Because I do not know the extent of the decay or how your son cooperated at his visit, it is difficult for me to tell you which option to choose. There are certain situations (if the decay is small and your son can cooperate) that sedation and novacaine is not necessary. Nonetheless, nitrous oxide is a very safe agent and as long as your son can breath through his nose it is a safe option. You can always try the nitrous oxide alone first to see how well he does. If it does not go well and your dentist cannot complete the procedure then you may want to consider the next option. Consider getting a second opinion to review your options and to see if others exist. Ultimately, you need to feel comfortable with the treatment. Dr. Woo