Implant prosthetics (part 2) – screwed or cemented?

Andreas Kunz, Dr. Insa Herklotz

Screwed or cemented in implant prosthetics – a question of preference or are there case-related decision factors?

In the first part of this article on implant prosthetics, the authors provided a brief general overview of abutments and then described cemented restorations in more detail, outlining their advantages and disadvantages. The second part of the article focuses on screw-retained restorations.

Screw-retained restorations 

The advantage of the screw-retained implant-supported reconstruction over the cemented implant crown is that it is easy to remove, as is the case e.g. B. may be necessary in the case of ceramic fractures or screw loosening. In addition, during insertion, the pressure on the tissue can be gradually adjusted by slowly tightening the occlusal screw (Fig. 8). The emergence profile is formed by the individually adapted mplant crown.

The biggest disadvantage of occlusally screw-retained implant crowns/bridges, especially with internal rotation-protected implant connections, is the direction of insertion. If the insertion direction of the implant axis in single crowns does not match the insertion direction of the approximal contact points, insertion is more difficult. Large interdental triangles are usually created unintentionally. A screw-retained bridge restoration with a parallel-walled, internal rotation-protected implant system requires the implants to be aligned approximately parallel (Fig. 9).

Fig. 8 With occlusally screw-retained implant crowns, the soft tissue can be gradually shaped.

Fig. 9: Internal rotation-protected, parallel-walled implant connections require an approximately parallel alignment of the implants in bridge restorations in order to enable occlusal screwing of the bridge restoration.

With a conical implant-abutment connection, different angulations of implant axes can be compensated for up to a certain degree, depending on the implant system. This simplifies integration. Occlusally screw-retained implant crowns must be closed occlusally after insertion (Fig. 10). The opening of the screw cap varies depending on the diameter of the screw. With the occlusally screw-retained hybrid abutment crown, it is possible to reduce the screw channel to the screwdriver diameter by inserting the final screw connection before bonding the titanium base. This allows for a minimal occlusal screw channel. The occlusal screw, whether cemented or screw-retained, is always tightened with the torque specified by the manufacturer. New and unused occlusal screws should also be used (Fig. 11).

Fig. 10: The occlusal opening of the screw channel, which has a reduced diameter, enables easier closure during treatment.

Fig. 11: Working with new and unused occlusal screws as well as screwing in with a torque wrench and torque according to the manufacturer's instructions are now the “gold standard” in implant prosthetics.

Decision factors “screwed” implant crown

Advantages

  • Accessible at any time, easy to remove.
  • No excess cement in the sulcus.
  • During insertion, optimal pressure can be exerted on the gingiva.

The disadvantages:

  • Chewing surfaces cannot always be designed optimally (screw opening).
  • Insertion direction depends on the approximal contacts.
  • Bridge restorations with a connection secured against internal rotation are more difficult to implement in terms of the direction of insertion.
  • Optimal implant alignment necessary to ensure optimal position for occlusal screw channel.

Conclusion implant prosthetics

Both fastening methods – screwing and cementing – have their place. No treatment option is superior to the other. Depending on the case-related situation, the advantages and disadvantages of both options must be discussed based on decision criteria. To avoid the risk of cement-induced peri-implantitis, implant-supported restorations should be screw-retained, especially in the posterior region, which is more difficult to access. In the aesthetic anterior tooth area, the bony structures do not always allow a palatally oriented implant position. In this case, cementing the implant crown onto an individualized abutment enables the implant position to be balanced without aesthetic restrictions.

The biggest disadvantage of occlusally screw-retained implant crowns/bridges, especially with internal rotation-protected implant connections, is the direction of insertion. If the insertion direction of the implant axis in single crowns does not match the insertion direction of the approximal contact points, insertion is more difficult. Large interdental triangles are usually created unintentionally. A screw-retained bridge restoration with a parallel-walled, internal rotation-protected implant system requires the implants to be aligned approximately parallel (see Fig. 9).

Read Implant Prosthetics (Part 2):

Part 1 of the article focuses on cemented restorations.

Further information is also available in the publication: Herzklotz I, Kunz A, Beuer F: Screwed or cemented – is that the question? Quintessence 2017;68(9):1-7

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