Will a retainer close a tiny gap?

Okay so I have had braces for a year and about 8 months, I had the power chain for 4 months On top and 3 months on bottom I get my braces off thursday. They took the power chain out and just put regular wires back in on my top 6 teeth and bottom 6 teeth while they wait for my retainers to come in. I noticed a week later that my top gap in my front two teeth reopened it's very tiny but I hate it. Should the retainers close this?