Dust/debris or scratches

[Legend33]

Have an iPhone 4 using a Speck fitted case. Noticed on the front glass around the edges that there appear to be marks - whether it's dust/debris under the screen or scratches I'm unsure. The top layer of the case is plastic - could it be scratching the screen? Some marks almost look like dust flakes under the screen - even though the glass/digitizer are fused, can dust still get under somehow? I do keep my phone in my pocket much of the time which has considerable lint - I'm just wondering if it's possible that can make it under the screen? I wipe the screen off constantly but noticed these marks today because my case actually broke and I took the time to clean the full screen. This in the whole scene of things is not a big deal but I'm that person who likes close to perfect screens. I am considering buying a glass replacement - but want to get more info before I go that route. Thanks!