essential and nonessential clauses

[flemingb]

In the sentence: Any employee who wishes to participate may contact our Human Resources Department.

According to our textbook answer, the essential clause is: who wishes to participate

If we were to change the sentence to: The employee who wishes to participate may contact our Human Resources Department.

Will the essential clause be the same or can we offset it with commas because it is now a nonessential clause.

Please explain.

Thanks

[Tdol]

You can't offset it because it is still defining the employee, IMO.