An implant (10) for fixing dental prostheses of the type comprising- an externally threaded intra-bone section (11),- an anchoring superstructure (15) for a prosthesis,- a pin (20) for fixing the anchoring superstructure (15) to the intra-bone section (11).The external thread (12) of the intra-bone section (11) has at least two first self-tapping longitudinal grooves (22) and at least two second longitudinal grooves (23) which prevent unscrewing.