| 摘要 |
<p>A device is provided for ascertaining the parallelism of flanks of rows of teeth which are to be prepared when working to produce a dental prosthesis. The device comprises a mirror 12 having a concave face 13 mirrored at 14 towards its concave side. The contour of the mirror is oval and larger than the arc of the row of teeth to be observed and is narrower at its broadest part than the maximum width to which the corner of the mouth can be stretched. The concave surface is part of a paraboloid of revolution such that the rays of light emanating from the row of teeth parallel with the geometrical longitudinal axis are thrown on the eye as a converging beam. <IMAGE></p> |
