Screw Loosening in Dental Implants

Screw Loosening in Dental Implants
2004
By Rafael Bustamante, DDS
Compton Implants
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INTRODUCTION Dental implants are becoming one of the fastest growing dental treatments today. They are used as replacements for single tooth loss, as the support for a bridge either to a natural tooth or to another implant, or to support prostheses, e.g. complete or partial dentures. The success or failure of the implant depends on the manner in which stresses such as occlusal forces, arising from varied chewing patterns, are distributed to the surrounding bone. Not only does an implant fail if it does not integrate with the surrounding bone, but also if the components that connect the prosthesis to the implant fail.
The method of attaching the prosthetic abutment to the implant is by means of screws. Utilizing screws in implant prosthetics allows for a much easier retrieval of the appliance if it becomes necessary 11.One of the major disadvantages of this method is that after some time screws loosen due to reasons that have been difficult to identify.
This problem is most common when dealing with single-tooth restorations 2. Studies show that between 26% and 38% of single tooth implants loosen after the first year 7. Overdentures are the second-most common type of prostheses where screw loosening occurs 9. Of the former, loosening occurs more frequently in the premolar and molar region than anterior implants 9. The process of loosening occurs in 2 stages 5. These come about as follows: 1) preload is lost as a result of external forces applied to the screw-implant joint. At this point, 2) the preload is below the optimum level thus facilitating turning of the screw upon further application of functional forces to the implant.
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