Device for injecting a fluid phase filling material into a channel cavity, said device comprising an adaptation nozzle (10), a self-mixer (11) attached to said adaptation nozzle, an intraoral injection nozzle (12) arranged in the upper end of said self-mixer, characterized in that said injection nozzle is a tube of which the distal end has an external diameter less than or equal to 1.5 mm in a length greater than or equal to 8 mm, in fact that said injection nozzle is made with a shape memory material, so that it can be folded according to a desired orientation, and by the fact that said injection nozzle consists on its outer surface of: - either circular ribs ( 1200) defining a throat, the upper end of the self-mixer (11) being molded into this throat so that said injection nozzle is locked in position at said upper end, keeping at the same time a degree of freedom of rotation around its axis of symmetry (A), - either one or several circular ribs (1201) parallel to each other, the upper end of the self-mixer (11) being molded on this circular rib so that said injection nozzle is locked in position at said upper end, while retaining a degree of freedom of rotation around its axis of symmetry (A).Dispositivo para inyectar en una cavidad de canal un material de relleno en fase fluida, constando dicho dispositivo de una boquilla de adaptación (10), un automezclador (11) unido a dicha boquilla de adaptación, una boquilla de inyección intraoral (12) dispuesta en el extremo superior de dicho automezclador, caracterizado por el hecho de que dicha boquilla de inyección es un tubo del que el extremo distal tiene un diámetro externo inferior o igual a 1,5 mm en una longitud superior o igual a 8 mm, por el hecho de que dicha boquilla de inyección se realiza con un material con memoria de forma, de manera que pueda doblarse según una orientación deseada, y por el hecho de que dicha boquilla de inyección consta en su superficie exterior de: - ya sea unas nervaduras circulares (1
