Mixing capsule for dental compositions

A capsule for a dental composition, said capsule comprising:

• a mixing chamber for mixing a dental composition, said mixing chamber containing a first component of the dental composition and having a bottom with an outlet opening for the dental composition;
• a piston positioned in an initial position at an upper end of said mixing chamber;
• said piston having at least one recess and an inner chamber containing a second component of the dental composition, said inner chamber having a bottom in the form of a temporary seal;
• a plunger positioned in an initial position at an upper end of said inner chamber of said piston, wherein upon depressing said plunger said temporary seal is broken to introduce said second component into the mixing chamber;
• a manually removable U-shaped locking member having two legs and a connecting bar connecting said two legs, wherein said connecting bar is elongate in a direction pointing away from said legs to form a grip portion, said locking member engaging with said legs said at least one recess of said piston for locking said piston relative to said mixing chamber;
• and
• wherein upon removal of said locking member said piston is slidable toward said outlet opening for releasing the dental composition.