CBCT Evaluation Of Alveolar Bone Changes Of The Mandibular Anterior Teeth With Periodontitis Intruded By MIA

Part 1: CBCT evaluation of alveolar bone changes of the mandibular anterior teeth with periodontitis intruded by MIAObjective To evaluate the alveolar bone changes of mandibular anterior teeth with chronic,periodontitis intruded by mini-screw implant anchorage(MIA).Methods Eighteen patients with pathologic migration of mandibular anterior teeth seeking for orthodontic-periodontal therapy were selected.MIA was used to intrude the mandibular anterior teeth,remove the occlusal trauma and correct the pathologic migration.CBCT was taken before and after treatment.Alveolar bone thickness and height in the labial side and lingual side were measured and analyzed.Results The pathologic migration of the lower anterior teeth was corrected.The thickness of the mandibular central incisors was increased from 6.00mm to 6.77mm,and the thickness of the mandibular lateral incisors increased from 6.07mm to 6.89mm.The distance from alveolar crest to CEJ of the mandibular central incisors in the labial side was reduced from 5.45mm to 3.93mm,while in the lingual side reduced from 4.79mm to 3.38mm.In the mandibular lateral incisors,the distance was reduced from 4.83mm to 3.79mm in the labial side and from 4.76mm to 3.58mm in the lingual side.Conclusion The lower anterior alveolar bone can be well reconstructed by the intrusion of mandibular incisors through MIA.Experiment 1 The effect of orthodontic tooth movement time on the reconstruction of alveolar bone defect after regenerative surgery in ratsObjectives:This study was to investigate the effect of orthodontic tooth movement time on the reconstruction of alveolar bone defect after regenerative surgery.Materials and Methods:Fifty-two healthy male SD rats of 6-weeks age(weighing 190±10g,SPF class)were selected.Under general anesthesia,mucoperiosteum flap opration was performed in the proximal mesial region of the mesial root of the left maxillary first molar.The partial alveolar bone(length×width×depth about 2×2×3mm)was removed with a slow dental motor drill and exposed the root cementum of the mesial surface of the mesial root.The periodontal tissues including periodontal membranes and cementum were removed by curettage.Thus,a model of alveolar bone defect was established.Subsequently,guided tissue regeneration(GTR)was performed by Bio-Oss bone powders and subsequent coverage of Bio-Gide membrane.The orthodontic tooth movement group after regenerative surgery was treated as the experimental group and the non-orthodontic tooth movement group was treated as the control group.In the experimental group,orthodontic tooth movement was carried out 1,2,3,and 6 months after the regenerative surgery.The maxillary left side of the rat was fixed with an orthodontic reinforcement device to pull the maxillary first molar mesially.The load force was 50 g,and the force was reloaded every week.After 8 weeks of tooth movement,the rats were sacrificed.The jawbone including maxillary left first molar of the experimental group and control group were obtained.HE staining was peformed.The changes of tissue reconstruction in the alveolar bone defect area in the experimental and control groups under different healing time were simultaneously observed.The proximal and distal edge of the bone defect area was considered to be measuring part.4 high power visual fields(×100 Magnification)were selected by random from the measured parts of each slice.The average number of osteoclasts and osteoblast lacunas in every vasial field of all the samples were calculated.The statistics of the experimental data were analysised by SPSS25.0.The difference between the experimental group and the control group was compared with one-way analysis of variance and the SNK method for multiple comparisons.P<0.05 was considered to be statistically significant.Results:When the orthodontic tooth movement was carried out at 1 month after regenerative surgery.The bone defect area in the 1-month control group was mainly fibrous tissue,and a small amount of new bone could be seen.In the 1-month experimental group,the fibrous tissue was increased in the bone defect area,and local inflammatory reaction and less newborn bone was observed.The number of osteoblast lacunas was increased from 3.53 in 1-month control group to 5.20 in the 1-month experimental group(P<0.05).The number of osteoblast was decreased from 9.76(1-month control group)to 5.25(1-month experimental group,P<0.05).When