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OBJECTIVE: The objective of this study was to 1) compare the stress corrosion coefficient (n) of a Y-TZP obtained by two fatigue tests: cyclic and dynamic and 2) evaluate the effect of frequency in the characteristic lifetime and the existence of interaction between the cyclic fatigue and slow crack growth. METHODS: A total of 145 Y-TZP specimens were produced in accordance with the manufacturer's instructions. These specimens, measuring 4.0 × 3.0 × 25.0 mm, were used for dynamic (n = 70) and cyclic fatigue tests (n = 75). The specimens were obtained from CAD/CAM blocks, sectioned, and sintered in a furnace at 1530 °C with a heating rate of 25 °C/min. They were tested in their "as-sintered" form without any additional surface treatment. The fatigue tests were conducted using a four-point bending to obtain the slow crack growth parameters (n). The cyclic fatigue test was also conducted in two frequencies (2 and 10 Hz), using stress levels between 350 and 600 MPa. Data from these tests were analyzed using ASTM C 1368-00 formulas and Weibull statistics. Scanning electron microscope (SEM) was used for fracture surface analysis to identify the origin of the fracture. Critical defect size was measured and used, along with flexural strength values, to estimate fracture toughness. Dynamic fatigue test data were used to obtain subcritical crack growth (SCG) parameters and perform Weibull statistical analysis. The cyclic fatigue data were used in the General Log-linear Model equation using the ALTA PRO software. Data were analyzed using one-way ANOVA followed by Tukey post-hoc tests and Student's t-test at a significance level of p ≤ 0.05. RESULTS: In the dynamic fatigue test, the values obtained for σfo and n were 667 and 54, respectively. This parameter indicates how the strength of the material diminishes over time due to internal cracks. The Weibull parameters obtained from the same test results were m = 7.9, σ0 = 968, 9 and σ5% = 767, which indicates the reliability of the material. The Weibull parameters obtained by cyclic fatigue were statistically similar for the two frequencies used, the m* was 0.17 (2 Hz) and 0.21 (10 Hz); characteristic lifetimes (η) were 1.93 × 106 and 40,768, respectively. The n values obtained by cyclic fatigue were 48 and 40 at frequencies of 2 and 10 Hz, respectively. There was no effect of the frequency, the stress level or the interaction of the two in the Y-TZP lifetime, when analysed by General Log Linear Model. SIGNIFICANCE: the n values obtained by cyclic and dynamic fatigue tests showed no statistically significant difference and the effect of frequency in the characteristic lifetime and the existence of interaction between the cyclic fatigue and subcritical growth were not observed in the tested specimens.

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PURPOSE: This study evaluated the fatigue failure load (FFL) and the number of cycles for fatigue failure (CFF) of traditional (porcelain layer up) and reversed (zirconia layer up) designs of porcelain-veneered zirconia samples prepared with heat-pressing or file-splitting techniques. MATERIALS AND METHODS: Zirconia discs were prepared and veneered with heat-pressed or machined feldspathic ceramic. The bilayer discs were bonded onto a dentin-analog according to the bilayer technique and sample design: traditional heat-pressing (T-HP), reversed heat-pressing (R-HP), traditional file-splitting with fusion ceramic (T-FC), reversed file-splitting with fusion ceramic R-FC), traditional file-splitting with resin cement (T-RC), and reversed file-splitting with resin cement (R-RC). The fatigue tests were performed using the stepwise approach at 20 Hz, 10,000 cycles/step, step-size of 200 N starting at 600 N, and proceeding until failure detection or up to 2600 N if enduring. The failure modes (from radial and/or cone cracks) were analyzed in a stereomicroscope. RESULTS: The reversed design decreased the FFL and CFF of bilayers prepared with heat-pressing and file-splitting with fusion ceramic. The T-HP and T-FC reached the highest results, which were statistically similar between them. The bilayers prepared by the file-splitting with resin cement (T-RC and R-RC) were similar to the R-FC and R-HP groups regarding FFL and CFF. Almost all reverse layering samples failed by radial cracks. CONCLUSIONS: The reverse layering design did not improve the fatigue behavior of porcelain veneered zirconia samples. The three bilayer techniques behaved similarly when used in the reversed design.

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Objective: The aim of this study was to evaluate the marginal gap of frameworks produced using the CAD-CAM system, from zirconia and lithium disilicate blocks, adapted to a tooth preparation and a gypsum die. Material and Methods: For this study, a human first molar tooth was used as a master model with a full crown preparation. It was molded 20 times to obtain the gypsum die and randomly divided into 2 groups (n=10) for the fabrication of zirconia and lithium disilicate frameworks. The frameworks were made using pre-sintered zirconia blocks and lithium disilicate blocks, both CAD-CAM systems. The marginal gap was measured in µm at four points (buccal, palatal, mesial, and distal) using a comparator microscope with 30x magnification, with the framework seated on the master model (tooth), and on the gypsum die. Marginal gap data (µm) were evaluated using two-way analysis of variance and Tukey's test with a significance level of 5%. Results: The results showed that there was no statistically significant interaction between the factors studied (p=0.223) or isolated factors (ceramic factor p=0.886 and die factor p=0.786). Conclusion: Both ceramics produced using the CAD-CAM technique did not exhibit statistical differences in marginal adaptation on the two types of substrates, both on tooth preparation and on the gypsum die (AU)

