Influência da angulação e espessura da camada de impressão na resistência à flexão, estabilidade dimensional e rugosidade de uma resina impressa / Influence of the angulation and thickness of the printing layer on the flexural strength, dimensional stability and roughness of a printed resin

Objetivo: Avaliar a influência da angulação e espessura da camada de impressão na resistência à flexão de três pontos (), estabilidade dimensional e rugosidade de uma resina provisória impressa. Metodologia: A partir da modelagem de uma barra (26 x 2,2 x 2,2mm) em software Meshmixer (Autodesk) e obtenção de arquivo STL, este foi exportado para o software da impressora 3D SLA (Forms2/Formlabs), onde 225 barras nas mesmas dimensões foram impressas com a resina Cosmos Temp, Yller (n=15) de acordo com os fatores "espessura da camada de impressão" (25µm;50µm;100µm) e "angulação" (0°; 30°; 45°; 60° e 90°). Após impressão, as amostras foram limpas com álcool isopropílico e encaminhadas ao pós-processamento em forno ultravioleta (Anycubic Wash e Cure Plus, Anycubic), por 15 minutos. As barras foram submetidas ao teste de  em máquina de ensaio universal (100KgF,1mm/min) e os dados (MPa) analisados com teste ANOVA 2 fatores, Tukey (5%) e análise de Weibull. Também foram realizadas as análises de rugosidade e estabilidade dimensional, cujos dados foram analisados pela ANOVA 2 fatores e Tukey (5%), além do MEV das superfícies. Resultados: Para a resistência à flexão, ANOVA 2 fatores revelou que o fator "Espessura da camada de impressão" (p<0,0001) foi estatisticamente significante, já o fator "Angulação" (p=0,8074) não apresentou significância estatística. Os grupos 30°/25µm (51,2±4,6AMPa), 60°/25µm (49,1±4,3ABMPa), 0°/25µm (48,6±6,6ABMPa), 90°/50µm (46,8±4,1ABCMPa) e 90°/25µm (46,2±4,9ABCMPa) apresentaram valores de  estatisticamente superiores aos grupos 0°/100µm (39,4±5,4DEFMPa), 60°/100µm (37,7±4,2DEFMPa), 90°/100µm (37,1±4,1EFMPa) e 30°/100µm (34,8±4,5FMPa), os quais foram semelhantes entre si. Para estabilidade dimensional, os grupos 0°/50µm (1746.9±61.80Aµm) e 0°/100µm (1704.7±84.30Aµm) apresentaram maiores alterações dimensionais, enquanto o grupo 90°/25µm (401.1±48.61Gµm) apresentou as menores alterações. Para rugosidade superficial, ANOVA relevou que os grupos 30°/100µm (0.90±0.10Aµm), 45°/100µm (0.79±0.07ABµm) e 60°/100µm (0.88±0.08Aµm) foram semelhantes entre si e apresentaram os maiores valores, enquanto a configuração 90°/100µm (0.23±0.08F) mostrou os menores valores. Conclusão: Quanto menor a espessura da camada de impressão, maior a resistência à flexão, independente da angulação escolhida. Adicionalmente, quanto menor a espessura da camada de impressão, maior foi a alteração dimensional, enquanto que objetos impressos verticalmente (90°) apresentam maior estabilidade dimensional. Para rugosidade superficial, quanto maior espessura da camada, maior rugosidade (AU).

Objective: To evaluate the influence of printing layer angulation and thickness on the three-point flexural strength (), dimensional stability and roughness of a printed provisional resin. Methodology: From the modeling of a bar (26 x 2.2 x 2.2mm) in Meshmixer software (Autodesk) and obtaining an STL file, it was exported to the SLA 3D printer software (Forms2/Formlabs), where 225 bars of the same dimensions were printed with Cosmos Temp resin, Yller (n=15) according to the factors "print layer thickness" (25µm;50µm;100µm) and "angulation" (0°; 30°; 45°; 60° e 90°). After printing, the samples were cleaned with isopropyl alcohol and sent to post-processing in an ultraviolet oven (Anycubic Wash and Cure Plus, Anycubic) for 15 minutes. The bars were submitted to the  test in a universal testing machine (100KgF,1mm/min) and the data (MPa) analyzed with 2-way ANOVA, Tukey (5%) and Weibull analysis. Roughness and dimensional stability analyzes were also performed, whose data were analyzed by 2- way ANOVA and Tukey (5%), in addition to the SEM of the surfaces. Results: For the flexural strength, 2-way ANOVA revealed that the factor "Print layer thickness" (p<0.0001) was statistically significant, while the factor "Angulation" (p=0.8074) did not show statistical significance. The 30°/25µm (51.2±4.6AMPa), 60°/25µm (49.1±4.3ABMPa), 0°/25µm (48.6±6.6ABMPa), 90°/50µm (46.8±4.1ABCMPa) and 90°/25µm (46.2±4.9ABCMPa) showed  values statistically higher than the 0°/100µm (39.4±5.4DEFMPa), 60°/100µm (37, 7±4.2DEFMPa), 90°/100µm (37.1±4.1EFMPa) and 30°/100µm (34.8±4.5FMPa), which were similar to each other. For dimensional stability, the 0°/50µm (1746.9±61.80Aµm) and 0°/100µm (1704.7±84.30Aµm) groups showed greater dimensional changes, while the 90°/25µm group (401.1±48.61Gµm) showed the smallest changes. For surface roughness, ANOVA revealed that the 30°/100µm (0.90±0.10Aµm), 45°/100µm (0.79±0.07ABµm) and 60°/100µm (0.88±0.08Aµm) groups were similar to each other and presented the highest values, while the 90°/100µm (0.23±0.08F) configuration showed the lowest values. Conclusion: The lower the printing layer thickness, the greater the flexural strength, regardless of the chosen angle. Additionally, the thinner the printing layer, the greater the dimensional change, while objects printed vertically (90°) have greater dimensional stability. For surface roughness, the greater the layer thickness, the greater the roughness (AU).

Erosive Potential of Industrialized Teas: An in vitro study

Objective: To evaluate the erosive potential of manufactured teas according to pH, titratable acidity and buffering capacity. Material and Methods: Eight types of manufactured teas of different brands and flavors acquired in supermarkets of João Pessoa, Brazil, were investigated. Indaiá® mineral water and Coca-Cola® were controls. The pH measurement and titratable acidity for pH 5.5 and 7.0 were performed in triplicate in 50 ml of each beverage. The buffering capacity was calculated based on pH and titratable acidity for pH 7.0. ANOVA, Tukey, and Pearson correlation, with p <0.05, were used for data analysis. Results: Data showed normal distribution by Kolmogorov-Smirnov test for all variables. There was a statistically significant relationship between groups analyzed in all variables (ANOVA, p <0.001). The pH of teas ranged from 2.70 (Black Tea with lemon-Leão Fuze®) to 4.03 (Natural Mate Tea - Matte Leão®). The following significant correlations (p <0.01) were observed: pH and titratable acidity; buffering capacity and pH; buffering capacity and titratable acidity. Conclusion: All teas analyzed were potentially erosive; however, Black Tea with lemon (Leão Fuze®) had the lowest pH, the highest titratable acidity and buffering capacity, demonstrating that the saliva will have greater difficulty in buffering this tea in the oral environment.