An example method of assembling a prophylaxis angle includes inserting a drive gear into a first axial bore defined within a neck of an angle body, the drive gear having a drive gear head and a locking flange axially-offset from the drive gear head. A driven gear is inserted into a second axial bore defined within a head of the angle body, the first and second axial bores being angularly-offset from each other and communicating at an intersection in the angle body. The body defines an opening that spans contiguous portions of both the neck and the head. The drive gear is coupled to the driven gear such that rotation of one rotates the other. A gear retainer is then installed on the head, the gear retainer having an annular body that defines an inner circumferential surface that extends about an outer surface of the head.
