Shall I opt for a screw-retained or a cement-retained implant crown?
Following the installation of an implant, we are always faced with the dilemma whether the permanent crown should be cement or screw-retained. In what follows we will explain the meaning of these two concepts discussing the pros and cons thereof, in order for you to be able to make up your mind as to the kind of crown you desire during the post-implant healing period.
Implant is the artificial root of a missing tooth installed into the bone underneath the gums. Once the implant has integrated into the bone (osseointegrated) (3 months) the tooth restoration (crown or bridge) is fixed on. The implant and the crown are connected by an abutment which is inserted into the implant to retain the crown in much the same way as a filed down tooth preparation (stump) does.
Cement retained and screw retained crowns require different kinds of abutments which also differ in terms of their price. The screw retained crowns are always a bit more expensive.
Cement-retained implant crowns
Cement-retained implant crowns or bridges are secured on the abutment by means of a special kind of luting cement.
What are the advantages of cement-retained tooth restorations over screw-retained ones?
- From the patient’s point of view its single greatest advantage lies in its appearance superior to that of a crew-retained crown. Cement-retained crowns are simply glued onto the abutment screwed into the implant.
- It is less expensive than a screw-retained crown since it is designed for a pre-fabricated abutment which the technician simply “picks out from the drawer”.
- As for the dentist, it is a whole lot easier and faster to install by which we can cut back on labour costs.
What are the indications for a cement-retained crown?
- If too many implant crowns are required and a screw-retained restoration is beyond the patient’s means.
- The crown is intended for the front region and has to comply with the highest aesthetic standards due to the patient’s work or social status.
What are the downsides of cement-retained tooth restorations in comparison with screw-retained ones?
- The major downside of cement-retained restorations is their inability of being removed non-destructively, i.e. they can only be cut off from the abutment. In such instances the crown has to be fabricated anew (translating into new impressions being taken, a new bite check, framework trial fitting, etc.). If the crown is damaged due to no fault on the dentist’s or the dental technician’s part, all financial liabilities shall be incurred by the patient (such as travel costs, fabrication of the new crown, etc.).
When to remove a cement-retained crown?
The most frequent reasons include:
- The ceramics chips off (sporting accident, biting on metal, bone, cherry stones, nutshell, etc.).
- Aesthetic reasons (bone decay or gum recession over the years, discoloration of adjacent teeth, etc.).
- The patient’s altered occlusion, tooth loss having occurred at other sites, or old teeth having worn off or chipped off which necessitate the adjustment of occlusion and the teeth.
- The fastening screw may also become loose or fatigued as a result of tooth grinding or clenching at night causing the tooth restoration to wiggle.
Screw-retained implant crowns
What actually is a screw-retained crown?
Screw-retained implant crowns are fastened to their abutment by means of a through-bolt as opposed to cement-retained ones which are luted onto the abutment. The bolt is tightened with a special torque wrench to the appropriate torque which results in perfect stability.
What are the advantages of a screw-retained solution over a cement-retained one?
- Its greatest advantage is the fact that in can be screwed off and repaired in the event of any injury. This also holds true if further tooth loss occurs or if an extensive tooth restoration becomes due
- Gingival inflammation or periimplantitis is easier to treat since the crown can easily be screwed off providing easy access to the surface to be treated, and once the treatment is done it can be screwed back on.
- It allows for a more thorough professional cleaning through being removable.
What are the drawbacks of screw-retained implant crowns?
- Their surface is inhomogeneous due to the through-bolt leaving a hole that needs to be covered with a filling once the crown has been screwed in place, which compromises aesthetics to some extent as compared to cement-retained solutions.
- Screw-retained implant crowns are more expensive than screw-retained implant crowns.
What are the indications for a screw-retained implant crown?
- Screw-retained implant crowns are, for the most part, indicated for implant-restorations of rear teeth due to the inhomogeneous surface of the crown, but custom requirements may also make them suitable for the front region.
Screw-retained crown having been placed in and filled with an aesthetic filling.
Summary
In our experience the benefits of screw-retained crowns outweigh those of cement-retained crowns and if the patient finds them within their means and is pleased with them in terms of aesthetics screw-retained implant crowns are advocated.
That said, we may also consider the workaround solution of securing the cement-retained crowns with long-term provisional, rather than permanent, luting cement. With this solution the crown will remain stable for months or even a year, but can be removed as required. It must be borne in mind, however, that if the cement recurrently gives way, luting the crowns back on will mean extra expenses (such as travel, accommodation, etc.) and sometimes we may not be able to remove crowns cemented on provisionally in much the same way as permanently cemented crowns.