Objetivo: O objetivo deste estudo foi avaliar o espaço marginal de estruturas produzidas usando o sistema CAD-CAM, a partir de blocos de zircônia e dissilicato de lítio, adaptadas a um preparo sobre dente e a um troquel de gesso. Material e Métodos: Para este estudo, um dente molar humano foi utilizado como modelo mestre com preparo para coroa total. Este foi moldado 20 vezes para obter o troquel de gesso e dividido aleatoriamente em 2 grupos (n=10) para a fabricação de estruturas de zircônia e dissilicato de lítio. As estruturas foram feitas usando blocos de zircônia pré-sinterizados e blocos de dissilicato de lítio, ambos sistemas para CAD-CAM. O espaço marginal foi medido em µm, em quatro pontos (bucal, palatal, mesial e distal), utilizando um microscópio comparador com ×30 de ampliação e com a estrutura assentada no modelo mestre (dente) e no troquel de gesso. Os dados de espaço marginal (µm) foram avaliados usando análise de variância bidirecional e teste de Tukey com um nível de significância de 5%. Resultados: Os resultados mostraram que não houve interação estatisticamente significativa entre os fatores estudados (p=0,223) ou isoladamente (fator cerâmica p=0,886 e fator troquel p=0,786). Conclusão: Ambas as cerâmicas produzidas usando a técnica CAD-CAM não apresentaram diferenças estatísticas em relação à adaptação marginal nos dois tipos de substratos, tanto na preparação dentária quanto no troquel de gesso(AU)

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PURPOSE: To evaluate the effects of 1 versus 2 glaze firings on the color and mechanical properties of an extrinsically characterized lithium disilicate ceramic after thermal cycling, brushing, or both. MATERIALS AND METHODS: Eighty specimens were divided into 2 groups: 1 glaze firing (GL1) and 2 glaze firings (GL2). Each group was subdivided into 4 groups (n = 10), according to the experimental conditions: thermal-cycling, brushing, thermal-cycling + brushing, and immersion in distilled water (control). Color variation, surface roughness, and Vickers microhardness were analyzed before each designated experiment and after the simulated periods of 2.5, 5, and 10 years. Three-way mixed ANOVA was used for all outcomes, followed by 1-way ANOVA, repeated measures 1-way ANOVA, Bonferroni post hoc test, and t-test to check for statistical differences (α = 0.05). RESULTS: Thermal cycling generated greater color changes in the GL1 group at 2.5 and 5 years (p < 0.001; p = 0.013). Brushing generated color changes in GL1 at 5 years (p = 0.003) and in GL2 at 10 years (p = 0.017). Regarding surface roughness, the GL1 group suffered alterations in thermal cycling + brushing at 5 years. In the control group, the GL1 group exhibited higher roughness values than GL2 (p < 0.05). Most of the groups experienced an increase in microhardness at 2.5 years (p < 0.05). In the GL1 group, thermal-cycling increased the microhardness at 5 years (p = 0.006); at 5 and 10 years, the GL1 group had a higher microhardness than the GL2 in thermal-cycling + brushing (p < 0.05). CONCLUSION: Ceramics with 1 glaze firing showed greater color, roughness, and microhardness changes compared to those submitted to 2 firings.

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PURPOSE: To evaluate the effect of different veneering ceramics and veneering techniques on the bond strength to zirconia. MATERIALS AND METHODS: 3Y-TZP zirconia blocks were sliced into 60 slabs, polished, and sintered. Each slab received one ceramic cylinder (Ø = 3.4 mm, 5 mm-high), according to the veneering ceramic type (feldspathic-FEL or lithium disilicate-based-LD) and the veneering technique (file-splitting with resin-based luting agent-RC, file-splitting with fusion ceramic-FC, or heat-pressing-HT), which resulted in six groups: FEL-RC, FEL-FC, FEL-HT, LD-RC, LD-FC, LD-HT. After preparation, the samples were immersed in distilled water for 24 h before the shear bond strength (SBS) test. The failure modes were classified as adhesive, predominantly adhesive, or cohesive. Representative failure mode images were taken in a Scanning Electron Microscope. The SBS data were analyzed by two-way ANOVA and Tukey's test. RESULTS: Both type of veneering ceramic and technique affected the bond strength. FC led to the highest SBS values. RC and HP provided similar results when compared within each veneering ceramic. Lithium disilicate achieved lower bond strength than feldspathic ceramic when the heat-pressing technique was applied. The most frequent failure modes were predominantly adhesive and adhesive for FEL and LD, respectively. CONCLUSION: File-splitting with fusion ceramic provided the highest adhesion to zirconia when feldspathic or lithium disilicate-based ceramics were used. The heat-pressing technique for veneering with lithium disilicate significantly decreased the bond strength when compared to the feldspathic ceramic.

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During ceramic veneer luting, resin cement polymerization is performed with interposition of the dental ceramic. Aim: To evaluate how and how much the photoactivation time affects the Vickers hardness of resin-based cements with interposed ceramic. Materials and Method: A total 24 specimens H mm in diameter and 1 mm thick were made from Paracore White Coltene (PC), Densell Resin Duo Cement (DC), 3MRelyX Veneer (RX) and Coltene Fill Up! (FU), interposing VitablockMarkII (Vita Zahnfabrik) feldspathic ceramic 0.6 mm thick during photoactivation. The materials were polymerized using 100% and 25% of the times indicated by the manufacturers with a Coltolux LED ((Coltene) light with intensity 1200 mW/cm2. Each polymerization time group consisted of three specimens of each material, which were stored dry in darkness at 37 °C for 7 days. Three Vickers microhardness measurements were made on the top and bottom surfaces of each specimen using a Vickers Future Tech FM300 microhardness tester (300 g, 5 s). The values were averaged, and the bottom/top ratios calculated. Results were analyzed by ANOVA. (p<0.05) complemented with multiple comparisons using Tukey's test (p<0.05). Results: Different photoactivation times were found to have a significant effect on hardness values of the cements evaluated, with significant differences between some of the cements. No statistically significant difference was found for the effect of photoactivation time on bottom/top microhardness ratio in those materials. Conclusions: Under the experimental conditions employed, it can be concluded that photopolymerization for shorter times and the interposition of restorative material significantly affectpolymerization quality as evaluated by microhardness, but the bottom/top ratio was unaffected by differences in polymerization time.

