Anchor having threads opposing unthreading

Abstract

A threaded implement, such as a dental or medical implant having a receptacle bearing a socket for receiving or securing a threaded shank for engaging material such as bone tissue, the threads bearing longitudinally oriented grooves for opposing spontaneous unthreading over time. Alternatively, the implement could be a general purpose anchor or an industrial fastener wherein resisting unthreading is important. The grooves extend from the lower end of the implant toward the upper portion. In a first embodiment, the grooves are shallow, and in another embodiment, are deep enough to impinge upon the shank. Each groove has a first face disposed perpendicularly or nearly so to the circumferential surface when viewed in side cross section and a second face disposed more closely to parallel to the circumferential surface when viewed in side cross section. The first face is oriented such that it faces away from the direction of advance when the implant is threaded into the bone. In a second embodiment, the grooves are replaced by outward projections which displace bone axially when the implant is being threaded into bone tissue. In other alternative embodiments, the grooves may abut one another, may be spaced apart along the circumferential surface, and may include a third face separating the first and second faces. In further alternative embodiments, the shank is tapered, the receptacle is cylindrical, and the receptacle has a non-cylindrical, plain walled cylindrical, or internally threaded cylindrical recess opening at the upper end of the receptacle.