Teeth don't move or shift. This is a myth perpetuated by the American Association of Orthodontists in 1963 in order to get every adolescent in braces.
I hope you mean that with a bit of sarcasm!
If they don't, then how come, IN MY OWN MOUTH, i've developed an open contact between the mesial of my implant crown on #29 and my natural, virgin #28 twice now? I had my implant restored about 10 years ago, to a tight contact with #28 and #30, I never wore any retention device and about 4 years later I had an open contact between 28 and 29 and still a tight contact between 29 and 30. I had my wife, and orthodontist, treat my mandibular arch to close the contact between 28 and 29 (as well as deal with some of the subtle lower anterior crowding that had started in my mouth in my 30's
🙁 ) and like most ortho patients, once I had the brackets taken off, I wore my retainer for maybe a couple of weeks, and low and behold another 5ish years later, that same open contact between 29 ans 28 is opening up again, and when I try and put my 5ish year old retainer in, it no longer fits, and the plastic of my retainer hasn't changed over that time
🙂 And my long term implant patients have seen similar things, not to mention my post teenage orthodontic patients, who now are in theire late 30's through early 50's who are seeking out a second round of orthodontic care to correct their reformed anterior crowding. I am 100% convinced that any tooth with a PDL in a living person who has the natural process of bone remodeling occurring, can and does move! How much movement is all a function of occlusion, time, periodontal health and parafunctional habits of the patient