Bone-borne accelerated sutural expansion: A microcomputed tomography study in rabbits.

Abstract

In this study, we evaluated the effect of bone-borne accelerated expansion protocols on sutural separation and sutural bone modeling using a microcomputed tomography system. We also determined the optimum instant sutural expansion possible without disruption of bone modeling. Sixteen New Zealand white rabbits, 20 to 24weeks old, were randomly divided into 4 experimental groups. Modified hyrax expanders were placed across their interfrontal sutures and secured with miniscrew implants located bilaterally in the frontal bone. The hyrax appliances were activated as follows: group 1 (control), 0.5-mm per day expansion for 12days; group 2, 1-mm instant expansion followed by 0.5mm per day for 10days; group 3, 2.5-mm instant expansion followed by 0.5mm per day for 7days, and group 4, 4-mm instant expansion followed by 0.5mm per day for 4days. After 6weeks of retention, sutural separation and sutural bone modeling were assessed by microcomputed tomography and quantified. Statistical analysis was performed using Kruskal Wallis and Mann-Whitney U tests and the Spearman rho correlation (P<0.05). Median amounts of sutural separation ranged from 2.84 to 4.41mm for groups 1 and 4, respectively. Median bone volume fraction ranged from 59.96% to 69.15% for groups 4 and 3, respectively. A significant correlation (r=0.970; P<0.01) was observed between the amounts of instant expansion and sutural separation. Pending histologic verifications, our findings suggest that the protocol involving 2.5mm of instant expansion followed by 0.5mm per day for 7days is optimal for accelerated sutural expansion. When 4mm of instant expansion was used, the sutural bone volume fraction was decreased.