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Forum Category: Implantology

Moderated by:
Jonathan Havener

Restoring Implants: Screw-Retained Vs Cemented Crowns

    The success rate and prognosis of implants in our day and age has made implants the gold standard in restoring an edentulous space. Clinicians placing implants have become very proficient, and when proper treatment planning with the end restoration in mind is utilized, patients are satisfied with the result. However, an increasing trend of failures has arose that deals not with the placement and retention of the titanium screw, but of an inflammatory nature that can be completely avoided.

     When a restorative dentist cements a crown on an abutment, especially on bone level abutments with limited view, they must be mindful of removing all residual cement. In, 2009 study was published by Dr. J Wilson in the Journal of Periodontology that looks at the positive relationship between excess cement and peri-implant disease. In 81% of the cases of peri-implantitis, residual cement was found to be the etiology of disease. This problem can be avoided by either adopting screw retained restorations which do not require cement, or utilizing a PVS custom abutment to gauge how much cement is needed. This PVS strategy is performed by injecting impression material into the crown to be cemented. After the material has set and the crown is ready to be cemented, the crown can be seated on the custom PVS abutment to extrude excess cement from the crown before permanently seating on the implant abutment. If clinicians want to avoid this lawsuit altogether, screw-retained crowns can be used. However, these crowns have disadvantages such as fracture propagation, decreased esthetics, and increased lab fees.

 It is ultimately up to the restorative dentist and the patient to discuss the alternatives and agree on a treatment plan.
    
 
    
 
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Restoring Implants: Screw-Retained Vs Cemented Crowns

10:06 PM | Jun 15,2016
I personally prefer using screw-retained crowns due to the above mentioned problem. It is very difficult to completely remove excess cement with cement-retained crowns which can lead to peri-implantitis problems. Given that implants are very costly, I would want to do the most I could to prevent any potential problems which may lead to implant failure. Granted, with screw-retained crowns there are disadvantages associated with them as well. It is truly up to the restorative dentist on what they feel most comfortable working with as well as the patient's input.

Restoring Implants: Screw-Retained Vs Cemented Crowns

10:06 PM | Jun 15,2016
I personally prefer using screw-retained crowns due to the above mentioned problem. It is very difficult to completely remove excess cement with cement-retained crowns which can lead to peri-implantitis problems. Given that implants are very costly, I would want to do the most I could to prevent any potential problems which may lead to implant failure. Granted, with screw-retained crowns there are disadvantages associated with them as well. It is truly up to the restorative dentist on what they feel most comfortable working with as well as the patient's input.

Restoring Implants: Screw-Retained Vs Cemented Crowns

07:59 PM | Apr 26,2016
I am currently a D3 student restoring my first implant and it is cement retained so I know i must be careful in removing all residual cements and have due diligence in ensuring that the site is clean. But, I do think that we should learn more about the difference in the types of implants and why one may be better for some patient than others. We did learn that the increase numbers in peri-implantitis is due to left over cement so that is something that we should definitely be careful about and maybe come up with some methods to ensure that cement isn't left over when a cement retained implant is necessary.

Restoring Implants: Screw-Retained Vs Cemented Crowns

05:56 PM | Dec 29,2015
This is very informative, I did not know about the PVS technique. I will certainly use that in the future. One thing that my school implemented to reduce the number of cement retained implant supported crowns was to make the fees the same for both, so we can explain to patients the advantage of have a screw retained crown and inform them that the price is the same. Most patients will go for it, especially in the posterior where most implants are placed in the undergrad clinic. Luckily the cement retained crowns are very retentive, when I placed the crown on the abutment for adjustments, I literally could not take it off and had to get pliers with rubber tips to take the crown off. I put a very small amount of cement and there was no excess that needed to be cleaned off. I always try to go for screw retained when I can, but cement retained can really make your life easier sometimes.

Restoring Implants: Screw-Retained Vs Cemented Crowns

11:33 AM | Dec 14,2015
Great insight by everyone! I wanted to take a moment and talk about the bicon implant system, which can be restored without screws or cement. With traditional implant systems, there are precise steps that the clinician must follow to impress, temporize, and restore implants. However, bicon offers a very simple and unique system for restoring implants. The IAC, or integrated abutment crown, does not use screws or cement and they are a breeze to restore. The actual implants feature a small well that houses the abutment. After impressing, the abutment and crown are fabricated by the lab. When it comes time to restore, a custom jig is used to simply tap the IAC into the implant well. There is no cement or screws to deal with. Another unique feature of this cementless, screwless implant system is highlighted in long term studies. With typical implant systems, it is expected to see about 1-2mm of bone loss around the implant. With the bicon system and the unique platform switching, studies have show that bone will grow around the implant. After reading a bit about the bicon system, I'm excited to start tx planning them for some of my patients. If you have a chance to restore this system, you won't want to use another system again.

