphate [10-MDP]) plus Clearfil porcelain bond activator (3-methacryloxypropyl-trimethoxy silane [3-MPS]) (CLE) or RelyX Ceramic Primer plus a layer of RelyX U100 adhesive-resin cement (REL). Composite resin cylinders were built on the Y-TZP treated surfaces. After thermocycling (6000 cycles, 5°C and 55°C, 30-second dwell time), an SBS test was carried out (n=14). Data were analyzed by 3-way ANOVA and the Tukey honest significant differences test (α=.05). The failure mode was analyzed. RESULTS: The 3-way ANOVA was not significant for aging (P>.05), but the APA (P<.001), bonding agent (P<.001), and their interaction (P<.001) were significant. APA with ALU or ROC did not influence the SBS of the groups bonded with CLE, but the REL APA with ROC provided higher SBS. The failure mode was adhesive for all specimens. CONCLUSIONS: Adhesion was not different on monoclinic partially transformed Y-TZP. The APA with ROC followed by REL was the most effective treatment for repairing Y-TZP.

Effect of Glaze Cooling Rate on Mechanical Properties of Conventional and Pressed Porcelain on Zirconia.

The aim of this study was to characterize a conventional and a pressed porcelain for zirconia core as to biaxial flexural strength (BFS), apparent fracture toughness (FT) and microstructure composition, and to investigate the effect of glaze cooling rate on the BFS of the zirconia/porcelain bilayers. Monolayers of conventional porcelain Vita VM9 and pressed porcelain Vita PM9 (n=15) (12 mm diameter x 1.2 mm thick) were prepared for the BFS test (MPa). Apparent fracture toughness (MPa.m1/2) was measured by indentation technique (n=15). t-Student test was performed for statistical analysis. Scanning electron microscopy and x-ray diffraction were used to analyze the porcelain's microstructure. For the BFS of bilayers, zirconia discs (12 mm diameter x 1 mm thick) (Vita In-Ceram YZ) were veneered with the two porcelains (1 mm thick). After the glaze firing simulation, the specimens were submitted to fast or slow cooling (n=15). Apparent fracture toughness (MPa.m1/2) was measured on the porcelain surface of bilayers (n=15) and residual stress was calculated. Two-way ANOVA (porcelain and cooling method) was used for the bilayer analysis (a=0.05). Vita PM9 monolayer exhibited significantly higher BFS (p<0.01), but there was no significant difference (p=0.41) in the FT between the porcelains. For bilayer specimens, the two-way ANOVA for BFS was significant for the porcelain variable only (p<0.01) better for Vita PM9/zirconia. Two-way ANOVA for the FT for the bilayers was not significant for any variable. All groups showed compressive residual stresses. The pressed porcelain seems to be mechanically more effective for zirconia veneering.

Effect of Glaze Cooling Rate on Mechanical Properties of Conventional and Pressed Porcelain on Zirconia

Abstract The aim of this study was to characterize a conventional and a pressed porcelain for zirconia core as to biaxial flexural strength (BFS), apparent fracture toughness (FT) and microstructure composition, and to investigate the effect of glaze cooling rate on the BFS of the zirconia/porcelain bilayers. Monolayers of conventional porcelain Vita VM9 and pressed porcelain Vita PM9 (n=15) (12 mm diameter x 1.2 mm thick) were prepared for the BFS test (MPa). Apparent fracture toughness (MPa.m1/2) was measured by indentation technique (n=15). t-Student test was performed for statistical analysis. Scanning electron microscopy and x-ray diffraction were used to analyze the porcelain's microstructure. For the BFS of bilayers, zirconia discs (12 mm diameter x 1 mm thick) (Vita In-Ceram YZ) were veneered with the two porcelains (1 mm thick). After the glaze firing simulation, the specimens were submitted to fast or slow cooling (n=15). Apparent fracture toughness (MPa.m1/2) was measured on the porcelain surface of bilayers (n=15) and residual stress was calculated. Two-way ANOVA (porcelain and cooling method) was used for the bilayer analysis (a=0.05). Vita PM9 monolayer exhibited significantly higher BFS (p<0.01), but there was no significant difference (p=0.41) in the FT between the porcelains. For bilayer specimens, the two-way ANOVA for BFS was significant for the porcelain variable only (p<0.01) better for Vita PM9/zirconia. Two-way ANOVA for the FT for the bilayers was not significant for any variable. All groups showed compressive residual stresses. The pressed porcelain seems to be mechanically more effective for zirconia veneering.

