Effect of Finishing Protocols on the Surface Roughness and Fatigue Strength of a High-Translucent Zirconia.

Purpose: In case of need for esthetical improvement of zirconia restorations, an individualization using extrinsic staining can be applied. This study aimed to evaluate the surface roughness and fatigue strength (survival) of high-translucency zirconia (3Y-TZP, YZ®HT, Vita Zanhfabrik) with extrinsic characterization and/or glaze. Methods: Sixty (60) zirconia discs (12 × 1.2 mm) were obtained, sintered, and randomly distributed among three groups (n = 20) according to the surface finishing protocol: C (control), C + G (extrinsic characterization followed by a glaze layer), and G (glaze layer). The surface roughness (Ra) was analyzed with a contact profilometer. Subsequently, the specimens were subjected to a fatigue load profile starting at 120 N during 20,000 cycles at 4 Hz frequency, with a 5% increase at each step until failure. The failed specimens were evaluated under a stereomicroscope. Surface roughness analysis was evaluated by using one-way ANOVA and post hoc Tukey tests (95%); while fatigue survival probability was analyzed with Kaplan-Meier and Mantel-Cox (log- rank, 95%). Results: One-way ANOVA revealed that surface roughness was affected by the finishing protocol, where C + G showed the highest mean value (0.46 ± 0.18 µm)A followed by G (0.30 ± 0.10 µm)B, and C (0.19 ± 0.02 µm)C. While for fatigue strength, the G protocol presented a higher mean value (243.00, and 222.36-263.63)A, followed by C + G (192.75 and 186.61-198.88)B and C (172.50 and 159.43-185.56)C. Conclusion: Surface finishing protocols modify the surface roughness and fatigue strength of high-translucent zirconia. Regardless of the surface roughness, both glazing protocols improved the ceramic fatigue strength, favoring the restoration's long-term survival.

Development of a cell phone application as an auxiliary teaching tool for the subject of complete dentures / Desenvolvimento de aplicativo de celular intitulado: "Manual de Prótese Total ­ Reabilitando sorrisos", como uma ferramenta didática auxiliar para a disciplina de prótese total

Objective: The study aimed to develop a cell phone application entitled: "Total Prosthesis Manual ­ Rehabilitating smiles", as an auxiliary teaching tool for teachers and students through digital technology, with a smartphone. Material and Methods: The tool was structured on the "Application Factory website", which allows the creation of mobile applications in different formats, with broad and interactive features on IOS and Android platforms. The expository format of the content is in slide format, containing descriptive theory and images about the stages of making a complete prosthesis; from necessary materials, photos and descriptive guidance of the steps. Results: The application is a complementary teaching resource to assist undergraduate and postgraduate students and professionals working in the area of complete prosthetics. The theoretical and practical content selected for the application covered all stages of understanding, development and possible complications associated with the manufacture of a complete bimaxillary prosthesis, from planning, impressions, models, orientation plans, tooth assembly, adaptations and delivery. Conclusion: The application provided a low-cost, expandable and easy-to-use teaching resource for teaching complete dentures. It is essential to develop various analyzes such as user experience tests, application effectiveness, development of new technologies and improvement of techniques, so that their potential for enriching learning in complete dentures and dentistry in general can be verified.(AU)

Objetivo: O estudo teve como objetivo desenvolver um aplicativo de celular intitulado: "Manual de Prótese Total ­ Reabilitando sorrisos", como uma ferramenta didática auxiliar para professores e alunos por meio da tecnologia digital, com smartphone. Material e Métodos: A ferramenta foi estruturada no "site da Fábrica de Aplicativos", que permite a criação de aplicativos móveis em diversos formatos, com recursos amplos e interativos nas plataformas IOS e Android. A modalidade expositiva do conteúdo é em formato de slides, contendo teoria descritiva e imagens sobre as etapas de confecção de uma prótese total; a partir de materiais necessários, fotos e orientação descritiva das etapas. Resultados: O aplicativo é um recurso didático complementar para auxiliar estudantes de graduação, pós-graduação e profissionais que atuam na área de prótese total. O conteúdo teórico e prático selecionado para a aplicação visou todas as etapas de compreensão, desenvolvimento e possíveis complicações associadas à confecção de uma prótese total bimaxilar, desde o planejamento, moldagens, maquetes, planos de orientação, montagem dos dentes, adaptações e entrega. Conclusão: O aplicativo trouxe um recurso didático de baixo custo, expansível e fácil de usar para o ensino de próteses totais. É fundamental desenvolver diversas análises como testes de experiência do usuário, eficácia de aplicação, desenvolvimento de novas tecnologias e aprimoramento de técnicas, de forma que possa ser verificado seu potencial de enriquecimento do aprendizado em prótese total e odontologia em geral(AU)

Effect of Different Surface Treatments on the Bond Strength of the Hybrid Ceramic Characterization Layer.

