Does Teeth Whitening Gel Expire Is Expired Day White Teeth Whitening Solution Safe? What Are The Negative Effects?

Is expired Day White teeth whitening solution safe? What are the negative effects? - does teeth whitening gel expire

I found an opening day without a solution syringe White Teeth Whitening, my dentist gave me 2 years ago. I have the tool to lighten the teeth. However, if you with the solution, the liquid is almost clear - usually a gel, and I had to press a part of the solution before I am able to combine white and transparent gels. To cause a greater use of this solution, damage to the teeth? Is it effective?