Durante la fijación de una carilla cerámica, la polimerización del cemento a base de resinas se realiza con la interposición de la cerámica dental. Objetivo: evaluar en qué forma y magnitud afecta el tiempo de fotoactivación en la dureza Vickers de los cementos a base de resinas con la cerámica interpuesta. Materiales y Método: se confeccionaron 24 probetas de 11 mm de diámetro y 1 mm de espesor con: Paracore White Coltene (PC), Resin Duo Cement de Densell (DC), RelyX Veneer de 3M (RX) y Fill Up! De Coltene (FU) interponiendo 0,6 mm de espesor de cerámica feldespática Vitablock Mark II (Vita Zahnfabrik) durante la fotoactivación. Se polimerizó utilizando el 100% y el 25% del tiempo indicado por el fabricante con lámpara Coltolux LED ((Coltene) con 1200 mW/cm2 de intensidad. Cada grupo quedó conformado con tres probetas de cada material que se almacenaron a oscuras y en seco a 37 °C durante 7 días. Se registraron tres mediciones de microdureza Vickers de las superficies top y bottom de cada probeta con un microdurómetro Vickers Future Tech FM300 (300 g, 5 s) y se calculó su promedio, así como la relación entre los valores registrados en cada una de sus caras. Los resultados fueron analizados por medio de la prueba de ANOVA. (p<0.05). complementada con comparaciones múltiples por medio de la prueba de Tukey (p<0.05). Resultados: se encontró un efecto significativo de la modificación del tiempo de fotoactivación en los valores de dureza de los cementos evaluados con diferencias significativas entre algunos de ellos. Simultáneamente no se encontró significación estadística en el efecto de ese factor sobre la relación microdureza bottom/top registrada en esos materiales. Conclusiones: en las condiciones experimentales empleadas puede concluirse que la fotopolimerización en menor tiempo e interposición de material restaurador afecta significativamente la calidad de polimerización evaluada mediante los valores de microdureza, pero la proporción bottom/ top no fue afectada en la variación en el tiempo de polimerización.

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An esthetically pleasing smile is a valuable aspect of physical appearance and plays a significant role in social interaction. Achieving the perfect balance between extraoral and intraoral tissues is essential for a harmonious and attractive smile. However, certain intraoral deficiencies, such as non-carious cervical lesions and gingival recession, can severely compromise the overall aesthetics, particularly in the anterior zone. Addressing such conditions requires careful planning and meticulous execution of both surgical and restorative procedures. This interdisciplinary clinical report presents a complex case of a patient with esthetic complaints related to asymmetric anterior gingival architecture and severely discolored and eroded maxillary anterior teeth. The patient was treated using a combination of minimally invasive ceramic veneers and plastic mucogingival surgery, resulting in a successful outcome. The report emphasizes the potential of this approach in achieving optimal esthetic results in challenging cases, highlighting the importance of an interdisciplinary team approach in achieving a harmonious balance between dental and soft tissue aesthetics.

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ABSTRACT During ceramic veneer luting, resin cement polymerization is performed with interposition of the dental ceramic. Aim: To evaluate how and how much the photoactivation time affects the Vickers hardness of resin-based cements with interposed ceramic. Materials and Method: A total 24 specimens H mm in diameter and 1 mm thick were made from Paracore White Coltene (PC), Densell Resin Duo Cement (DC), 3MRelyX Veneer (RX) and Coltene Fill Up! (FU), interposing VitablockMarkII (Vita Zahnfabrik) feldspathic ceramic 0.6 mm thick during photoactivation. The materials were polymerized using 100% and 25% of the times indicated by the manufacturers with a Coltolux LED ((Coltene) light with intensity 1200 mW/cm2. Each polymerization time group consisted of three specimens of each material, which were stored dry in darkness at 37 °C for 7 days. Three Vickers microhardness measurements were made on the top and bottom surfaces of each specimen using a Vickers Future Tech FM300 microhardness tester (300 g, 5 s). The values were averaged, and the bottom/top ratios calculated. Results were analyzed by ANOVA. (p<0.05) complemented with multiple comparisons using Tukey's test (p<0.05). Results: Different photoactivation times were found to have a significant effect on hardness values of the cements evaluated, with significant differences between some of the cements. No statistically significant difference was found for the effect of photoactivation time on bottom/top microhardness ratio in those materials. Conclusions: Under the experimental conditions employed, it can be concluded that photopolymerization for shorter times and the interposition of restorative material significantly affectpolymerization quality as evaluated by microhardness, but the bottom/top ratio was unaffected by differences in polymerization time.

RESUMEN Durante la fijación de una carilla cerámica, la polimerización del cemento a base de resinas se realiza con la interposición de la cerámica dental. Objetivo: evaluar en qué forma y magnitud afecta el tiempo de fotoactivación en la dureza Vickers de los cementos a base de resinas con la cerámica interpuesta. Materiales y Método: se confeccionaron 24 probetas de 11 mm de diámetro y 1 mm de espesor con: Paracore White Coltene (PC), Resin Duo Cement de Densell (DC), RelyX Veneer de 3M (RX) y Fill Up! De Coltene (FU) interponiendo 0,6 mm de espesor de cerámica feldespática Vitablock Mark II (Vita Zahnfabrik) durante la fotoactivación. Se polimerizó utilizando el 100% y el 25% del tiempo indicado por el fabricante con lámpara Coltolux LED ((Coltene) con 1200 mW/cm2 de intensidad. Cada grupo quedó conformado con tres probetas de cada material que se almacenaron a oscuras y en seco a 37 °C durante 7 días. Se registraron tres mediciones de microdureza Vickers de las superficies top y bottom de cada probeta con un microdurómetro Vickers Future Tech FM300 (300 g, 5 s) y se calculó su promedio, así como la relación entre los valores registrados en cada una de sus caras. Los resultados fueron analizados por medio de la prueba de ANOVA. (p<0.05). complementada con comparaciones múltiples por medio de la prueba de Tukey (p<0.05). Resultados: se encontró un efecto significativo de la modificación del tiempo de fotoactivación en los valores de dureza de los cementos evaluados con diferencias significativas entre algunos de ellos. Simultáneamente no se encontró significación estadística en el efecto de ese factor sobre la relación microdureza bottom/top registrada en esos materiales. Conclusiones: en las condiciones experimentales empleadas puede concluirse que la fotopolimerización en menor tiempo e interposición de material restaurador afecta significativamente la calidad de polimerización evaluada mediante los valores de microdureza, pero la proporción bottom/ top no fue afectada en la variación en el tiempo de polimerización.

