| [Objective] Based on a pre-established animal model of retractive force with implant anchorage on the maxilla of Rhesus Monkey and on the molecular biological level, the study explored the mechanism of suture remodeling under mechanical force in inner environment and the expression of important factors in suture remodeling. It also revealed the mechanism of applying the retractive force on the maxilla with implant anchorage for orthopedic effect.[Method] An animal model of retractive force with implant anchorage on the maxilla of Rhesus Monkey had been established. The study applied it as a experimental model to do some research on the related sutures (zygomaticomaxillary suture, pterygopalatine suture, transverse palatine suture, frontomaxillary suture, median palatine suture, zygomaticotemporal suture, zygomaticofrontal suture, sphenozygomatic suture).1.Histological Study:By means of hematoxylin-eosin (HE),a conventional staining, and tartrate-resistant acid phosphatase staining (TRAP),a special staining, histological changes on the sutures of the retractive force with implant anchorage on the maxilla of Rhesus Monkey were observed.2.Molecular Biology:By means of in situ hybridization, the expression of RANKL and OPG mRNA of the retractive force of implant anchorage on the maxilla of Rhesus Monkey was detected, and the molecular biological basis on orthopedic effect of retractive force with implant anchorage on the maxilla was also analyzed.[Results]1. The results of histological changes showed as follow:after the maxilla had been affected by an external force, the sutures around the maxilla and zygomatic bone had non-physiological alterations and had no pathological damage of bone. Compared with control group, active osteoclast reaction was observed in the sutures around maxilla (zygomaticomaxillary suture, pterygopalatine suture, and frontomaxillary suture) under compressive force.Some wave-shape bone absorption lines, minor grooves and bone resorption pits appeared on the surface of the bone. There were single core or multi-core osteoclasts in minor grooves and bone resorption pits. The fiber bundles were arranged in disorder and were curly. Different from other sutures reaction, transverse palatine suture and median palatine suture mainly had osteogenic reaction. The zygomaticotemporal suture, zygomaticofrontal suture and sphenozygomatic suture, as sutures around anchorage bone, were influenced by the tension. Densely arranged osteoblasts on the bone surface were observed on the edge of the suture. Immature bone tissue formed and was deposited on the bone surface. Subjected to stretch, fiber bundle within the sutures was neat and orderly. No positive osteoclasts were observed by tartrate resistant acid phosphatase (TRAP), which was different from the results of HE staining and in situ hybridization and needed further analysis.2. The expression of Osteoprotegerin (OPG) and receptor activator of nuclear factor κβ ligand (RANKL) mRNA showed the same results with the histological observation. The expression of RANKL mRNA in zygomaticomaxillary suture, pterygopalatine suture and frontomaxillary suture was strong, with the expression of OPG mRNA relatively weak to RANKL mRNA, which showed the osteoclast activity was stronger than osteoblastic activity and the forward growth of the maxilla was inhibited. The expression of OPG mRNA in the transverse palatine suture and median palatine suture was stronger than RANKL mRNA indicated that lateral growth of the maxilla was not inhibited and continued to grow under the the retractive force. In the zygomaticotemporal suture, zygomaticofrontal suture and sphenozygomatic suture, as the sutures around anchorage bone, the expression of OPG mRNA was stronger than control group and RANKL mRNA, which indicated that the osteoblastic activity was stronger than osteoclast activity[Conclusions] Affected by the retractive force of the implant anchorage on the maxilla,3sutures (zygomaticomaxillary suture, pterygopalatine suture, and frontomaxillary suture) around the maxilla had non-physiological alterations. Osteoclast activity and resorption of bone got stronger. Thus, bone formation and the forward growth of the maxilla were inhibited. Though as sutures around the maxilla, transverse palatine suture and median palatine suture had different reactions from that of other sutures, which was mainly in osteogenic reaction. The lateral growth of the maxilla was not inhibited and continued to grow. On the contrary, to the sutures around the maxilla,3sutures around anchorage bone (The zygomaticotemporal suture, zygomaticofrontal suture, and sphenozygomatic suture) mainly had osteogenic reaction,which was different from the mechanism of the traditional extraoral headgear effect and needed a further study. The results provided an experimental basis for the application of intraoral implant anchorage to inhibit the maxilla growth. |
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