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Unlabelled: The recent introduction of the new systems of intraosseous anchorages called mini-screw, allowing an immediate loading, has revolutioned the clinical and biomechanical approach of anchorage in orthodontics. Trans-gingival insertion by a manual screwdriver is done easily and most frequently without before-hole. The goal of this experimental study is to show that the realization of a before-hole limits the intraosseous constraints during screwing. This having short-term effects on the primary stability of the mini-screws and long-term effects on their maintenance., Materials and Methods: two self-drilling and self-tapping mini-screws Aarhus Medicon of 1.6 and 1.3 mm diameters are screwed with a manual screwdriver, without then with a before-hole, in a plate of cortical bone fixed on a sensor measuring the forces and the couple., Results: the realization of a before-hole in the cortical bone significantly decreases the maximum vertical force (FVM) at the beginning of screwing (p < 0.0001) and the maximum screwing couple (CVM) at the end of the screwing (p < 0.0001), this independently the diameter of the screw., Conclusion: screwing without before-hole led to the alteration of the osseous surface layer caused by micro fractures which limit the possibilities of blocking of the mini-screws.

Classical orthodontic approaches to bicuspid extractions in closed bite cases do not always reach the esthetic goal. To avoid worsening the profile concavity and undesired alterations in the nasolabial angle, incisor retraction must be discussed individually. We report third molar extraction cases with optimized changes in facial profiles.