Comparative of flexural strength, hardness, and fluoride release of two bioactive restorative materials with RMGI and composite resin

ABSTRACT

Aim: This study was fulfilled to evaluate the flexural strength, micro-hardness, and release of two fluoride ions of bioactive restorative materials (Cention N and Activa Bioactive), a resin modified glass ionomer (Fuji II LC), and a resin composite (Filtek z250). Methods: Forty samples from four restorative materials (Activa Bioactive, Fuji II LC, Cention N, and Filtek Z250) were provided according to the current standards of ISO 4049/2000 guide lines. Subsequently, the samples were stored for 24 hours and 6 months in artificial saliva, and successively, flexural strength and micro-hardness of the samples were measured. For each studied groups the pH was decreased from 6.8 to 4 in storage solution. The rate of changes in fluoride ion release was measured after three different storage periods of 24 hours, 48 hours, and 6 months in distilled water, according to the previous studies' method. Two-way ANOVA, One-way ANOVA, Tukey HSD Pair wise comparisons, and independent t-tests were used to analyze data (α= 0.05). Results: The highest flexural strength and surface micro-hardness after 24 hours and also after 6 month were observed for Cention N(p<0.001).Flexural strength of all samples stored for 6 months was significantly lower than the samples stored for 24 hours(p<0.001). The accumulative amount of the released fluoride ion in RMGI, after six-month storage period in distilled water was considerably higher (p<0.001) than 24 hours and 48 hours storage. The amount of fluoride ion release with increasing acidity of the environment (from pH 6.8 to 4) in Fuji II LC glass ionomer was higher than the bioactive materials (p<0.05). Conclusion: The flexural strength of RMGI was increased after storage against the Activa Bioactive,Cention N and Z250 composite. Storage of restorative materials in artificial saliva leads to a significant reduction in micro hardness. The behavior and amount of released fluoride ions in these restorative materials, which are stored in an acidic environment, were dependent on the type of restorative material: