In severely protrusive patients, anchorage loss can occur with the use of conventional sliding mechanics for closure of first pre-molar extraction spaces. Direct skeletal anchorage from mini-screws is often used to avoid this problem. The preferred miniscrew location to achieve the proper force vector, directed toward the center of resistance (CRes) of the posterior teeth, is between the roots of the second premolar and first molar or the first and second molars.
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