Photoelastic, microhardness and roughness analysis of zirconia and stainless steel crowns for primary molars.

PURPOSE: To compare the stress distribution through photoelasticity, microhardness and roughness of intact crowns of primary molars (CC) and the preformed crowns of stainless steel (SSC) and zirconia (ZC) used in dental restorations in pediatric dentistry. METHODS: Six healthy primary molars were selected. For the photoelastic models, the teeth were fixed in photoelastic resin. A load of 100 N was applied, and the models were analyzed by transmission polariscope. The Tardy method was used to quantify the fringe order which calculates the maximum stress (T) value in each selected point. The teeth were prepared for cementation of the crowns. The photoelastic test was repeated for each experimental crown. Knoop microhardness was assessed on the buccal surfaces of the CCs, SSCs, and ZCs using a microhardness tester. Parameters were 50 gf for 5 seconds. Roughness was evaluated using a confocal 3-D laser scanning microscope/software at 216x magnification. Roughness average (Ra) values from each model (expressed in µm) were collected and group means were calculated. The stress distribution, microhardness, and roughness data were compared by using one-way ANOVA and the Tukey's test (α= 0.05). RESULTS: There was no difference in the stress distribution for the CCs, SSCs and ZCs. For the microhardness analysis, the ZCs obtained the highest values compared to the CCs and the SSCs (P< 0.001). The CCs were significantly higher than the SSCs (P= 0.027). There was no difference in roughness for the three models (P= 0.615). The SSCs and ZCs showed satisfactory mechanical behavior. CLINICAL SIGNIFICANCE: The use of preformed crowns, especially those made of esthetic materials, is currently increasing in the field of pediatric dentistry. The knowledge of mechanical properties of stainless steel- and zirconia-prefabricated crowns provides scientific foundation for safe clinical application, especially in primary teeth.

Fluoride concentration in toothpaste marketed to children in Brazil and Mexico, and discussion on current regulations.

Fluoride toothpastes market to children should contain a minimum concentration of 1000 ppm of fluoride (F), which must be chemically soluble to provide anti-caries effect. Therefore, we determined the concentrations of total fluoride (TF) and total soluble fluoride (TSF) in toothpastes marketed to children in Brazil and Mexico and analyzed the current regulations in force in both countries. Twenty-four brands were found and purchased in Brazil (19 formulated with NaF/SiO2, three with Na2FPO3/CaCO3 and two with Na2FPO3/SiO2) and six in Mexico (all with NaF/SiO2). TF and TSF concentrations were determined after the purchase (fresh samples) but fluoride stability in Na2FPO3/CaCO3-formulations was checked after 18 months. The analyses were performed with an ion-specific electrode and the results expressed in ppm F (mg F/kg). The TF concentrations found ranged from 476.0 to 1385.3 ppm F and they were close the declared by the manufactures (500 to 1450 ppm F). The TF concentrations found were not greater than 1500 ppm F, in accordance with the current regulations of both countries. However, toothpastes presenting TSF concentrations lower than 1000 ppm F were found either in low fluoride toothpaste (500 ppm F) formulated with NaF/SiO2 as in fresh and aged Na2FPO3/CaCO3-toothpastes, originally fabricated with 1000-1100 ppm of TF. In conclusion, although most toothpastes analyzed showed TSF concentration higher than 1000 ppm F, the regulations in force in both countries allow that products not in agreement with the best available evidence are available in the market.

Os dentifrícios fluoretados comercializados para crianças devem conter concentração mínima de 1000 ppm de fluoreto (F), que deve ser quimicamente solúvel para ter efeito anticárie. Portanto, determinamos as concentrações de fluoreto total (FT) e fluoreto solúvel total (FST) em dentifrícios comercializados para crianças no Brasil e no México e analisamos as regulamentações vigentes em ambos os países. Vinte e quatro marcas foram encontradas e adquiridas no Brasil (19 formuladas com NaF/SiO2, três com Na2FPO3/CaCO3 e duas com Na2FPO3/SiO2) e seis no México (todas com NaF/SiO2). As concentrações de FT e FST foram determinadas após a compra (amostras frescas), e a estabilidade do fluoreto nas formulações de Na2FPO3/CaCO3 foi verificada após 18 meses. As análises foram realizadas com eletrodo íon-específico e os resultados expressos em ppm F (mg F/kg). As concentrações de FT encontradas variaram de 476,0 a 1.385,3 ppm F e foram próximas às declaradas pelos fabricantes (500 a 1.450 ppm F). As concentrações de FT encontradas não ultrapassaram 1.500 ppm F, de acordo com as regulamentações vigentes de ambos os países. No entanto, dentifrícios com concentrações de FST inferiores a 1.000 ppm F foram encontrados tanto em dentifrício com baixa concentração (500 ppm F) formulado com NaF/SiO2 como em dentifrícios com Na2FPO3/CaCO3 frescos e envelhecidos, originalmente fabricados com 1.000-1.100 ppm de FT. Em conclusão, embora a maioria dos dentifrícios analisados apresentasse concentração de FST superior a 1.000 ppm F, as regulamentações vigentes em ambos os países permitem que produtos que não estejam de acordo com a melhor evidência disponível estejam presentes no mercado.

