**1. Introduction**

Distraction osteogenesis (DO) is an effective method used for bone regeneration. Advance‐ ment of the maxilla by use of rigid external distraction (RED) device has been performed

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successfully and many other internal devices have been introduced for better results regard‐ ing the patient's comfort [1].

Patients with cleft lip and palate and maxillary hypoplasia usually present with a collapsed maxillary dental arch and impaired forward and downward growth of the maxilla [2–4]. Two factors have been proposed for the growth deficiency [2]: One such factor is the intrinsic factor, mainly introduced by developmental deficiency leading to the formation of a cleft and the growth potential of midfacial skeleton. The other factor is the iatrogenic factor, including surgical repair. Therefore, management of cleft-related maxillary hypoplasia is more complex due to the larger degree of malocclusion and advancement, the risk of post-surgical relapse and the potential velopharyngeal incompetence following maxillary advancement [1, 5].

The general aim of this chapter is to present a brief review of sagittal distraction osteogenesis in sagittal maxillofacial advancement and the biomechanical effects of maxillary sagittal distraction osteogenesis both in patients with unilateral cleft lip and palate and in patients with no cleft.
