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Volume 29 , Issue 4
July/August 2014

Pages 819825

Microcomputed Tomographic and Biomechanical Analysis of Orthodontic Microscrew Stability Under Continuous or Intermittent Force

Yeke Wu, PhD/Zheng Jing, MS/Wenlu Jiang, MS/Xiaoyan Sun, MS/Jingwen Zheng/Lijun Tan, PhD/Zhihe Zhao, DDS, PhD/Lixing Zhao, DDS, PhD/Pu Yang, PhD/Yu Li, PhD/Tian Tang, PhD

PMID: 25032761
DOI: 10.11607/jomi.3191

Purpose: To evaluate and compare the influence of continuous and intermittent forces on stability of titanium microscrews. Materials and Methods: One hundred forty-four microscrews were inserted bilaterally in the intraradicular zones of the maxillary first molar and second premolar in 36 beagles. Loads were delivered consecutively in the continuous group (n = 12), in cycles of 12 hours on/paused for 12 hours in intermittent group A (n = 12), and in cycles of 24 hours on/paused for 24 hours in intermittent group B (n = 12). The on/off cycles were repeated for 1, 3, 5, or 7 weeks, after which the animals were sacrificed, and microcomputed tomography (micro-CT) and pull-out testing were performed. Results: The micro-CT parameters of the microscrews in all three groups increased gradually with loading time. The value of peak load at extraction (Fmax) increased and reached a peak at week 5 but dropped slightly at week 7. In the continuous group, all measurements were lower than those in the intermittent groups at all times examined. All values in intermittent group A were higher than those in intermittent group B. Conclusion: An intermittent loading regimen appears to be more favorable for obtaining stability than continuous loading, and a 12-hour/12-hour on/off loading cycle is superior to a 24-hour/24-hour on/off protocol in promoting bone-implant contact.

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