Wright, Brittany M (2015-05). The Effects of Corticotomies on Frontonasal Suture Expansion and Bone Modeling in Mature Rabbits. Master's Thesis.
Thesis
The purpose of this split skull study was designed to evaluate whether corticotomies enhance bone modeling and reduces the resistance of surrounding articulations during expansion in mature rabbits.
Nine adult female New Zealand White (NZW) rabbits, 8 to 9 months old, had miniscrew implant (MSI) supported expansion devices with 150 g open-coil nickel-titanium springs placed bilaterally across the frontonasal sutures. Corticotomies were performed on one randomly chosen side, anterior and posterior to the frontonasal suture; the other side served as the control. Sutural separation was measured bi-weekly for 7 weeks. Using microCT scans of each specimens, bone material density (mg HA/ccm) and bone volume fraction (BV/TV) were measured. Qualitative histologic analyses of the suture tissues were performed using H&E staining.
Most (94.4%) of the MSIs remained stable throughout the experiment. There was significantly (p <.05) more sutural separation on the corticotomy side (3.73 mm) than the control side (2.83 mm). There was no statistically significant side difference in bone volume fraction (p =.26) and bone density (p=.11). The amount of expansion that occurred was negatively correlated (R=-.860; p=<.001) with bone density. Blinded histological examination showed an increased density of osteoblasts, with a blastema-like appearance, along the bone fronts on the corticotomy side. Numerous elongated Sharpey's fiber insertions and a mixture of immature woven bone, with numerous osteocytes, were visible at the sutural margins on the corticotomy side, indicating the formation of new bone.
In conclusion, mature sutures expanded with adjunctive corticotomies undergo 31% more separation than sutures expanded without corticotomies with the amount of expansion that occurs being inversely related to bone density.
