Recycling CAD/CAM lithium disilicate ceramic: effect of surface treatment and aging on the bond strength to resin cement.

PURPOSE: To investigate the effect of recycling of lithium disilicate (LD), surface treatment and thermocycling (TC) on the bond strength (SBS) to resin cement. MATERIALS AND METHODS: Blocks of LD were made according to the recycling cycle, with 24 blocks for each strategy: Control-conventional sintering; 1R (1 recycling cycle) and 3R (3 recycling cycles). For the recycling groups, blocks were waxed (10x10x3mm), mounted in a silicone ring, poured with investment material, and then residues of sintered LD blocks were pressed by the lost wax technique. The residual LD was reused as described until reach 3R. Afterwards, the blocks were embedded in acrylic resin, sanded and divided (n=15) according to the factors "surface treatment" (HF20s+Silane and HF120s+Silane and Monobond Etch&Prime- MEP) and TC (with/10.000 cycles and without). After surface treatment, cylinders (Ø:2mm) of resin cement were made and submitted to SBS test (100KgF,1mm/min). Data (MPa) were analyzed by 3-way ANOVA, Tukey's test (5%) and Weibull analysis. Failure analysis was performed with stereomicroscope. RESULTS: ANOVA revealed that all factors were significant (P=.000*). The group 3RMEP(105.09±19.49) presented the highest SBS among the experimental groups. 1RHF20sTc(7.50±1.97) group had the lowest SBS, similar to the CHF20sTc(15.69±3.77), 1RHF20s(15.12±3.03), 1RHF120sTc(14.60±3.43) and 3RHF20sTc(15.65±0.97). The Weibull modulus and characteristic strength varied among the experimental groups (P=0.0). Failure analysis revealed adhesive and mixed types. CONCLUSION: The recycling of DL ceramics increases the SBS to resin cement when the ceramic is treated with HF120s+S or MEP.

Effect of Adhesive Resin Application on the Durability of Adhesion to CAD/CAM Glass-Ceramics after either Hydrofluoric Acid Etching or Self-etch Primer Application.

PURPOSE: To evaluate the effect of two surface conditioning methods, namely conventional hydrofluoric acid vs self-etching primer, and the application of adhesive on the bond strength of resin cement to CAD/CAM glass-ceramics. MATERIALS AND METHODS: Blocks (N = 96) (12 x 10 x 2.5 mm) were manufactured, 24 for each tested ceramic type: lithium silicate ceramic (LS), polymer-infiltrated ceramic (PIC), leucite-reinforced feldspathic ceramic (FD), and lithium-disilicate glass-ceramic (LD). For bond strength testing, 64 blocks were randomly divided into 16 groups (4 blocks per group) according to the following factors: ceramic: 4 levels; etching: 2 levels (HFS: hydrofluoric acid + silane or Monobond Etch & Prime [MEP]); and adhesive application: 2 levels, with (signified as A) and without. Then for each group, 15 resin cement cylinders (AllCem Dual, FGM) were built up. All specimens were subjected to thermocycling (10,000 cycles) and to shear bonding strength testing (SBS) (100 kgf, 0.5 mm/min). Mean shear stresses (MPa) were statistically analyzed by three-way ANOVA, Tukey's test, and Weibull analysis. RESULTS: The mean bond strength of group PIC-HFS-A (28.45 ± 7.6 MPa) was significantly higher than that of groups LS-HFS-A (12.11 ± 2.7MPa) and FDHFSA (20.86 ± 2.0MPa). Group PIC-HFS bond strength (25.02 ± 6.5 MPa) was significantly higher only when compared to group LS-HFS (15.82 ± 4.4 MPa). The LS group presented lower SBS compared to all other groups. No significant differences were found between HFS and MEP surface treatments. CONCLUSION: Surface treatment with MEP promotes adhesion similar to that of HFS. Additional application of adhesive after the surface treatments did not improve the bond strength.

Effect of different surface treatments on the micro tensile bond strength to dentin, biaxial flexural strength and roughness of CAD/CAM resin composite and polymer infiltrated ceramic.

OBJECTIVES: To evaluate the biaxial flexural strength (BFS), surface roughness (Ra) and micro tensile bond strength (µTBS) of two CAD/CAM materials after different surface treatments. MATERIALS AND METHODS: For µTBS, 64 human molars were used and 32 blocks of resin composite (RC-Lava Ultimate) and polymer-infiltrated ceramic (PIC -Vita Enamic). The blocks and teeth were distributed into 16 groups according to the factors "surface treatment" (HF: 10% hydrofluoric acid; APA: Al2O3 sandblasting; SC: silicate-Al2O3 sandblasting; MEP: Monobond Etch and Prime) and "thermal cycling" (TC). After cementation, the blocks were sectioned into 1 mm2 bars. Half of the specimens were thermocycled and submitted to µTBS test. For BFS, RC and PIC discs were made and distributed according to the surface treatments and after mechanical cycling, submitted to BFS test. Roughness, EDS, SEM, and Weibull analyses were also performed. Data were analyzed by (1 or 2-way) ANOVA and Tukey test (α = 0.05). RESULTS: For RC, SC and HF after TC showed significantly higher µTBS values. For PIC HF after TC showed higher µTBS than the other groups. For RC, the BFS was higher for MEP than Al2O3 and SC. For PIC, none of the surface treatments influenced BFS. CONCLUSION: The highest µTBS for RC was obtained with SC followed by silanization and for PIC, HF followed by silanization. The RC showed lower strength after Al2O3 blasting. For PIC all surface treatments resulted in similar BFS.

