The purpose of this study was to evaluate whether complex, mature sutures could be separated using skeletal anchorage and light, continuous forces. Twelve adult female New Zealand White (NZW) rabbits, 8 to 9 months old, were randomly assigned to three groups (0 g, 42 days, n=3; 100 g, 42 days, n=7; or 100 g, 105 days, n=2). Open-coil nickel-titanium springs delivered constant forces of 100 g across the sagittal suture to miniscrew implants (MSI's) placed bilaterally in the frontal bone. Sutural separation was measured bi-weekly. Bone formation (mineral apposition) on both the endocranial and ectocranial surfaces was measured with fluorescent labels and micro-computed tomography (uCT). Qualitative histologic analyses of the suture tissues were performed using H&E staining; osteoclasts were evaluated using tartrate resistant acid phosphatase (TRAP) staining. All 24 MSIs remained stable throughout the experiment. There was no statistically significant sutural separation in the control group. In the experimental groups, sutural separation was significant (p < .05) at all time points up to 42 days. The rate of separation was linear during the first 42 days, and decreased between 42 to 105 days. There were moderate correlations (R=0.59-0.89; p=<.05) between MSI separation and bone marker separation. Mineral apposition rate (MAR), which was not measureable in the control group, showed significant deposition of bone in the experimental group. MAR was greater between 14-28 days than between 28-38 days, and it was greater on the ectocranial than endocranial surface, but neither of these differences were statistically significant. Based on the uCT analysis, 3D sutural volume of the experimental group increased significantly (p=0.02), whereas the increase in surface area was not significant (p=0.26). Based on these results, it is possible to separate the sagittal suture of mature rabbits. Sutural separation is limited, indicating involvement of other sutural articulations.