Resumo Este estudo teve como objetivo caracterizar uma porcelana convencional e uma prensada indicadas para infraestrutura de zircônia em termos de resistência à flexão biaxial (RFB), tenacidade à fratura aparente (TF) e composição microestrutural, e investigar o efeito da taxa de resfriamento do ciclo de glaze na RFB de espécimes bicamada de zircônia/porcelana. Espécimes monocamada de porcelana convencional Vita VM9 e porcelana prensada Vita PM9 (n=15) (12 mm de diâmetro x 1,2 mm de espessura) foram preparados para o ensaio de RFB (MPa). Tenacidade à fratura aparente (MPa.m1/2) foi mensurada pela técnica da indentação (n=15). O teste de t-Student foi aplicado para as análises estatísticas. Microscopia eletrônica de varredura e difração de raios-X foram utilizadas para análise microestrutural da porcelana. Para o ensaio de RFB nos bicamadas, discos de zircônia (12 mm de diâmetro x 1 mm de espessura) (Vita In-Ceram YZ) foram recobertos com as duas porcelanas (1 mm de espessura). Após a simulação da queima de glaze, os espécimes foram submetidos ao método de resfriamento rápido ou lento (n=15). A tenacidade à fratura aparente (MPa.m1/2) foi mensurado na superfície da porcelana dos bicamadas (n=15) e o estresse residual foi calculado. Foi utilizado ANOVA a dois fatores (porcelana e método de resfriamento) para análise estatística dos espécimes bicamada (a=0,05). Monocamadas de Vita PM9 exibiram valores de resistência à flexão biaxial significativamente maiores (p<0,01), mas não houve diferença estatística (p=0,41) em relação à TF entre as porcelanas. Para os espécimes bicamada, ANOVA a dois fatores para RFB foi significante apenas para a variável porcelana (p<0,01), com superioridade para Vita PM9/zircônia. ANOVA a dois fatores para TF dos espécimes bicamadas não apresentou significância para nenhuma variável. Todos os grupos apresentaram estresse residual de compressão. Porcelanas prensadas parecem ser mecanicamente mais efetivas para recobrimento de zircônia.

Effect of surface treatments on the shear bond strength of luting cements to Y-TZP ceramic.

STATEMENT OF PROBLEM: Because zirconia is a glass-free material, alternative surface treatments such as airborne-particle abrasion or silica coating should be used for long-term bonding. However, these surface treatments in combination with different bonding agents and luting cements have not yet been studied. PURPOSE: The purpose of the study was to evaluate the effect of surface treatments on the shear bond strength (SBS) of luting cements to Y-TZP ceramic. MATERIAL AND METHODS: Zirconia disks (N=240) were airborne-particle abraded with the following particles (n=48): 50 µm Al2O3; 120 µm Al2O3; 30 µm silica-coated Al2O3 (Rocatec Soft); 120 µm Al2O3+110 µm silica-coated Al2O3 (Rocatec Plus); and Rocatec Plus. After silanization of the zirconia surface, composite resin disks were bonded with (n=12) RelyX Luting 2; RelyX ARC; RelyX U100; and Panavia F. The bonded specimens were thermocycled (10 000 cycles) and tested for SBS. Failure mode was determined with a stereomicroscope (×20). The morphology and elemental composition of airborne-particle abraded surfaces were evaluated with scanning electron microscopy (×500) and energy-dispersive x-ray spectroscopy (×50). RESULTS: Surface treatments, cements, and their interaction were significant (P<.001). For RelyX ARC, Rocatec Soft and Rocatec Plus provided the highest SBS. In general, surface treatments did not influence the SBS of RelyX U100 and Panavia F. Regardless of the cement, no significant difference was found between 50 µm and 120 µm Al2O3 particles, between Rocatec Soft and Rocatec Plus, or between Rocatec Plus and 120 µm Al2O3 particles+Rocatec Plus. All groups showed adhesive failures. Different particle sizes provided differences in morphological patterns. The elemental composition comprised Al and Al/Si for alumina and silica-abraded zirconia. CONCLUSIONS: Particle size did not influence the SBS of the groups abraded exclusively with alumina or silica-coated particles. RelyX ARC was more surface-treatment dependent than RelyX U100 or Panavia F.

Effect of surface and heat treatments on the biaxial flexural strength and phase transformation of a Y-TZP ceramic.