the orthodontic tooth movement was carried out at 2 months after regenerative surgery,a small amount of new bone was formatted in the bone defect area in the 2-month control group.The osteogenesis was active and fibroblasts were decreased.The new bone in the bone defect area of the 2-months experimental group was less than that of the 2-months control group.The osteogenesis was not active.The number of osteoblast lacunas was increased from 3.75(2-month control group)to 5.46(2-month experimental group,P>0.05).The number of osteoblast was decreased from 15.69(2-month control group)to 11.26(2-month experimental group,P<0.05).When the orthodontic tooth movement was carried out at 3 months after regenerative surgery,there was more new bone formation in the bone defect area in heeling 3-month group.The mature bone was increased significantly,and the osteogenesis was active and the ratio of fibrous tissue was decreased.The amount of new bone and osteogenesis in the bone defect area of the 3-months experimental group was increased more than that of the control group and fibrous tissue was decreased.The number of osteoblast lacunas were decreased from 5.02(3-month control group)to 3.55(3-month experimental group,P<0.05).While the number of osteoblast was increased from 20.09(3-month control group)to 28.87(3-month experimental group,P<0.01).When the orthodontic tooth movement was carried out at 6 months after regenerative surgery,the new bone of the 6-month control group in heeling 6 month group was significantly increased than that in the 6-month experimental group.The osteogenesis was active and the proportion of fibrous tissue was decreased further.The bone quantity and calcification degree of the new alveolar bone in the experimental group were increased and the ratio of fibrous tissue was reduced compared to the control group.The number of osteoblast lacunas were decreased from 4.81(6-month control group)to 3.92(6-month experimental group,P<0.05).While the number of osteoblast was increased from 22.56(6-month control group)to 29.25(6-month experimental group,P<0.01).Conclusion:According to the limited data in this study,the conclusion could be drawn as follows:1.The application GTR and Bio-Oss bone grafting could effectively repair alveolar bone defects and consecutively promote periodontal tissue regeneration.2.Orthodontic tooth movement is appropriate after 3 months of regenerative surgery for alveolar bone defect.Experiment 2 The study of the effect of different orthodontic force on the reconstruction of alveolar bone defect in ratsObjectives:This study was to investigate the best loading force of orthodontic tooth movement after regenerative surgery.Materials and Methods:Twenty-eight healthy male SD rats of 6-week age(weighing 190 ±10g,SPF class)were selected.The animal models of regenerative surgery of alveolar bone defect and tooth movement were chosen as part 1.The orthodontic tooth movement group after regenerative surgery was treated as the experimental group and the non-orthodontic tooth movement group was treated as the control group.After 3 months of regenerative surgery,the experimental group was applied with different loading force:50 g,80 g,and 100 g for tooth movement.After 8 weeks of tooth movement,the rats were sacrificed.The jawbone including maxillary left first molar of the experimental group and control group were obtained.HE staining was peformed.The changes of tissue reconstruction in the alveolar bone defect area in the experimental and control groups under different orthodontic force were observed.The proximal and distal edge of the bone defect area was considered to be measuring part.4 high power visual fields(X 100 Magnification)were selected by random from the measured parts of each slice.The average number of osteoclasts and osteoblast lacunas in every vasial field of all the samples were calculated.The statistics of the experimental data were analysised by SPSS25.0.The difference between the experimental groups and the control groups was compared with one-way analysis of variance and the SNK method for multiple comparisons.P<0.05 was considered to be statistically significant.Results:1 The movement speed of the left maxillary first molar in loaded 50 g and 80 g force group was 0.228mm/week and 0.233mm/week and the clinical tooth mobility was I degree in all the two groups.The speed of tooth movement in loading 100 g force group was 0.315mm/week,while the clinical tooth mobility was increased to Ⅱ degree.2 In the control