LAUGHTER may be the best medicine, but it can be hell on prosthetic dentistry. We thought we’d seen it all until we read retired-dentist-turned-theater-critic Stanley Greenberg’s review of the Off-Broadway hit “Old Jews Telling Jokes” in the Syosset-Jericho Tribune. After seeing the production at the Westside Theatre on June 27, Greenberg wrote that he and his wife saw an “old man looking forlornly under his chair.” Asked by the critic what he was searching for, the man replied, “‘I lost my teeth, my dentures.’” According to Greenberg, the man had “laughed so hard that his teeth popped out of his mouth.” Fortunately, an usher with a flashlight located the catapulted cuspids. A rep for the show confirms the incident.