An 8 year old male patient complains of food lodgement in his lower right back teeth. On intra-oral examination, occlusal caries is seen with 46, which is non tender on percussion. Multiple restorations are also seen. The dentist decides to use Ariston pHc for the restoration. Which of the following ions is not released by this material?

Ariston is a light-cured filling material indicated for posterior restoration. Its monomer matrix consists of a mixture of dimethylmethacrylates and inorganic fillers include alkaline glass, Ba-Al fluorosilicate glass, ytterbium trifluoride and highly dispersed silicon dioxide. It also contains a catalyst and stabilizers. Its color is white so that, for aesthetic reasons, it is more acceptable than amalgam. According to the first research reports, Ariston is releasing three different types of ions (fluoride, calcium, hydroxyl). The release of these ions depends on the pH value. When the pH value in the oral cavity is low due to active plaque, Ariston releases significantly higher amounts of ions than it does with neutral pH values. The ion effects are as follows: Fluoride ions hamper demineralization, promote remineralization and inhibit bacterial growth. Calcium ions hamper demineralization and promote remineralization. Hydroxyl ions neutralize the acid produced by cariogenic bacteria and inhibit bacterial growth. Ref: Kukletová M, Kuklová J, Christoforidis G. Ariston pHc restorative material. Clinical and morphological study. Scripta Medica (BRNO). 2003 Jan;76(1):39-48.