Journal List > J Korean Acad Prosthodont > v.48(1) > 1034645

J Korean Acad Prosthodont. 2010 Jan;48(1):61-68. Korean.
Published online Jan 31, 2010.  https://doi.org/10.4047/jkap.2010.48.1.61
Copyright © 2010 The Korean Academy of Prosthodontics
Biomechanical considerations for the screw of implant prosthesis: A literature review
So-Min Im, DDS,1 Dae-Gon Kim, DDS, MSD,1 Chan-Jin Park, DDS, PhD,1 Min-Sang Cha, DDS, MSD,2 and Lee-Ra Cho, DDS, PhD1
1Department of Prosthodontics and Research Institute of Oral Science, College of Dentistry, Gangneung-Wonju National University, Gangneung, Korea.
2Gangneung Asan Hospital, Collge of Medicine, University of Ulsan, Gangneung, Korea.

Corresponding Author: Lee-Ra Cho. Department of Prosthodontics, College of Dentistry, Gangneung-Wonju National University, 1, GangneungDaehangno, Gangneung, Gangwon-Do, 210-702, Korea. +82-33-640-3163: Email: lila@gwnu.ac.kr
Received December 21, 2009; Revised January 14, 2010; Accepted January 15, 2010.

Abstract

Purpose

This article attempted to determine the factors affecting the preload and screw loosening.

Methods

Available clinical studies from 1981 to 2008 from the PUBMED that presented screw loosening data and review articles regarding screw joint stability were evaluated. Eleven studies dealing the biomechanical principles of the screw mechanics were reviewed. Moreover, the results of our data were included.

Results

The frequency of screw loosening was consequently reduced due to the advancement in torque tightening with torque wrench, screw material, coating technique for reducing the frictional force, and thread design, etc. If preload in the screw falls below a critical level, joint stability may be compromised, and the screw joint may fail clinically. The types of fatigue failure of screw were divided to adhesive wear, plastic deformation, and screw fracture.

Conclusion

An optimum preload is essential to the success of the implant-abutment complex. To maintain optimum preload, using a torque wrench and re-tightening at recall time were needed.

Keywords: Preload; Screw; Screw loosening; Torque

Figures


 Fig. 1
Clinical images and SEM images of fractured screws. Arrow indicates the starting point of crack line.
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Fig. 2
Marginal bone loss around the fractured abutment screw. From first fracture, the other fractures were consequently happened (Fig. 1).
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Fig. 3
Estimation of fatigue life of gold screw; theoretical failure and realistic failure.
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Fig. 4
A, Electronic torque controller; B, Torque limiting device; C, Torque indicating device; D, Contra-angle torque device.
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Fig. 5
Loosening torque of titanium screw at 20 Ncm and 30 Ncm tightening torques.
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Fig. 6
Mechanical tolerance of various implants.

A, Implantium (Dentium, Seoul, Korea); B, Astra (Astratech, Mölndal, Sweden); C, GS (Osstem, Pusan, Korea); D, M implant (Shinhung, Seoul, Korea).
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Fig. 7
Spiralock system of Biohorizon (Detroit Tool Industries, Madison Heights, MI).
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Fig. 8
Schematic diagram of the mechanism of adhesive wear of screws in implant prostheses. (Upper thread indicates much milder state, while lower thread indicates much severe state of wear).
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Tables


 Table I
Screw loosening in single implant prosthesis
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Table II
Multiple factors for screw loosening
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