Morphological Changes in the Midface of Beagle Dogs Treated by Trans-Sutural Distraction

Abstract

Trans-sutural distraction is a biological process that induces the formation of new bone and changes the position of bone by pulling on growing suture under the action of external forces. Currently, therapy to midfacial hypoplasia treated by trans-sutural distraction has been applied. In this study, Beagle dogs were selected as experimental animals, and a traction device designed by ourselves was applied to Beagle dogs to simulate the treatment process of trans-sutural distraction in human face, so as to provide a basis for the subsequent research on the related mechanism of trans-sutural distraction. The objective is that the animal model can provide the basis for the follow-up study of transsutural distraction. 45 month beagle dogs were randomly divided into two groups 3 in experiment group and 3 in control group. Implant nails were implanted as the bone marker in the bilateral zygomatic temporal suture, zygomandibular maxillary suture and palatine transverse suture in experimental group. The traction of the maxilla was carried out by the external cranial traction frame with canine fossa as bearing point, 800g force each side, elastic traction for 15 days. The control group only implanted the implant nail as the bone marker on both sides of the bone suture. The distance between two implant nails was measured by vernier calipers and X-ray examination, compared with preoperative and postoperative changes. X-ray and cephalometric measurements were used to measure change in the cranial basal angle . HE staining was used to observe the width of the bone seams, the morphology and structure of the cells and the tissue of the new bone under the phase contrast microscope. Then descriptive statistical analysis and t-test between two independent samples are carried out for the measurement data. The experimental group had a good retention of the beagle traction frame. In the experimental group, the maxillaries of dogs were protrudent in the process of traction gradually and the occlusal relationship changed to type II malocclusion. When the traction is 15 days, the coverage distance is about 8~9 mm. Before and after the traction, the distance between landmark points indicated that the spacing between the transverse palatine suture was the largest (experimental group: 5.52±0.19 mm control group 1.31±0.06 mm P<0.05), and zygomaticotemporal suture was the second (experimental group: 3.12±0.15 mm, control group 0.73±0.04 mm, P<0.05), and zygomaticomaxillary suture was less (experimental group: 2.60±0.34 mm, control group 0.53±0.05 mm, P<0.05). The cranial basal angle was no change before and after operation (controlgroup: 32.3±1.3°, experimental group: 33.2±1.1° P>0.05. Histology showed that the collagenous fibers in the suture of the control group were denser and the osteoblasts were visible on the edge of the suture, showing osteogenic activity. The experimental group significantly widened suture (experimental group:1209.388±42.714 µm, control group 248.276±22.864 µm, P<0.05), the number of fibroblasts increased significantl...