Which Zirconia Surface-cleaning Strategy Improves Adhesion of Resin Composite Cement after Saliva Contamination? A Systematic Review and Meta-Analysis.

PURPOSE: To identify the most effective cleaning method for saliva-contaminated zirconia surface before adhesive cementation through a systematic review and meta-analysis. MATERIALS AND METHODS: PubMed, Scopus, and Web of Science databases were searched to select in vitro studies published through October 2021. Studies that did not perform aging methods, had a sample size less than 5 per group, or did not present a group with zirconia contaminated only with saliva were excluded. Data were extracted and risk of bias was assessed. Statistical analysis comparing the cleaning methods was conducted, and the standardized mean difference was assessed using the R software program. RESULTS: Among 804 potentially eligible studies, 36 were selected for full-text reading, of which 13 were included in qualitative analysis, and 11 of these were subsequently included in the quantitative analysis. A meta-analysis revealed a significant difference in the bond strength between the cleaning methods. Sandblasting with Al2O3  showed a higher bond strength than cleaning solution (Ivoclean, Ivoclar Vivadent) (p < 0.01, I2 = 65%), and both methods promoted higher resin-bond strength to zirconia than water cleaning. In addition, there was no significant difference in the bond strength between alcohol (p = 0.35, I2 = 79%), phosphoric acid (p < 0.23, I2 = 90%), and water cleaning. CONCLUSION: Sandblasting with Al2O3 seems to be the best method for zirconia surface cleaning before adhesive luting, promoting better resin-bond strength to zirconia.

Restabelecimento da Dimensão Vertical de Oclusão com JIG estético modificado e Prótese Parcial Removível Overlay: relato de caso / Reestablishment of occlusal vertical dimension with a modified aesthetic JIG and an overlay removable partial denture: a case report

A reabilitação de pacientes parcialmente edêntulos com desgaste dentário severo e dimensão vertical de oclusão reduzida é desafiadora e complexa. Objetivo: Descrever o restabelecimento da dimensão vertical de oclusão e parâmetros estéticos com uma prótese parcial removível do tipo overlay (PPRO) com auxílio de um JIG estético modificado. Relato de caso: Paciente do sexo masculino, 58 anos de idade, procurou serviço odontológico queixando-se de insatisfação com a estética do sorriso e perda dos dentes posteriores. Ao exame clínico, foram observados desgaste dentário excessivo e edentulismo parcial nas arcadas superior e inferior. Então, foi proposto tratamento em 2 etapas (provisória e definitiva) com PPRO em maxila. O JIG estético foi usado como guia de referência para incrementos em resina composta fotopolimerizável e o restabelecimento da dimensão vertical de oclusão foi determinado a partir de métodos métrico, fonético e estético. Os dentes desgastados foram aumentados e os dentes ausentes substituídos por dentes artificiais a partir de uma PPRO provisória. Após 2 meses de adaptação, a reabilitação final com PPRO definitiva foi conduzida baseando-se na reabilitação com a PPRO provisória. Conclusão: O paciente relatou satisfação com a estética e desempenho funcional com o tratamento. Portanto, o JIG estético beneficia o planejamento e o tratamento para restabelecer a dimensão vertical de oclusão. Além disso, a PPRO é uma alternativa reversível, de baixo custo, para reabilitar a estética e a função de pacientes com desgaste severo e perda parcial dos dentes.

The rehabilitation of partially edentulous patients with severe tooth wear and reduced occlusal vertical dimension is challenging and complex. Objective: To describe the reestablishment of occlusal vertical dimension and aesthetic parameters with an overlay re-movable partial denture (ORPD) with the aid of a modified aesthetic JIG. Case report: A 58-year-old man sought dental service complaining of dissatisfaction with the aesthetics of his smile and a loss of posterior teeth. At clinical examination, excessive tooth wear and partially edentulism in the lower and upper arches were observed. A two-step treatment (interim and definitive) with an ORPD in the upper arch was proposed. The aesthetic JIG was used as a reference guide for the increments in light-curing resin composite, and the reestablishmentthe occlusal vertical dimension was determined using aesthetic, phonetic, and metric methods. The worn teeth were increased, and the missing natural teeth were replaced by artificial teeth using a temporary ORPD. After two months of adaptation, de-finitive rehabilitation with a definitive ORPD was performed based on the interim ORPD. Conclusion: The patient reported satisfaction with the esthetic and functional performance of this treatment. Therefore, the aesthetic JIG benefits the planning and treatment of reduced vertical dimension. Moreover, the ORPD is a reversible and lower-cost alternative to rehabilitate the aesthetics and function of patients with severe teeth wear and partial teeth loss.

