When the screws come loose in cement-retained implant crowns

When screws come loose—and I would anticipate that it will happen to all of us at some point—what’s your protocol?

You can’t let the status quo remain and yet, due to the age of the implant restoration, you have nothing to go off of except what the patient tells (or sometimes can’t) tell you. If you’re fortunate, you can request records from the oral surgeon and restoring dentist, and it’s a slam dunk. However, in the event that those records are inaccessible, you need to have a game plan in place.

Despite this, there are clues to the puzzle one can gain by asking simple questions that may offer insight or give you the edge you need to resolve the situation. In the case of these two particular patients, it was a salt-and-pepper mix of just about everything.

Patient no. 1

This patient was new to my practice. She presented with a chief complaint that one of her two front implants had come loose, and she wanted to know if I could fix whatever was wrong. She pointed to no. 9.

Radiographic assessment revealed implant-supported crowns on teeth nos. 8 and 9 (figure 1). Clinically, no. 9 was mobile in all directions, but no. 8 also had a slight buccolingual rock to it.

Upon inquiry, the patient told me who the surgeon was. After a few phone calls, I found out that the dentist who restored them back in 2005 had retired, and the records for this patient had subsequently been purged. I was able to acquire information for the implant system from the oral surgeon, but that was as far as I got.

Tooth no. 8 was a Straumann tapered RN (regular neck); no. 9 was a standard RN. With this, at least I knew what screws I needed to have on hand. The existing screws had rotated out and new ones would be needed—this, of course, depended on everything else being stable and healthy. The tricky part was figuring out where the access point was.

I really didn’t want to go in and destroy the patient’s crowns, so I asked if she recalled any information that the dentist told her when these implants were restored. She said he “didn’t want to screw them in because when she bit down, her bottom teeth would hit where the screw went in.”

Bingo! That was the golden ticket as far as I was concerned, because it gave me a pragmatic starting point as to where to access these crowns—from the lingual. As we all are aware, it is not uncommon for anterior implant crowns to have that access point on the facial, so this information was key.

I approached it more or less like an endo, and I got lucky (figure 2). After careful removal of the outside porcelain layer, I was able to cut through the metal and came upon the cotton pellet and, subsequently, the screwhead (figure 3). I removed the crown and noted slight inflammation with the tissue (figure 4), but overall, everything else checked out fine. I did the same thing with tooth no. 9 (figures 5 and 6). Both crowns were placed back in with new screws, torqued to 32 Ncm, and closed up. Bite was assessed and adjusted, and the patient

was dismissed. 

Patient no. 2

This patient had been seeing me for four years. During his recall appointment, I noted that the cement-retained implant crown on no. 10 was loose due to, once again, a backed-out screw. The patient was unaware of the mobility. Like before, we were able to get the information for the implant system that was used (Steri-Oss) and the placement date (2003). The restoring dentist could only tell me that it was cement retained with no access point reference—facial, incisal, or lingual.

I ordered three different screws that could be potential replacements, but again, there was no definitive data or notes reflecting the specifics. I surmised that if I could retain the crown without remaking it, then I would have a good chance of having a replacement screw; if not, I could see what was there and order the correct one from the rep.

Once again, the access point was on the lingual (lucky!), and the overall integrity of the crown was intact. The screws, due to the interfacing component, were either too short or too wide. I took a photo (figure 7) and sent it to my implant rep, who promptly ordered the definitive screw. Case closed. 

Talking points

There has been a lot of discussion about the pros and cons of screw-retained versus cement-retained implants. Suffice it to say that each has a time and place in dentistry, but generally speaking, screw-retained implants are the better way to go for the reasons described in the two cases above—not to mention the issue with cement overflow and subsequent peri-implantitis.

These aren’t my first cases of backed-out screws, nor will they be my last. What makes them challenging is that they are cement retained; unless you have access to thorough data, the access points are generally unknown. The last thing patients want to hear is that they need a new crown, but unfortunately, we can’t save them all. A rule of thumb is to tell your patients from the get-go: “We hope for the best but plan for the worst.”

In the event a crown does need to be cement retained, I would advise the following. Torque down the abutment and then take a photo prior to cementing the crown. That way, if you or another provider needs to access the screw, you have a reference point. A new crown may still be on the dock, but if you can salvage the existing one, it’s a win-win all the way around. And, if you’re really lucky, you may even be able to pop the crown off the abutment, which is even better.

As the longevity of implants continues to increase, I believe these types of issues will also continue to rise. It is prudent, therefore, that we be diligent in assessing radiographs and clinical signs/variances with the bite, proximal tissue irritation, and crown mobility. Patients in these situations often don’t even know there is an issue. One thing is certain—if the status quo doesn’t change, we risk implant failure and additional unwanted complications.

Editor's note: This article originally appeared in Breakthrough Clinical, a clinical specialties newsletter from Dental Economics and DentistryIQ. Read more articles at this link.

Stacey L. Gividen, DDS, a graduate of Marquette University School of Dentistry, is in private practice in Hamilton, Montana. She is a guest lecturer at the University of Montana in the Anatomy and Physiology Department. Dr. Gividen is the editorial director of Endeavor Business Media’s clinical dental specialties e-newsletter, Breakthrough Clinical,and a contributing author for DentistryIQ, Perio-Implant Advisory, and Dental Economics. She also serves on the Dental Economics editorial advisory board. You may contact her at [email protected].