Usually, dental implants are not painful. The entire procedure is done under local anaesthetic, which means the patient will not feel any pain while the work is being done. When the local anaesthetic is administered and the jaw and face are numbed up, it does not matter if it is a simple filling or surgical procedure - the patient will not feel any pain.
For single implant placements, there is usually no pain even after the procedure as the surgical site is small and the gum heals quite quickly. Multi implant placements or more complex procedures like bone grafting or sinus lifting can cause a bit of pain which can easily be controlled by over-the-counter pain killers.