Effect of different surface treatments on the biaxial flexure strength, Weibull characteristics, roughness, and surface topography of bonded CAD/CAM silica-based ceramics.

OBJECTIVE: To investigate the influence of different surface treatments on biaxial flexure strength, roughness, and surface topography of lithium silicate/disilicate-based ceramics. METHODS: 225 discs (∅: 12 mm; 1.2 mm - ISO 6872) were made from three ceramics: IPS e.max CAD (LD - Ivoclar Vivadent), Suprinity (LSS - Vita) and Celtra Duo (LSC - Dentsply). The samples were randomly divided into 5 groups (n = 15): no treatment (C); 10% hydrofluoric acid + silane (HF); sandblasting Al2O3 + silane (SB); silicatization + silane (SC); and self-etching ceramic primer (SEP). After surface treatment, a resin cement layer was applied to the disc surface (RelyX U200, 3M ESPE), mechanical cycled (1.2 × 106 cycles, 50 N, 3.8 Hz) and submitted to biaxial flexural strength test (1 mm/min, 1000 Kgf). Roughness, EDS and SEM were also performed. Data were analyzed by one-way ANOVA, Tukey test (5%) and Weibull. RESULTS: ANOVA revealed that the "surface treatment" factor was significant for all ceramics (p < 0.05). The groups LD-HF (289.30 ± 40) LD-SEP (298. 87 ± 53.29), LSC-HF (195.51 ± 42.12), LSS-HF (269.58 ± 27.07) and LSS-SEP (207.45 ± 28.63) presented significantly higher biaxial flexure strength than respective control groups, except for the LSC-SEP (165.41 ± 33.86), which was statistically similar to the control. The Weibull modulus was significantly higher for the LD-SB, LSC-SC groups. Additionally, the LD-SB, LSC-SC and LSS-HF groups showed higher roughness compared to the other treatments. SIGNIFICANCE: HF etching followed by silanization and self-etching ceramic primer are the most suitable surface treatments for lithium silicate/disilicate-based glass-ceramics.

Effect of different surface treatments and multimode adhesive application on the Weibull characteristics, wettability, surface topography and adhesion to CAD/CAM lithium disilicate ceramic.

METHODOLOGY: This paper aims to evaluate the effect of different surface treatments on surface topography, wettability, and shear bond strength of resin cement to glass ceramic. For SBS test, 32 blocks (7x7x2 mm) of lithium disilicate were obtained and randomly divided into eight groups (four blocks per group) according to each surface treatment (HF 20 s, 60 s, 120 s + silanization/S or Scotch Bond Universal/ SBU) and the Monobond Etch & Prime - MEP application followed or not by SBU. On each treated surface ceramic block, up to four dual-curing resin cement cylinders were prepared and light-cured for 40s (N=120/n=15). The specimens were thermocycled (10,000 cycles, 5-55°C, 30 s) and the SBS test (50KgF, 0.5 mm/min) was performed. Furthermore, failure analysis, wettability, AFM, and SEM were carried out. SBS data (MPa) were analyzed using Student's t-test, two-way ANOVA, Tukey's test (5%) and Weibull's analysis. RESULTS: For HF experimental groups, two-way ANOVA presented the factors "etching time" and "bonding agent" as significant (p<0.05). After silane application, the HF groups presented similar bond strength. SBU application compromised the SBS, except for 120s etching time (HF120sS: 23.39ᵃ±6.48 MPa; HF120sSBU: 18.76ᵃ±8.81MPa). For MEP groups, SBU application did not significantly affect the results (p=0.41). The MEP group presented the highest Weibull modulus (4.08A) and they were statistically different exclusively from the HF20sSBU (0.58B). CONCLUSION: The HF 20s, 60s, 120 s followed by silane, promoted similar resin-bond strength to ceramic and the SBU application after HF or MEP did not increase the SBS.

Effect of glazing application side and mechanical cycling on the biaxial flexural strength and Weibull characteristics of a Y-TZP ceramic.

