Embedding A Zipper Onto to Lips?

Hi there:
I have a tight head shot of a guy and I need to embed a steel zipper onto his face so that it looks like his mouth has been sealed shut by the zipper. This needs to look as realistic as possible.
I have shot both and am about to morph them together. I do not have issues with close cutting the zipper it is more about how to "embed" it so that it looks realistic.

Any help on what to do or where to go to get more info would be really helpful.

Thanks

William

Mind posting the two images? Might make it easier to walk you through it if we can see what you are trying to do.