Method of manufacturing a mouthpiece for simultaneously brushing at a plurality of dental positions, the mouthpiece being of the type comprising a body defining a recess which is lined with bristles (24, 29; 52; 82) and has a J-shaped or U-shaped length direction and an at least partly U-shaped cross-section transverse to the length direction; wherein the method comprises a pad manufacturing step in which at least one pad (50; 60, 61; 70, 71) with bristles is made; the pad (50; 60, 61; 70, 71) consisting of a pliable plastic foil (51; 81) and plastic bristles (24, 29; 52; 82) projecting from a front surface of the foil (51; 81); the foil (51; 81) having a back surface opposite the front surface; and the pad manufacturing step comprising - providing bristles (24, 29; 52; 82) with a fixed end (55; 84) and a free end, - providing a prefabricated foil (51; 81) having a thickness of at most 700 μm, and - fusing the fixed ends (55; 84) of the bristles (24, 29; 52; 82) with the prefabricated foil (51; 81), resulting in the bristled pad (50; 60, 61; 70, 71) to be made; wherein the method further comprises a body providing step in which a body of the mouthpiece to be manufactured is provided; the body providing step comprising providing a body with a recess and at least one bristle carrier; the recess having a J-shaped or U-shaped length direction and an at least partly U-shaped cross-section transverse to the length direction and being configured for encompassing a dental arch of multiple dental positions; the at least one bristle carrier delimiting the recess; and wherein the method further comprises a pad attaching step in which, during or after the body providing step, the foil of one or more bristled pads (50; 60, 61; 70, 71) is attached to the at least one bristle carrier to line the bristle carrier with bristles (24, 29; 52; 82) such that: a) the back surface of the foil faces the bristle carrier, b) the back surface of the foil follows the shape of the surface of the bristle carrier to which it is attached, and c) the front surface of the foil faces away from the bristle carrier into the recess. wherein the method comprises a pad manufacturing step in which at least one pad (50; 60, 61; 70, 71) with bristles is made; the pad (50; 60, 61; 70, 71) consisting of a pliable plastic foil (51; 81) and plastic bristles (24, 29; 52; 82) projecting from a front surface of the foil (51; 81); the foil (51; 81) having a back surface opposite the front surface; and the pad manufacturing step comprising - providing bristles (24, 29; 52; 82) with a fixed end (55; 84) and a free end, - providing a prefabricated foil (51; 81) having a thickness of at most 700 μm, and - fusing the fixed ends (55; 84) of the bristles (24, 29; 52; 82) with the prefabricated foil (51; 81), - providing bristles (24, 29; 52; 82) with a fixed end (55; 84) and a free end, - providing a prefabricated foil (51; 81) having a thickness of at most 700 μm, and - fusing the fixed ends (55; 84) of the bristles (24, 29; 52; 82) with the prefabricated foil (51; 81), resulting in the bristled pad (50; 60, 61; 70, 71) to be made; wherein the method further comprises a body providing step in which a body of the mouthpiece to be manufactured is provided; the body providing step comprising providing a body with a recess and at least one bristle carrier; the recess having a J-shaped or U-shaped length direction and an at least partly U-shaped cross-section transverse to the length direction and being configured for encompassing a dental arch of multiple dental positions; the at least one bristle carrier delimiting the recess; and wherein the method further comprises a pad attaching step in which, during or after the body providing step, the foil of one or more bristled pads (50; 60, 61; 70, 71) is attached to the at least one bristle carrier to line the bristle carrier with bristles (24, 29; 52; 82) such that: a) the back surface of the foil faces the bristle carrier, b) the back surface of the foil follows the shape of the surface of the bristle carrier to which it is attached, and c) the front surface of the foil faces away from the bristle carrier into the recess. wherein the method further comprises a body providing step in which a body of the mouthpiece to be manufactured is provided; the body providing step comprising providing a body with a recess and at least one bristle carrier; the recess having a J-shaped or U-shaped length direction and an at least partly U-shaped cross-section transverse to the length direction and being configured for encompassing a dental arch of multiple dental positions; the at least one bristle carrier delimiting the recess; and wherein the method further comprises a pad attaching step in which, during or after the body providing step, the foil of one or more bristled pads (50; 60, 61; 70, 71) is attached to the at least one bristle carrier to line the bristle carrier with bristles (24, 29; 52; 82) such that: a) the back surface of the foil faces the bristle carrier, b) the back surface of the foil follows the shape of the surface of the bristle carrier to which it is attached, and c) the front surface of the foil faces away from the bristle carrier into the recess. a) the back surface of the foil faces the bristle carrier, b) the back surface of the foil follows the shape of the surface of the bristle carrier to which it is attached, and c) the front surface of the foil faces away from the bristle carrier into the recess.