November 2022
Preop. radiograph
The patient presented for recovery of an abutment and abutment screw from a Straumann 4.8 BL RC implant in the #30 site. The history described restorative failures of two previous crowns, both of which most likely pointed to difficulty in handling limited vertical running room. Clearing the way for a third restorative effort, the drive geometry of the existing abutment screw was lost precipitating at least two unsuccessful appointments to retrieve the current abutment and abutment screw. The last appointment utilized a “special recovery kit”. As all recovery attempts were unsuccessful, the patient was referred to our office. Once the occlusal plug was removed, the previous efforts were evaluated under the clinical microscope and found to be eccentric with drilling directed into both the screw head and the abutment wall. Unfortunately, there was no possibility of reestablishing a drive geometry due to the amount of prior drilling. Therefore, the initial plan was to remove the screw head to release the preload on the screw, recover the abutment and then recover the remaining screw fragment. The integral piece to recovering the screw safely was to reestablish concentricity which was possible by using the clinical microscope to direct the drilling effort. There were remnants of the original purple anodizing and a substantial portion of the screw head top which supplied the roadmap to find the center point on the screw head. The Straumann RC abutment screw head has a tapered screw head seat, and the bottom of the taper resides below the top of the implant (See the cross section below). Therefore, to separate the screw at the top of the screw shaft, the drilling effort has to go below the implant top and be concentric enough to cut through the screw shaft below the tapered screw head seat without wandering through the side wall of the abutment into the implant. Again, using the microscope to direct the drilling effort, the bore was placed quite concentric. Instead of continuing to complete separation of the screw head, I was able to retrieve the screw with a 1mm “easy-out” type tool which engaged the screw shaft well enough to transmit the required torque to retrieve the screw intact. This is the first time I had actually attempted this, and it avoided retrieving the screw fragment in two pieces. Overall, this clearly demonstrated the value of using magnification to sort out the clinical situation and direct the clinical progress thereby saving time and avoiding treatment complications.
There was no implant damage with any of the abutment / screw retrieval efforts. Fortunately, the prior eccentric drilling stopped before the sidewall of the abutment was penetrated.
