| Objective:To establish the animal model of Orthodontic tooth movement,observe the tooth movement distance and periodontal tissue remodeling in rats,compare the effects of low level laser,micro-osteoperforatios and their combination in accelerate the orthodontic tooth movement.Methods:1.The Best Effective Laser Dose:Twenty one SD rats were randomly divided into three groups:Laser Group(n=15,Orthodontic forces+laser irradiation),Control Group(n=3,Orthodontic forces)and Blank Group(n=3).According to the irradiation duration,Laser Group was divided into 5subgroups(Group A:10s,Group B:25s,Group C:50s,Group D:75s and Group E:100s).The Orthodontic model of bilateral maxillary first molars were established to Laser Group and Control Group,and each Laser Group was required to continuously irradiated the laser once/day during the 0-6 days of modeling.The rats were killed on the 7th day when the model was establishment.The Secondary Impression Method was adopted to record the tooth movement distance before and after the model establishment,then we took the upper jaw bones of the rats to make tissue slices,observed the alveolar bone remodeling as well as changes in tissue morphology and cell composition of pericementum after HE staining,screened out the laser dose able to accelerate the tooth movement effectively for the follow-on experiment.2.The Effect of Orthodontic Tooth Movement by Different Interventions:Sixty SD rats were randomly divided into 4 groups:LLL Group(Orthodontic forces+laser irradiation),MOPs Group(Orthodontic forces+micro-osteoperforations),Combined Group(Orthodontic forces+laser irradiation+micro-osteoperforations)and Control Group.Each group contained 15 rats and three rats were killed on the 1st,3rd,5th,7th and 14th day separately after model establishment.The same method was then we took the upper jaw bones of the rats to make tissue slices,observed the alveolar bone remodeling as well as changes in tissue morphology and cell composition of pericementum after HE staining,counted the osteoclast amount and observed the cell morphology and location after TRAP staining.Results:1.Effects of Different Laser Irradiation DosesThe tooth movement distances of rats in each group were measured after the Orthodontic forces added for 7 days.The tooth movement distances of Group A and Group B were not significant increased compared with that of Control Group;the tooth movement distances of rats in Group C was the largest compared to those of rats in other groups;the tooth movement distances of Group D and Group E have decreased compared with that of Group C,but still increased compared with that of Group A and Group B and Control group.However,statistical results showed that there was no signifapplied to record the tooth movement distance before and after the model establishment,icant difference in tooth movement between each Laser Group and Control Group(P>0.05).The pressure side of periodontal tissue was observed that the amount of osteoclasts was less and the bone resorptions were decreased for rates in Control Group and Group A;a few osteoclasts with rich cytoplasm in bone resorption pits for rats in Group B;capillary proliferation in pericementum was visible and numerous metabolism-active multinucleate osteoclasts closely attached to the edge of the alveolar bone side by side to form a large area of rodent resorption pits for rats in Group C;capillary proliferation in pericementum is able to be seen for rats in Group D and E;however the amount of osteoclasts was obviously less than that of rats in Group C.For rats in each group,the change of periodontium on the tension side was similar;fibroblasts in pericementum proliferated actively;the body and nucleus of the cells were larger;the outline was clear and the nucleolus was larger and obvious.2.Effects of Different InterventionsOn the 1st day and 3rd day of Orthodontic force loading,the tooth movement distances had no significant difference for rats in each group;on the 5th day,the tooth movement was obvious for rats in Combined Group;the tooth movement distance for rats in Combined Group had statistic difference compared with that of rats in Control Group(P<0.05);on the 7th day,statistic difference was more obvious compared with Control Group(P<0.01).On the 14th day,the tooth movement distance for rats in each Intervention Group increased more than that of rats in Control Group;significant difference appeared in LLL Group compared with that of rats in Control Group(P<0.05);there was significant statistic difference between MOPs Group and Control Group(P<0.01);there was quite significant statistic difference between Combined Group and Control Group(P<0.001).The histology observation suggested that on the 1st day,the change of periodontium in each group had no significant difference;on the 3rd day,the alveolar bone surface on the pressure side for rats in Combined Group started to emerge rodent resorption pits;on the 5th day,the same bone resorption emerged for rats in Control Group,LLL Group MOPs Group;on the 7th day,the alveolar bone for rats in each group emerged resorption of different degrees;the periodontal gap width on the pressure side recovered somewhat;fibroblasts on the tension side proliferated actively;a small number of osteoblasts scattered on the surface of the alveolar bone;on the 14th day,the osteoblasts reduced significantly and bone resorption activity slowed for rats in Control Group;the periodontium on the pressure side for rats in each Intervention Group still contained numerous osteoblasts and bone resorption activity still proceeded.The alveolar bone surface on the tension side for rats in each group emerged straticulate osteoid and the cuboidal osteoblasts closely attached in the pericementum on the edge of osteoid.Conclusion:1.10J/cm~2 Low level laser(wave length 810nm;irradiation duration 50s;output power 100mW;facula area 0.5cm~2)could be uesd to promote the alveolar bone remodeling of rats and accelerate the tooth movement.2.Micro-osteoperforatios could be uesd to promote the alveolar bone remodeling of rats and accelerate the tooth movement.3.The combination of low level laser and micro-osteoperforatios possesses the synergistic effect,which can obviously promote the alveolar bone remodeling of rats as well as accelerate the Orthodontic tooth movement. |
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