PURPOSE: To evaluate the effect of grinding and airborne-particle abrasion on the biaxial flexural strength (BFS) and phase transformation of a Y-TZP ceramic, and examine whether sintering the veneering porcelain renders the previous heat treatment recommended by the manufacturer unnecessary. MATERIALS AND METHODS: Lava zirconia specimens (N = 108) were obtained with the following dimensions: 14.0 mm diameter × 1.3 mm thickness (n = 36) and 14.0 mm × 1.6 mm (n = 72). The thicker specimens were ground with diamond burs under irrigation and received (heat-treated groups) or not (non-heat-treated groups) a heat treatment (1000°C for 30 min) prior to the four firing cycles applied to simulate the sintering of the veneering porcelain. All specimens were air abraded as follows (n = 12): 1) 30-µm silica-modified Al2O3particles (Rocatec Soft); 2) 110-µm silica-modified Al2O3particles (Rocatec Plus); and 3) 120-µm Al2O3particles, followed by Rocatec Plus. Three specimens of each group were analyzed by x-ray diffraction (XRD) to assess the monoclinic phase content (%). The BFS test was performed in a mechanical testing machine (Instron 8874). Data (MPa) were analyzed by two-way ANOVA (grinding × airborne-particle abrasion and heat treatment × airborne-particle abrasion) and Tukey's post-hoc test (α = 0.05). The strength reliability was analyzed using the Weibull distribution. RESULTS: Grinding significantly decreased the BFS of the non-heat-treated groups (p < 0.01). Within the ground groups, the previous heat treatment did not influence the BFS (p > 0.05). Air abrasion only influenced the BFS of the ground/heat-treated groups (p < 0.01). For the non-heat-treated groups, the grinding did not decrease the Weibull modulus (m), but it did decrease the characteristic strength (σ0). For Rocatec Soft and 120-µm Al2O3particles + Rocatec Plus, the heat-treated groups presented lower m and higher σ0 than the ground/non-heat-treated groups. The independent variables did not seem to influence phase transformation. Air-abraded surfaces presented higher monoclinic zirconia content than the as-sintered and ground surfaces, which exhibited similar content. CONCLUSION: Even under irrigation, grinding compromised the Y-TZP ceramic strength. The sintering of the veneering porcelain rendered the previous heat treatment recommended by the manufacturer unnecessary. Airborneparticle abrasion influenced the strength of heat-treated zirconia.

Evaluation of roughness, wettability, and morphology of an yttria-stabilized tetragonal zirconia polycrystal ceramic after different airborne-particle abrasion protocols.

STATEMENT OF PROBLEM: Airborne-particle abrasion is an effective method of roughening a zirconia surface and promoting micromechanical interlocks with luting cements. However, the effect of different airborne-particle abrasion protocols on the micromechanical retention mechanism has been poorly investigated. PURPOSE: The purpose of the study was to evaluate the effect of airborne-particle abrasion protocols on the surface roughness, wettability, and morphology of an yttria-stabilized tetragonal zirconia polycrystal ceramic. MATERIAL AND METHODS: A total of 140 zirconia specimens (14 × 14 × 1.4 mm) were made from Lava and divided into 7 groups. Their surfaces were treated as follows (n = 20): as-sintered (control); airborne-particle abraded with 50-µm Al2O3 particles; 120-µm Al2O3 particles; 250-µm Al2O3 particles; 30-µm silica-coated Al2O3 particles (Rocatec Soft); 110-µm silica-coated Al2O3 particles (Rocatec Plus); and 120-µm Al2O3 particles followed by Rocatec Plus. The surface roughness (Ra) and wettability analyses were performed on the same specimens of each group. The test liquid used for the wettability analysis was the silane RelyX Ceramic Primer. Two additional specimens (6.0 × 6.0 × 1.0 mm) per group were prepared to evaluate the surface morphology with scanning electron microscopy. The roughness (Ra) data were analyzed by 1-way ANOVA and the Dunnett C test (α = .05), and the wettability data with 1-way ANOVA (α = .05). The Spearman correlation analysis was applied to test for a possible correlation between roughness and wettability. RESULTS: The control group (0.35 µm) exhibited the lowest mean roughness value (Ra), which was followed by Rocatec Soft (0.40 µm), 50-µm Al2O3 particles (0.52 µm), Rocatec Plus (0.69 µm), 120-µm Al2O3 particles (0.80 µm)/120-µm Al2O3 particles + Rocatec Plus (0.79 µm), and 250-µm Al2O3 particles (1.13 µm). No significant difference was found among the groups concerning wettability. No correlation (rs = -0.09; P = .27) was found between the 2 dependent variables. The scanning electron microscopy analysis indicated that the different airborne-particle abrasion protocols produced differences in the morphologic patterns. CONCLUSIONS: Although roughness and morphology of the zirconia surface varied according to the airborne-particle abrasion protocol, no close relationship was found between them. The roughness increase seemed to have followed the size of the particles.

Efficacy of surface treatments on the bond strength of resin cements to two brands of zirconia ceramic.

