2024
The patient presented on referral from his periodontist after he could not retrieve a fractured abutment screw from a Nobel external hex RP implant in the #14 site. This implant was originally placed in 1992 and has been in function since it was restored. There had been numerous issues with screw loosening in the early years of function, but the mechanics of the case had been stable for many years, until this abutment screw fracture occurred. Prior retrieval efforts were reported to be minimal, initially with a periodontal probe for about 5 minutes and then a screw retrieval tool, of unknown design or manufacturer, used in a slow speed handpiece for about 1 minute. Noting the deep position of the fragment in the implant threads, there was initial concern that an upper thread could have been altered in this prior initial recovery attempt. The use of unguided rotary instruments, even for a short period of time, can be problematic and complicate the next retrieval effort, especially when they have been used next to exposed threads. We routinely request as much information as possible to help predict what our efforts will require. In this example, there was no mention of any guidance used, so the possibility that a recovery tool had inadvertently nicked a thread, above the screw fragment, creating a locked fragment, was a real possibility. The preoperative plan predicted the case to be either a Type III or Type IV case, depending on the screw fragment mobility.
The problem summary section from the IMR Intake Specialty Case Referral form
Fortunately, when the case was evaluated clinically, under microscopic magnification at 25x, the screw fragment was found to be mobile and was rotated up and clear of the implant without difficulty. The only instruments used were the microscope, mouth mirror, and basic hand instrument setup, consisting of an endodontic explorer and modified endodontic spoon excavator.
Recovered components and the actual reason the fragment was residing deep into the threading
Initially, when evaluating the position of the screw fragment, I had thought there was the possibility the fragment had moved down, deeper into the implant, during the prior, first recovery attempt. This is not an uncommon occurrence. Often there is a discrepancy between the fragment position as viewed on the initial radiograph, prior to any retrieval efforts, and the current fragment position when evaluated clinically in our office. The difference is due to post radiograph recovery attempts. However, this was not the case here, as the following photographs illustrate. This fragment had not moved, as the design of this external hex implant carries the threading to the top of the implant hex. Therefore, the screw threads reside deeper into the implant threads, so when the screw fractures at the top of the screw threads, the fracture will be residing about 6 threads down inside of the implant. So, this case actually started as a Type III case, where the top of the screw fragment resides below the top of the first implant thread, with the fragment mobile with an endodontic explorer.
For additional information regarding these procedures, there are additional case studies posted on our website.
Charlie Mastrovich, DDS