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Minimally invasive dentistry is a considered process that requires the clinician to be prepared with the ideal sequence and the tools needed. This report describes a well-planned ultraconservative approach using only two ceramic laminate veneers for the maxillary central incisors to significantly improve the patient's overall smile. A 30-year-old female presented with the chief complaints of having diastemas between the central and lateral incisors as well as incisal wear. Diagnostic wax-up and mock-up were performed, and the patient approved the minimally invasive treatment with veneers only for central incisors. A reduction guide aided the conservative tooth preparations, and hand-crafted feldspathic veneers were bonded under total isolation with a rubber dam. The two final conservative veneers significantly improved the smile and fulfilled the patient's expectations. Following proper planning and sequencing, predictable outcomes were obtained and fulfilled the patient's esthetic demands. Minimally invasive restorative dentistry with only two single veneers can impact the entire smile frame. Overtreatment in the esthetic zone is unnecessary to meet a patient's esthetic expectations.

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This study evaluated the effect of resin cement coating with high and low viscosities on the flexural fatigue strength of machined lithium disilicate glass-ceramic. Discs (IPS e.max CAD; Ivoclar Vivadent) were prepared and divided according to the surface condition (machining [M]-CEREC inLab; and polishing [P]-laboratory procedures), resin cement coating (with or without), and cement viscosity (high [H] and low [L]). The ceramic bonding surface was etched/primed by a one-step primer application followed by resin cement application (Variolink N base + high or low viscosity catalyst; Ivoclar Vivadent). Biaxial flexural fatigue strength was evaluated on a piston-on-three-ball set by the step-test method (n = 15) (initial stress: 60 MPa; incremental steps: 20 MPa; 10,000 cycles/step, at 20 Hz). Weibull statistics were used for fatigue data. Contact angle, topographic, and fractographic analysis were also performed. Machining produced statistically lower contact angle than polishing and a significant detrimental effect on the fatigue behavior (σ0 M = 247.2 [246.9-268.3]; σ0 P = 337.4 [297.8-382.4]). Machined groups followed by resin cement coating (σ0 MH = 297.9 [276.0-321.5]; σ0 Ml = 301.2 [277.1-327.4]) behaved similarly to the polished and coated groups (σ0 PH = 342.0 [308.9-378.5]; σ0 PL = 357.3 [324.7-393.1]), irrespective of the cement viscosity. Therefore, cement coating has able to revert the detrimental effects of the machining on the fatigue strength of lithium disilicate glass-ceramic. High and low viscosity cements behaved similarly in the improvement of CAD-CAM lithium disilicate fatigue strength.

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Objetivos: Avaliar as propriedades mecânicas, atividade antimicrobiana e citocompatibilidade da zircônia translúcida 5Y-PSZ revestida por vidros experimentais contendo boro e prata. Métodos: Discos 5Y-PSZ (KATANA UTML™, Kuraray Noritake) foram processados e divididos em quatro grupos: polido, sem nenhum revestimento (Controle), aplicação de glaze comercial (Glaze) e vidros experimentais contendo prata (AgCoat) e boro (BCoat). As amostras foram submetidas aos testes de dureza Vickers, testes de flexão biaxial, análise fractográfica e rugosidade através de perfilometria óptica. O potencial antimicrobiano foi caracterizado usando biofilmes de espécie única de Streptococcus mutans e Candida albicans. Foi realizada a quantificação de unidades viáveis formadoras de colônias (UFC), atividade metabólica (CV), ensaios de matriz polissacarídica extracelular (EPS) e biovolume. Biofilmes foram visualizados por microscópio eletrônico de varredura (MEV) e microscopia confocal de varredura a laser (CLSM). A citocompatibilidade foi determinada usando os testes WST-1 e LIVE&DEAD usando células-tronco do ligamento periodontal (PDLSCs) por 24 h. Todas as caracterizações biológicas foram realizadas em triplicatas técnicas e biológicas usando amostras independentes. As análises estatísticas foram realizadas por ANOVA de uma via, teste de Tukey, análise de Weibull e análise de correlação de Pearson. Resultados: BCoat, AgCoat e Glaze alcançaram dureza semelhante, que foi menor que o Controle. BCoat teve a maior resistência à flexão e parâmetros de Weibull (m = 11,5, sF 625 MPa, s0 620) seguido por AgCoat (m = 5,3; sF 464 MPa, s0 478 MPa). BCoat diminuiu significativamente a formação de biofilmes, conforme mostrado pela menor UFC (5,94 log-UFC/mm2) e atividade metabólica (0,17 a.u.) em comparação com os outros grupos (AgCoat: 6,44 log-UFC/mm2, 0,89 a.u.; Glaze: 6,81 log UFC/mm2, 1,21 a.u.; Controle: 6,82 logUFC/mm2, 1,25 a.u.). BCoat e AgCoat apresentaram os menores valores de EPS (0,11 a.u.), seguidos por Glaze e Controle (0,13 a.u.; 0,14 a.u., respectivamente). MEV e CLSM revelaram que os biofilmes no BCoat eram finos, esparsos, com menor biovolume, enquanto os outros grupos produziram biofilmes robustos com maior biovolume. Os ensaios de viabilidade celular não mostraram toxicidade para PDLSCs para todos os grupos. Conclusão: 5Y-PSZ revestida por vidro experimental contendo boro surge como uma estratégia potencial para melhorar as propriedades mecânicas e antimicrobianas do material (AU).

