The Use of a Dental Surgical Microscope to Aid Retrieval of a Fractured Implant Abutment Screw: A Clinical Report Rishi D. Patel, BDS, MS, 1 Joseph Y.K. Kan, DDS, MS, 2 Lars B. Jonsson, DDS, MS, 1 & Kitichai Rungcharassaeng, DDS, MS 3 1 Center for Prosthodontics and Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA 2 Department of Restorative Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA 3 Department of Orthodontics and Dentofacial Orthopedics, Loma Linda University School of Dentistry, Loma Linda, CA Keywords Screw; screw fracture; abutment; screw retrieval; implant screw. Correspondence Rishi D. Patel, Center for Prosthodontics and Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA 92350. E-mail: rdpatel@llu.edu The authors declare they have no financial interests in any of the instruments or products used in the clinical report. Accepted September 16, 2009 doi: 10.1111/j.1532-849X.2010.00644.x Abstract This clinical report outlines a method to retrieve a fractured implant abutment screw through the use of high-power magnification and ultrasonic instrumentation. Fur- thermore, the use of manufacturer’s specific components is highlighted to minimize occurrences of such clinical complications from arising. Implant abutment/prosthetic screw loosening and fracture have been among the most common complications reported in im- plant prosthodontics. 1,2 A systematic review of the literature by Goodacre et al reported an incidence rate of up to 19% for implant prosthetic screw fracture. 3,4 Most reported implant abutment screw fractures were attributed to framework mis- fit, extended period of clinical use, or repeated retightening of loose screws. 5-9 Many early problems of screw loosening and fracture have been overcome through improvements in screw design and materials used that allow the appropriate preload to be applied. 3 Since then, the overall incidences of screw loosening has decreased from as high as 45% to 8%. 3 This makes instances of screw fracture a rare and stressful occurrence. In implant prosthodontics, applying an appropriate level of torque to the prosthetic screws will create a clamping force (preload) between the abutment and implant interface. This minimizes the potential for abutment/prosthetic screw loos- ening and hence, fracture. 10 The recommended torque varies among manufacturers due to differences in screw designs and the materials used; 10 however, if the torque applied to the screw exceeds the yield strength 11 of the screw, fracture re- sults. Haack et al 11 demonstrated that under manufacturer’s recommended torque, stresses calculated for gold and titanium abutment screws did not exceed 60% of their respective yield strength, thus providing a significant buffer zone that prevents screw fracture. 11 Nonetheless, the importance of the appropri- ate clinical torque application cannot be overemphasized. The importance of using manufacturer’s specific torque wrenches with the proper maintenance has also been high- lighted in the literature. Gutierrez et al 12 reported that the ac- curacy of torque wrenches diminishes following periods of ex- tended clinical use and repeated sterilization. In fact, after 36 months of use and 72 sterilizations, the mean torque generated can exceed the designated 10 Ncm by 455%. 12 This diminished accuracy was also seen in the 20 Ncm and 32 Ncm wrenches. The authors attributed these discrepancies to corrosion of the internal components of the torque wrench, which were found to be sensitive to heat and chemical sterilization. 12 Further- more, Goheen et al 13 demonstrated the importance of using manufacturer-specific components and that the use of dissimi- lar components could possibly result in inaccurate tightening. They found that experimentally determined values of torque generated by a noncompatible wrench ranged from 12% below to 43% above the specified value. 13 A number of methods have been described in the literature for the removal of fractured dental instruments and compo- nents. 14,15 Krell et al 14 outlined the use of ultrasonic instruments for the retrieval of broken instruments and dowels. Williamson and Robinson 15 described using a modified no. 1 (Brasseler USA, Savannah, GA) bur with a slow-speed handpiece in a reverse fashion to remove a fractured abutment screw. The 630 Journal of Prosthodontics 19 (2010) 630–633 c  2010 by The American College of Prosthodontists