Answer and Explanation:
I would feel confident in completing the procedure because I have been working on these procedures for twelve years, as shown in the text above. These twelve years created a great experience and that experience would give me confidence. In addition, the presence of the dentist, watching what I do, would give me more security, as I know he would interfere if I started doing something wrong and would help me with any doubts I had.
I think the dentist's request was made to assess my knowledge and see how resourceful I was in completing a task on my own. Probably, the dentist is testing my knowledge and plans to give me greater activities within the work, which will enhance my knowledge and my professionalism.