Objectives: To evaluate the mechanical and antimicrobial properties of boroncontaining coating on translucent zirconia (5Y-PSZ). Methods: 5Y-PSZ discs (Control) were coated with a glaze (Glaze), silver- (AgCoat), or boron-containing (BCoat) glasses. The coatings' antimicrobial potential was characterized using S. mutans and C. albicans biofilms through viable colony-forming units (CFU), metabolic activity (CV), and the extracellular polysaccharide matrix (EPS). Biofilm architectures were imaged under scanning electron and confocal laser scanning microscopies (SEM and CLSM). Cytocompatibility was determined at 24 h via WST-1 and LIVE&DEAD assays using periodontal ligament stem cells (PDLSCs). The coatings' effects on mechanical properties were characterized by Vickers hardness, biaxial bending tests, and fractography analysis. Statistical analyses were performed via one-way ANOVA, Tukey's tests, Weibull analysis, and Pearson's correlation analysis. Results: BCoat significantly decreased biofilm formation, having the lowest CFU and metabolic activity compared with the other groups. BCoat and AgCoat presented the lowest EPS, followed by Glaze and Control. SEM and CLSM images revealed that the biofilms on BCoat were thin and sparse, with lower biovolume. In contrast, the other groups all yielded similarly robust biofilms with higher biovolume without compromising PDLSC viability. BCoat, AgCoat, and Glaze also presented similar hardness significantly lower than Control. BCoat had the highest flexural strength, characteristic strength and Weibull parameters (sF : 625 MPa; s0: 620 MPa; m = 11.5), followed by AgCoat (sF : 464 MPa; s0: 478 MPa; m = 5.3). Significance: BCoat is a cytocompatible glass with promising antimicrobial properties that can improve the mechanisms and reliability of 5Y-PSZ (AU).

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Abstract The demands for dental materials continue to grow, driven by the desire to reach a better performance than currently achieved by the available materials. In the dental restorative ceramic field, the structures evolved from the metal-ceramic systems to highly translucent multilayered zirconia, aiming not only for tailored mechanical properties but also for the aesthetics to mimic natural teeth. Ceramics are widely used in prosthetic dentistry due to their attractive clinical properties, including high strength, biocompatibility, chemical stability, and a good combination of optical properties. Metal-ceramics type has always been the golden standard of dental reconstruction. However, this system lacks aesthetic aspects. For this reason, efforts are made to develop materials that met both the mechanical features necessary for the safe performance of the restoration as well as the aesthetic aspects, aiming for a beautiful smile. In this field, glass and high-strength core ceramics have been highly investigated for applications in dental restoration due to their excellent combination of mechanical properties and translucency. However, since these are recent materials when compared with the metal-ceramic system, many studies are still required to guarantee the quality and longevity of these systems. Therefore, a background on available dental materials properties is a starting point to provoke a discussion on the development of potential alternatives to rehabilitate lost hard and soft tissue structures with ceramic-based tooth and implant-supported reconstructions. This review aims to bring the most recent materials research of the two major categories of ceramic restorations: ceramic-metal system and all-ceramic restorations. The practical aspects are herein presented regarding the evolution and development of materials, technologies applications, strength, color, and aesthetics. A trend was observed to use high-strength core ceramics type due to their ability to be manufactured by CAD/CAM technology. In addition, the impacts of COVID-19 on the market of dental restorative ceramics are presented.

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Este estudo avaliou o efeito do jateamento com óxido de alumínio prévio à camada de caracterização no comportamento adesivo e mecânico de zircônias de segunda e terceira gerações. Na parte A, foi realizado um estudo de resistência flexural. Para isso, discos de cada zircônia (3Y-TZP, 4Y-PSZ ou 5YPSZ) foram confeccionados. Após polimento e sinterização, os discos foram divididos de acordo com os tratamentos de superfície: Polimento, Jateamento com Al2O3 50 µm e Jateamento com Al2O3 110 µm (n = 30). A superfície tratada de todos os discos recebeu uma fina camada de pigmentação e uma fina camada de glaze. O ensaio de flexão biaxial foi realizado na configuração pistonon-three-balls e as superfícies fraturadas foram observadas em Microscopia Eletrônica de Varredura (MEV). Os dados foram submetidos à Análise de Weibull. Na parte B, avaliou-se o efeito dos diferentes tratamentos de superfície prévio à camada de caracterização no comportamento à fadiga das diferentes zircônias. Discos de 3Y-TZP, 4Y-PSZ e 5Y-PSZ foram confeccionados e distribuídos entre os tratamentos de superfície: Polimento ou Jateamento Al2O3 50 µm (n = 15), que foram realizados conforme a parte A deste estudo. Os discos foram cimentados adesivamente a um análogo de dentina (NEMA G10). Os testes de fadiga foram realizados pelo método stepwise, com aplicação de carga axial por um pistão hemisférico (carga inicial: 400 N, step: 100 N, ciclos/step: 10.000, frequência: 20 Hz). Na parte C, avaliou-se a resistência de união entre as diferentes zircônias e a camada de caracterização. Foram preparados os mesmos grupos descritos na "parte A" (n = 15). Cilindros de stain seguido por glaze foram construídos nas superfícies das zircônias. A resistência de união foi avaliada pelo teste de cisalhamento. Os tipos de falha (adesiva, predominantemente adesiva ou coesiva) foram analisados em estereomicroscópio e MEV. Análises complementares em perfilômetro e goniômetro foram realizadas. Para a parte A, o jateamento com Al2O3 110 µm aos menores valores de resistência à flexão, seguido do jateamento com as partículas de Al2O3 50 µm. Os maiores valores foram observados no grupo que não recebeu jateamento prévio à camada de caracterização. Esses resultados foram observados em todos os materiais. Na parte B, o jateamento com Al2O3 reduziu significativamente a carga e o número de ciclos para falha em fadiga de todos os materiais. Na parte C, os melhores valores de resistência de união foram atribuídos para o tratamento de superfície com Al2O3 110 µm, seguido de jateamento com Al2O3 50 µm e polimento. Dessa forma, o jateamento prévio à camada de caracterização reduz a resistência mecânica de zircônias de segunda geração e melhora a resistência de união entre os dois materiais (AU)