Fluoride concentration in toothpaste marketed to children in Brazil and Mexico, and discussion on current regulations

Resumo Os dentifrícios fluoretados comercializados para crianças devem conter concentração mínima de 1000 ppm de fluoreto (F), que deve ser quimicamente solúvel para ter efeito anticárie. Portanto, determinamos as concentrações de fluoreto total (FT) e fluoreto solúvel total (FST) em dentifrícios comercializados para crianças no Brasil e no México e analisamos as regulamentações vigentes em ambos os países. Vinte e quatro marcas foram encontradas e adquiridas no Brasil (19 formuladas com NaF/SiO2, três com Na2FPO3/CaCO3 e duas com Na2FPO3/SiO2) e seis no México (todas com NaF/SiO2). As concentrações de FT e FST foram determinadas após a compra (amostras frescas), e a estabilidade do fluoreto nas formulações de Na2FPO3/CaCO3 foi verificada após 18 meses. As análises foram realizadas com eletrodo íon-específico e os resultados expressos em ppm F (mg F/kg). As concentrações de FT encontradas variaram de 476,0 a 1.385,3 ppm F e foram próximas às declaradas pelos fabricantes (500 a 1.450 ppm F). As concentrações de FT encontradas não ultrapassaram 1.500 ppm F, de acordo com as regulamentações vigentes de ambos os países. No entanto, dentifrícios com concentrações de FST inferiores a 1.000 ppm F foram encontrados tanto em dentifrício com baixa concentração (500 ppm F) formulado com NaF/SiO2 como em dentifrícios com Na2FPO3/CaCO3 frescos e envelhecidos, originalmente fabricados com 1.000-1.100 ppm de FT. Em conclusão, embora a maioria dos dentifrícios analisados apresentasse concentração de FST superior a 1.000 ppm F, as regulamentações vigentes em ambos os países permitem que produtos que não estejam de acordo com a melhor evidência disponível estejam presentes no mercado.

Abstract Fluoride toothpastes market to children should contain a minimum concentration of 1000 ppm of fluoride (F), which must be chemically soluble to provide anti-caries effect. Therefore, we determined the concentrations of total fluoride (TF) and total soluble fluoride (TSF) in toothpastes marketed to children in Brazil and Mexico and analyzed the current regulations in force in both countries. Twenty-four brands were found and purchased in Brazil (19 formulated with NaF/SiO2, three with Na2FPO3/CaCO3 and two with Na2FPO3/SiO2) and six in Mexico (all with NaF/SiO2). TF and TSF concentrations were determined after the purchase (fresh samples) but fluoride stability in Na2FPO3/CaCO3-formulations was checked after 18 months. The analyses were performed with an ion-specific electrode and the results expressed in ppm F (mg F/kg). The TF concentrations found ranged from 476.0 to 1385.3 ppm F and they were close the declared by the manufactures (500 to 1450 ppm F). The TF concentrations found were not greater than 1500 ppm F, in accordance with the current regulations of both countries. However, toothpastes presenting TSF concentrations lower than 1000 ppm F were found either in low fluoride toothpaste (500 ppm F) formulated with NaF/SiO2 as in fresh and aged Na2FPO3/CaCO3-toothpastes, originally fabricated with 1000-1100 ppm of TF. In conclusion, although most toothpastes analyzed showed TSF concentration higher than 1000 ppm F, the regulations in force in both countries allow that products not in agreement with the best available evidence are available in the market.