April 2024
Another Example of a Fractured TiBase Abutment Requiring an IMR
The patient presented for retrieval of a fractured abutment from a Neodent GM implant in the #19 site. This implant was placed on 05.13.2022. It was restored on 10.13.2022 and fractured after about 17 months in function. The patient was referred to our office as neither the fractured abutment screw nor the retained abutment fragment could be retrieved. After reviewing the recent history with the patient, he described the crown was loose first and then the crown displaced second. This was indicative of the abutment fracturing first with the crown still retained by the abutment screw, and then the screw fractured, and the crown displaced.
Following a conservative exposure of the implant top, the previous recovery effort was evident, as the junction of the titanium abutment screw and the abutment fragment had been smeared together in the effort. The perimeter of the screw fragment was first exposed so the screw shaft could be seen, and the screw fragment was backed out first using a custom .8mm left hand drill. With the through bore clear, a modified screw extractor was seated into the through bore and the abutment fragment was “wobbled” and recovered. The implant was cleaned and found to be clear of any structural issues when examined at 25x under the microscope. As no healing abutment was supplied, a silicone plug was placed to help control the tissue until he could return to his restorative dentist to deliver a titanium healing abutment and restore the implant.
So why did this abutment fracture in such a short time in function?
When abutment fractures are retrieved, I routinely measure the fracture area using my optical comparator in my machine shop. There seems to be a high correlation between the cross sectional area and the robustness of that area. This case was no exception, as the fracture zone of this abutment was approximately 3.17 sq.mm. This was approximate as the top of the abutment was more difficult to measure with absolute accuracy as can be seen in the two images below.
The outside diameter of the abutment was about 3.5mm with a .3mm shoulder and a through bore of about 1.65mm. The wall thickness in the fracture zone was about .625mm. This appeared to be a TiDesign type of abutment and with a wall thickness of about 3.17sq. mm it is in the general range of many fractured TiBase abutments I have measured. These fractures tend to be at or near the base of the vertical cylinder where it joins the shoulder. This one was slightly above. At this time, the manufacturer of the abutment is unknown.
The theorical maximum cross sectional area at the top of the GM interface is about 7.07 sq.mm as the outside diameter is 3mm with a through bore of 1.61mm. Therefore, by using this abutment design, the fracture area moved up to a weaker cross section which was about 55% less in surface area. CAM