Restoring Implants: Screw-Retained Vs Cemented Crowns

02:34 PM | Jun 16,2015
Very insightful comments everyone! I agree that screw-retained implants are the first option. There are some scenarios though, that a cement-retained design is maybe the only way to go: 1.In the anterior zone, the surgeon who places the implant may not be able to achieve an ideal angulation of the implant because of bone support compared with the natural inclination of anterior teeth. Because of this, the screw access hole may go straight through the incisal edge of the crown. I believe there are some angled screw-retained abutments coming out, however, if the angle is too disparate, an angled cement-retained abutment must be used to make this correction. Does anyone have experience with angled screw-retained or cement-retained abutments? 2. The other scenario again finds itself in the anterior zone - this time with deep bites/class II div II malocclusion. In these cases, we were taught that screw-retained designs won't work because of the bulk of composite needed to cover the screw access. Furthermore, when cement-retained implants are chosen, use of a radiopaque cement and post cementation radiograph can aid you in locating areas of excess cement.

Restoring Implants: Screw-Retained Vs Cemented Crowns

08:23 PM | Jun 15,2015
Thank you KLeeDMD for sharing your thoughts of on the subject. Well said. I have only had a little experience with implants so far in my dental career but I have seen the importance of retrievability first hand. I was assisting an upperclassman on insertion of two implant screw-retained crowns. We had done many checks on the contacts and occlusion. The student did the final torque and sealed the screw entrance with cotton and resin. He did one more check of the contacts and the one contact was too tight. If it had been cement retained it would have been a large issue however since it was screw-retained we were able to fix the problem in under a half hour. I cannot think of any other disadvantages to screw-retained other than esthetics. I think it is important to learn both restorative procedures but I feel like screw-retained will become more of the standard of care.

Restoring Implants: Screw-Retained Vs Cemented Crowns

10:34 PM | Dec 07,2014
From my experience so far patients tend to choose cement retained crowns because they are familiar with this method. Personally I would like to use screw retained because of the issues with cement causing inflammation, but I have to be able to explain why they would be better off using a screw retained implant. Screw retained is the better option long term, but it will take time for patients to adopt this thinking.

Restoring Implants: Screw-Retained Vs Cemented Crowns

11:13 PM | Dec 04,2014
Screw-retained crowns have many benefits over cement-retained crowns. One major advantage is retrievability. Screw-retained crowns are recoverable without damage to the crown. This is useful because it makes it easier to clean components, remove calculus, assess surrounding soft tissue, tighten screws, and replace or repair components. It also gives the provider the option of temporarily removing an implant crown to facilitate treatment of an adjacent tooth or to protect the implant crown during treatment of an adjacent tooth. Retrievability is especially valuable with long span prosthetic restorations, allowing the provider to salvage the restoration should complications arise rather than cutting and destroying it. As previously mentioned, another big advantage of screw-retained crowns is the absence of cement. It can be difficult to remove all the residual cement when margins are subgingival despite best efforts to do so. It has also been shown that removing excess cement with various instruments including stainless steel, gold, and even plastic scalers can leave scratches and gouges on the surfaces of the abutment and crowns. Roughened surfaces facilitate plaque and bacteria accumulation which lead to soft tissue inflammation. Left untreated over time this can even cause bone loss. Since one of the hallmarks of implant success is absence of inflammation, peri-implant mucositis, and peri-implantitis, then minimizing any contributing factors that can cause inflammation is advantageous. Since screw-retained crowns don’t need cement, they have less risk of soft-tissue inflammation. However, there are also downsides to screw-retained crowns. Esthetics are a concern where the screw access channel is located. Applying a layer of opaquer under composite can significantly help with achieving more esthetic results. The porcelain around the screw hole can be more prone to fracture but careful patient selection can help with this. It is important to identify if the patient has any parafunctional habits such as bruxism. A nightguard can be prescribed in these cases and occlusion should be carefully assessed and adjusted to achieve balanced occlusion avoiding heavy contacts on the implant crowns near the more susceptible porcelain. Cement crowns have their advantages as well. They are easy to deliver without any extra tools and follow the same protocols as delivering traditional tooth borne cemented crowns. They typically cost less and can work with implants that have less than ideal angulation. Overall, patient and case selection are key along with provider preference. Ultimately, it is possible to achieve good results and long term success with either choice as long as the provider is proficient with the chosen modality and takes all necessary steps to ensure a good outcome.