RESUMEN
The present study aimed to characterize the microstructure of a temporary 3D printing polymer-based composite material (Resilab Temp), evaluating its optical properties and mechanical behavior according to different post-curing times. For the analysis of the surface microstructure and establishment of the best printing pattern, samples in bar format following ISO 4049 (25 × 10 × 3 mm) were designed in CAD software (Rhinoceros 6.0), printed on a W3D printer (Wilcos), and light-cured in Anycubic Photon for different lengths of time (no post-curing, 16 min, 32 min, and 60 min). For the structural characterization, analyses were carried out using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The mechanical behavior of this polymer-based composite material was determined based on flexural strength tests and Knoop microhardness. Color and translucency analysis were performed using a spectrophotometer (VITA Easy Shade Advanced 4.0), which was then evaluated in CIELab, using gray, black, and white backgrounds. All analyses were performed immediately after making the samples and repeated after thermal aging over two thousand cycles (5-55 °C). The results obtained were statistically analyzed with a significance level of 5%. FT-IR analysis showed about a 46% degree of conversion on the surface and 37% in the center of the resin sample. The flexural strength was higher for the groups polymerized for 32 min and 1 h, while the Knoop microhardness did not show a statistical difference between the groups. Color and translucency analysis also did not show statistical differences between groups. According to all of the analyses carried out in this study, for the evaluated material, a post-polymerization time of 1 h should be suggested to improve the mechanical performance of 3D-printed devices.
RESUMEN
O presente estudo teve como objetivo caracterizar a microestrutura de uma resina temporária de impressão 3D (Resilab Temp), avaliando as propriedades óticas, o comportamento mecânico e a resistência à tração de coroas cimentadas com diferentes cimentos temporários. Todas as propriedades foram também avaliadas após a simulação de envelhecimento térmico. Para a análise da microestrutura superficial e estabelecimento do melhor padrão de impressão, amostras em formato de barras seguindo a ISO 4049 (25 x 10 x 3 mm) foram desenhadas em software (Rhinoceros 6.0), impressas na impressora W3D (Wilcos do Brasil) e fotopolimerizadas na Anycubic Photon em diferentes tempos (sem cura, 16 minutos, 32 minutos e 1 hora). Para a caracterização estrutural foram realizadas as análises em FTI-R (Espectroscopia de infravermelho com transformada de Fourier) e Microscopia Eletrônica de Varredura (MEV). O comportamento mecânico da resina foi feito com base nos testes de resistência à flexão, mensuração do módulo elástico e microdureza de Knoop. A análise de cor e translucidez foi feita com um espectrofotômetro (VITA Easy shade Advanced 4.0), o qual foi avaliado seguindo o CIELab, utilizando os fundos cinza, preto e branco. Todas as análises foram realizadas imediatamente após a confecção das amostras e repetidas após o envelhecimento térmico com 2 mil ciclos (5-55 ï°C). Coroas de resinas foram fabricados da mesma forma que os espécimes anteriores e foram cimentadas sobre preparo padronizados em resina Nema G10 (análogo à dentina). Foram usados 3 cimentos temporários: hidróxido de cálcio (HC), óxido de zinco sem eugenol (OZNE) e ionômero de vidro (IOV). Os espécimes foram ensaiados com teste de resistência à tração das coroas, antes e após o mesmo envelhecimento térmico. Os resultados obtidos foram analisados estatisticamente com nível de significância de 5%. A análise de FTI-R mostrou cerca de 46% de grau de conversão na superfície e 37% no centro da amostra da resina. A resistência à flexão foi maior para os grupos polimerizados por 32 min e 1h, enquanto a microdureza Knoop não apresentou diferença estatística entre os grupos. A análise translucidez também não mostrou diferenças estatísticas entre os grupos, entretanto a cor foi alterada pelo tempo de polimerização e envelhecimento. No ensaio de resistência à tração, todos os fatores mostraram diferenças estatisticamente significantes. Antes do envelhecimento, o grupo IOV foi estatisticamente superior ao HC e OZNE; Entretanto, após o envelhecimento, não houve diferença entre os grupos. De acordo com todas as análises realizadas nesse estudo, o tempo de pós polimerização de 1 hora apresentou o melhor desempenho mecânico e estabilidade de cor, e o cimento de ionômero de vidro possui a melhor retenção imediata após a cimentação, apesar de todos os cimentos temporários usados no estudo possam ser indicados. (AU)
The present study aimed to characterize the microstructure of a 3D printing temporary resin (Resilab Temp), evaluating the optical properties, mechanical behavior and tensile strength of crowns cemented with different temporary cements. All properties were also evaluated after simulated thermal aging. For surface microstructure analysis, bar-shaped specimens following ISO 4049 (25 x 10 x 3 mm) were designed in software (Rhinoceros 6.0), printed in the W3D printer (Wilcos do Brasil) (n=36) and photopolymerized in the Anycubic Photon at different times (no curing, 16 minutes, 32 minutes and 1 hour). For structural characterization FTI-R (n=72) (Fourier transform infrared spectroscopy) and Scanning Electron Microscopy (SEM)(n=4) analyses were carried out. The mechanical behavior of the resin was done based on flexural strength tests, elastic modulus measurement (n=12) and Knoop microhardness (n=20). The color and translucency analysis was done with a spectrophotometer (n=40) (VITA Easy shade Advanced 4.0), which was evaluated following the CIELab, using the gray, black and white backgrounds. All analyses were performed immediately after making the samples and repeated after thermal aging with 2,000 cycles (5-55 C). Resin crowns were fabricated (n=48) in the same manner as the previous specimens and were cemented on standardized preparations in Nema G10 resin (dentin analog). Three temporary cements were used: calcium hydroxide (HC), zinc oxide without eugenol (OZNE) and glass ionomer (IOV). The specimens were tested with crown tensile strength test before and after the same thermal aging. The results obtained were statistically analyzed with 5% significance level. FTI-R analysis showed about 46% degree of conversion on the surface and 37% in the center of the resin sample. The flexural strength was higher for the groups polymerized for 32 min and 1h, while Knoop microhardness showed no statistical difference between groups. Translucency analysis also showed no statistical difference between groups, however the color was altered by polymerization time and aging. In the tensile strength test, all factors showed statistically significant differences. Before aging, the IOV group was statistically superior to HC and OZNE; however, after aging, there was no difference between the groups. According to all analyses performed in this study, the 1-hour post-curing time showed the best mechanical performance and color stability, and the glass ionomer cement has the best immediate retention after cementation, although all temporary cements used in the study can be indicated (AU)
