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Abstract

Purpose: Infrazygomatic crest (IZC) miniscrews have useful clinical applications. They are applied with angular insertion to the bone surface. However, appropriate angles for the maximum stability of the miniscrew have not yet been well documented. This study aimed to compare the primary stability of different angles of orthodontic miniscrew insertion by analyzing maximum insertion torque (MIT) and pull out strength (PS).

Materials and methods: Sixty miniscrew implants were divided into 3 groups which underwent different angular insertion, with 20 samples in each group. Three pairs of bearing devices were constructed with an angulation of 30, 40 or 50 degrees. An angulation of 30, 40 or 50 degrees were tested with synthetic bone block. MIT and PS were measured by the digital torque gauge and universal testing machine. The data was then subjected to statistical analyses.

Results: The 30-degree group had a significantly greater MIT compared with the 40- and 50-degree groups while the MIT of 40- and 50-degree groups were not significantly different. The 50-degree group had significantly greater PS than that of the 40-degree group in which the PS was also significantly greater than in the 30-degree group.

Conclusions: As the angular insertion of 30 degrees showed the greatest maximum insertion torque, IZC miniscrew placement at 30 degrees to the bone surface should be employed in cases where there is enough buccal bone thickness; however, further studies are necessary to draw more definite conclusions concerning the benefits of angular insertion.

Figure 1.jpg (119 kB)
The miniscrew was inserted into the synthetic bone block with an angular insertion of 50 degrees.

Figure 2.jpg (191 kB)
Experimental models. The miniscrews were inserted into the synthetic bone blocks with an angular insertion of 30 degrees (A), 40 degrees (B) and 50 degrees (C).

Figure 3.jpg (182 kB)
Pull out strength testing. The experimental model was set in the UTM.

Table 1.jpg (27 kB)
Maximum insertion torque and pull out strength (Mean±SD)

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