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Home arrow Resources arrow Implant Dentistry arrow An In Vitro Analysis of Implant Screw Torque Loss With External Hex and Internal Connection...
An In Vitro Analysis of Implant Screw Torque Loss With External Hex and Internal Connection...
Written by Implant Dentistry - Most Popular Articles   
Thursday, 30 November 2006

Purpose: The purpose of this study was to examine, in a controlled environment, effects of connection design upon screw stability. Implant fixtures have 2 types of connections to the abutment: internal connection and external hex. Four implant systems were tested: Bio-Lok (external hex; Bio-Lok International, Inc., Deerfield Beach, FL); Zimmer (internal connection; Zimmer Dental, Carlsbad, CA); Nobel Biocare (external hex; Nobel Biocare USA, Inc., Yorba Linda, CA); and Astra Tech (internal connection; Astra Tech Inc., Waltham, MA). Materials and Methods: Ten samples of each system, including base, implant, abutment, and molar crown, were loaded to 200 N for 1 x 106 cycles. Screws were tightened to manufacturers' recommendations,and torque audits done at 2.5 x 105, 5 x 105, 7.5 x 105, and 1 x 106 cycles. Results: The Bio-Lok samples lost an average of 10% of the original torque values, the Astra Tech group lost almost all of the torque and loosened, while the Zimmer and Nobel Biocare samples lost an average of 50% of the torque but did not loosen (P <= 0.05). Conclusions: It may be concluded from this study that although internal connections are clinically favored, this study did not show any advantage relative to screw loosening. However, screw design may be a significant factor in loosening of the joint. (C) 2006 Lippincott Williams & Wilkins, Inc.

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