| Summary: | 碩士 === 中原大學 === 醫學工程研究所 === 96 === Miniscrew is used as an anchorage for orthodontic tooth movement, and
loosening of miniscrews might lead to orthodontic failure. In previous clinical
studies, loosening rates of miniscrews are usually related to their stabilities, but
these results can not reflect the inner stress distribution around miniscrews and
jaw bone, neither show the relationship to the thread design. Therefore, this
study investigated the combined strength between miniscrews and the jaw bone.
The purpose of this study was to investigate the influence of thread designs on
the stability of orthodontic miniscrews, by using biomechanical test and finite
element analysis and to provide references for designing new miniscrews in the
future. The study was divided into two main parts. Part 1: Using bending test
and pullout test to estimate the effect of thread geometric designs, such as thread
heights, degrees of taper and circles of tapering portions, to obtain the bending
and pullout mechanical behavior. In the biomechanical test, we manufactured
four of the fore-mentioned miniscrews, and inserted them to the foam bones
(Sawbones® ) and used the material test machine to perform the pullout test.
The results revealed that increasing degrees of taper and circles of tapering
portions can increase bending strength and pullout strength, and increasing the
thread heights can increase the pullout strength, but there is upper limit.
Biomechanical test and finite element analysis have the same trend. Part 2: To
investigate the three different commercial miniscrews, and use the material
testing machine to perform the pullout test, the results indicate the J-screw
(J-screw®) have best bending and pullout strength and the following was
Osstem and Mondeal(mini-2000) in order. In conclusion, finite element model
of the study could reliably reflect the results of biomechanical tests, and could
assist dentists in choosing the miniscrew in clinics, and provide references as
new miniscrew design.
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