group,there were more new bone and mature bone in the repair area of the alveolar bone defect.The number of osteoblasts was 20.09 and the number of osteoblast lacunas was 5.02.While in the loading 50 g force and 80 g force group,the new bone and mature bone was more than that in the control group.The proportion of fibrous tissue was decreased,and the number of osteoblast was increased to 28.83(P<0.05),and the number of osteoblast lacunas was reduced to 3.65 in the loading 50 g force group(P>0.05).The number of osteoblast was increased to 26.53(P<0.05),and the number of osteoblast lacunas was reduced to 3.86(P<0.05)in the loading 80 g force group.But in the loading 100 g force group,the bone and mature bone was less than that in control group.The proportion of inflammatory cells and fibers was increased significantly,the number of osteoblast was decreased to12.54(P<0.01),and the number of osteoblast lacunas was increased to 7.65(P<0.01).Conclusion:According to the limited data in this study,the conclusion could be drawn as follows:When the orthodontic tooth movement was carried out at 3 months after regenerative surgery,the application of certain light force(50 or 80g)could induce and accelerate the restoration of alveolar bone defect after regenerative surgery.While loading with a heavy force(100g)may lead to the reduction of the bone formation and negatively affect the reconstruction of alveolar bone.Experiment 3 The effect of bone remodeling related to cytokines on the reconstruction of alveolar bone defect by orthodontic tooth movement in ratsObjectives:This study was to investigate the expression changes of bone remodeling related cytokines after regenerative surgery of alveolar bone defect under different orthodontic tooth movement time.Materials and Methods:Fifty-two healthy male SD rats of 6-weeks age(weighing 190±10g,SPF class)were selected.The animal models of regenerative surgery of alveolar bone defect and tooth movement were chosen as the part 1.The orthodontic tooth movement group after regenerative surgery was treated as the experimental group and the non-orthodontic tooth movement group was treated as the control group.In the experimental group,orthodontic tooth movement was carried out at 1,2,3,and 6 months after regenerative surgery.The loading force was 50 g.After 8 weeks of tooth movement,the rats were sacrificed.The jawbone including maxillary left first molar of the experimental group and control group were obtained and the paraffin section was made.Immunohistochemical staining was performed.The proximal and distal edge of the bone defect area was considered to be measuring part.4 high power visual fields(X 100 Magnification)were selected by random from the measured parts of each slice.The average number of the expression of osteoclast resistant tartaric acid phosphatase(TRAP),Osteoprotegerin(OPG),osteoclast differentiation factor(RANKL),bone morphogenetic protein(BMP)and chemotaxis factor CXCL12(stromal derived factor-1,SDF-1)in each vasial field of all the samples were calculated.The pathological image analysis system was used to make a semi quantitative analysis of the sections after immunohistochemical staining.The statistics of the experimental data were analysised by SPSS25.0.The difference between the experimental group and the control group was compared with one-way analysis of variance and the SNK method for multiple comparisons.P<0.05 was considered to be statistically significant.Results:The number of osteoblast lacunas was increased in the 1-month and 2-month experimental groups when the orthodontic tooth movement was carried out at 1 month and 2 months after regenerative surgery(P<0.01),and decreased in the 3-month and 6-month experimental group(P<0.05).The expression of OPG,BMP and SDF-1 was increased in the 1-month and 2-month experimental groups(P<0.05)and decreased in the 3-month and 6-month experimental group(P<0.05).The expression of RANKL was decreased in the 1-month and 2-month experimental groups(P<0.05)and increased in the 3-month and 6-month experimental group(P<0.05).Conclusion:According to the limited data in this study,the conclusion could be drawn as follows:Under the action of tooth movement in alveolar bone defect,OPG,RANKL,BMP and SDF-1 could play an important regulatory role in bone remodeling,proliferation,differentiation of osteoblasts and osteoclasts,as well as maintenance of bone function,bone resorption and formation during the orthodontic process.However,the mechanism of action should be further studied.