OBJECTIVE: Glaze application on monolithic zirconia (Y-TZP) can be a practical approach to improve the mechanical properties of this material. Our study evaluated the effect of glazing side and mechanical cycling on the biaxial flexure strength (BFS) of a Y-TZP. METHODOLOGY: Eighty sintered Y-TZP discs (Ø:12 mm; thickness: 1.2 mm - ISO 6872) were produced and randomly assigned into eight groups (n=10), according to the factors "glazing side" (control - no glazing; GT - glaze on tensile side; GC - glaze on compression side; GTC - glaze on both sides) and "mechanical aging" (non-aged and aged, A - mechanical cycling: 1.2×106, 84 N, 3 Hz, under water at 37°C). Specimens were subjected to BFS test (1 mm/min; 1,000 Kgf load cell) and fractured surfaces were analyzed by stereomicroscopy and SEM. Hsueh's rigorous solutions were used to estimate the stress at failure of glazed specimens. Two-way ANOVA, Tukey's test (5%), and Weibull analysis were performed. RESULTS: The "glazing side", "mechanical aging" and the interaction of the factors were significant (p<0.05). Groups GC (1157.9±146.9 MPa), GT (1156.1±195.3 MPa), GTC (986.0±187.4 MPa) and GTC-A (1131.9±128.9 MPa) presented higher BFS than control groups (Tukey, 5%). Hsueh's rigorous solutions showed that the maximum tensile stress was presented in the bottom of zirconia layer, at the zirconia/glaze interface. Weibull characteristic strength (σo) of the GC was higher than all groups (p<0.05), except to GT, GTC-A and GTC, which were similar among them. The fractography showed initiation of failures from zirconia the tensile side regardless of the side of glaze application and fatigue. CONCLUSION: Glazing zirconia applied on both tensile and compression sides improves the flexural strength of Y-TZP, regardless the mechanical aging.

Influence of Acid Etching and Universal Adhesives on the Bond Strength to Dentin.

The purpose of this study was to evaluate the influence of the application mode of three universal adhesive systems on interfacial physical properties of indirect composite restorations adhesively cemented to dentin cavities. Seventy-eight bovine lower incisors were selected and a slice of dentin (thickness: 2 mm) between the buccal surface and pulp chamber was obtained for each tooth. Conical cavities were made on this surface. The internal walls of the cavities were then coated with a hydrophilic gel, filled with composite resin and photopolymerized. The dentin/cone sets were divided into 6 groups (n=10) according to type of universal adhesive (TETRI: Tetric N Bond, FUT: Futura Bond U, SBU: Single Bond Universal) and acid etching on dentin (A: with acid etching; WA: without acid etching). The acid etching and the adhesive systems were applied to the surface of the dentin. All composite resin cones were sandblasted (Al2O3, 20 s) and silanized. After surface treatment, the cones were cemented (RelyX Ultimate) into the dentin cavity and photopolymerized. After thermocycling (10,000 cycles), samples were submitted to marginal adaptation analysis (using caries detector dye), push-out test (0.5 mm/min), and failure mode analysis. Additional samples were prepared for nanoleakage analysis (SEM). The data (MPa) were analyzed by two-way ANOVA and Tukey's post-test (5%). The groups in which the dentin was acid etched showed significantly lower bond strength values in the push-out test (p<0.01). Dentin acid etching significantly reduced the bond strength between universal adhesive systems and dentin in indirect restorative procedures.

Influence of acid etching and universal adhesives on the bond strength to dentin

Abstract The purpose of this study was to evaluate the influence of the application mode of three universal adhesive systems on interfacial physical properties of indirect composite restorations adhesively cemented to dentin cavities. Seventy-eight bovine lower incisors were selected and a slice of dentin (thickness: 2 mm) between the buccal surface and pulp chamber was obtained for each tooth. Conical cavities were made on this surface. The internal walls of the cavities were then coated with a hydrophilic gel, filled with composite resin and photopolymerized. The dentin/cone sets were divided into 6 groups (n=10) according to type of universal adhesive (TETRI: Tetric N Bond, FUT: Futura Bond U, SBU: Single Bond Universal) and acid etching on dentin (A: with acid etching; WA: without acid etching). The acid etching and the adhesive systems were applied to the surface of the dentin. All composite resin cones were sandblasted (Al2O3, 20 s) and silanized. After surface treatment, the cones were cemented (RelyX Ultimate) into the dentin cavity and photopolymerized. After thermocycling (10,000 cycles), samples were submitted to marginal adaptation analysis (using caries detector dye), push-out test (0.5 mm/min), and failure mode analysis. Additional samples were prepared for nanoleakage analysis (SEM). The data (MPa) were analyzed by two-way ANOVA and Tukey's post-test (5%). The groups in which the dentin was acid etched showed significantly lower bond strength values in the push-out test (p<0.01). Dentin acid etching significantly reduced the bond strength between universal adhesive systems and dentin in indirect restorative procedures.

