A polymer shell (commonly known as a mouthpiece) that is worn over natural teeth to change the perceived color of the tooth and to provide orthodontic support selectively. The shell (commonly called mouthpiece) is made by thermoforming a selected polymer sheet containing optical additives； the optical additive has a desirable appearance due to the combination of shell (commonly called mouthpiece) and teeth. Bring. It is desirable that the shell (commonly called mouthpiece) has a transparency of 75% or more, particularly 85% or more. [Selection] Figure 7歯牙の知覚色を変える為に、そして、歯列矯正支持を、選択的に提供する為に、天然歯の上に装着するポリマー製シェル（通称マウスピース）。本シェル（通称マウスピース）は、光学添加物を含む選択されたポリマーシートを、熱成形する事によって、作成される；光学添加物は、シェル（通称マウスピース）と歯牙の組み合わせにより、望ましい外観を、もたらす。 本シェル（通称マウスピース）は、７５％以上、特に、８５％以上の透明度を有する事が、望ましい。【選択図】図７
