It's obvious that teeth must be able to move - otherwise orthodontics couldn't work. I had teeth that were quite misaligned when i was young. Orthodontic practicioners won't work on kids, because they are still growing, and their teeth won't stay still [my orthodontist told me this]. He said that i was just barely old enough that it was worth 'doing' my teeth - because they would probably stay where he put them. This was years ago, before 'glue on' posts became popular. I had the full bands - all around each tooth. They were made to fit each tooth ahead of time, and then 'installed' a few at a time. After they were all in place, stiff wires were placed through each set of posts on each band, and much smaller wires used to attach the bands around the teeth to the stiff wires. This constant force would, over time, cause the teeth to move. What you are noticing is the 'play' that develops when you put a strain on teeth over time. I suspect you are gritting your teeth (perhaps whilst asleep), or while you study. I would recommend watching out for this, and when you catch yourself doing it - stop! Rubber 'bite rings' are sold for people who grind their teeth together when they sleep. I've been told that this can lead to tooth loss if it is done long term. The teeth get looser and looser, and then out they come - if you don't stop. Cheers.