| 摘要 |
<p>The dilating device consists of an element made of two mobile parts facing each other, each part being adapted to be embedded in a block of resin shaped to the area of the palate; one part includes a driving worm with an actuating head and a threaded element located in a housing provided in the said part; the other mobile part includes a rack received in a suitably shaped cavity in the first mobile part, the cavity communicating with the housing of the driving worm; the threads of the driving worm engage with the teeth of the rack whereby rotation of the worm causes the rack to slide in the cavity and produces relative movement between the two parts either towards or away from each other.</p> |
