Composite resin reinforced with silk nanoparticles from Bombyx mori cocoon for dental applications

Abstract The objective of this work was to evaluate the mechanical performance of Z350 resin composite modified with Bombyx mori cocoons silk nanoparticles for dental applications. Four experimental groups were analyzed G0% = Filtek Z350 resin composite (control); G1% = Filtek Z350 with 1% of silk nanoparticles; G3% = Filtek Z350 with 3% of silk nanoparticles; G5% = Filtek Z350 with 5% of silk nanoparticles. It was employed scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, 3-point flexural strength test, Knoop hardness test, and surface roughness. From 3-point flexural strength tests the control group presented the best results G0% = 113.33 MPa (±23.73). The higher flexural modulus was shown by groups G3% = 29.150 GPa (±5.191) and G5% = 34.101 GPa (±7.940), which are statistically similar. The Knoop microhardness test has shown statistical difference only among the G3% group between the top 80.78 (± 3.00) and bottom 68.80 (±3.62) and no difference between the groups. The roughness test presented no statistical difference between the groups. The incorporation of silk nanoparticles reduced the flexural strength of Z350 resin composite. The surface roughness and microhardness tests showed no changes in any of the groups studied.

Resumo O objetivo deste trabalho foi avaliar o desempenho mecânico da resina composta Z350 modificada com nanopartículas de seda Bombyx mori cocoons para aplicações odontológicas. Quatro grupos experimentais foram analisados: G0%) Resina Z350 apenas (grupo controle); G1%) Reforço com 1% de nanopartículas de seda; G3%) Reforço com 3% de nanopartículas de seda; e G5%) Reforço com 5% de nanopartículas de seda. Foi empregado microscopia eletrônica de varredura, espectroscopia de energia dispersiva de raios X, difração de raios X, teste de resistência à flexão de 3 pontos, teste de dureza Knoop e rugosidade superficial. Nos testes de resistência à flexão de 3 pontos o grupo controle apresentou melhores resultados G0% = 0.113 GPa (±0.024). O maior módulo de flexão foi demonstrado pelos grupos G3% = 29.151GPa (±5.191) e G5% = 34.102 GPa (±7.94), que são estatisticamente semelhantes. O teste de microdureza Knoop mostrou diferença estatística apenas entre o grupo G3% entre os 80.78 superiores (± 3.00) e os 68.80 inferiores (±3.62). Não há diferença entre os grupos. O teste de rugosidade não apresentou diferença estatística entre os grupos. A incorporação de nanopartículas de seda reduziu a resistência à flexão da resina composta Z350. Os testes de rugosidade superficial e microdureza não apresentaram alterações em nenhum dos grupos estudados.

A new method for evaluating the retentive efficacy of different denture adhesives

Aim: The aim of this study was to evaluate a new method for measuring the retention values of different denture adhesives. Methods: The adhesive strength values of three different commercial denture adhesives (Corega powder, Corega adhesive tape and Ultra Corega cream) were evaluated using three different moisturizing agents (distilled water, artificial saliva and natural saliva). The adhesive test was performed on a universal testing machine, after applying the adhesive products to acrylic resin specimens, under two different test conditions (wetting or dipping). Tensile bond strength values in MPa were obtained for each denture adhesive presentation and test condition. Viscosity of the denture adhesives mixed with the different moisturizing agents was determined using a rotary rheometer. Maximum viscosity values were analyzed using the one-way ANOVA test. Tensile bond strength data was analyzed using Kruskal-Wallis and the Tukey's test. Pooled data of each denture adhesive presentations for all test conditions was also carried out. Correlation between viscosity and pooled tensile strength values was analyzed through linear regression analysis. A significance level of α=0.05 was set for all analyses. Results: Results showed that statistically higher adhesion strength was obtained with tape and cream adhesives when using natural saliva as moisturizing agents (p<0.05). The adhesive strength values obtained with the dipping method were similar to those obtained with the conventional wetting method. The denture retention strength was influenced by both the denture adhesive type and moisturizing agent used. Conclusion: The dipping method showed to be a reliable test capable to simulate the oral conditions and should be better explored in further studies

Coronal microleakage of endodontically treated teeth with intracanal post exposed to fresh human saliva

