Just curious - the glass top of the iPad seems to be well sealed - was the 'dirt' present on purchase or appear later? If so, what is the explanation?
About the only thing that comes to mind is using the device on a sandy beach w/ wind & kids (or a comparative scenario)? Wondering for others who may want to protect their iPad from a similar problem.
I suspect that Apple would have to dissemble the glass from the machine to remove the 'dirt' -
Because everyone has the flat thing to take the digitizer off. And I would probably rip a ribbon cable.
I would just get more dust under it by taking the screen off.
And void you warranty in the process.