Relativity Of The Mouth Wiping Behavior And Root Resorption In Rats During Orthodontic Force

BackgroundResearchers found that the mouth wiping behavior was believed to changeobviously in rats suffered from emotional stress during the experimental toothmovement by orthodontic force.And additional emotional stress led to increased rootresorption.The behavior of mouth wiping response to orthodontic force was externaland easy to observe.While the root resorption was internal and tangible pathologiclesion. As a result，orthodontic doctors should focus on research about the relatedrelationship between them.It provided a reference for prevention and reduction of rootresorption in the clinic.While there is a relationship between the mouth wipingbehavior and root resorption in rats，researchers have not reported.PurposeThis study investigated the mouth wiping behavior and root resorption during theexperimental tooth movement in rats by orthodontic force.The aim was to discuss therelationship between the mouth wiping behavior and root resorption.It provided areference for prevention and reduction of root resorption in the clinic. MethodsForty-two8-week-old male Sprague Dawley rats (266.67±20.46)g wererandomly divided into a control group and experimental group.The control group wasjust for the blank of6rats.The first left upper molar and the upper incisors of36ratswere subjected to a constant orthodontic force of50g by means of a NiTi closed coilspring in the experimental group. As two incisors for the anchorage，the left maxillaryfirst molar were moved mesially. There were three parts.The behavior was evaluatedby means of mouth wiping test on the1st，2nd，3rd，5th，7th，14th day.The totaltime of mouth wiping in5minutes were analyzed in part one.In part two，after theexperimental period, the rats were sacrificed.The left upper first molar and maxillarybone were sliced serially into sections. For visualization of the root resorption，sections were stained with hematoxylin and eosin.The magnitude of root resorptionwas measured by Biosens Digital Imaging System v1.6soft.The mouth wipingbehavior and root resorption had a correlation analysis in part three.The SPSS17.0soft was used for statistical analysis.Results1. Evaluation of the mouth wiping test showed that the behavior in theexperimental group was significantly differen（tP=0.018） in contrast with the controlgroup after treatment. And on the1st day the time of the mouth wiping in rats was themost. Then it had been decreased to the threshold of the control group on the14thday.2. HE staining measured the mesial side apical root of first left upper molar. Inthe control group，the periodontal ligament fibers were oriented and the cellular andtissue reactions were normal.Although there was no root resorption on the1st and2ndday in the experimental group， the fibers of the periodontal ligament werecompressed and the inflammatory cells were located in the cementum. Disorientionand distortion of the periodontal ligament fiber arrangement were encountered on the3rd and5th day.And an accumulation of osteoclasts was often found in the resorptionlacunae of the root surface.The structure of the periodontal ligament fibers were completely lost，and cells could not be distinguished on the seventh day.The rootresorption was the most severe and the resorption lacunae was the most.On the14thday，the periodontal ligament fibers had been arranged and the cell had beennormal.During this phase of arrest, root resorption was rare and reparative dentin wasappeared.3. Compared with the control group，the root resorption was evident in thestatistically significant difference (P<0.01) by the measurement of root resorptionlacunae area.And on the3rd day，the root resorption lacunae had already started onthe root surface. It had been increased to the top on the7th day.And then there was adownward trend until it was terminated on the14th day.4. The mouth wiping behavior and root resorption both had a correlation withtime of orthodontics force applied according to rank correlation.And the mouthwiping behavior was earlier than root resorption.But there was no directedrelationship between them.Conclusions1. The mouth wiping behavior in rats is increased obviously during experimentaltooth movement by orthodontics force.And then it is decreased to the threshold of thecontrol group.2. The root resorption is occurred during experimental tooth movement byorthodontics force in rats.And on the3rd day，the root resorption lacunae starts on theroot surface. It is increased to the top on the7th day.And then there is a downwardtrend until it is terminated on the14th day.3.The mouth wiping behavior and root resorption both have a correlation withtime of orthodontics force applied. And the mouth wiping behavior is earlier than rootresorption.This behavior may be able to a warning signal for root resorption.