Soft tissue stability after segmental distraction of the anterior mandibular alveolar process: a 5.5 year follow-up

Soft tissue changes were analysed retrospectively in 17 patients following distraction osteogenesis (DO) of the mandibular anterior alveolar process. Lateral cephalograms were traced by hand, digitized, superimposed, and evaluated at T1 (17.0 days), after DO at T2 (mean 6.5 days), at T3 (mean 24.4 days), at T4 (mean 2.0 years), and at T5 (mean 5.5 years). Statistical analysis was carried out using Kolmogorov-Smirnov test, paired t-test, Pearson's correlation coefficient, and linear backward regression analysis. 5.5 years postoperatively, the net effect for the soft tissue at point B' was 88% of the advancement at point B while the lower lip (labrale inferior) followed the advancement of incision inferior to 24%. Increased preoperative age was correlated (p < 0.05) with more horizontal backward movement (T5 T3) for labrale inferior and pogonion'. Higher NI/ML' angles were significantly correlated (p < 0.05) to smaller horizontal soft tissue change at labrale inferior (T5 T3). The amount of advancement at point B was significantly correlated with an upward movement (T5 T3) of labrale inferior (p < 0.01) and stomion inferior (p < 0.05). It can be concluded that further change in soft tissues occurred between 2.0 and 5.5 years postoperatively. The physiological process of ageing and loss of soft tissue elasticity should be considered as possible reasons.