Marilyn Monroe had a chin implant put in early on, to make her chin symmetrical. I don't know what they were made of, back in the day. They're quite tiny, usually.
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yes,back in the 80's, but not an implant, Her oral surgeon moved her lower jaw forward. A chin implant only works in the very end of the chin
If you look at her from the 50's early/60's, you will see she also had eyelid surgery to open up her eyes, to good effect.

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I had the same orthognathic surgery as Burnett except my jawbone was moved back. I had an underbite instead of the proper overbite in my teeth. The only way to correct it was to move my jawbone back a half centimeter. I was under general anesthesia in the operating room.

she had it done back in the early 80's not for aging,but because she didn't like her receding chin

This sounds so very painful & un-necessary, ewwww! I like seeing older people with their road map showing, LOL!

She had her jaw moved forward by an oral surgeon, not a chin implant

People who don't have a prominent chin have a few options today. One is surgery that involves cutting the jaw bone on both sides and lowering it. This procedure will extend it outward and a chin implant may also be used w/this procedure. The downside is the jaw is wired shut for over a month while the bones heals.

I hadn't either until I heard about her implant. Pretty cool