[Contribution and limitations of MIS(®) screwed expanders in the jaws: illustration from clinical cases and comparison of the osseous volume from three-dimensional radiographic pictures]. / Intérêts et limites des expanseurs vissés de MIS(®) aux maxillaires : illustration à partir de cas cliniques et comparaison du volume osseux à partir de clichés radiographiques tridimensionnels.

INTRODUCTION: Implanting on an atrophic maxilla alveolar ridge may require bone augmentation. Screwed expanders may sometimes be used, thus avoiding a more invasive bone graft. It allows bone density to increase and results in alveolar ridge expansion, by using bone elasticity and adaptation, allows the optimization of the available bone volume, with low morbidity. TECHNICAL NOTE: Despite its apparent simple implementation, the technique should be adapted to each type of bone so as to optimize results. We present two clinical cases, use of screwed expanders, their action on the crestal bone, and the limitations of this technique depending on ridge configuration. DISCUSSION: Screwed expanders are non-traumatic easy-to-use tools. They can be inserted like implants because they have a good self-tapping effect. Their use is more secure in narrow spaces; they are more comfortable for the patient than impacted expanders use. They allow increase of cancellous bone density, which improves primary stability in case of low density bone. Bone volume preservation and avoiding bone grafts can shorten the implant treatment procedure and decrease costs for the patient. Unfortunately, this technique does not allow alveolar ridge height increase. If this is required, onlay graft or guided tissue generation are the best alternatives.