Resumo O objetivo deste estudo foi avaliar a influência do modo de aplicação de três sistemas adesivos universais nas propriedades físicas interfaciais de restaurações indiretas de compósito adesivamente cimentadas a cavidades dentinária. Setenta e oito incisivos inferiores bovinos foram selecionados e uma fatia de dentina (espessura: 2 mm) entre a face vestibular e a câmara pulpar foi obtida para cada dente. Cavidades cônicas foram feitas nesta superfície. As paredes internas das cavidades foram então revestidas com um gel hidrofílico, preenchidas com resina composta, e fotopolimerizados. Os conjuntos dentina/cone foram divididos em 6 grupos (n=10) de acordo com o tipo de adesivo universal (TETRI: Tetric N Bond, FUT: Futura Bond U, SBU: Single Bond Universal) e ácido na dentina (A: com condicionamento ácido; WA: sem condicionamento ácido). O condicionamento ácido e os sistemas adesivos foram aplicados na superfície da dentina. Todos os cones de resina composta foram jateados (Al2O3, 20 s) e silanizados. Após o tratamento superficial, os cones foram cimentados (RelyX Ultimate) na cavidade dentinária e fotopolimerizados. Após a termociclagem (10.000 ciclos), as amostras foram submetidas a análise de adaptação marginal (usando corante detector de carie), teste push-out (0,5 mm/min) e análise do modo de falha. Amostras adicionais foram preparadas para análise de nanoinfiltração (MEV). Os dados (MPa) foram analisados por ANOVA dois fatores e pós-teste de Tukey (5%). Os grupos em que a dentina foi condicionada por ácido apresentaram valores significativamente menores de resistência de união no teste push-out (p<0,01). O condicionamento ácido da dentina reduziu significativamente a resistência de união entre sistemas adesivos universais e dentina em procedimentos restauradores indiretos.

Effect of Air-Particle-Abrasion Protocols on Surface Roughness and Early Biofilm Formation of Zirconia.

PURPOSE: The air-particle-abrasion on zirconia in the gingival area of connectors and pontics in fixed partial dentures appears to increase fracture resistance. This study evaluated 'in situ' biofilm formation on the zirconia surface after different air-particle-abrasion protocols. MATERIALS AND METHODS: Ninety sintered blocks (5 × 5 × 2 mm) of yttrium partially stabilised zirconia (Y-TZP) were obtained and randomised among nine groups according to the factors 'type of particle' (Alumina 50 and 110 µm; Cojet and Rocatec) and 'pressure' (2.5 and 3.5 bar) used for sandblasting for 10 s. The surface roughness (Ra/Rz) was measured before and after sandblasting. For the in-situ analyses, custom-made removable intraoral devices n = 10 with one sample of each group attached to the buccal area were used by volunteers for 8 h at night. The specimens were analysed under confocal microscopy to quantify both biovolume and thickness of the initial biofilm formed. One-way analysis of variance (ANOVA) and Dunnett's tests were performed (5%). RESULTS: The roughness values ranged from 0.05 to 0.39 µm for Ra and from 0.35 to 2.11 µm for Rz, p = 0.00. Mean biofilm thickness ranged from 0.06 and 0.54 µm (p = 0.005), while the biovolume values were between 0.02 and 0.61 µm3/µm2 (p = 0.002). Values statistically significant for biofilm thickness and biovolume were found in groups sandblasted with Rocatec using 3.5 bar. CONCLUSION: In order to increase the fracture resistance of zirconia fixed partial dentures (FPDs), the air particle abrasion of zirconia with SiO2 (110 µm/3.5 bar), in the gingival area of connectors and pontics, should be avoided.

Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics.

The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM - Vita Mark II - Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey's test. Only the factor "HF concentration" was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.

Effect of different surface treatments and multimode adhesive application on the Weibull characteristics, wettability, surface topography and adhesion to CAD/CAM lithium disilicate ceramic

Abstract This paper aims to evaluate the effect of different surface treatments on surface topography, wettability, and shear bond strength of resin cement to glass ceramic. Methodology: For SBS test, 32 blocks (7x7x2 mm) of lithium disilicate were obtained and randomly divided into eight groups (four blocks per group) according to each surface treatment (HF 20 s, 60 s, 120 s + silanization/S or Scotch Bond Universal/ SBU) and the Monobond Etch & Prime - MEP application followed or not by SBU. On each treated surface ceramic block, up to four dual-curing resin cement cylinders were prepared and light-cured for 40s (N=120/n=15). The specimens were thermocycled (10,000 cycles, 5-55°C, 30 s) and the SBS test (50KgF, 0.5 mm/min) was performed. Furthermore, failure analysis, wettability, AFM, and SEM were carried out. SBS data (MPa) were analyzed using Student's t-test, two-way ANOVA, Tukey's test (5%) and Weibull's analysis. Results: For HF experimental groups, two-way ANOVA presented the factors "etching time" and "bonding agent" as significant (p<0.05). After silane application, the HF groups presented similar bond strength. SBU application compromised the SBS, except for 120s etching time (HF120sS: 23.39ᵃ±6.48 MPa; HF120sSBU: 18.76ᵃ±8.81MPa). For MEP groups, SBU application did not significantly affect the results (p=0.41). The MEP group presented the highest Weibull modulus (4.08A) and they were statistically different exclusively from the HF20sSBU (0.58B). Conclusion: The HF 20s, 60s, 120 s followed by silane, promoted similar resin-bond strength to ceramic and the SBU application after HF or MEP did not increase the SBS.

