I just did 17 amalgams (over last 5-6 months, 2 per visit) and didn't take vit-C IV. Vitamin C has half-life in your blood of 1/2 hour. You can achieve nearly the same peak effect as IV by taking 100-500mg every 1/2 to 1 hour or so, throughout the day. It is best to cycle between several different types of vit C for each dose (esther C, plain ascorbic acid, sodium/calcium ascorbate, bioflavonoid versions, time release,... etc) to avoid unbalancing other minerals or overworking any single metabolic pathway.

To determine the optimum dose of Vitamin C, you increase the daily quantity until it causes diarrhea, then back off a litte and that is your optimum dose. This optimum, though, varies with your health state (usually 2-10 grams). For example, if you have a cold, the diarrhea threshold increases several times, the worst the cold the higher the threshold, going with some people into hundred or more grams. Similarly, if you smoke or if you are chronically exposed to various environmental stresses on immune system (such as amalgams), your baseline diarrhea threshold will be higher.

Usually there is a warning, as Sandy noted, that vit C will prevent novocain from working. That would thus preclude oral vit C method described above before the dental procedures. My solution was not to use novocain or any anesthesia at all (see the earlier post on how to do this). Once you try it the right way and then experience how much faster and better your teeth and gums heal this way, you won't ever go back to novocain.