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Mise en place des mini-vis : avec ou sans avant-trou ? Volume 78, issue 2, Juin 2007

Authors
1 Faculté d'odontologie, Département d'Orthodontie, Montpellier
I, 545 avenue du Pr Jean-Louis Viala, 34193 Montpellier Cedex 5, France
2
INSERM ADR 08 , 99 rue Puech Villa, 34197 Montpellier Cedex 5, France
* lmassif@yahoo.fr
Cet article a obtenu le 1er prix des meilleurs jeunes conférenciers lors des Journées de l’Orthodontie en novembre 2004

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$^{\circledR}$ 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.