Hydrofluoric acid concentration, time and use of phosphoric acid on the bond strength of feldspathic ceramics

Abstract The objective of this study was to evaluate the influence of hydrofluoric acid (HF) concentration, etching time, and application of phosphoric acid (PA) followed by neutralization with sodium bicarbonate on the bond strength between a feldspar ceramic and resin cement. Thus, 80 blocks (10 x 12 x 2 mm) of glass ceramic (VM - Vita Mark II - Vita Zahnfabrik) were made and randomly assigned to eight groups (n = 10) according to the factors: HF concentration (5 and 10%), etching time (60 and 120 s), and use of phosphoric acid (PA) (with and without). According to the experimental group, 37% PA (Condac, FGM) was applied after HF etching for 60s. Afterwards, samples were immersed in sodium bicarbonate for 1 min then in an ultrasonic bath in distilled water (5 min) for cleaning. After surface bonding treatment, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block. The samples were then stored in water (37ºC) for 90 days and submitted to the shear bond test (50 KgF, 1 mm/min). Failure analysis was performed by stereomicroscope and scanning electron microscopy. Data (MPa) were analyzed with 3-way ANOVA and Tukey's test. Only the factor "HF concentration" was significant (p = 0.02). Most failures were of cohesive in ceramic (40%) and mixed types (42.5%). The 10% HF resulted in higher shear bond strength value than the 5% HF. Surface cleaning with phosphoric acid followed by sodium bicarbonate and HF time (60 or 120 seconds) did not influence the resin bond strength to feldspar ceramic.

Effect of glazing application side and mechanical cycling on the biaxial flexural strength and Weibull characteristics of a Y-TZP ceramic

Abstract Glaze application on monolithic zirconia (Y-TZP) can be a practical approach to improve the mechanical properties of this material. Objective Our study evaluated the effect of glazing side and mechanical cycling on the biaxial flexure strength (BFS) of a Y-TZP. Methodology Eighty sintered Y-TZP discs (Ø:12 mm; thickness: 1.2 mm - ISO 6872) were produced and randomly assigned into eight groups (n=10), according to the factors "glazing side" (control - no glazing; GT - glaze on tensile side; GC - glaze on compression side; GTC - glaze on both sides) and "mechanical aging" (non-aged and aged, A - mechanical cycling: 1.2×106, 84 N, 3 Hz, under water at 37°C). Specimens were subjected to BFS test (1 mm/min; 1,000 Kgf load cell) and fractured surfaces were analyzed by stereomicroscopy and SEM. Hsueh's rigorous solutions were used to estimate the stress at failure of glazed specimens. Two-way ANOVA, Tukey's test (5%), and Weibull analysis were performed. Results The "glazing side", "mechanical aging" and the interaction of the factors were significant (p<0.05). Groups GC (1157.9±146.9 MPa), GT (1156.1±195.3 MPa), GTC (986.0±187.4 MPa) and GTC-A (1131.9±128.9 MPa) presented higher BFS than control groups (Tukey, 5%). Hsueh's rigorous solutions showed that the maximum tensile stress was presented in the bottom of zirconia layer, at the zirconia/glaze interface. Weibull characteristic strength (σo) of the GC was higher than all groups (p<0.05), except to GT, GTC-A and GTC, which were similar among them. The fractography showed initiation of failures from zirconia the tensile side regardless of the side of glaze application and fatigue. Conclusion Glazing zirconia applied on both tensile and compression sides improves the flexural strength of Y-TZP, regardless the mechanical aging.

Interfacial Properties and Bottom/Top Hardness Ratio Produced by Bulk Fill Composites in Dentin Cavities.

The aim of this study was to evaluate the bond strength, bottom/top hardness ratio, marginal adaptation, and interfacial nanoleakage of regular viscosity bulk fill composites (RVBFC) and regular viscosity traditional composites (RVTC). Two RVBFC (Filtek Bulk Fill and Aura Bulk Fill) and two RVTC (Filtek Z250XT and Aura) were assessed. Forty conical cavities (4.8×2.8×4.0) were prepared in bovine dentin and restored with composites (n=10). After 24h in water, marginal adaptation was evaluated by staining with a caries detector. The top and bottom surfaces of the conical restorations were stained for five seconds and the gap percentage in the composite/dentin interface was determined using digital images on a measurement program (ImageTool). The Vickers microhardness was measured and the bottom/top microhardness ratio (B/T) was determined. Push-out bond strength test was performed in a universal testing machine (0.5mm/min) and failure modes were evaluated in a stereomicroscope (20×). Other specimens (n=3) were produced for interfacial nanoleakage evaluation. Data were analyzed using one and two-way ANOVA and Tukey's test (α=0.05). The gap percentage was higher in the bottom compared to the top. The B/T ratio of the Aura Bulk Fill was statistically lower than other composites. Push-out bond strength were similar among composites. The RVBFC presented lower nanoleakage than the RVTC in the bottom of the conical restoration and there was no difference among the materials in the top surfaces. In conclusion, Filtek Bulk Fill performed better than Aura Bulk Fill regarding the analyzed properties.

