Retention is more important, poor retention can lead to many problems, can make the abutment teeth secondary decay, periodontal tissue damage can not play a good role in chewing function or even swallowing and other damage.
Types of retainers: intracrown retainers, extracoronal retainers, and intra-root retainers
Improve the retention force of the retention body: Since the fixed teeth connect the abutment teeth as one, the force response is different from that of the individual teeth, and the retention force is higher than that of individual teeth restoration.
(1) The retention force of the full crown is the best, and the occlusal polymerization should not be too large when making the retainer. The 3/4 crown should be made in the adjacent axial groove to prevent rotational dislocation. The inlay point angle and line angle are clear.
(2) The design of the retention force of the retention body is compatible with the size of the occlusion force, the span of the bridge body and the curvature of the bridge body. The longer the span of the bridge body, the more curved, and the greater the occlusion force, the higher the retention force of the retained body.
(3) The retention force of the abutment retainer at both ends of the double-ended fixed bridge should be basically equal: if the retention force of the two ends of the retaining body is very different, the retaining body at the end of the retaining force is easy to loosen. The retaining body at the end with strong retention force has not fallen off temporarily, and the patient is not easy to detect the secondary caries of the loose end abutment.
(4) When selecting a retainer, it must be considered that there should be a common position between each retainer.
(5) If the abutment tooth is defective or deformed, it should be repaired when designing the retainer. If the crown of the abutment tooth already has a filling, the edges of the retainer should be covered with the filling as much as possible to avoid loosening the filling and affecting the retention of the retainer.
(6) The design of the retaining body should prevent the apex crack of the abutment teeth, and the outer crown retainer will not occur because the occlusion surface of the abutment tooth is covered with metal. However, if the intracrown retainer, especially the maxillary bicuspids, is adjacent to the inlay, because its cheek and tongue tip are very steep, it is easy to cause tooth tip cracking.
(7) Retention body design of severely defective teeth in crowns: such teeth are mostly dead pulp teeth, as long as the defect does not reach deep under the gingival and the teeth are stable, they should be preserved as much as possible. First, after thorough root canal treatment, a retaining nail or pile is inserted and glued into the root canal, a nuclear shape is formed with silver amalgam or resin, and then a full crown retention body is made.
(8) Retention body design of inclined abutments: first, the axial direction of abutment teeth can be changed by orthodontics; secondly, a modified 3/4 crown is used for retention; Socket crown retainer can be used again for repair