Ion-releasing Influences to Surface Hardness of Bioactive Filling Material

Objectives: The purpose of this study was to investigate surface hardness, surface chemical analysis and ion-releasing of bioactive materials storing in water or artificial saliva at different times.
Methods: Twelve specimens of each material (Activa Bioactive, Beautifil II, Equia Forte Fil, Ketac Universal, Fuji II LC and Filtek Z350XT) were prepared in disc-shape (5 mm diameter, 2mm height). The specimens were stored in 100% humidity at 37°C for 24h, and then six specimens were randomly divided and stored either in deionized water or artificial saliva at 37°C for 42d. The storage medium was changed weekly. The Vickers hardness test was conducted under a load of 100 grams and performed at 24h, 7d, 21d and 42d. Chemical analysis of specimen surface was performed in two specific periods of time (24h and 42d) using SEM-EDX. Ion-releasing of material was analyzed from the deionized storage medium using ICP-MS. The hardness data was statistical analyzed using three-way ANOVA and Tukey multiple comparison test (α = 0.05).
Results: All factors (materials, storage medium and time) were influence to the surface hardness (p<0.05). The surface hardness decreased after 42d in both mediums excepting for Equia Forte Fil and Ketac Universal. SEM-EDX revealed the increasing of P,K,Ca,Mg element after storage in artificial saliva. Element of F,Al,Na,Si increased in the surrounding matrix for all materials excepting for Filtek Z350XT after 42d. ICP-MS revealed the element releasing of GI and RMGIc, that Na releasing was high, while Ca,Mg,P releasing were low.
Conclusions: The surface hardness of conventional glass ionomer was relatively constant in deionized water and significantly increased in artificial saliva. Therefore, the various kinds of element releasing and deposition influenced to the material surface hardness.