Carbon Creek - S2-E2
Factual error: The story takes place in 1957 (Sputnik is already in orbit). At the end, T'Mir sells her invention, which ends up being Velcro (technically hook and loop fastener). However, George de Mestral obtained the patent for Velcro in 1955, and by 1957 he had already expanded into the United States.
Answer: The obvious answer is that it would be very difficult to fit actor Scott Bakula with braces for an episode. As for the in universe rules, we can assume that items permanently attached to one's body (dental work, pacemakers, artificial joints, etc), would stay with the original body. Otherwise Sam would suffer agony when someone's fillings were jammed into his teeth. You have to have some suspension of disbelief when it comes to things like this. Why weren't Sam's shoes constantly too big or too small? Why does everyone look him in the eye, even when he's posing as someone much taller or shorter?
Brian Katcher