Stabilization of an abutment under a rigidly fixed bridge by holographical-speckle interferometry*

Stabilization of an abutment under a rigidly fixed bridge by holographical-speckle interferometry*
Received May 30, 2006; Accepted January 29, 2007.
Yan-zhen Zhang,‹1 Yan-chun Zhou,2 Li Liu,3 Yang Lu,‹·4 and Yatani Hirofumi5
Journal of Zhejiang University Science
PubMed Central

Copyright © 2007, Journal of Zhejiang University Science

1Department of Stomatology, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
2Department of Stomatology, Hospital of Zhejiang University, Hangzhou 310027, China
3Affiliated Stomatology Hospital of Zhejiang University, Hangzhou 310006, China
4Department of Mechanics, Zhejiang University, Hangzhou 310027, China
5Department of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan
·Corresponding Author
‹E-mail:zyz85@hotmail.com, double_zh@yeah.net

Abstract
Objective: There are no detailed reports of three-dimensional measurement of abutment teeth in mastication, because it is knotty to observe the rotation in chewing directly, and inexact to estimate indirectly. This work studies the three-dimensional stability of rigidly fixed bridge under the stresses of distributed loads and concentrated loads by optical method that gives the tip angle and rotation angle calculated directly based on measurement data. Methods: The specimen, taken from a 25-year-old male, was a left mandible without the second premolars and the first molars. As abutments, first premolar and second molar have complete periodontium. The specimen was soaked in formaldehyde solution. The bridge was fixed between two abutment teeth (first premolars and second molars), and the mandible was cemented in a steel box. The load was increased from 0 kg to 23 kg. Laser holographic technique was used to measure the three-dimensional bit shift of the dens, both buccolingual bit shift and mesiodistal bit shift, and determine tip angle and rotation angle. Results: The effects of stress distribution on the rigidly fixed bridge were evaluated, and stabilization of the bridge under the stresses of distributed loads and concentrated loads, respectively, were analyzed. The results showed that the tips of two abutments were very similar, and no distinct difference was observed between the distributed load and the concentrated load. However, the maximum rotation angle for the distributed load was two to four times as large as that for the concentrated load. In the experiment, the tip angle of the abutment teeth was no more than 0.65 degree, and the rotation angle was no more than 0.60 degree. All maximum angles occurred in the second molar. Conclusion: The fixed bridge is considered to be safe. In addition, a method for measuring the rotation angle was provided effectively.

Keywords: Rigidly fixed bridge, Tip angle, Maximum rotation angle, Laser holographical-speckle interferometry

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