This study evaluated the effect of aluminum oxide sandblasting prior to the characterization layer on the adhesive and mechanical behavior of second- and third-generation zirconia. Part A consisted of a flexural strength study. Discs of each zirconia (3Y-TZP, 4Y-PSZ, or 5Y-PSZ) were prepared. After polishing and sintering, the discs were divided according to the surface treatments: Polishing, Sandblasting with Al2O3 50 µm and Sandblasting with Al2O3 110 µm (n = 30). The treated surface of all discs received a thin layer of stain and a thin layer of glaze. The biaxial bending test was performed in a piston-on-three-balls set-up. The fractured surfaces were observed by Scanning Electron Microscopy (SEM). Data were subjected to Weibull Analysis. In part B, the effect of different surface treatments prior to the characterization layer on the fatigue behavior of different zirconia was evaluated. Discs of 3Y-TZP, 4Y-PSZ and 5Y-PSZ were prepared and divided among the surface treatments: Polishing or Sandblasting Al2O3 50 µm (n = 15), which were performed according to part A of this study. The discs were adhesively cemented to a dentin-analogue (NEMA G10). Fatigue tests were performed using the stepwise method, with an axial load application by a hemispherical piston (initial load: 400 N, step: 100 N, cycles/step: 10,000, frequency: 20 Hz). Part C evaluated the bond strength between the different zirconia and the characterization layer. The same groups described in part A (n = 15) were prepared. Stain cylinders followed by glaze were built on the zirconia surfaces. The bond strength was evaluated by the shear test. The types of failure (adhesive, predominantly adhesive or cohesive) were analyzed using a stereomicroscope and SEM. Complementary analyzes in profilometer and goniometer were carried out. In part A, sandblasting with Al2O3 110 µm led to the lowest flexural strength results, followed by sandblasting with Al2O3 50 µm. Polishing group achieved the highest values. These results were observed in all tested ceramics. In part B, sandblasting with Al2O3 50 µm significantly reduced the fatigue failure load and the number of cycles for fatigue failure. In part C, the highest bond strength results were reached by sandblasting with Al2O3 110 µm, followed by sandblasting with Al2O3 50 µm, and polishing. Therefore, aluminum oxide particles sandblasting diminishes the mechanical behavior of second- and third-generation zirconias and improves the bond strength between the two materials. (AU)

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OBJECTIVE: To evaluate the effect of different acid etching time and bonding agent (silane and/or adhesive system) on biaxial flexural strength and physico-chemical properties of a lithium disilicate ceramic. MATERIAL AND METHODS: One hundred twenty ceramic discs were made and divided into 8 groups (n = 15) according to factors "etching time" (20 and 120 s) with hydrofluoric acid (HF) and "bonding agent" (C, no bonding agent; S, silane, A, adhesive; and SA, silane + adhesive). After surface treatment, a resin cement layer was applied to the surface and all specimens were subjected to biaxial flexural strength (BFS) test with treated surfaces loaded in tension (1 mm/min). The Weibull analyses and complementary analyses were also performed. Statistical analysis was done with 2-way ANOVA and the Tukey test (α = 0.05). RESULTS: ANOVA revealed that the factors "etching time" (p = 0.0003) and "bonding agent" (p = 0.007) were statistically significant. In the overall analysis, the HF120S group (272.02 ± 35.30A MPa) presented significantly higher BFS than that of HF120C (218.45 ± 17.15CD MPa) and HF20S (228.40 ± 37.83BCDMPa). On the other hand, the HF20A group (208.92 ± 31.16D MPa) had significantly lower BFS than HF120S (272.02 ± 35.30A), HF120A (254.42 ± 26.87ABC) and HF120SA (259.30 ± 36.55AB) groups (Tukey). The Weibull modulus (m) of all groups was significantly different from each other (p = 0.000). CONCLUSIONS: Regardless of etching time, the application of silane alone is sufficient to increase the flexural strength of glass ceramic, eliminating the need for the application of adhesive systems. Moreover, if only silane or adhesive is applied, 120-s HF application should increase the flexural resistance of the lithium disilicate ceramic. CLINICAL SIGNIFICANCE: Applications of adhesive systems after silanization can be suppressed from the surface treatment protocol of glass ceramics, since it does not improve their mechanical strength.

