The Influence Of Corticotomy Assisted Orthodontic Tooth Movement To Premolar Intrusion Of Beagle-three-dimensional Morphological Research

Segmental intrusion of teeth is one of the difficulties in orthodontictreatment. In the clinical, overeruption maxillary molars is common if thepatient losed one or more mandibular molar in early time, some patients haveopen bite deformity, all of them need Segmental intrusion of teeth.Previously, Orthodontic doctors can not find a stable anchorage forSegmental intrusion, the invention of Mini-implant anchorage (MIA) hassoved this problem. But some research reported that MIA assisted toothintrusion can lead to the resorption of root tips and root furcation.Corticotomy is a kind of alveolar surgery. In this way, we can achievethe purpose of accelerating tooth movement. The characteristic ofcorticotomy is smaller trauma and easy to operation. Many clinical researchsreported that the joint application of corticotomy-assisted orthodontictreatment and MIA can accelerate tooth intrusion.Recently, most of theanimal experiment reseachs about corticotomy-assisted orthodontictreatment has focused on the retrusion and the sagittal tooth movement.About the influence of corticotomy-assisted orthodontic treatment to root resorption and Alveolar reconstruction during intrusion, there is not relatedresearch.Therefore, it is necessary to establish an animal model ofcorticotomy-assisted Segmental intrusion. Compare the differences betweensimply using MIA and joint application of corticotomy-assisted orthodontictreatment with MIA,Compare the contents of the rate of tooth movement,root resorption and bone remodelingObjective： Establish an animal experiment model ofcorticotomy-assisted Segmental intrusion for beagle dogs. Self-controldesign used to Compare the influence of corticotomy-assisted orthodontictreatment to premolar intrusion of Beagle and the change ofthree-dimensional morphology. At the same time explore the effects of time，the difference of root resorption and bone remodeling.Methods：1. Establish an animal experiment model ofcorticotomy-assisted Segmental intrusion for beagle dogs. Eight adult maleBeagle dogs were randomly divided into four groups,Each dog wererandomly assigned left and right side of the jaw as the experiment side andthe control side. Experiment side using MIA and corticotomy assistedintrusion of P3, P4while the control side using MIA to directly intrusion.After2,4,8,12weeks, execute two dogs each time and obtain the specimens.2. Not loaded implant was implanted as a marker. Measured andcalculated the amount of tooth movement at each time. Drawing curve for the amount of movement following time.Comparative analysis the differentbetween experiment side and control side about the rate of toothmovement.3. CBCT analysis of teeth intrusion amount, root resorption and boneremodeling. Each dog conducted CBCT examination before and afterintrusion. The Data was passed into three-dimensional measurementsoftware Invivo5.0. Compared the experiment side and the control sideabout the effect of tooth intrusion,root resorption and the alveolar boneremodeling.4. Micro-CT analysis of ROI (Region of interest) trabecular under theroot furcation.After the dogs were executed, fixed and trimmed thespecimens,conducted Micro-CT scanning. Compared the trabecularStructure of experiment side and the control side of ROI.Results:1. Successfully established an animal experiment model ofcorticotomy-assisted Segmental intrusion for beagle dogs. Laid thefoundation for the detection of three-dimensional morphology, histology andimmunohistochemical analysis.2. Direct measurement results: About the amount of Segmentalintrusion, there is no significant difference between experiment side andcontrol side at2weeks. But the amount of tooth intrusion of experiment sideis larger than control side at4,6,8,10,12weeks. The difference wasstatistically significant (P <0.05), The results suggest that corticotomy can accelerate the the rate of Segmental tooth intrusion.3. CBCT measurements suggest that except two weeks group, intrusionvolume of other three group of experiment side is larger than the control side(P <0.05). At12weeks group, root resorption of experiment side is less thanthe control side (P <0.05). At8weeks and12weeks groups, decrease amountof alveolar bone height of experiment side is larger than the control side (P<0.05), but combination the amount of intrusion,about the proportion ofalveolar bone height reduced to the intrusion distance,experiment side isless than the control side. The results suggest that corticotomy may reducethe amount of root and alveolar bone resorption.4. Micro-CT results suggest that:4and8weeks group, trabecular bonevolume fraction of experiment side is less than the control side (P <0.05),4weeks group trabecular number of experiment side is less than the controlside (P <0.05),8weeks group, trabecular space of experiment side issignificant larger than the control side (P <0.05), no significant differenceamong other indexs.Conclusions: Corticotomy and MIA assisted Segmental tooth intrusioncan accelerate tooth movement and achieve more intrusion amount. Moreactive alveolar bone remodeling may reduced the amount of root resorptionand the absorption of alveolar bone after Corticotomy.