PURPOSE: To compare the shear bond strengths (SBS) of two cements to two Y-TZP ceramics subjected to different surface treatments. MATERIALS AND METHODS: Zirconia specimens were made from Lava (n = 36) and IPS e.max ZirCAD (n = 36), and their surfaces were treated as follows: no treatment (control), silica coating with 30-µm silica-modified alumina (Al2O3) particles (CoJet Sand), or coating with liners Lava Ceram for Lava and Intensive ZirLiner for IPS e.max ZirCAD. Composite resin cylinders were bonded to zirconia with Panavia F or RelyX Unicem resin cements. All specimens were thermocycled (6000 cycles at 5°C/55°C) and subjected to SBS testing. Data were analyzed by three-way ANOVA and Tukey's (HSD) post-hoc test (α = 0.05). Failure mode was analyzed by stereomicroscope and SEM. RESULTS: CoJet Sand and liners promoted significantly higher SBS than their control groups, but had similar results to one another. Panavia F provided significantly higher SBS values than RelyX Unicem (p < 0.01) for nontreated zirconia specimens of both brands. When Lava and IPS e.max ZirCAD were abraded with CoJet Sand, RelyX Unicem promoted significantly higher SBS values than Panavia F (p < 0.001). There was no significant difference between the two cements when the zirconia specimens were treated with their respective liners. The nontreated specimens and those treated with CoJet Sand exhibited a high percentage of adhesive and mixed A failures, while the specimens treated with liners presented an increase in mixed A and mixed C failures as well as some cohesive failure in the bulk of Lava Ceram for both cements. CONCLUSION: CoJet Sand and liners provided the best surface treatment for Lava and IPS e.max ZirCAD. The best surface treatment/cement combinations were CoJet Sand/RelyX Unicem and liner/Panavia F. SBS of Panavia F and RelyX Unicem was not influenced by the zirconia brand.

The effect of different surface treatments on the shear bond strength of luting cements to titanium.

STATEMENT OF PROBLEM: Although titanium presents attractive physical and mechanical properties, there is a need for improving the bond at the titanium/luting cement interface for the longevity of metal ceramic restorations. PURPOSE: The purpose of this study was to evaluate the effect of surface treatments on the shear bond strength (SBS) of resin-modified glass ionomer and resin cements to commercially pure titanium (CP Ti). MATERIAL AND METHODS: Two hundred and forty CP Ti cast disks (9.0 × 3.0 mm) were divided into 8 surface treatment groups (n=30): 1) 50 µm Al(2)O(3) particles; 2) 120 µm Al(2)O(3) particles; 3) 250 µm Al(2)O(3) particles; 4) 50 µm Al(2)O(3) particles + silane (RelyX Ceramic Primer); 5) 120 µm Al(2)O(3) particles + silane; 6) 250 µm Al(2)O(3) particles + silane; 7) 30 µm silica-modified Al(2)O(3) particles (Cojet Sand) + silane; and 8) 120 µm Al(2)O(3) particles, followed by 110 µm silica-modified Al(2)O(3) particles (Rocatec). The luting cements 1) RelyX Luting 2; 2) RelyX ARC; or 3) RelyX U100 were applied to the treated CP Ti surfaces (n=10). Shear bond strength (SBS) was tested after thermal cycling (5000 cycles, 5°C to 55°C). Data were analyzed by 2-way analysis of variance (ANOVA) and the Tukey HSD post hoc test (α=.05). Failure mode was determined with a stereomicroscope (×20). RESULTS: The surface treatments, cements, and their interaction significantly affected the SBS (P<.001). RelyX Luting 2 and RelyX U100 exhibited similar behavior for all surface treatments. For both cements, only the group abraded with 50 µm Al(2)O(3) particles had lower SBS than the other groups (P<.05). For RelyX ARC, regardless of silane application, abrasion with 50 µm Al(2)O(3) particles resulted in significantly lower SBS than abrasion with 120 µm and 250 µm particles, which exhibited statistically similar SBS values to each other. Rocatec + silane promoted the highest SBS for RelyX ARC. RelyX U100 presented the highest SBS mean values (P<.001). All groups showed a predominance of adhesive failure mode. CONCLUSIONS: The adhesive capability of RelyX Luting 2 and RelyX U100 on the SBS was decisive, while for RelyX ARC, mechanical and chemical factors were more influential.

Effect of different airborne-particle abrasion/bonding agent combinations on the bond strength of a resin cement to a base metal alloy.

