Effect of extraosseous devices designed for vertical distraction of extreme resorbed mandibles on backward rotation of upper bone segments.

Abstract: We studied the result of vertical distraction osteogenesis in 34 patients as a method of restoring vertical bone height in atrophic mandibles. Cephalometric radiographs were obtained preoperatively, immediately after the installation of the distractor, at the end of the active distraction period (1–2 weeks), before placement of implants, after a consolidation period of 12 weeks, and annually thereafter. Particular attention was paid to the changed position of the upper segment in relation to the basal segment, compared with before and after active distraction. To monitor the position of the distracted upper bone segment, both the improvement in bony height and the angle of the distracted upper bone segment were scored using the menton-pogonion line as a reference plane. Surprisingly in nearly all patients there was a backward rotation of the segment with lingual-tipping of the upper segment by a mean of 12° that meant that in such cases only 87% of the maximum gain in bony height could be achieved. As a consequence of the backward tipping of the top of the distracted alveolar ridge, the position of the implants was also more lingually directed. However, in all cases sufficient bony volume was achieved to allow placement of implants. Distraction osteogenesis is a successful way of restoring atrophic mandibles to gain sufficient bony volume to allow placement of implants. However, the vector of distraction is unpredictable. [Copyright &y& Elsevier]