Interfacial properties and bottom/top hardness ratio produced by bulk fill composites in dentin cavities

Abstract The aim of this study was to evaluate the bond strength, bottom/top hardness ratio, marginal adaptation, and interfacial nanoleakage of regular viscosity bulk fill composites (RVBFC) and regular viscosity traditional composites (RVTC). Two RVBFC (Filtek Bulk Fill and Aura Bulk Fill) and two RVTC (Filtek Z250XT and Aura) were assessed. Forty conical cavities (4.8×2.8×4.0) were prepared in bovine dentin and restored with composites (n=10). After 24h in water, marginal adaptation was evaluated by staining with a caries detector. The top and bottom surfaces of the conical restorations were stained for five seconds and the gap percentage in the composite/dentin interface was determined using digital images on a measurement program (ImageTool). The Vickers microhardness was measured and the bottom/top microhardness ratio (B/T) was determined. Push-out bond strength test was performed in a universal testing machine (0.5mm/min) and failure modes were evaluated in a stereomicroscope (20×). Other specimens (n=3) were produced for interfacial nanoleakage evaluation. Data were analyzed using one and two-way ANOVA and Tukey's test (α=0.05). The gap percentage was higher in the bottom compared to the top. The B/T ratio of the Aura Bulk Fill was statistically lower than other composites. Push-out bond strength were similar among composites. The RVBFC presented lower nanoleakage than the RVTC in the bottom of the conical restoration and there was no difference among the materials in the top surfaces. In conclusion, Filtek Bulk Fill performed better than Aura Bulk Fill regarding the analyzed properties.

Resumo O objetivo deste estudo foi avaliar a resistência de união, razão base/topo de microdureza, adaptação marginal e nanoinfiltração interfacial de resinas compostas bulk fill (BF) e tradicional (RT) de viscosidade regular.: Duas BF (Filtek Bulk Fill e Aura Bulk Fill) e duas RT (Filtek Z250XT e Aura) foram testados. Quarenta cavidades cônicas (4,8×2,8×4,0) foram preparadas em dentina bovina e restauradas com os compósitos (n=10). Depois de 24 h em água, a adaptação marginal foi avaliada por meio do corante com detector de cárie. As faces de topo e base das restaurações cônicas foram coradas por cinco segundos e a porcentagem de fendas na interface compósito/dentina foi determinada utilizando-se imagens analisadas num programa (ImageTool). A microdureza Vickers foi mensurada e a razção base/topo de microdureza (B/T) foi determinada. A resistência de união por push-out foi executada numa máquina de ensaios universal (0,5mm/min) e o padrão de fratura avaliado num estereomicroscópio (20x). Espécimes adicionais (n=3) foram confeccionados para avaliação da nanoinfiltração interfacial. Os dados foram analisados por meio de ANOVA a dois fatores e teste de Tukey (a=0,05). A porcentagem de fendas foi maior na base que no topo. A B/T da Aura Bulk Fill foi estatisticamente menor que os demais compósitos. A resistência de união por push-out foi similar entre os compósitos. As BF apresentaram menos nanoinfiltração que as RT na base das restaurações cônicas e não houve diferenças entre os materiais no topo. Conclui-se que a Filtek Bulk Fill comportou-se melhor que a Aura Bulk Fill considerando-se as propriedades analisadas.

Effect of hydrofluoric acid concentration and etching time on resin-bond strength to different glass ceramics.

