are replaced by a plurality of orifices 20 and 21 producing two multiple jets 22 and 23 forming two sprays from opposite directions with regard to the two water jets 17 18 from opposite directions in fig2 and 3 and similarly the two multiple water jets 22 23 from opposite directions in fig4 it should be noted that these jets are parallel but are offset in the direction of the length of the body 1 of the instrument as is clearly visible in fig2 to 4 in fig5 the two orifices 15 and 16 provided in the two arms 2 and 3 are directed so as to produce two oblique water jets 17 and 18 inclined in the ginggivatooth direction the two jets are thus directed properly with no risk of causing detachment of the gingiva prejudicial to good periodontal health in fig6 one of the two needle eyes 4 and 5 namely the needle eye 5 of the arm 3 of the fork shaped instrument receives a radial hair brush 24 the body 25 of which is fitted from inside the fork into the needle eye 5 and is held therein by friction or by a catching shoulder or ring 26 such that the radial hair brush 24 projects from the arm.