Angiogenesis in Distraction Osteogenesis / 대한정형외과학회잡지

PURPOSE: Distraction osteogenesis is now a standard method for bone lengthening. However, little is known about the exact mechanism of new bone formation. This study was undertaken to investigate the temporal and spatial changes of angiogenesis during the periods of distraction osteogenesis; the three-dimensional microarchitecture of newly formed vessels and their origin; and the role of angiogenesis with reference to mineralization. MATERIALS AND METHODS: Sprague-Dawley rat's tibia was osteotomized subperiosteally and was distracted at a rate of 0.5 mm per day for two weeks after one week of latency period. Vascular corrosion casting using Mercox was done on the hindlimbs before osteotomy, and at the 1st, 2nd, 3rd, 4th, and 6th weeks postoperatively. Replicated microvascular structures and their distribution patterns at the distraction site and adjacent parent bone were observed temporally and spatially under scanning electron microscope. These findings were compared with radiographical and histological observations. RESULTS: 1. At postoperative first week and second week, proliferation of periosteal vessels were more pronounced than that of endosteal vessels, which corresponded to the early new bone formation in subperiosteal area on histologic sections. 2. At postoperative third week, arterial branches from the medulla of parent bone entered into the distraction gap. Multiple longitudinal vascular branches sprouted out from the newly formed vascular network, and ran towards the interzone. 3. At postoperative fourth week, there was vascular proliferation in the periosteal side of interzone, from which branches arose towards the parent bone. 4. At postoperative sixth week, vascular networks of both sides connected to each other, and few angiogenetic findings were observed. CONCLUSIONS: In distraction osteogenesis, angiogenesis occurred actively during the distraction period and then gradually decreased with time. Taken together with radiographical and histological findings, close temporal and spatial relationship between the angiogenesis and new bone formation at the distraction site was revealed.

An experimental study on the vascular changes of rat molar periodontal ligament following orthodontic tooth movement using vascular corrosion casting method / 대한치과교정학회지

This study was undertaken to investigate the three dimensional vascular changes of periodontal ligament following orthodontic tooth movement. Experimental tooth movement was carried out in 96 Sprague-Dawley rats with the weight of 250g. They were divided into four experimental groups (each 24 rats). The left maxillary first molar was moved mesially with 25g force in group I, and with 75g force in group II. Each three animals were sacrificed after 1, 6, 12, 24 hours, and 3, 7, 14, 21 days. In group III, 25g mesial force was applied for 3 days, and in group IV, 75g mesial force was applied for 3 days. Then the appliances were removed, and each three animals were sacrificed after 1, 6, 12, 24 hours, and 3, 7, 14, 21 days from removal of appliance. The contralateral molars were used for control group. Casting media was injected via left ventricle and polymerized in warm water. After corrosion of surrounding soft tissue, three dimensional vascular changes were examined using scanning electron microscopy. The findings of this study were as follows: 1. Pressure side of group I and II showed degenerative vascular changes such as vascular compression, reduction of vasculature, leakage of casting media. But, regenerative changes were dominant after 7 days of tooth movement. Although the degenerative vascular changes were more severe in group II, which was exposed to heavy force, the timing of these changes was not different between two groups. 2. Periodontal vasculature was reestablished by the growth of new capillaries and their differentiation and union from the remaining periodontal vessels and vessels of alveolar bone marrow. Although vascular regeneration was more rapid in group I, which was exposed to light force, the vasculature was not fully normalized in both groups even after 21 days. 3. There was no remarkable changes in tension side of group I and II, but looping of capillary, new capillary growth, dilation of vessels, redirection of vessels in the direction of tensile force were occurred. 4. In pressure side of group III and IV, in which appliance was removed after 3 days of orthodontic force, bone resorption was continued even after removal of appliance. Regeneration of vasculature was initiated after 1-6 hours, and it was more rapid in group III than group IV. In both groups, the vasculature was not fully normalized even after 21 days. 5. After removal of appliance, tension side of group III and IV showed vascular compression and loss of vasculature.