The objective of this study was to evaluate the effect of the hydrofluoridric acid (HF) concentration and time of acid conditioning on bond strength of three glass ceramics to a resin cement. Thus, fifty blocks (10 mm x 5 mm x 2 mm) of each ceramic (LDCAD: IPS e.max CAD; LCAD: IPS Empress CAD and LDHP: IPS e.max Press) were made and embedded in acrylic resin. The surfaces were polished with sandpaper (#600, 800, 1000, and 1200 grits) and blocks were randomly divided into 15 groups (n = 10) according to the following factors: Concentration of HF (10% and 5%), conditioning time (20 s and 60 s) and ceramic (LDCAD, LDHP, and L). After conditioning, silane (Prosil / FGM) was applied and after 2 min, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block using a Teflon strip as matrix and light cured for 40 s (1,200 mW/cm2). Then, the samples were thermocycled (10,000 cycles, 5/55°C, 30s) and submitted to the shear bond test (50 KgF, 0.5 mm/min). The data (MPa) were analyzed with 3-way ANOVA and Tukey's test (5%). Failure analysis was performed using a stereomicroscope (20x) and a scanning electron microscope (SEM). ANOVA revealed that the "concentration" factor (p = 0.01) and the interaction "acid concentration X ceramic" (p = 0.009) had a significant effect, however, the "ceramic" (p = 0.897) and "conditioning time" (p = 0.260) factors did not influence the results. The LDHP10%60s (10.98 MPa)aA* group presented significantly higher bond strength than LDHP10%20s (6.57 MPa)bA, LCAD5%20s (6,90 ±3,5)aB and LDHP5%60s (5.66 ± 2,9MPa)aA* groups (Tukey). Failure analysis revealed that 100% of specimens had mixed failure. In conclusion, etching with 5% HF for 20 seconds is recommended for lithium disilicate and leucite-reinforced CAD/CAM ceramics. However, for pressed lithium disilicate ceramic, 10% HF for 60 s showed significantly higher bond strength to resin cement.

Effect of different loading pistons on stress distribution of a CAD/CAM silica-based ceramic: CAD-FEA modeling and fatigue survival analysis.

PURPOSE: This study evaluated the effect of different loading pistons, made of various materials and with different elastic moduli acting as antagonist material, on stress distribution and fatigue behavior of a CAD/CAM silica-based ceramic. MATERIALS AND METHODS: Discs of CAD/CAM made silica-based ceramic (N = 60) (VITA MARK II) were divided into six groups (n = 10 per group), according to the test method (M: Monotonic; F: Fatigue) and the antagonist piston material (T: Tungsten; S: Steel; G: Epoxy resin). FT, FS and FG combinations were submitted to mechanical cycling (2 × 106 cycles, 4 Hz, 45 N). The bending stress after fatigue were also valuated using Weibull analysis and the parameters η (eta), ß (beta) and the mean time to failure (MTTF) were calculated. Fractographic analysis and Finite Element Analysis (FEA) were performed. Data were analyzed using ANOVA and Tukey's tests (alpha=0.05). RESULTS: MG presented significantly less bending strength (MPa) (75.6) compared to MT (87.8) and MS (84.4) (p < 0.05). Six specimens from FT (MMTF: 8.3 × 106; ß:0.60; η:5.6 × 106), four from FS (MMTF: 1.9 × 106; ß:1.2; η:2.0 × 106) and one from FG (MMTF: 1.3 × 106; ß:0.48; η:0.64 × 106) survived the fatigue test. The stress peak on the tensile surface of S was similar to that of T and both were less than that of G. The failure origins were on the tensile surface. CONCLUSION: The epoxy resin pistons were able to decrease the bending stress, and life expectancy (faster failure) of a silica-based ceramic compared to tungsten and steel.

Effect of hydrofluoric acid concentration and etching time on resin-bond strength to different glass ceramics

Abstract: The objective of this study was to evaluate the effect of the hydrofluoridric acid (HF) concentration and time of acid conditioning on bond strength of three glass ceramics to a resin cement. Thus, fifty blocks (10 mm x 5 mm x 2 mm) of each ceramic (LDCAD: IPS e.max CAD; LCAD: IPS Empress CAD and LDHP: IPS e.max Press) were made and embedded in acrylic resin. The surfaces were polished with sandpaper (#600, 800, 1000, and 1200 grits) and blocks were randomly divided into 15 groups (n = 10) according to the following factors: Concentration of HF (10% and 5%), conditioning time (20 s and 60 s) and ceramic (LDCAD, LDHP, and L). After conditioning, silane (Prosil / FGM) was applied and after 2 min, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block using a Teflon strip as matrix and light cured for 40 s (1,200 mW/cm2). Then, the samples were thermocycled (10,000 cycles, 5/55°C, 30s) and submitted to the shear bond test (50 KgF, 0.5 mm/min). The data (MPa) were analyzed with 3-way ANOVA and Tukey's test (5%). Failure analysis was performed using a stereomicroscope (20x) and a scanning electron microscope (SEM). ANOVA revealed that the "concentration" factor (p = 0.01) and the interaction "acid concentration X ceramic" (p = 0.009) had a significant effect, however, the "ceramic" (p = 0.897) and "conditioning time" (p = 0.260) factors did not influence the results. The LDHP10%60s (10.98 MPa)aA* group presented significantly higher bond strength than LDHP10%20s (6.57 MPa)bA, LCAD5%20s (6,90 ±3,5)aB and LDHP5%60s (5.66 ± 2,9MPa)aA* groups (Tukey). Failure analysis revealed that 100% of specimens had mixed failure. In conclusion, etching with 5% HF for 20 seconds is recommended for lithium disilicate and leucite-reinforced CAD/CAM ceramics. However, for pressed lithium disilicate ceramic, 10% HF for 60 s showed significantly higher bond strength to resin cement.