Prostho Plus by Piers Anthony

As it was, he knew that transistors were semi-conductor devices able to take the place of many electron tubes. This mouth could be the chassis of a radio set, each tooth performing a specific function in the circuit. Current low? Clench the teeth!
    Which put the problem clearly beyond his competence. This was a case in which formal galactic training would be invaluable. Trach had mentioned a Galactic University of Dentistry, but had stressed the difficulties of admittance: "You have to have a high potential to begin with. They won't even consider you unless you are sponsored by an accredited planet. All the universities are like that. And few worlds will bother to sponsor an alien, when they have so many of their own people eager to make the attempt."
    "You'd advise me to forget it, then?" he had asked, disappointed.
    Trach had agreed. How could an ignorant Earthman aspire to advanced training, when he couldn't even afford his own contract? Yet the dream wouldn't die. One of these planets he would make a bad mistake. If he wished to remain at large in the galaxy, he needed a galactic diploma.
    Not that he wanted anything more than a prompt return to Earth. A secure practice at home. Certainly.
    The Electrolytic teeth returned to focus. At least he could clean up the minor tarnish visible on the inlays. No risk there. The previous dentist must have been a trifle careless, for gold seldom tarnished unless there were impurities in the alloy. Apart from that, the work was expert.
    He finished the polishing quickly. As for the language problem—there was nothing he could do about that. Under no circumstances would he drill into one of those fantastic teeth.
    Thank you," the patient said. "That tastes much better. What recompense may I offer you?'.
    The guide quivered. "Your gibber—I mean, your aphasia. It's gone!"
    "What do you mean, gone? You were the one who gabbled gibberish, sweetcore."
    The guide addressed "Dillingham. "O omniscient healer! You have cured my husband! How did you do it?"
    Dillingham backed off. "I didn't do it. I merely removed a little tarnish from his reconstructions."
    "You must have done something, Doctor," the patient said. "For weeks I've been trying to make my imperious wishes plain to this pebblehead, but she gave me increasingly unintelligible answers. My acquaintances have been even worse. It was as though they'd all blown their signal-coding teeth. But you understood readily enough, and somehow you brought them back to their senses. I really must reward you properly."
    "I assure you, I did not—"
    "You replied to my salutation, and you eliminated the bad taste in my mouth, just as requested. An excellent job, not to mention this other inconvenience you alleviated."
    Discretion told him to let the matter ride, but something else overrode it. That little bit of polishing could not have affected the internal circuitry, and he could not accept credit for more than he had done. It was against professional ethics. The aphasia might return at any time, perhaps much worse than before, if the cause were neglected.
    "You must stay for supper," the husband said. "It's such a relief to hear intelligible shunk again."
    There was a gasp (courtesy of the transcoder) from the wife. Dillingham saw his worst fear realized, and forestalled her comment the only way he could think of at the moment. "Sir, may I check your teeth once more? While you were shunking I remembered a place I may have missed."
    "Certainly." The great lid hinged up and the chunky teeth were exposed again.
    Dillingham saw nothing new, but occupied time by re-polishing all the teeth carefully. He needed to think this out. Had he done something that might affect the speech mechanism? Could mere tarnish somehow influence signal modulation? Tarnish was caused, in gold inlays, by electrochemical interaction of the saliva with impurities, but—
    Full-blown, he had the answer.
    "What were you saying, a moment ago?" he asked the Electrolyte. "That it