STATEMENT OF PROBLEM: Investigation of surface treatments to improve the bond of resin cements to metals may contribute to the longevity of metal ceramic restorations. PURPOSE: The purpose of this study was to evaluate the efficacy of surface treatments on the shear bond strength (SBS) of a resin cement to nickel-chromium (NiCr) alloy. MATERIAL AND METHODS: Eighty cast NiCr alloy disks (9 × 3 mm) were divided into 8 groups (n=10), which received 1 of the following surface treatments: 1) 50 µm Al(2)O(3) particles + silane; 2) 120 µm Al(2)O(3) + silane; 3) 30 µm silica-modified Al(2)O(3) (Cojet Sand) + silane; 4) 120 µm Al(2)O(3) followed by 110 µm silica-modified Al(2)O(3) (Rocatec) + silane; 5) 50 µm Al(2)O(3) + metal primer; 6) 120 µm Al(2)O(3) + metal primer; 7) 30 µm silica-modified Al(2)O(3) (Cojet Sand) + metal primer; and 8) 120 µm Al(2)O(3) followed by 110 µm silica-modified Al(2)O(3) (Rocatec) + metal primer. The silane was RelyX Ceramic Primer and the metal primer Alloy Primer. RelyX ARC resin cement was bonded to NiCr alloy surfaces. Specimens were thermally cycled before shear mode testing. Data (MPa) were analyzed by 1-way ANOVA and the Tukey test (α=.05). Failure mode was determined with a stereomicroscope (×20). RESULTS: The results revealed that surface treatment was significant (P<.001). There was no significant difference between 50 µm and 120 µm Al(2)O(3) particles, regardless of the bonding agent used (silane or metal primer). Cojet Sand provided lower SBS than Rocatec, both in the groups treated with silane (P<.001) and metal primer (P<.01). No significant difference was observed between silane and metal primer in the groups abraded with 50 µm and 120 µm Al(2)O(3) particles. Metal primer decreased the SBS of both Cojet Sand and Rocatec groups (P<.001). Rocatec + silane had the highest SBS and Cojet Sand + metal primer the lowest. All groups presented 100% adhesive failure. CONCLUSIONS: Particle size influenced SBS only in the groups abraded with silica-modified Al(2)O(3). The bonding agent did not affect SBS in the groups abraded with Al(2)O(3). Alloy Primer was not chemically compatible with silica-modified Al(2)O(3). Both mechanical (particle size) and chemical (silica/silane interaction) factors contributed to the high SBS of Rocatec + silane.

Efficacy of air-abrasion technique and additional surface treatment at titanium/resin cement interface.

PURPOSE: To evaluate the effect of surface treatments on the shear bond strength (SBS) of a resin cement to commercially pure titanium (CP Ti). MATERIALS AND METHODS: Two hundred cast CP Ti disks were divided into 5 groups (n = 40), which were treated with one of the following air-abrasion techniques: (1) 50-µm Al2O3 particles; (2) 120-µm Al2O3 particles; (3) 250-µm Al2O3 particles; (4) 30-µm silica-modified Al2O3 particles (Cojet Sand); (5) 50-µm Al2O3 particles followed by 110-µm silica-modified Al2O3 particles (Rocatec Plus). For each air-abrasion technique, the following additional surface treatments were used (n = 10): (1) none; (2) adhesive Adper Single Bond 2; (3) silane RelyX Ceramic Primer; (4) silane plus adhesive. RelyX ARC resin cement was bonded to CP Ti surfaces. All specimens were thermocycled (5,000 cycles) before being tested in shear mode. Data (MPa) were analyzed using two-way ANOVA and Tukey's test (α = 0.05). Failure mode was determined with a stereomicroscope (20X). RESULTS: The results revealed that the air-abrasion technique (p < 0.001), additional surface treatment (p < 0.001) and their interaction were significant (p < 0.001). Except for the 50-µm Al2O3 + adhesive group, 250-µm Al2O3 particles promoted significantly higher SBS than 50-µm Al2O3 particles (p < 0.001), while Rocatec Plus provided bond strengths that were similar to or higher than those of Cojet Sand. Of the additional surface treatments, the adhesive provided the best results in combination with the 3 air-abrasion techniques (50-µm, 120-µm, and 250-µm Al2O3), whereas in the groups abraded with silica-modified Al2O3 particles (Cojet Sand and Rocatec Plus), the best results were obtained with additional silane. The two combinations that promoted the highest SBS were 250-µm Al2O3 + adhesive and Rocatec Plus + silane. All groups showed 100% adhesive failure. CONCLUSION: The selection of the best additional surface treatment varied according to the air-abrasion technique. Particle size was the decisive factor in determining the bond strength when micromechanical retention was the only bonding mechanism. When both mechanisms were present, in addition to particle size, the material applied as the additional surface treatment also contributed to determining the bond strength.