The main reason that patients seek sedation dentistry is to avoid the pain that they had during previous dental care. Some patients have experienced pain even after receiving local anesthetic because the did not reach a state of profound anesthesia(no feeling). Sedation does increase the effectiveness of local anesthetics.
Making Sure You Are Numb
Also, as covered in blog posts there are three reasons that patients do not get numb. Fortunately, there are techniques and alternate anesthetics that Dr. O'Neill uses that can overcome these issues with local anesthetic. So, no you will not feel pain. Really.