Effects Of Pamidronate On Orthodontic Root Resorption And Tooth Movement

In the process of orthodontic treatment,orthodontic force on alveolar bone and cementum this two similar biological tissue were effective. Under the appropriate force,the teeth move in the constantly rebuild alveolar bone while thecementum maintain relatively stable. One of the research focus of modern orthodontic is move the teeth fast and do no harm to the teeth or their surrounding tissue as far as possible.Cementum under orthodontic pressure,however,is sometimes inevitably absorbed.Root resorption is a common clinical complications,almost orthodontic patients,especially adults,have root resorption in some degree,however,most are within the allowable range in the physiological.Root resorption can make root shorter,making the crown and root of imbalance, In severe cases, will affect the stability and health of teeth and have a negative impact on orthodontic treatment and stability.so how to avoid、reduce root absorption have becomed the topic of growing number of scholars.But the research about reducing root absorption is still not much.Recent studies have confirmed the low-intensity pulsed ultrasound、 recombinant human soluble receptors、Emdogain (EMD)、NO,etc.can accelerate root repair,reduce resorption,However,the application of these methods have some limitations due to expensive or clinical use.Bisphosphonates are developed in the past twenty years,a class of drugs as anti-mebalolic bone disease,its mainly used for the treatment of osteoporosis caused by increased risk of bone fragility and fractures characterized by reduced bone mass and bone structural damage.The mechanism of root resorption and bone resorpition is essentially similar,osteoclasts are the main bone resorption cells,cementoclasts are the main cells of root resorption, cementoclast and osteoclasts are very similar in form and function.pamidronate is a second generation bisphosphonates and can effectively inhibit the dissolution of hydroxyapatite and inhibit the activity of osteoclasts and prevent bone resorption.In this study,firstly an experimental animal model of the orthodontic tooth movement of the rats was consructed.Then inject bisphosphonates pamidronate sodium in the first molar, exploring the effects on root absorption during rat tooth movement, while observing the role on tooth movement.Purpose:First, construct an experimental animal model of the orthodontic tooth movement,Choose48female6weeks old SPF Wistar rats,Every rat maxillary divided into experimental and control sides.Experimental side,injected with50μl of pamidronate on the first permanent molars in the palatal mucoperiosteal, while the control side injected with0.9%normal saline50μl, based on the model exploried the effects of pamidronate on root absorption during tooth movement, This experiment evaluated by Pamidronate on root resorption and tooth movement during orthodontic tooth movement in rats mainly through degree of root resorption in the scanning electron microscope、the number of cementoclast in the pressure side of the toot,expression of ODF,root reportion index and tooth movement.Methods:48female6weeks old SPF Wistar rats((180-200g) were chosen, feed the disinfection solid particles in the clean-level Experimental Animal Center of Shandong University West Campus.The rats were fed for a week, Then the orthodontic appliance was loaded to the rats through the previous method.2%Ketamine(Ketamine Hydrochloride Injection) was injected to the abdominal cavity of rats. The rats were fixed to the operation table and use0.20mm wire through the first molar and second molar adjacent gap, ligate in the mesial first molar. Grind a groove deep about0.2mm in upper two incisorlabial, tongue, distal surface adjacent to the gingival margin of tooth neck, the groove at about the same level of the central incisors. Ligate with the two central incisors Ni-Ti extension spring were loaded between upper central incisor and first molar. Tracted the first molar in mesial direction with60g force,then the experimental animal model of orthodontic tooth movement was established. fed rats with Sterile nutrient Feed inject of gentamicin to the rat for3consecutive days.Each rat maxillary divided into experimental and control side,the first experimental side injected with50μl of pamidronate on the first permanent molar in the palatal mucoperiosteal,while the control side injected with0.9%normal saline50μl,injected every3days since beginning injecting before establishing rat model. keep the force about60g,16rats were killed separately on3,7,14days. remove the first molar of8rats completely both sides, after fixation, dehydration, freezing, spray of gold coating, scanning by electron microscope、Taking pictures,observed the root absorption; the other8rats separated the rat skull, after heart perfusion fixed, measured the molar moved; produced periodontal tissue sections of the maxillary first molar,eaconh tooth make10sections,immunohistochemistry5sections Observe the number of cementoclast through the expression of ODF observing osteoclast; staining5sections with HE and make computer image processing, calculatie root absorption index, Finally all data were made statistical analysis.Result:1. Electron microscope shows that on3,7,14days, root resorption lacunae on experimental side is less than control side, on3days there was no statistically significant,on7,14days the two were statistically significant;2.Light microscopy shows that on3,7,14days cementoclast on mola r pressure side the experimental group is less than the control group, on3days there was no statistically significant,on7,14days the two were statistically significant;3. Immunohistochemistry shows that on3,7,14days experimental side is less than the control side about the express of ODF, on3days there was no statistically significant,on7,14days the two were statistically significant;4. On3,7,14days root resorption index of the experimental side is small than the control side,on3days there was no statistically significant,on7,14days the two were statistically significant;5. On3,7,14days the first molar movement distance of the experimental side is less than the control side, on3days there was no statistically significant,on7,14days the two were statistically significant.Conclusion:l.pamidronate can reduce root resorption during orthodontic tooth movement;2.Pamidronate caninhibit teeth movement speedin the orthodontic process.