Abstract
Background. The design of an orthodontic mini-implant is a significant factor in determining its primary stability and its clinical success. The aim of this study was to measure the relative effect of mini-implant design factors on primary stability of orthodontic mini-implants. Methods. Thirty-two 3-dimensional assemblies of mini-implant models with their surrounding bone were generated using finite element analysis software. The maximum displacement of each mini-implant model was measured as they were loaded with a 2-N horizontal force. Employing Taguchi’s design of experiments as a statistical method, the contribution of each design factor to primary stability was calculated. As a result of the great effect of the upper diameter and length, to better detect the impact of the remaining design factors, another set of 25 models with a fixed amount of length and diameter was generated and evaluated. Results. The diameter and length showed a great impact on the primary stability in the first set of experiments (P<0.05). According to the second set of experiments, increased taper angle in the threaded and non-threaded area decreased the primary stability. There was also an optimum amount of 2.5 mm for threaded taper length beyond which the primary stability decreased. Conclusion. It is advisable to increase the diameter and length if primary stability is at risk. In the second place, a minimum amount of taper angle, both in the threaded and non-threaded area with an approximate proportion of 20% of threaded taper length to MI length, would be desirable for MIs with a moderate size.
Highlights
Mini-implants (MIs) have been increasingly utilized in orthodontic treatment during the last decade; they eliminate the need for patient compliance and inconvenient extraoral appliances.[1]
The design of an orthodontic mini-implant is a significant factor in determining its primary stability and its clinical success
The aim of this study was to measure the relative effect of mini-implant design factors on primary stability of orthodontic mini-implants
Summary
Mini-implants (MIs) have been increasingly utilized in orthodontic treatment during the last decade; they eliminate the need for patient compliance and inconvenient extraoral appliances.[1]. Sufficient primary stability is one of the determining factors.[3,4,5] A better primary stability is attainable by altering the design of MI by increasing the length and diameter,[3,6,7] increasing the intrabony length of MI,[8] modifying the thread pitch,[9] modifying the taper shape as in cylindrical, conical or combination designs,[9,10] eliminating threads in the MI neck,[11] modifying the thread shape,[12] fluting,[13] and altering the thread depth.[14] On the other hand, design alteration without mechanical support should be interpreted with caution.[15] In vitro mechanical experiments are challenging because of the inaccurate parameter control and differences between the samples. The design of an orthodontic mini-implant is a significant factor in determining its primary stability and its clinical success. The aim of this study was to measure the relative effect of mini-implant design factors on primary stability of orthodontic mini-implants
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