Techniques for Removing a Fractured Screw

When a retaining screw [Fig. 1] breaks in an implant, the fracture usually occurs immediately above or below the implant’s hex [Fig. 2]. Consequently, there will be approximately 2-3 mm of screw fragment (threads and residual shaft) left in the implant. Most screws are retained by approximately 2.5 to 5 threads (or approximately 2.5 to 5 complete turns). Once the abutment is removed, the only thing retaining the broken screw fragment is the residual interface between the screw threads and the implant threads, provided that no thread “sealants” (e.g., Lock-Tite, Omni-Bond, Silicon, etc) were used. Consequently, if the remaining screw shaft can be engaged, the screw fragment should be retrievable with minimum effort.

Several methods for removing the remaining portion of the screw are listed below, each of which is slightly more aggressive than the previous method. If the clinician fails to remove the screw with one method, he or she should progress down the list to the next technique below it. Before attempting any of these techniques, however, the clinician should completely clean and rinse the area of the broken screw and, if possible, add a small drop of lubricant (mineral oil) to help alleviate frictional retention between the components. It is also a good idea to order a thread tap to have on hand after the removal of the broken component to true up the threads and ensure that replacement parts will both thread in and retain in the implant.

Technique No. 1: Unthread the Screw Fragment with a Pointed Instrument: Press the pointed end of an explorer [Fig. 3] or a sharp-tipped Hollenback instrument onto the exposed end of the broken screw and try to unscrew it. This method often works in a clean environment where a drop of mineral oil has been placed on top of the screw, but it takes a little time.

Technique No. 2: Unthread the Screw Fragment by Vibrating with a Cavitron Unit: Place a small tip on a Cavitron unit on top of the outside edge of the screw [Fig. 4] and move the tip in a counter-clockwise motion to vibrate the screw out of the implant. The addition of mineral oil greatly facilitates the procedure. 

Technique No. 3: Unthread the Screw Fragment with the Side of a Round Bur. Place #2 round bur [Fig. 5] in slow-speed (10-20 rpm) reduction, contra-angle, and lay the tip of the bur sideways on the outside top of the screw fragment. In a clockwise (forward) direction, carefully spin the screw fragment out of the implant by using the end of the bur as a gear. As previously stated, this technique works best in a clean environment with a drop of mineral oil.

Technique No. 4: Unthread the Screw Fragment with a Modified Drill. Use a “thin” cut-off disk, a separating disk, or a side-cutting bur (557 or thinner) to produce multiple serrations on the tip of an old bur [Fig. 6]. Most burs will work, but a long-shanked burs with a tip that has broken off works the best. Make the end of the bur as rough and uneven as possible. Place the bur in a handpiece set on slow-speed “reverse” and press it onto the uneven surface of the broken screw by applying occlusal pressure with the handpiece. Spin the broken screw out.

Technique No. 5: Use Zimmer Dental’s Broken Screw Removal Kit. Contact a Zimmer Dental Customer Service or Technical Service representative to request a Broken Screw Removal Kit. Follow the directions that come with the kit. Each implant platform has a different kit based on the implant interface: Spline, internal hex, Omniloc, Threadlock. Swiss Plus, etc.

Technique No. 6a: Unthread the Screw Fragment with the Top of a #557 Bur. Place a #2 round bur in the handpiece and create a 1mm (or deeper) concavity in the exposed shaft of the broken screw by cutting at high-speed in the “forward” direction [Fig. 7]. Replace the #2 round bur with a #557 side-cutting bur. Wedge the tip of #557 side-cutting bur into the 1 mm concavity, place the handpiece in slow-speed “reverse,” and slowly unthread the broken screw. Using the Broken Screw Removal Kit, you can go into the hole made by the #2 round bur and try again if the #557 bur is not successful.

Technique No. 6b: Drill Out the Screw Fragment with a #557 Bur. Insert the tip of a #557 side-cutting bur into the 1 mm concavity created by a #2 round bur, as described in Technique No. 6a above, and drill straight down through the middle of the screw at highspeed in the “forward” cutting direction [Fig. 8]. Once you have gone completely through the screw, use an explorer to remove the “shell” of the screw. Use a thread tap to reform or clean-up the implant threads.

Technique No. 7: Drill out the Screw Fragment and the Internal Threads of the Implant. If all other attempts have been unsuccessful or if the threads of the implant have been too greatly damaged to accept or retain a new screw, use a #2 round bur or a #557 sidecutting bur to drill out the remaining threads in the implant as much as possible. Lubricate the internal with petroleum jelly, and make an impression using conventional techniques to pick up the inside of the implant body, with a root canal impression. Instruct the laboratory to fabricate a traditional post and core, which will be cemented into the implant using traditional dental “metal-to-metal” cement. The abutment can be designed to be either a “fixed abutment” for a cemented crown and bridge restoration, or screw receiving for a screwretained prosthesis. The new restoration may be fabricated at the time of abutment fabrication or after cementation, depending on the situation.