| Objective: The aim of the study was to investigate the effects of piezosurgery in accelerating the rate of orthodontic tooth movement and the expression of receptor activator of nuclear factor kappa-Β ligand(RANKL)and proliferating cell nuclear antigen(PCNA).It can provide a theoretical basis and reference for the clinical application of piezosurgery facilitated accelerated orthodontics.Methods: Thirty New Zealand white rabbits(NZW),aged 20 weeks,weighing 2 to 2.5 kg,were used in this study.The animals were randomly divided into 5 groups according to different force application time(1 d,3 d,5 d,7 d,14 d).Each group had 6 rabbits.A split-mouth design randomized controlled trial was performed.One side of the mandible was randomly selected as the experimental side and the other side as a control.The piezosurgery was performed on the mandible of first molar of the experimental side.Both the experimental side and the control side of the rabbit were placed with the orthodontic force application,of which the force was 80 g between the first molar and central incisors at the same time.The temperature of the alveolar bone surface at the incision site was detected by the SEEK THERMAL smartphone-based thermal imager when being cut by the piezosurgery.Staticimages were taken at multiple time points up to 20 seconds.The animals were scanned by Cone-beam computed tomography(CBCT)before being sacrificed.The rabbits were sacrificed by intravenous injection of excessive Su-Mian-XinⅡvia the auricular margin at the end of different force application placed time(1 d,3 d,5 d,7 d,14 d).The mesial movement distance of the first molar(the distances between the first molar and the second molar)were then measured by an electronic vernier caliper.Haematoxylin and eosin(HE)staining was performed to detect the histopathological changes in periodontal tissues of the first molar.Immunohistochemical(IHC)staining and image analysis techniques were performed to detect the expression of RANKL of periodontal tissue in the pressure side of the first molar and the expression of PCNA of periodontal tissue in the tension side of the same molar.Real-time quantitative polymerase chain reaction(QPCR)was used to detect the mRNA expression of RANKL and PCNA in the periodontal tissues of the first molars.Independent-Samples t test with SPSS 17.0 software package was used for statistical analysis.Results: 1.The temperature of bone surface increased with the cutting duration time,and the temperature was not more than 34±1 ℃ after 20 s of continuous cutting.2.The first molar on the experimental side on days 1,3,5,7 and 14 moved significantly more rapidly than that on the control side(P < 0.05).3.There was no significant root resorption or periodontal diseases were observed by CBCT after 7 and 14 days of the operation.4.HE: On day 1,the periodontal ligament of the tension side of the experimental side was wider than that of the control side.The cellular components in the periodontal ligament increased,and no absorption of bonelacunaes were found.The control alveolar bone was continuous.By day 3,the fibers of the periodontium of the experimental side were disordered and the cellular components increased.The multinucleated osteoclasts were seen on the periodontal side of the alveolar bone at the pressure side,and osteoblasts were observed in the bone marrow cavity.By day 7,the gaps between the periodontal ligaments and the tooth of the experimental side.The fiber arrangement became rough and irregular,and the periodontal ligaments showed marked hyalinization.Osteoclasts were seen on the pressure side of the experimental side,and the bone resorption became active.Many bone resorption lacunae were found on the surface of the alveolar bone.There were more osteoblasts of the alveolar surface than that of the control side.The number of osteoclasts was reduced compared with the day 3.By day 14,the bone trabeculae at the tension side of the experimental side and the control side was thick,where the marrow cavity was small.While the bone trabecula at the pressure side was thin and the bone marrow cavity was large.The osteocytes in lacunae of the tension side of the experimental side were immature,large in size,deeply stained in the nucleus,with large cell density,and the bone-like matrix was deposited,suggesting the alveolar bone and cementum were newly formed.5.IHC: RANKL protein levels in the experimental sides were higher than those in the control sides on days 3 and 7,reaching its peak on day 3(P < 0.05).However,RANKL protein levels in the experimental sides were higher than those of the control sides on days 1,5 and 14(P > 0.05).PCNA protein levels in the experimental sides were higher than those in the control sides on days 1 and3,reaching its peak on day 3(P < 0.05).However,PCNA protein levels in the experimental sides were higher than those of the control sides on days 5,7 and14(P > 0.05).6.QPCR: RANKL mRNA levels in the experimental sides were significantly higher than those in the control sides on days 3 and 7,reaching its peak on day 3(P < 0.05).However,RANKL mRNA levels in the experimental sides were higher than those in the control sides on days 1,5 and 14(P > 0.05).PCNA mRNA levels in the experimental sides were significantly higher than those of the control sides on days 1 and 3,reaching its peak on day 3(P < 0.05).However,PCNA mRNA levels in the experimental sides were higher than those of the control sides on days 5,7 and 14(P > 0.05).Conclusion: In conclusion,piezosurgery may significantly accelerate the the rate of orthodontic tooth movement.It can enhance the expressions of osteoclast related cytokines,promote the cell proliferation,and increase periodontal tissue remodeling in the early stage.The piezosurgery produces less heat,and will not increase the risk of root absorption.It is a minimally invasive and effective method to accelerate the orthodontic tooth movement. |
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