I had my lower teeth straightened 12 years ago at age 45. After treatment, he left in place an invisible gold retainer behind the lower front 6 teeth. After ten years, I asked to have it removed so I would have an easier time flossing and he gave me a plastic retainer for wear at night.
My teeth were very crowded. I had no teeth removed. All teeth are now still straight. He seems interested in the follow up even 12 years after treatment. He is very pleasant. I feel I can go back to him if any problem ever does arise.