| 摘要 |
The tooth crown has an opening through it contg. means working with auxiliary ones to allow the adhesion between the crown and the part of the tooth below it to be broken. This can consist of a screw thread in the opening wall, or a widened portion of the opening near the bottom, so as to form a collar. There can also be a further widened portion at the top, forming a second collar. - The crown itself can be of metal, or of porcelain on a metal frame, the latter incorporating the screw thread. |
