Dental Implants: Retrievability

I have not experienced those kind of problem because I use neither screws or cement for my implant restorations.

I think it depends on the case. I use cemented crowns when I`m shure the implant is perfectly osseointegrated. I also use screw retained crowns when I want to take it away and see inside the implant. I think we must learn to see case by case, instead of doing always the same treatment. Remember: every case is a new case

Retrievability versus Cementation: In my opinion, I cement the crown, especially the anteriors, where the occlusal forces are quite minimum. Whereas in the posterior where the masticatory forces are enormous, screw-retained restoration probably is the better choice. The reasons are obvious. Nevertheless, it's a case by case situation and also personal preference. Another thing is, cost is to be taken into consideration. Anyway, do what you feel right.

The retrievability factor is still the key. In my prosthodontic residency we were higly encouraged to do screw-retained fixed bridges. Eleven years later - I do 95% cementable. I saw/see too many problems with porcelain fracture around occlusal access holes. When I discuss an implant treatment plan for implant retained fixed bridges I tell the patient that I will only seat the bridge with temporary cement. Yes, I have had some bridges "pop" loose from time to time, and if the patient gives me a cross look or any verbal grief I remind them that I never permanently cement implant crown and bridge work. When they resist or try to insist that I use a permanent cement this time I simply tell them like it is. "I have inherited many patients over the years with implant bridges that were permanently cemented by their general dentists. They came to me as a specialist to save the day because their dentist could not retrieve the bridge - the bad news for them is that the bridges can rarely be tapped off or otherwise retrieved without drilling it off and starting over." I go on and tell them about spring loaded tappers, ultrasonic vibration, and varied fulcrum/leverage removal techniques that run a great risk of damaging the bridge. I proceed to tell them that I have cut many lingual or palatal holes into other dentists' bridges in an attempt to break the cement seal and pop them off for frustrated patients. I highlight that the porcelain adjacent to my cement access hole frequently ends up being chipped in the process. It is a risky proposition at best! Bottom line - When a patient chips porcelain or loosens an abutment abutment screw underneath a permanently cemented bridge there is very little chance of getting it out unharmed. A patient returns to their dentist expecting a simple repair and recement only to become upset and frustrated. Permanent cement rarely allows retrievability without damage. I would far rather recement the crown/bridge with temporary cement every few years and reiterate my temporary cement mantra to them than have to cut off the bridge and start over! I use Fynal(modified ZOE) with a dab of vaseline in the mix with great success. Improv is also excellent. Anecdotally, I heard Charlie English (an incredibly knowledgable prosthodontist) describe the long term crystallization and irretrievability of 'Tempbond' used for implant/bridgework cementation. If you choose to permanently cement your implant crown and bridge, be prepared to cut it off, re-temporize and remake it if there is any problem. Just my $.02

Excellent comment of Dr. Sean Yockus, I´m totally agree with him, I think that everyone of us who involved in Implantology practice must had/have some problems throw the years. In my practice I had some situations with loosen abutment´s screws and of course, I had to cut and remade the whole process since the beginning and dealing with the costs. I´m also agree with Dr. Javier Higuera, every case is a new case. Main point of discussion with him is that I think only perfectly osseointegrated implats has to be restored.

I used to follow many of the prescriptions outlined above - now I just cement with the same cement I'm using for adjacent crowns on natural teeth, usually a resin cement. Prior to cementation, I have my technician make me a 'retrieval' jig - an impression is made of the final crowns on the abutments and a plastic 'retainer' is made with the mini-star machine - then, you simply remove the crowns from the master-cast and place the 'retainer' over the abutments and make a small opening in the occlusal surface directly over the screw - in this way, if in the future you have an abutment screw loosen you simply pull out the 'retrieval' jig and you know exactly where to make you 'endodontic access opening' - you just need a large enough hole to re-insert your torque wrench. Works wonders in the posterior - anterior is more difficult due to the fact that screw access maybe through the facial of a tooth. By the way, zinc phosphate is a wonderful cement for dental implants - due to long abutments, having too much cement to get the restoration to place can be a problem - zinc phosphate can be mixed 'thin' and placed via a benda brush to allow full seating of a prosthesis on long abutments.

