hey there, its something i've noticed with some of my older phones, what this basically indicates is that the seal round the screen whether external or internal is not complete. The dust will only get in if the seal around the screen is damaged or not complete, which could potentially down to the manufacturing process or something else.
its not an issue i've heard of amongst large smartphone screen phone owners, but be warned once it starts yes, it does only get worse, dust collects very easily and finds its way into nooks and crannies very easily. you will eventuall end up with a dusty effect either across the screen or concentrated to one point, which would indicate where it is getting in.
Personally i would take it in to whereever you would take it, its not something that should be inevitable, perhaps if a phone is very old then perhaps but nothing any time soon.