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OBJECTIVE: This study evaluated the microshear bond strength of a resin cement to Y-TZP after different methods of TiO2 nanotubes (nTiO2) incorporation on pre-sintered Y-TZP surfaces. METHODS: nTiO2 were synthesized and incorporated on Y-TZP slices as follows (n = 15): 1) nTiO2 mixed with isopropyl alcohol/manual application (MAl); 2) nTiO2 mixed with acetone/manual application (MAc); 3) nTiO2 mixed with isopropyl alcohol/high-pressure vacuum application (HPVAl); 4) nTiO2 mixed with acetone/high-pressure vacuum application (HPVAc). As controls, surfaces were sandblasted with Al2O3 (OX) or Rocatec silicatization (ROC). All ceramics were sintered after nTiO2 incorporation. Surface treatments of OX and ROC were made after sintering. Surfaces were characterized by confocal laser microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Resin composite cylinders (1.40 mm diameter and 1 mm height) were cemented with a resin cement, stored in water at 37 °C for 24 h and thermocycled for 10 000 cycles before microshear bond strength evaluation. Data were analyzed with one-way ANOVA and Games-Howell (α = 0.05), and fracture analysis was performed using a stereomicroscope. RESULTS: EDS confirmed the presence of TiO2 on treated Y-TZP. The confocal analysis showed higher roughness for HPVAc and OX. There were significant differences between surface treatments (p < 0.001). HPVAl (22.96 ± 10.3), OX (34.16 ± 7.9) and ROC (27.71 ± 9.4) showed higher microshear bond strengths and were statistically similar (p > 0.05). MAC showed intermediary values, and HPVAc and MAl presented decreased bond strength, with a high percentage of premature debonding. CONCLUSION: High-pressure vacuum application of nTiO2 mixed with isopropyl alcohol was able to produce bond strength values compared to conventional air abrasion and Rocatec silicatization. SIGNIFICANCE: The infiltration of TiO2 nanostructures on the pre-sintered Y-TZP is an interesting approach that can improve bond strength without the need of sandblasting methods.

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OBJECTIVES: This study aimed to evaluate the impact of mechanical fatigue cycling using the step-stress approach along with hydrothermaldegradation (134 ºC with a constant pressure of 2 bars for 20 h), and a novel intercalated hydrothermal/fatigue aging protocol on different aspects of the aging resistance of three generations of dental zirconias. METHODS: "Y"Z T (VITA), INCORIS "T"ZI (Dentsply Sirona) and "K"ATANA UTML (Noritake Kuraray) - 1st, 2nd and 3rd generation, respectively-, zirconia disks (N = 153), were divided into 6 groups (n = 3) for monotonic testing and 9 groups (n = 15) for mechanical fatigue testing, according to 3 proposed treatments for each zirconia: CF (control - only mechanical fatigue cycling); AF (aging in hydrothermal reactor at 134 °C for 20 h + mechanical fatigue cycling); AFA (Alternating protocol: 4 steps of 5 h of hydrothermal aging intercalated with mechanical fatigue cycling). Mechanical fatigue aging was performed according to the step-stress approach through biaxial flexural setup (piston-on-3-balls, initial strength: 100 MPa, step: 50 MPa/10,000, frequency: 20 Hz) until failure. Data were analyzed using Kaplan-Meier and Mantel-Cox test (α = 0.05), in addition to Weibull analysis. Fractured disks were analyzed in stereomicroscope, Scanning Electron Microscopy and X-Ray Diffraction. RESULTS: Continuous hydrothermal and mechanical fatigue cycling decreased the fatigue strength of YAF group (516 ± 38 MPa), while the alternating protocol increased it (730 ± 58 MPa). KATANA UTML showed no differences for both treatments and did not undergo t-m phase transformation. The TAF group showed the highest fatigue strength (810 ± 76 MPa) and cycles for failure (147,000.00 cycles). The fracture origin for all specimens was on the tensile side in pre-existing defects. SIGNIFICANCE: INCORIS TZI zirconia had higher fatigue strength and survival rates after hydrothermal and mechanical fatigue aging. Although less resistant, KATANA UTML did not suffer chemical degradation.

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OBJECTIVES: To evaluate the edge chipping resistance (ReA) and the fracture toughness (KC) of 3Y-TZP bilayers produced with the following materials/processing combinations: fluorapatite glass-ceramic applied on zirconia using the traditional layering and hot-pressing (press-on) techniques; feldspathic porcelain using rapid layer technology (RLT); and lithium disilicate glass-ceramic using CAD-on method. The influence of the cooling rate (slow and fast) was analyzed for layering and hot-pressing. METHODS: Bilayer bars (25x4x2 mm) were made following manufacturers' instructions. The edge chipping test was performed in an universal testing machine, using a coupled Vickers indenter. ReA was calculated dividing the critical load at fracture by the edge distance. Fracture toughness was calculated by a regression fit with a fixed slope of 1.5 correlating the critical chipping load regarding edge distance and also with indentation fracture (IF) method. Data were statistically analyzed using ANOVA and Tukey's test (α = 5%). RESULTS: ReA and KC was significantly higher for the CAD-on bilayers. RLT showed intermediate ReA means, and layering and hot-pressing techniques showed the lowest ReA values. For both processing methods there was no effect of the cooling protocol on the ReA and fracture toughness. CONCLUSIONS: There is a significant effect of the material/processing association on the edge chipping resistance and fracture toughness of the bilayers. There was no effect of the cooling protocol on the edge chipping resistance and fracture toughness for the specimens processed by both the layering and hot-pressing techniques.

