If your iPad is still under warranty Apple may replace it. Check on that first. If you are no longer covered by the warranty, repairing it on your own will be tricky. If you look over the guide for replacing the front panel you will see it is a very difficult task. I can't recommend it for the faint of heart or any one new to tinkering with delicate electronic devices, but replacing the adhesive strips is likely the only way to properly fix your troubles. Using glue is probably a bad idea. A liquid adhesive will have unpredictable effects on internal components; any solvents in the glue could damage cables, the glue could be squeezed into the home button, the adhesive could dissolve the black coating on the back of the glass panel, and the glue could fail to fix the problem. This might leave you with more trouble than what you have now. As ugly as it would be, and if removing the front panel is out of the question, I would lay a piece of gaffer's tape over the loose edge. I know, it's a heretical suggestion, but it will keep the gap from getting worse and save you the heart stopping front panel removal.