A guide tube to enable the boring of orifices in the bone portion of the maxilla or jawbone of a patient, including at least a first outer tube segment having a first axial through aperture and at least a second inner tube segment having at least a free end and a second axial through aperture, the second tube segment being inserted inside the first axial through aperture of the first tube segment, and wherein an integrated axial prolongation projects from the free end of the inner tube segment.