Abutment Screw Loosening: Is This Inevitable?

The issue with abutment screws is usually due movement of the abutment/implant interface. Many systems to not provide enough resistance and therefore rely on the screw to hold the whole complex together. This is one reason there were so many screw fractures with externally hexed implants. Internal connections are better, but many designs have internal connections which are only 1.5-2mm in depth. Morse tapered implants are deeper, but up until recently lacked indexing, which was a restorative disadvantage in my eyes. Many companies try to solve the issue by using gold screws in order to have them deform under load and "cold weld". I do not necessarily want my components to deform. A solid implant/abutment interface is what will resist the movement that results in screw loosening. An implant like Camlog which has a 5.4mm tube that resists lateral forces and transmits them down the length of the implant and screw seems to have solved this problem. Also, they only require 20N/cm of torque to hold it all together. If you speak with Cmlog users and look at the literature out there, you will be hard pressed to find screw loosening issues with the system.

The world is an imperfect place, screws fall out all the time... Implant restorative dentistry was originally designed to all be retrievable. these concepts have been forgotten to save time and money. Additionally, cement can cause big issues in some cases, even when done correctly. Any implant dentistry done in my mouth would be screw retained. I have ssen beautiful screw retained anterior work, so the esthetic argument does not hold water for me either...

some times screws do not only loosen they even fracture! With FDA approval and even with CE. I´ve experienced three screw fractures with (Zimmer) Sulzer/Calcitek `s implants with spline interface- all three after 8 years duty. Two implants had to be removed (the abutment could not be fixed again because of residual screw fragment). Asked company to alert collegues to replace screws after max. seven years. Never received an appropiate answer. Same failures were reported occasionaly on this blog with implants originating from other companies. I use single piece implants since then- Camlog is a reliable solution but offers a large diamterer through the penetration zone of the soft tissue. As a solution to your question- a provisionary cementation(TempBond) offers an exit strategy regarding costs/ maintenance in case of screw losening and avoids gap discussion. High "resistence" of implant/abutment complex shows more bone collapse around implants in the long run especially in bridge construction. Higher "resilience" shows more fracture in implant/abutment complex (usualy screw). IMZ was not a bad idea. I will leave single piece implants only for intelligent implant systems (titan implant/ carbon post /defined and selective resilient interface). Implant has to meet bone and not dentist the industry.

I found in this context the implant with cold well seal,like bicon to use in the areas where we feel that it would take the load that can creat the fractue of the screw or loosenig.

I am the owner of KAT Implants, LLC. KAT (Key Assisted Transfer) Implant system is based on a screwless locking taper connection. Activation of the locking taper is done with a torque wrench and 15 Ncm of torque. No hammering needed. No retention screws are needed to hold the abutment in place. Implant/abutment interface can withstand at least 425 N of force over 5 million cycles at 30 degree angle (tests done on a 3.5mm implants). Available for sale in US next month.

I have seen many screws loosen over the years. I would argue that it is almost a sure thing with external hex implants. I have seen it less with internal hex implants, but it is still common... ie replace select. The advent of a long tapered connection (morse or not) seems to have done wonders as I have only seen 2 screws loosen with those systems (Ankylos, Astra, Stauman bone level, Active....) It is my opinion that a tapered connection between the abutment and implant greatly reduces the risks of forces being transfered to the screw... and is thus the current standard of care. You will notice that most of the new implants coming onto the market have such a connection. Screw retained restorations also seem to work well in the hands of very particular dentists... just remember that those screws can and do loosen also. Although much easier to manage. Keep in mind that it is always wise to replace the screws that have issues. Retightening them is risky, especially if they have been plastically deformed on torqueing.

Hi everybody, thanks for good discusion it is interesting point I agree with long tapered connection concept as a better way to reduce the micro movment and reduce secrew loosning

Abutment screws do loosen, so plan on it! For screw retained abutments/cement on crowns or pros. cement on with tempbond or the least retentive cement that will hold.If loosening occurs pull off the crown or pros tighten the abutment screw and recement. If repeated loosening occurs the patient might be bruxing or have a parafunctional habit if so have them wear a niteguard etc. There are advantages to screw retained abutments with cement on crowns or pros when you deal with multiple angulated implants. We usually use screw retained pros when we are lacking in verticle height.

These are my observations after 20+ years of restoring Nobel implants in my restorative practice. The early screw technology did have problems, but with the advent of the "hardened screw" that would allow deformation of the threads at a certain level of torque, I have had no screw issues using Nobel Biocare Replace Select as the implant system. In my opinion, most screw loosening and/or implant loss is a result of improper force loads on the crown or bridge. I suggest using custom abutments for best mechanical retention and cement with Improv. It cleans up with no worry about cement in the sulcus.

I think the locking taper connection is the future of implant dentistry, don't know why everyone is waiting n debating. . .

How do you remove cement retained crowns and bridges? What cement to use? Some coat abutment and intaglio with vaseline to make removal easier. Advantage of cement retained is that you can make impressions for implants almost the same way you do things for natural teeth. You can also adjust the thickness of the die spacer to provide completely passive insertion. Any tips for the less experienced?

Screw loosening can be avoided by using a Bicon or an internal hex implant. Also stay away from gold screws.

using implants with deep internal hex provides a resistance to screw loosening problems. One piece implants is definitely an excellent option. There are systems that even come with an angled abutment (zimmer one piece implants). I use cement retained restorations as i believe that screw retained are difficult to fabricate and time consuming(espcially for dental tech. in my part of the world). i use temp bond temp. cement, which provides a long term retention for the crowns. i tighten the screws at 25 n/cm. i always tell my patients that the implant itself is a solid foundation and that after years of service it is expected to change the components that go on top (screw, abutment and even the crown).