OBJECTIVE: The aim of this study was to investigate the coronal microleakage of endodontically treated teeth prepared to receive an intracanal post and teeth with an intracanal post but without a prosthetic crown and exposed to contamination by fresh human saliva. MATERIAL AND METHODS: A mechanical-chemical preparation following the step-back technique was carried out in 35 extracted single-rooted human teeth. The teeth were randomly divided into five groups: G1=root canals instrumented, obturated, and prepared to receive an intracanal post (N=10); G2=root canals with cemented posts but without coronal sealing (N=10); PC1=positive control root canals instrumented and open (N=5); PC2=positive control 2 root canals without instrumentation and open (N=5); and NC=negative control healthy teeth (N=5). The crowns were removed except for the control group of intact teeth. The root canals were obturated and sterilized with cobalt 60 gamma irradiation and were then adapted in an apparatus using a Brain Heart Infusion (BHI) medium and fresh human saliva for contamination. Microbial growth was indicated by the presence of turbidity in the BHI liquid medium. RESULTS: Data were submitted to the Kaplan-Meier Survival Analysis and the Holm-Sidak statistic method, which observed an index of 90% of microleakage in root canals after 24 hours for G1 and 70% of microleakage in samples at the end of 40 days for G2. CONCLUSION: The results show that root canals with an intracanal post but without a prosthetic crown can be recontaminated when exposed to fresh human saliva in a short period. .

Social and demographic profile of Unified Health System users in a medium-sized city of southern Brazil

Aim: The use of health services is a complex behavior and results from a series of determinantsthat includes the users’ social and demographic characteristics. The current survey interprets thesocial and demographic profile of Unified Health System (UHS; SUS in Portuguese) users fromPelotas RS Brazil, which was conducted by interviews with 333 users from five Health Basic Units(HBUs). Methods: The social and demographic characterization was deployed by the variablessex, age, occupation, city/town or district of origin, number of family members, use of continuousmedication, diseases and family income. Results: HBU users were mostly women (82.4%),within the 30-40-year-old age range (21.4%), housewives (36.3%) from Pelotas (96.2%) andfrom the district of Fragata (26.1%). Families of users comprise mostly two to four members(66.6%), with an income of one to two minimum wages (66.2%). Fifty-one percent of theinterviewees do not use continuous medication, while hypertension was the most cited disease(51.8%). Conclusions: An understanding of HBU users’ characteristics and their associatedsocial and demographic context may contribute towards a better reception and may confirm theUHS contribution towards universality and equality of public health care.

Effect of surface sealant on the color stability of composite resin restorations

This study investigated the effect of sealant application on the color stability of composite resin restorations. Cavities in bovine incisors were restored with composite resin (Opallis; FGM) and the teeth were assigned to 4 groups (n=10). A sealant (Fill Glaze; Vigodent) was applied over the restorations of 2 groups. Baseline color measurements based on the CIEL*a*b* system were carried out using a spectrophotometer. Half the number of specimens was immersed in distilled water, and half was immersed in coffee 4 h/day. Color measurements were repeated after 1 h, 24 h, 7 days and 3 months. Data for each immersion solution were separately subjected to a two-way repeated measures ANOVA and Tukey’s test (α=0.05). For the group without sealant immersed in water, no significant differences were observed among the periods (p≥0.138), but the color was different compared with baseline (p<0.001). For the group with sealant application, the periods baseline, 1 h and 3 months presented similar results (p≥0.924). For groups immersed in coffee, when the sealant was not used, no significant differences were detected between the baseline and the periods 1 h and 24 h (p≥0.499), but the color changed significantly thereafter (p≤0.003). In the group with sealant, significant differences were detected for all periods compared with each other (p<0.001). In conclusion, application of sealant dramatically increased the staining of the restorations exposed to coffee.

Este estudo avaliou o efeito da aplicação de selante na estabilidade de cor de restaurações de compósito. Cavidades foram restauradas em incisivos bovinos com resina composta (Opallis, FGM) e os dentes separados em quatro grupos (n=10). O selante (Fill Glaze; Vigodent) foi aplicado sobre as restaurações em dois grupos. Aferição inicial de cor baseada no sistema CIEL*a*b* foi realizada com espectrofotômetro. Metade do número de espécimes foi imersa em água destilada, e metade imersa 4 h/dia em café. Aferições de cor foram repetidas após 1 h, 24 h, 7 dias e 3 meses. Os dados para cada solução de imersão foram submetidos separadamente à Análise de Variância de 2 vias para medidas repetidas e teste de Tukey (α=0,05). Para o grupo sem selante imerso em água, não foram observadas diferenças entre os períodos (p≥0,138), mas a cor foi diferente comparada à inicial (p<0,001). Para o grupo com selante, os períodos inicial, 1 h e 3 meses apresentaram resultados similares (p≥0,924). Para os grupos imersos em café, quando o selante não foi utilizado, não foram detectadas diferenças entre os períodos inicial, 1 h e 24 h (p≥0,499), mas a cor alterou significativamente após (p≤0,003). No grupo com selante, diferenças significativas foram detectadas para todos os períodos comparados entre si (p<0,001). Em conclusão, a aplicação de selante aumentou drasticamente o manchamento das restaurações expostas ao café.