Korean J Orthod.  2022 May;52(3):201-209. 10.4041/kjod21.217.

Influence of late removal after treatment on the removal torque of microimplants

• Kim HJ
• Park HS

• KMID: 2529943
• DOI: http://doi.org/10.4041/kjod21.217

Abstract

Objective
To compare the removal torque of microimplants upon post-use removal and post-retention removal and to assess the influencing factors.
Methods
The sample group included 241 patients (age, 30.25 ± 12.2 years) with 568 microimplants. They were divided into the post-use (microimplants removed immediately after use or treatment) and post-retention (microimplants removed during the retention period) removal groups. The removal torque in both groups was assessed according to sex, age, placement site and method, and microimplant size. Pearson correlation and multiple linear regression analyses were performed for evaluating variables influencing the removal torque.
Results
The mean period of total in-bone stay of microimplants in the postretention removal group (1,237 days) was approximately two times longer than that in the post-use removal group (656.28 days). The removal torques in the post-retention removal group (range, 4–5 N cm) were also higher than those in the post-use removal group. The mandible and pre-drilling groups demonstrated higher placement and removal torques than did the maxilla and no-drilling groups, respectively. In the no-drilling post-use removal group, the placement torque and microimplant length positively correlated with the removal torque. In the post-retention removal group, unloading in-bone stay period and microimplant diameter positively correlated with the removal torque in the no-drilling and pre-drilling methods, respectively.
Conclusions
The removal torques differed according to the orthodontic loading and removal time of microimplants. With prolonged retention of microimplants inserted using the no-drilling method, the removal torque was clinically acceptable and positively correlated with the unloading in-bone stay period.

Keyword

Microimplant; Stability; Retention; Removal torque

Figure

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  Figure 1 Flow chart of the sampling performed in the study.

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  Figure 2 Dimensions of the microimplants used in the study.

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  Figure 3 Measurement of the placement and removal torques by using a digital torque gauge.

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  Figure 4 Error-bar plot of the overall placement and removal torques in the post-use and post-retention removal groups. ***p < 0.001.

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  Figure 5 Orthodontic force application for additional correction or retention after treatment by using retained microimplants and elastics.

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