PURPOSE: Using the microshear bond strength (µSBS) test, this study investigated the bond strength between a hybrid ceramic and the extrinsic characterization layer after different ceramic surface treatments. MATERIALS AND METHODS: Hybrid ceramic blocks (Vita Enamic, Vita Zahnfabrik) were sectioned and randomly divided into 4 groups (N = 120) according to the surface treatment and aging (n = 15): P: polishing; E: acid etching with HF; A: aluminum oxide blasting; S: self-etching ceramic primer. The specimens were silanized, then cylinders of light-curing characterization material (Vita Enamic Stain, 1.6 mm diameter x 2 mm height) were fabricated, followed by glazing. The specimens were subsequently immersed in distilled water for 24 h and subjected to the µSBS test using a universal testing machine (load cell 0.5 mm/min, 50 kgf) or tested after thermocycling for 10,000 cycles in water (5°C-55°C). After treatment, the specimen surfaces were analyzed using SEM, with failure types defined as adhesive, predominantly adhesive, or cohesive. The data were analyzed by two-way ANOVA followed by Tukey's test (p < 0.05). RESULTS: The most frequent failure type was predominantly adhesive between ceramic and the characterization layer. There were statistically significant differences between the surface treatments (p < 0.05). Thermocycling did not lead to statistically signifcant different results (p > 0.05). For groups P and A, a sharp decrease in SBS was observed. CONCLUSION: The absence of surface treatment drastically reduced the microshear bond strength between the ceramic and the characterization layer. Conditioning with 5% hydrofluoric acid for 60 s is the most suitable treatment for adhesion of the characterization layer to hybrid ceramic.

Efeito da caracterização extrínseca na microestrutura e na probabilidade de sobrevivência à fadiga de uma zircôniade alta translucidez / Effect of extrinsic characterization on the microstructure and on the fatigue survival probability of a high translucent zirconia

Este estudo avaliou a rugosidade superficial e a resistência à fadiga (probabilidade de sobrevivência) de zircônia polidas e caracterizadas com pigmentação extrínseca e/ou glaze. Blocos de zircônia de alta translucidez (YZ®HT, Vita Zanhfabrik, Bad Säckingen, Alemanha) foram usinados em forma de cilindro e fatiados em uma máquina de corte de precisão, com refrigeração constante em água. Os discos foram polidos com lixas de carbeto de silício de granulação crescente (#400, #600, #800, #1200) em máquina politriz semi-automática, e foi realizada limpeza em banho ultrassônico com álcool isopropílico durante 5 minutos. Desta forma, foram obtidos 60 discos com 12 mm de diâmetro e 1,2 mm de espessura, distribuídos aleatoriamente entre os Grupos: P-somente polimento, CG-caracterização e glaze, e G-somente glaze. Os tratamentos foram realizados após a sinterização, de acordo com as recomendações do fabricante. Foram realizadas leituras através de um rugosímetro de contato (Surftest SJ 400, Mitutoyo, Tóquio, Japão) para avaliar a rugosidade média da superfície. Os discos foram submetidos ao teste de flexão biaxial em uma máquina de testes universal, como velocidade constante (0,5 mm/min) até a falha (n=3), para determinar a carga média de fratura, a fim de estabelecer o perfil de carga do teste de fadiga. O perfil de carga usado iniciou em 120 N com acréscimo de 5% da carga inicial a cada step, em intervalos de 20.000 ciclos na frequência de 4Hz. O modo de fratura foi avaliado com o auxílio do estereomicroscópio. Os valores de rugosidade inicial foram analisados com teste ANOVA 1-fator e Teste de Tukey (95%), que mostraram que os três grupos possuem rugosidades médias estatisticamente diferentes, sendo o grupo CG o grupo com maiores valores. A análise de probabilidade de sobrevivência foi realizada com Kaplan-Meier e Mantel-Cox (Log-rank, 95%), indicando que o grupo G apresentou uma maior resistência à fadiga e um número maior de ciclos necessários para a fratura, sendo diferente estatisticamente dos outros grupos. Assim, é possível concluir que caracterização superficial altera o comportamento mecânico da zircônia de alta translucidez. A zircônia de alta translucidez somente polida possui menor resistência à fadiga do que o tratamento superficial com glaze, que promove maior probabilidade de sobrevivência a longo prazo.

This study evaluated the surface roughness and fatigue strength (probability of survival) of polished zirconia and characterized with extrinsic pigmentation and/or glaze. High translucency zirconia blocks (YZ® HT, Vita Zanhfabrik, Bad Säckingen, Germany) were machined in cylinder shape and sliced in a precision cutting machine, with constant water cooling. The discs were polished with silicon carbide sandpaper with decreasing grains (#400, #600, #800, #1200) in a semiautomatic polishing machine, and cleaning was carried out in an ultrasonic bath with isopropyl alcohol for 5 minutes. Thus, 60 discs with 12 mm in diameter and 1.2 mm in thickness were obtained, randomly distributed among the Groups: Ppolishing only, CG-characterization and glaze, and G-glaze only. The treatments were performed after sintering, according to the manufacturer's recommendations. Readings were taken using a contact roughness meter (Surftest SJ 400, Mitutoyo, Tokyo, Japan) to assess the average surface roughness. The discs were submitted to the biaxial flexion test in a universal testing machine, at constant speed (0.5 mm/min) until failure (n=3), to determine the mean fracture load, in order to establish the loading profile for fatigue test. The load profile used started at 120 N with an addition of 5% of the initial load at each step, at intervals of 20,000 cycles at the frequency of 4Hz. The fracture mode was evaluated with the aid of a stereomicroscope. The initial roughness values were analyzed using the one-way ANOVA test and Tukey test (95%), which showed that the three groups have statistically different mean roughnesses, with the CG group being the group with the highest values. The survival probability analysis was performed with Kaplan-Meier and Mantel-Cox (Log-rank, 95%), indicating that group G presented greater fatigue resistance and a greater number of cycles were required for the fracture, being statistically different of the other groups. Thus, it is possible to conclude that surface characterization alters the mechanical behavior of high translucency zirconia. High translucency zirconia only polished has lower fatigue resistance than surface treated with glaze, which promotes a greater long-term probability of survival.