The retention of high inlay mainly depends on the retention of nail holes on the surface. When preparing the tooth, if the surface is in contact with the opposite jaw, the affected tooth surface should be uniformly reduced along the surface shape, and a gap of at least 0.5 ~ 1.0mm should be prepared. The embedded surface should include the edge of the tooth surface and the working tip. If your face is already low, you should trim it a little and remove the sharp ridges.

Four nail holes are often used to hold molars, and if there is a local defect, a small box-shaped holding form is also used. Nail holes are scattered in mesial and distal fossa and buccal and lingual sulcus, and the depth exceeds the enamel dentin boundary, generally 2mm, and the diameter is 65438 0 mm. The preparation is carried out along the long axis of teeth, and the nail holes must be parallel to each other. Therefore, a bending machine with parallel controllers can be used. After the first nail hole is completed, the parallel controller can master the direction of the nail hole, and the skilled person can control the direction of the nail hole by visual inspection.