US Patent 4,187,611
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
A dental retention pin has a threaded longitudinally grooved lower shaft section, an intermediate sealing section for sealing the hole in which the pin is threaded, and an upper section embeddable in a surrounding body of restorative material. A pinhole is drilled in a tooth and the pin is inserted therein by rotation to cut threads in the dentin as fluids are vented through the groove. The sealing section then enters the pinhole to establish a sealing relationship therewith.
Chan, Kai C. Dental retention pin and method. US Patent 4,187,611 filed October 07, 1977 and issued February 12, 1980. https://ir.uiowa.edu/patents/20