Is it possible for dental retainers damage or scratch the surface of your teeth (over time, maybe)?

Yes: The metal clasps that slide over the enamal surfaces of teeth have been known to wear teeth. This is especially common if the patient has soft teeth due to poor dental hygiene or genetics. The acrylic of the retainer is softer than enamal and would less likely wear . If a retainer clasp is designed to grip with minimal force and oral hygiene is good, no problems are likely.

Probably not: Since the wires that make up the retainer are not as hard as the enamel of the teeth, there should be no damage to the enamel of your teeth when you wear your retainers. If the wires are in your bite, the teeth will wear the wires away and break them before any possible damage to your enamel . I have been prescribing retainers for over 30 years and have not seen such damage.

No: I suppose it depends on the material used, but they should not.

Not if they fit: As well fitting retainer will not scratch normal tooth enamel. If you didn't wear your retainer for a while and allowed your teeth to move you may need to have it adjusted to fit properly again.

Retainer: No. Teeth are harder than the retainers. However if your teeth have had damage and then repaired you may want to remind your dentist that you are wearing a ret.Ainer.

No: Tooth enamel is harder than retainer materials. Properly adjusted, they will do no harm.