| 摘要 |
The root pin is used to build up an artificial crown for deeply damaged teeth. It comprises an apical part, a coronal part and a handle. The handle is connected to the coronal part by an intended breaking point. The coronal and apical parts are provided with retention devices. The retention device of the apical part comprises a screw thread and a spiral groove. The spiral groove makes the screw thread self-tapping, is retentive and serves as a conveying means for the surplus fixing cement.
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