| BackgroundDelayed replantation refers to the tooth that is dried in vitro for 60 min or longer.In this case,the periodontal membrane cells on the surface of the root are basically necrotic.When a large number of dead cells are left on the root surface,the necrotic tissue and cells may activate the associated inflammatory cells and osteoclasts,and then accelerate root absorption process.This is the main reason of replantation failure.Therefore,it is suggested that the necrotic periodontal membrane should be removed from the root surface before the delayed replantation.At present,the methods of removing necrotic periodontal membrane include mechanical method and chemical method.All the studies used a single method to remove the necrotic periodontal membrane on the surface of the root.Combined chemical-mechanical method have not been done on the same tooth.ObjectivesTo observe the effect of combined chemical-mechanical method on the removal of necrotic periodontal membrane in delayed replantation.To observe the effect of combined chemical-mechanical method on periodontal healing in delayed replantation.MethodsChapter 1.To observe the effect of combined chemical-mechanical method on removing the necrotic periodontal membrane in delayed replantation.40 premolars extracted for orthodontic reason were collected,dried at room temperature for 1 hour,and stained with methylene blue for 5min.Samples were randomly divided into four groups(n=10):the control group,the mechanical group(periodontal membranes were wiped by gauze),chemical group(periodontal membranes were soaked in 1%sodium hypochlorite),combined chemical-mechanical group(periodontal membranes were wiped by gauze and soaked in 1%sodium hypochlorite later).The removal processes of periodontal membranes all were 15min.Optical microscope and scanning electron microscope were performed respectivelyChapter 2.To observe the effect of different concentrations of sodium hypochlorite on removing the necrotic periodontal membrane in delayed replantation.210 premolars extracted for orthodontic treatment were collected,dried for 1 hour at room temperature,and stained with methylene blue for 5min.The teeth were randomly divided into 7 groups(n=30):the negative control group(soaked in physiological saline 15min after gauze wipe),soaked respectively in 1%、2%、5.25%sodium hypochlorite solution for 15 min,gauze+ 1%sodium hypochlorite 15 min group,gauze+2%sodium hypochlorite solution 15min group,and gauze+5.25%sodium hypochlorite 15 min group.Optical microscopy and scanning electron microscopy were performed,X-ray energy spectrometry was performed,and cell adhesion and proliferation were detected.Chapter 3.The animal models of delayed replantation were established to observe the effect of combined chemical-mechanical method on the periodontal healing in delayed replantation.4-week old male Wistar rats were randomly divided into four groups(n=6):immediate replantation group,positve control group(replantation after drying at room temperature for 1 hour without any root surface management),the mechanical group(replantation after removal of the periodontal ligament with gauze wipe),the combined chemical-mechanical group(replantation after removal of the periodontal ligament with gauze wipe and soked in 1%sodium hypochlorite for another 15min),MicroCT scan root for 3D imaging was performed,root absorption were counted.ResultsChapter 1.In the blank control group,necrotic periodontal membrane was observed throughout the surface of the root of the tooth,periodontal membrane residue was observed in the mechanical group and the chemical group,no periodontal membrane residue was observed in the combined chemical and mechanical group,and cementum integrity was observed in the four groupsChapter 2.In the gauze+normal saline group,the necrotic periodontal membrane was observed throughout the surface of the root of the tooth.In the 1%sodium hypochlorite group,the periodontal membrane remained and the surface of the root of the tooth was complete.No residual periodontal membrane was observed in other groups.Cracks were observed on the surface of root treated with 2%sodium hypochlorite for 10min and 5.25%sodium hypochlorite for 5min.There was no statistically significant difference in the mass percentage of some elements between the chemical group and the combined chemical-mechanical group.Compared with the effect of 2%sodium hypochlorite for 10 minutes and 5.25%sodium hypochlorite for 5 minutes,the mass percentage of sodium and chlorine elements on the cementum surface was significantly different from that of 1%sodium hypochlorite for 15 minutes(p<0.05).The mass percentage of sodium and chlorine is positively correlated with the concentration of sodium hypochlorite.Compared with the effect of 2%sodium hypochlorite for 10 minutes and 5.25%sodium hypochlorite for 5 minutes,the mass percentage of phosphorus and calcium elements on the cementum surface was significantly different from that of 1%sodium hypochlorite for 15 minutes(p<0.05).The mass percentage of calcium and phosphorus was negatively correlated with the concentration of sodium hypochlorite.There were statistically significant differences in the adhesion and proliferation of periodontal membrane cells in each group(p<0.05).At the same concentration,there was no significant difference in OD values between the chemical group and the combined chemical-mechanical group(p<0.05).When the cells were cultured for 24h,there was a statistically significant difference in OD value between the chemical group/combined chemical-mechanical group and the gauze+physiological saline group(p<0.05).As the concentration of sodium hypochlorite increased,OD value decreased gradually.When the cells were cultured for 72h,there was no statistically significant difference in the OD value between 1%sodium hypochlorite treated for 15min and gauze+physiological saline group(p<0.05).The OD values of 2%sodium hypochlorite for 10min and 5.25%sodium hypochlorite for 5min were statistically different from those of gauze+physiological saline group(p<0.05).As the concentration of sodium hypochlorite increased,OD value decreased graduallyChapter 3.There were significant differences in the number of normal cementum sites and the number of extracellular resorption sites in the immediate replantation group,the positive control group,the mechanical group and the combined chemical-mechanical group(p<0.05).The number of extracorporeal resorption sites was in order from high to low:the positive control group>mechanical group>combined chemical-mechanical group>immediate replantation group.There was a statistical difference in the absorptivity of root sites between the four groups(p<0.05),and the results from high to low were as follows:the positive control group>mechanical group>combined chemical-mechanical group>immediate replantation group.ConclusionsIn this study,in vitro and in vivo experiments found that the safe concentration of sodium hypochlorite was 1%and the appropriate time for the removal of necrotic periodontal membrane was 15 minutes in delayed replantation.The combined chemical-mechanical method was effective in removing the necrotic periodontal membrane completely,without damaging the root surface,or inhibiting cell proliferation.The combined chemical-mechanical method reduced the root absorption in delayed replantation. |
PDF Full Text Request