RESUMO
BACKGROUND: This in vitro study analysed the effect of different fluoride concentrations in acidic or neutral liquid dentifrices in protecting enamel and dentine from erosive and abrasive wear. METHODS: Bovine enamel and dentine specimens (n = 132) were randomly allocated to 11 groups (each n = 12): experimental liquid dentifrices with 550 ppm F, 1100 ppm F, 5000 ppm F or 0 ppm F/placebo (each at pH 4.5 and pH 7.0); and commercial dentifrices with 550 ppm F (Colgate Baby, pH 7.0), 1100 ppm F (Crest, pH 7.0) and 5000 ppm F (Duraphat, pH 7.0). The specimens were subjected to erosion for 90 seconds, 4 times/day, over 7 days. Immediately after the first and last erosion, the specimens were brushed for 15 seconds using one of the dentifrices. Tooth wear was measured profilometrically (µm) and analysed by ANOVA (p < 0.05). RESULTS: All fluoridated liquid dentifrices significantly reduced enamel wear compared to the placebo and commercial dentifrices. Only liquid dentifrices with 1100 and 5000 ppm F significantly reduced dentine wear compared to placebo dentifrice. The pH had no effect, but the consistency had a significant impact on the effect of dentifrices. CONCLUSIONS: Liquid dentifrices with high F concentration appear to be a good option to prevent tooth wear.
Assuntos
Dentifrícios/química , Fluoretos/farmacologia , Abrasão Dentária/prevenção & controle , Erosão Dentária/prevenção & controle , Animais , Bovinos , Esmalte Dentário/efeitos dos fármacos , Humanos , Concentração de Íons de Hidrogênio , Lactente , Distribuição AleatóriaRESUMO
Coproduction of poly-beta-hydroxybutyrate (PHB) and exopolysaccharides (EPS) was investigated with Azotobacter chroococcum strain 6B isolated from soil samples. The bacterium was cultured using various carbon sources solely or with 0.1 g/L of ammonium sulfate. Ammonium addition resulted in reduced PHB and EPS production with glucose, fructose, and sucrose media, but cellular mass remained constant except for sucrose. Protein was nearly twofold higher in ammonium-grown cultures. Glucose and fructose alone biosynthesized high amounts of EPS (maximum 2.1 and 1.1 g/L, respectively, at 72 h), whereas PHB was accumulated only in glucose-grown cells. Sucrose almost did not produce EPS. Conversely, PHB content was the highest obtained from all experimented conditions (1.1 g/L at 48 h, 40% cell dry wt). When a complex carbon source such as sugar cane molasses was utilized, PHB was accumulated concomitant with EPS production from the initial time to 48 h (0.75 g/L, 37% cell dry wt and 0.6 g/L, respectively), and then PHB decayed at 72 h (0.2 g/L). On the other hand, EPS continued to be biosynthesized (1.1 g/L, 72 h). PHB fractions of total intra- and extracellular biopolymers were calculated. Sucrose-modified Burk's medium without ammonium addition is suggested as a medium capable of diverting the carbon source for the production of intracellular PHB rather than EPS with A. chroococcum 6B.
RESUMO
A microorganism (Azotobacter sp.) was isolated from soil samples from the Agronomy Faculty campus and its ability to accumulate poly-beta-hydroxyalkanoate (PHAs) polymers was analyzed. The isolated strain (named No 8) accumulated 8 micrograms PHA/m of culture media as intracytoplasmic granules. The following properties of the strain were analyzed: utilization of different carbon sources, antibiotic resistance, optimal pH and temperature, pigment production, nitrogen fixation, proteolytic activity, acid and hydrogen sulphide production, optimal growth temperature, cyst formation, growth on phenol and sodium fluoride, catalase, pleomorfism and mobility. The synthesized polymer showed valuable properties respect to organic solvents resistance.
Assuntos
Azotobacter/metabolismo , Biopolímeros/biossíntese , Hidroxiácidos/síntese química , Microbiologia do Solo , Argentina , Azotobacter/efeitos dos fármacos , Azotobacter/crescimento & desenvolvimento , Azotobacter/isolamento & purificação , Biodegradação Ambiental , Biopolímeros/química , Carbono/metabolismo , Grânulos Citoplasmáticos/metabolismo , Resistência Microbiana a Medicamentos , Metabolismo Energético , Hidroxiácidos/química , SolubilidadeRESUMO
A microorganism (Azotobacter sp.) was isolated from soil samples from the Agronomy Faculty campus and its ability to accumulate poly-beta-hydroxyalkanoate (PHAs) polymers was analyzed. The isolated strain (named No 8) accumulated 8 micrograms PHA/m of culture media as intracytoplasmic granules. The following properties of the strain were analyzed: utilization of different carbon sources, antibiotic resistance, optimal pH and temperature, pigment production, nitrogen fixation, proteolytic activity, acid and hydrogen sulphide production, optimal growth temperature, cyst formation, growth on phenol and sodium fluoride, catalase, pleomorfism and mobility. The synthesized polymer showed valuable properties respect to organic solvents resistance.
RESUMO
A microorganism (Azotobacter sp.) was isolated from soil samples from the Agronomy Faculty campus and its ability to accumulate poly-beta-hydroxyalkanoate (PHAs) polymers was analyzed. The isolated strain (named No 8) accumulated 8 micrograms PHA/m of culture media as intracytoplasmic granules. The following properties of the strain were analyzed: utilization of different carbon sources, antibiotic resistance, optimal pH and temperature, pigment production, nitrogen fixation, proteolytic activity, acid and hydrogen sulphide production, optimal growth temperature, cyst formation, growth on phenol and sodium fluoride, catalase, pleomorfism and mobility. The synthesized polymer showed valuable properties respect to organic solvents resistance.