Impladent's implant does not have this problem either.

Much like coughing & sneezing are "symptoms" of something bad like a cold or the flew, screw loosenings are often a sign of something worse like bruxing, hyper occlusion or an over angulated single implant needing to be corrected with an aggressively angled abutment. Assuming the implant system is credible and doesn't have a reputation for routine screw loosenings and the abutment has been properly torqued, my suggestion is that when a screw comes loose to look deeper for the possible causes of the screw coming loose... Is the patient now bruxing because of undue stress? Is the crown hyper-occluded? Was the implant placed at a big angle? Has the patient's oral inviornment changed in any way since the implant was placed that may warrant changing the implant prosthesis, etc? My problem with using an implant where the screw will "never" come loose, regardless of the undue stresses it may face (based on clinical era, or changes in adjacent/opposing teeth over the years, etc.) is that there's one less mechanism in place to discover that there is something wrong with the prosthetic design based on the patient's current oral enviornment and therefore, it's not until the implant loses significant crestal bone or the implant fails all together that you discover the problem could have been fixed by simply adjusting or redesigning the prosthesis. Believe it or not, sometimes there is an advantage to have a screw come loose if we look closer to the possible underlying causes...

Marcus Hines: Excellent thoughts!

I normally leave slight protruberances on the lingual surfaces of the crowns thus allowing for easier removal.I cement implant supported crowns with temp bond.Likewise on tooth supported crowns I also leave the protruberance.Patients are normally not delighted but get used to them in a short time.

Periodontists want Prosthodontists to do Srew Retain Procedures because they want patients to go back for maintainance GP(s) convince patients to perform Fixed bridges on implants explaining them that they do not need to go back for maintainance Prosthodontists (today) hire Periodontists for doing maintainance in their own dental offices for not sending them back to Periodontists... Implants in malposition (wrong occlusal scheme)lead into screw loosening screws Implants in good position (well occlusal scheme) remain stable. Teeth in an hour with implants placed with computerized programs,in direction to NY ,LA and Miami----will lead into screw loosening. Simple!

I noticed that problem a lot after the crown was placed for a while. What I discovered, that patients who are using an electric tooth brush have more problems with loose screws. It is probably not the only reason, but when we are looking at ultrasonic systems for teeth cleaning, it has the same effect to separate two substances from each other (Plaque/Calculus or Tatar and the natural tooth substance). Would be interesting who experienced the same pattern.

Best is to use a MORSE TAPER Implant system which provides a cold welding between abutment and implant. You will hardly find any screw loosening once you start using a Morse taper Implant syestem. LEONE(ITALY) and BICON are two implant syestems with morse taper

it partly depends on the system used. if internal connection system is used, the screw loosening occurs in 3.6-5.3% (Levine et al 1999) for external hex systems, it goes up to 38%

There are several implant systems sold today that have a reputation for no screws loosening due to their design, Camlog being one of them. The external hex era was to blame for the push to use screw retained restorations, but I believe that the great majority of restoring dentists agree that cement retained restorations are the way to go unless you have a crown space height problem.

Screw loosening ,screw fracture or cement fracture are very common complications of implant therapy.I thınk ıt wıll be better to dıscuss the causes of the complication. 1)If the height ratio of the abutment and the ımplant is not 1:1 I mean if the abutment ıs longer than the ımplant 2)If the occlusal table of the crown ıs very large and the tubercules are very sharp 3)If the ımplants do not obey the rules of paralelısm 4)If the patient has bruxism 5)If the diameter of the implant ıs not bıg enough to hold the forces of occlusion at that special region Above complications may occur. Seconly lets look at the mechanısm that hold the abutment and the ımplant together 1)The tention ın the fixation screw which is formed durıng the torquing period (If torque exceedes the necessary values ıt may couse screw fracture) 2)The frictıonal force between ırregularıtıes of the surface of the threds of the screw and the threads of the implant (If agaın gıven values of torgue ıs exceeded ırregularities are lost and thus frictional force is lost causing screw loosenıng ) I thınk ıf we keep ın mınd the above factors we will be able to keep the complications at a mınımum level.

Hello, I had an abutment and crown placed and experienced minor rotation after three days. The crown was placed with temp bond but the GP was unable to remove the crown to tighten the abutment screw. The only solution offered is to drill through the top of the crown to access the screw, re-tighten, and then place a composite filling. What are your recomendations and what would you do if this happened to you. Take care.

you can minimize potential complications on your implant cases by retightening the screw 10 minutes after first tightening. It will reduce the chance of loosening big time. However, if occures again, check for the other possibilities like: passive fit occlusion parafunction habits

Very helpful (and therapeutic) to read all the comments so far. I use Nobel Biocare internal trichannel implants and have been placing for 5 years. I had my first loose screw case recently and found it quite stressful. I managed to find the screw, undo it, remove and clean up the abutment (I had removed the crown), replace it back onto the implant with a new screw, take an impression and provisionalise.My question to the forum is: in general, would an all porcelain crown (eg LAVA)be preferrable to bonded metal/porcelain for cement retained situations;at least then, if you have to remove it to get at the screw, the metal abutment should be far easier to identify making a difficult situation that bit easier ? Any thoughts or comments much appreciated. Thanks.

Very good site.I am new to implants and have recently seen a pt whose cement retained implant bridgefrom 35-37 has come off completely.The anterior abutment is loose.The implant bridge was done overseas and is an Osstem system.How do I go about treating this case? maria g