December 2016
Preop radiograph
This case involves a fractured Atlantis zirconia abutment in an Ankylos 4.5 implant in the #3 site. This case had been restored for approximately 4 months when the fracture occurred. He presents with the crown still in place by an intact abutment screw. The clinical situation was explained to the patient and the probable recovery steps. Following infiltration with 1.5 carpules of Septocaine, an occlusal access hole was placed in the ceramic crown to find the abutment screw head. The screw head was removed, and the crown recovered. The abutment screw was then rotated up by OD grinding at the top of the conus fracture with a high speed 56 carbide bur so as to keep the screw up as high as possible removing as much of the screw shaft as possible, while keeping the screw threads up as high as possible. This was done to attempt to avoid the complication of a locked screw fragment following the conus removal. The screw fragment was then vertically reduced and rotated down to the 3mm level. Once the through bore was clear, the zirconia conus fragment was evaluated and found to be free of vertical fractures. This necessitated a tedious process of carefully thinning the conus with custom modified course round diamonds. Once the walls were reduced to paper thin, the residual zirconia was in-fractured with small root tip picks and mallet and the pieces removed. Fortunately, a portion of the zirconia indexing feature was dislodged as well. With the screw re-rotated up, clear of the implant threads, the remaining screw and zirconia was blown clear with an air water syringe. The implant was cleaned, and a healing abutment was placed finger tight. The implant was not damaged secondary to the recovery and the patient was instructed to return to Dr. A. for re-restoration. Time in the office to complete this recovery was 3.25 hours.
In the future, it seems prudent to avoid zirconia as a posterior abutment material especially in an Ankylos implant. This implant has a very limited abutment cross section and therefore is mechanically unreliable when placed under posterior occlusal loads magnified by the torsional loading of a molar sized crown. Additionally, I have also recovered many fractured titanium abutments from Ankylos implants that have been subjected to similar loads, although the time frame generally has a longer horizon to failure. C.A.M.
