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Int J Oral Maxillofac Implants. 2014 Jul-Aug;29(4):819-25. doi: 10.11607/jomi.3191.

Microcomputed tomographic and biomechanical analysis of orthodontic microscrew stability under continuous or intermittent force.

Abstract

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.

PMID:
25032761
[Indexed for MEDLINE]
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