Influence of powder/liquid ratio on the radiodensity and diametral tensile strength of glass ionomer cements

Clinicians tend to make reductions in glass ionomer power/liquid (P/L) ratios since some materials are difficult to mix and flow into small cavities, grooves or pits. In general, changing the P/L ratio decreases the physical and mechanical properties of conventional glass ionomer cements (GICs) and resin modified glass ionomer cements (RMGICs), but alterations seem to depend on their composition. OBJECTIVE: To determine the influence of P/L ratio on the radiodensity and diametral tensile strength (DTS) of glass ionomer cements. MATERIAL AND METHODS: There were 2 factors under study: P/L ratio (manufacturer's recommended P/L ratio and a 50 percent reduced P/L ratio), and materials (Vitro Molar, Vitro Fil, Vitro Cem conventional GICs and Vitro Fil LC, Ortho Glass LC RMGICs. Five 1-mm-thick samples of each material-P/L ratio were produced for radiodensity evaluation. Samples were x-ray exposed onto Digora phosphor plate and radiodensity was obtained using the software Digora for Windows 2.5 Rev 0. For DTS, five (4.0x8.0 mm) cylinder samples of each material were tested (0.5 mm/min). Data were subjected to one- and two-way ANOVA (5x2) followed by Tukey's HSD test, or Kruskal-Wallis and Dunn's method. For paired comparisons, t-test or Mann-Whitney test were used (α=0.05). RESULTS: There was a significant interaction (P=0.001) for the studied factors (materials vs. P/L ratio). Reduced P/L ratio resulted in significantly lower DTS for the RMGICs, but radiodensity was affected for all materials (P<0.05). CONCLUSIONS: Reduced P/L ratio affected properties of the tested glass ionomer cements. RMGICs were more susceptible to lower values of DTS, but radiodensity decreased for all materials following P/L ratio reduction.

Comparative study of physico-chemical properties of MTA-based and portland cements

The purpose of this investigation was to evaluate the physicochemical properties of gray and white structural and nonstructural Portland cement, gray and white ProRoot MTA and MTA BIO. The water/powder ratio, setting time, solubility and pH (hydrogen-ion potential) changes of the materials were evaluated. Tests followed specification #57 from the American National Standard Institute/ American Dental Association (2000) for endodontic sealing materials and pH was determined by a digital pHmeter. The test results were statistically analyzed by variance analyses for global comparison and by the complementary Tukey's test for pairwise comparisons (5%). Considering the water/powder ratio, no significant difference (p>0.05) was observed among the cements. MTA BIO (33.10±2.30) had the lowest setting time (p<0.05), gray Pro- Root MTA (10.10±2.70) had the highest (p<0.05). White nonstructural Portland cement (2.55±0.08) had the highest solubility (p<0.05), while gray ProRoot MTA (1.03±0.12) had the lowest (p<0.05), although all materials showed solubility values in compliance to ANSI/ADA. No difference (p>0.05) was observed among materials when considering pH evaluation. The pH levels were highly alkaline immediately after immersion in solution, remaining stable throughout the test period. The authors conclude that the cements had similar water/powder proportions. MTA BIO had the shortest setting time and gray ProRoot MTA had the lowest solubility. All cements had similar behavior in the pH analysis.

A proposta desse trabalho foi de avaliar as propriedades fisicoquimicas dos cimentos Portland cinza e branco estrutural e nao estrutural, do ProRoot MTA cinza e branco e do MTA BIO. Foram avaliadas a proporcao po-liquido, tempo de endurecimento, solubilidade e variacao do pH dos cimentos. Os testes seguiram as normas que determinam a especificacao numero 57 da ANSI/ ADA para cimentos obturadores e a variacao de pH foi analisada por meio de pHmetro digital. Os resultados dos testes foram analisados estatisticamente por meio de teste de analise de variancia e pelo teste de Tukey para comparacao entre pares, com nivel de significancia de 5%. Nao foram evidenciaram diferencas estatisticamente significantes (p>0,05) entre os cimentos no que se refere a proporcao po-liquido. O MTA BIO (33,10±2,30) mostrou os menores valores de tempo de endurecimento (p<0,05), enquanto o ProRoot MTA cinza (102,10±2,70) mostrou os maiores resultados (p<0,05). Todos os materiais mostraram valores de solubilidade dentro dos padroes da ANSI/ADA, sendo que o cimento ProRoot MTA cinza (1,03±0,12) apresentou a menor solubilidade (p<0,05) e o Portland branco nao estrutural (2,55±0,08), a maior (p<0,05). No que se refere a variacao do pH, nao foram determinadas diferencas significantes entre os materiais (p>0,05). Os niveis de pH mostraram-se altamente alcalinos, imediatamente apos a imersao em agua, mantendo-se estavel ao longo do periodo de teste. Concluiu-se, que os cimentos estudados tiveram proporcoes po-liquido similares. O MTA BIO apresentou tempo de endurecimento mais curto e a menor solubilidade foi apresentada pelo ProRoot MTA cinza. Todos os cimentos tiveram comportamento semelhante na analise do pH.

Uso de fibra dietética de nopal en la formulación de un polvo para flan / Use of nopal dietary fiber in a powder dessert formulation

The development of diverse types of foods of low caloric value and with high content in dietary fiber have occupied a preponderant place in the food industry in the last years, due to the growing interest of the consumers for a healthy and nutritious diet. Pre-cooked or quick to prepare foods are attractive for the time they save; if to this you add their nutritious value, the attractiveness is even greater. For this reason, this study analyzes different formulations of a powder to prepare a dessert (flan), with different percentages of incorporation of nopal flour, as a source of dietary fiber (16 per cent, 18 per cent, 20 per cent). Two flavors (melon and banana) were tried. It was observed that the flan flavored with banana and with 16 per cent of nopal flour, reached better sensorial characteristics. Greater percentages of nopal flour negatively affected the sensorial characteristics, mainly flavor, color and texture. The analysis showed that the powder presented 5.7 per cent of moisture, low water activity (0.48) and therefore a low total recount of microorganisms. The content of protein was high (27.2 per cent), the ether extract low (2.0 per cent) similar to the caloric contribution (40 Kcal/portion). The flan showed a 9.8 per cent of total dietary fiber, being greater the contribution of soluble fiber (6.1 per cent) than that of insoluble fiber (3.7 per cent). Due to these characteristics this formulation could be considered as a food that provides benefits for the human health.