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OBJECTIVE: To investigate the influence of different finishing/polishing techniques and in situ aging on the flexural strength (σ), surface roughness, and Candida albicans adherence of 5 mol% yttria-stabilized zirconia (ultratranslucent zirconia). MATERIALS AND METHODS: A total of 120 zirconia bars (Prettau Anterior, Zirkonzahn) with dimensions of 8 × 2 × 0.5 mm were divided into 8 groups (n = 15) according to two factors: "in situ aging" (non-aged and aged (A)) and "finishing/polishing" (control (C), diamond rubber polishing (R), coarse grit diamond bur abrasion (B), and coarse grit diamond bur abrasion + diamond rubber polishing (BR)). Half of the samples from each group were subjected to a 60-day in situ aging by fixing the bars into cavities prepared in the posterior region of the base of complete or partial dentures of 15 patients. The samples were then subjected to the mini flexural (σ) test (1 mm/min). A total of 40 zirconia blocks (5 × 5 × 2 mm) were prepared and subjected to roughness (Ra) analyses and fungal adherence and complementary analyses (X-ray diffraction (XRD) and scanning electron microscopy (SEM)). The data of mean σ (MPa) and roughness Ra (µm) were statistically analyzed by two-way and one-way ANOVA, respectively, and Tukey's test. The Weibull analysis was performed for σ data. The fungal adhesion (Log CFU/mL) data were analyzed by Kruskal-Wallis tests. RESULTS: For flexural resistance, the "finishing/polishing" factor was statistically significant (P = 0.0001); however, the "in situ aging" factor (P = 0.4458) was not significant. The non-aged (507.3 ± 115.7 MPa) and aged (487.6 ± 118.4 MPa) rubber polishing groups exhibited higher mean σ than the other techniques. The non-aged (260.2 ± 43.3 MPa) and aged (270.1 ± 48.8 MPa) bur abrasion groups presented lower σ. The coarse-grit diamond bur abrasion group (1.82 ± 0.61 µm) presented the highest roughness value (P = 0.001). Cell adhesion was not different among groups (P = 0.053). Group B presented the most irregular surface and the highest roughness Ra of 0.61 m. CONCLUSIONS: The finishing of ultratranslucent zirconia might be preferably done with a diamond rubber polisher. Moreover, the protocols used did not interfere with Candida albicans adhesion. CLINICAL RELEVANCE: Coarse-grit diamond burs might be avoided for finishing ultratranslucent monolithic zirconia, which might be preferably performed with a diamond rubber polisher.

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OBJECTIVE: To understand the stress development in porcelain-veneered zirconia (PVZ) and porcelain-veneered lithium disilicate (PVLD) crowns with different veneer/core thickness ratios and cooling rates. To provide design guidelines for better performing bilayer restorations with the aid of Viscoelastic Finite Element Method (VFEM). METHODS: The VFEM was validated by comparing the predicted residual stresses with experimental measurements. Then, the model was used to predict transient and residual stresses in the two bilayer systems. Models with two different veneer/core thickness ratios were prepared (2:1 and 1:1) and two cooling protocols were simulated (Fast: ∼300 °C/min, Slow: ∼30 °C/min) using the heat transfer module, followed by stress analysis in ABAQUS. The physical properties of zirconia, lithium disilicate, and the porcelains used for the simulations were determined as a function of temperature. RESULTS: PVLD showed lower residual stresses than PVZ. The maximum tensile stresses in PVZ were observed in the cusp area, whereas those in PVLD were located in the central fossa. The 1:1 thickness ratio decreased stresses in both layers of PVZ. Slow cooling slightly decreased residual stresses in both systems. However, the cooling rate effect was more evident in transient stresses. SIGNIFICANCE: Slow cooling is preferable for both systems. A thinner porcelain layer over zirconia lowers stresses throughout the restoration. The different stress distributions between PVZ and PVLD may affect their failure modes. Smaller mismatches in modulus, CTE, and specific heat between the constituents, and the use of low Tg porcelains can effectively reduce the deleterious transient and residual tensile stresses in bilayer restorations.

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OBJECTIVE: A silica-based nanofilm has been successfully deposited via Room-Temperature Atomic Layer Deposition (RT-ALD) on the surface of a glass. The purpose of this study was to evaluate the mechanical performance of a hybrid interface created between yttria-stabilized zirconia (Y-PSZ) transformed layer and silica-based nanofilm via RT-ALD. MATERIAL AND METHODS: Fully-sintered Y-PSZ (14 × 4.0 × 1.5 mm) specimens in different translucencies (MO, MT, LT; IPS e.max Zircad, Ivoclar Vivadent) were distributed in 5 groups: control (C - no treatment); hydrothermal treatment (HT- 15h, 134°C, 2 bar); alumina blasting (B - 50 µm Al2O3); RT-ALD silica deposition (S); HT followed by silica deposition (HTS). RT-ALD cycles consisted of the sequential exposure of specimens to tetramethoxysilane orthosilicate (TMOS - 60s) and ammonium hydroxide (NH4OH - 10 min) vapors in 40 cycles. Mechanical performance was analyzed by flexural strength (FS) (n = 10) and fatigue failure load (staircase method; n = 20) tests. Surface hardness (H) and Young's modulus (YM) were analyzed by nanoindentation. For surface chemical and topographical characterization, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were performed. Data from surface H, YM, FS, and fatigue limit (FL) were analyzed by two-way analysis of variance (ANOVA). RESULTS: The interaction between material and treatment had a significant effect on FS (p < 0.001). The FS values ranged from 436.23 MPa to 856.65 MPa. HT resulted in the highest FS (856.65 MPa) for LT and the lowest FS (436.23 MPa) for MO zirconia. For all materials, S and B treatments resulted in similar FS values (p > 0.410). S did not affect FL when compared to the C group (p > 0.277) for any material investigated. HTS resulted in higher FL than S for LT and MO materials (p < 0.001). Surface hardness and modulus were similar between control and S-treated specimens for all materials analyzed. XPS analysis showed homogeneous silica content after 20 and 40 RT-ALD cycles, and SEM did not show significant changes in surface morphology between C and S-treated specimens. CONCLUSION: RT-ALD resulted in effective silica deposition without any deleterious effect on zirconia-based materials mechanical properties. Alumina blasting promoted higher alteration on surface topography. HT prior to S resulted in superior FL (for MO and MT) and flexural strength (MO) for some of the materials investigated.

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