A Study Of The Orthodontic Implant Site-switching Technique

The long-term functional success of implant placement requires an adequate volume of hard tissue.Therefore,bone augmentation procedures have always been a hot research topic in the field of oral implantology.According to the biological basis of bone remodeling in orthodontic treatment,when a tooth moves,new bone formation will appear on the tension side.Therefore,under the concept of multidisciplinary joint treatment,it is worthwhile to investigate if the bone increment caused by orthodontic treatment can improve bone volume at the implant site under certain conditions.When a tooth is extracted due to periodontal disease or the tooth is congenitally missing,the alveolar ridge will be absorbed to varying degrees.Bone augmentation procedures need to be applied before the insertion of the dental implant for patients with bone deficiency.However,the surgical augmentation of resorbed bone is associated with several limitations,including the invasive features and complications associated with the grafting technique.Compared with invasive bone augmentation surgery,the orthodontic implant site-switching technique（OISS）is a feasible and non-invasive method for the generation of new bone,particularly when patients require additional orthodontic therapy.It involves moving the adjacent teeth into the bone-deficient edentulous area,closing the edentulous space and creating an implant site adjacent to the original edentulous area.The specific method is as follows:The anatomy of the first and second premolars,as well as the first and second molars,was comparable.When the bone quantity at the implant site is insufficient（due to a long period elapsing since the loss of teeth）,an orthodontic procedure can be used to move another identical tooth to the area left by the missing tooth.The newly developed edentulous area may have sufficient bone for implant placement because it represents the consequence of natural tooth movement.However,there is no conclusive evidence that OISS can be used in clinical practice.The purpose of this study was to explore the feasibility and safety of OISS.First,this experiment was designed to explore whether the alveolar bone condition of the newly formed edentulous area can meet the specific requirements of implant placement.Second,the purpose of this experiment was to analyze the changes in alveolar bone height and width in the bone defect area and the new edentulous area before and after tooth movement.Finally,in order to assess whether OISS can be safely implemented,a retrospective clinical study was conducted to explore whether periodontal support can be maintained when a tooth is moved into a bone defect.Methods:Experiment 1 was to verify the feasibility of the orthodontic implant site-switching technique.Five beagles were selected for the self-control study.The bilateral maxillary first premolars of five beagle dogs were extracted and bone defects were created.The right and left sides of the maxilla were randomly divided into control and experimental sides.On the experimental side,the maxillary second premolar was mesially moved into the position of the missing first premolar.On the control side,the second maxillary premolar was extracted.Six months later,the beagles were euthanized.Microcomputer tomography and toluidine blue staining of tissue sections were used to assess the quantity and quality of bone in the two groups and compare the alveolar bone condition of the experimental group’s second premolar removal area to the alveolar bone condition of the control group following the second premolar extraction.The reasons for selecting the control group are as follows.The research^[2]showed that for the posterior tooth area where the periodontal tissue was not obviously damaged,there was no need for additional alveolar bone preservation or bone augmentation after tooth extraction.The osteogenic ability of natural healing of the alveolar fossa can promote the formation and maturation of bone trabecula,and the delayed implantation here can obtain good long-term stability.In theory,the alveolar bone condition following minimally invasive tooth extraction should be better than that following periodontal disease and even better than that following the traumatic loss of teeth.Therefore,this research aimed to compare the condition of the alveolar bone in the newly formed edentulous area following orthodontic tooth movement with the best-case scenario of tooth loss.If the condition of the alveolar bone in the newly formed edentulous area is better than the condition of the alveolar bone after healing of the extraction socket,the newly formed edentulous area can be considered suitable for implant placement.Experiment 2 analyzed the changes in bone volume at each site before and after OISS.CBCT was used to analyze the change in alveolar bone height of the second premolar before and after entering the bone defect area.The height and width of alveolar bone in the bone defect area before and after orthodontic treatment were measured.The height and width of alveolar bone in the new edentulous area were measured before and after orthodontic treatment.Experiment 3 was to verify the security of OISS.We selected 20 adult patients who closed the missing space of the first molar by moving the second and third molars.The height of the mesial and distal alveolar bones of the second mandibular molar,the absorption of the mesial and distal roots,and the height of the mesial alveolar bone of the third mandibular molar were the measurement indices.Simultaneously,the correction factor was introduced to reduce the impact of different magnifications.If the second and third molars were moved to the alveolar bone atrophy area,their alveolar bone height could be maintained at the original ideal level,proving that OISS can be applied safely.Results:Experiment 1:The bone volume per tissue volume and trabecular thickness were significantly higher in the experimental group than in the control group（P<0.05）.Trabecular bone pattern factor and trabecular separation were significantly higher in the control group than in the experimental group（P<0.05）.There was no significant difference in the trabecular number between the two groups（P>0.05）.Alveolar bone height was significantly higher in the experimental group than in the control group（P<0.05）.The bone trabecula in the new edentulous area was thicker than that in the control group.Experiment 2:There was no significant difference in the height of the mesial buccal,mesial lingual and distal buccal alveolar bone of the second premolar before and after orthodontic treatment（P>0.05）.The height of the distal lingual alveolar bone was significantly higher than that before orthodontic treatment（P<0.05）.The height and width of alveolar bone in the bone defect area were significantly greater than those before the second premolar was moved into the bone defect（P<0.05）.The height and width of alveolar bone in the new edentulous area were significantly smaller after the second premolar was moved into the bone defect（P<0.05）.Experiment 3:There was no statistical difference in the height of the mesial alveolar bone of the second and third molars before and after orthodontic treatment（P>0.05）.The height of the distal alveolar bone of the second molar after orthodontic treatment was higher than that before orthodontic treatment（P<0.05）,with a difference of 0.25±0.49mm.The length of the mesial and distal roots of the second molar after treatment was smaller than that before treatment（P<0.05）,and the root resorption was 1.12±1.44mm and 0.93±1.51mm,respectively.Conclusion:1.When compared to normal healing after tooth extraction,the bone quality and bone quantity of the new edentulous sites generated after the teeth had moved into the atrophic alveolar bone following orthodontic treatment were better at the same time point.It showed that the newly formed edentulous area could meet the requirements of implant placement.Thus,our data confirmed the feasibility of the OISS for clinical application.2.Alveolar bone height was maintained when the second premolar was moved into the bone defect.The alveolar bone height and width in the bone defect area increased after tooth movement.The height and width of alveolar bone in the new edentulous area decreased following tooth movement.3.Our analysis showed that periodontal support was maintained when a tooth was moved into the bone defect.It showed that the OISS could be implemented safely.