Hoax, plot, conspiracy. . . words used equally often by both the pros and the antis in the ongoing controversy (since the '50's) over fluoridation of the water supply. It's doubtful, by medical journalist Gotzsche's evidence, that there's any benefit to be had from fluoridation; but she argues vehemently that an overdose has effects ranging from mottled teeth (you may have heard of ""Texas teeth"" or ""Colorado stain"") and bone disease to goiter, kidney and heart disease, mutagenic mental retardation, cancer (she claims asbestos contains fluoride -- it doesn't). Gotzsche blames both the influence of U.S. dentistry (because their reputation is ""irrevocably bound"" to the fate of fluoride) and an ""anonymous group of industrialists"" -- fluoride is a by-product of companies like Aluminum Co. of Canada and American Chemway Corp. In a final chapter, Gotzsche attacks ""the great dental myth"" -- suggesting the entire profession is as rotten as the cavities they're supposed to (and don't) prevent. Ralph Nader, Adelle Davis and Herbert Denenberg are among better-known opponents of fluoridation. Despite her own emotionalism, there will be some to whom this will be of speculative interest. To us, it sounded like overkill.