BEGIN AND END V

The partial words below can be completed by adding the same three letters, in the same order, at both the beginning and at the end.  (One of the words is a proper name.)

1.  _ _ _ TO _ _ _
2.  _ _ _ ST _ _ _
3.  _ _ _ MEN _ _ _
4.  _ _ _ IZAT _ _ _
5.  _ _ _ ERGRO _ _ _
6.  _ _ _ RATIAT
7.  _ _ _ ISCOVE _ _ _
8.  _ _ _ ERTAINM _ _ _
9. _ _ _ IOXID _ _ _

HINTS:
The first of the three letters are:
1. R
2. E
3. T
4. I
5. U
6. I
7. R
8. E
9. A

Answers:

1. RESTORES
2. EINSTEIN
3. TORMENTOR
4. IONIZATION
5. UNDERGROUND
6. INGRATIATING
7. REDISCOVERED
8. ENTERTAINMENT 
9. ANTIOXIDANT