After reading all the coments I have to say that most of them are clear and quite to the point. In my experience after 12 years and more than 2000 implants loaded with crowns and bridges I must say that I cement arround 50% of my cases and screw the other 50%. When I cement a crown or bridge I do it so with temporary cement (only on supragingival cases and it usually lasts 3 to 5 years or more)or after placing a litlle vaseline inside crown i use a resin based cement (so i can retrieve the crown if needed in subgingival cases). But after all this time i have only had a few ocations in wich i had to retrieve the work. In the case of screw retained, the access holes are mostly palatal in anterior crows, and oclusal in the posterior ones. The anterior ones present no challenge at all, the posterior ones if metal- ceramic I use an opaquer and then composite resin. In the last 5 or so years I have only used Full ceramic abutments and crowns or bridges, with those there is no problem, a well done composite resin and some tinctions are more than enough. Cheers

Improv is a temporary cement that is approved for use with implants. It is eugenol free so clean up is simple and efficient. It is predictable and dependable and can be used for either implants or natual dentition.If you want the restoration to be retreivable, lubricate the inside of the casting. If you don't, it becomes a permanent cement. I know this sounds like a commercial but think we should consider the properties of the cement we use for the results we want.

Dear Friends, I used to screw all my crowns to the implants. However with the reliability of implants surpassing my crown and bridge work, cementation is now definitely the prefered choice. The key is now the concensus of torque you place on these abutment at 30 to 35 ncm-1. I think with this torque on single crown, there shouldnt be a problem of long term loosening of single crown. This is especially true when you're trying to restore anterior teeth. Screw holes are not aesthetically acceptable. The torque on multiple abutments can be as low as 25ncm-1. My oldest cemented case is 7 years old... so far so good. In terms of retrievability as a rationale for implant dentistry, I feel that this concept should be re-assessed since it is claimed that implants are more reliable than crown and bridges. Infact think about it... shouldnt we be screwing crown and bridges to natural teeth since retrievability here is more important to check for underlying caries? ... :) and we should cement all our implant case...

Comment to all the above: Good clinical observations...I guess everybody has their favorite formula...So here is my position as a prosthodontist in 2005: over 20 years of experience and of course different approaches taken over this time...in the early days screw retained was all that was available but we also came to appreciate the retrievability because the early platforms allowed for loosening and we were grateful for the opportunity to remove the restoration without damage to deal with the frustration of repairing and or replacing the offending components. Personally I did not observe porcelain fracture to be a significant issue with proper frame design. Cement retained restorations gained more popular use due to an increased awareness to provide more esthetic restorations and also to diminish the loosening of components on Flat-top implants. The cement seemed to provide a dampening effect on the abutment screws and diminished loosening. However, this did not eliminate the problem entirely and many wre frustrated in trying to remove cemented restorations without damage. Therefore we have all this discussion on how to best remove restorations for serviceability of prosthetic components that perform less than adequately. When I changed to an implant system with a stable prothetic platform (Astra Tech) in 1992 my approach to design became what best served the case performance as opposed to worrying about when the support components were going to loosen! Today I will comfortably cement all single restorations with durable cement without concern that the supporting components will cause me and my patients unexpected disappointment. For multi-unit restoration design some restorations continue to be best served with screw retained components and with good frame design this works extremely well when indicated. However with more precise implant placement today and a greater emphasis on esthetics ,I find that most of my multi-unit restorations are combination designs incorporating cement type abutments in the anterior region and at least one screw retained abutment posteriorly for unilateral bridges and at least two screw retained abutments for bilateral cases to allow for predictable retrievabilty to meet whatever needs may occur over the long term. SUMMARY- reliable implant system + smart restorative design = predictable restorative performance for our patients!

There are strong arguments in each direction for screw vs cement. I have two points to make: 1. Patients are concerned about security when we say 'temporary' cement. I prefer to tell them it is 'provisional' cement. Their reaction is much less anxious! 2. I have always avoided 'flat top' implants. or thse with a shallow hex, because they depend for stability on the ongoing efficacy of the screw, whose mechanical retention depends on tension in the screw that in time may release. I prefer the cone attachment such as Straumann or Ankylos where the abutment shape is very retentive and is supported by the implant and does not depend on the continued stress resistance of the tiny screw.