Effects Of Quercetin On Bone Formation In The Mid-palatal Suture Of Rats During Maxillary Expansion

Malocclusion is a common disease in oral clinic,characterized with poor facial beauty,and often affect the normal social intercourse of patients and damage their mental health.Rapid maxillary expansion(RME)is often used to correct malocclusion,such as high arch of palatal vault,crowding of dentition,narrow dental arch and crossbite of anterior or posterior teeth caused by insufficient maxillary transverse development.While the palatal suture was expanded by mechanical tension in the process of REM,osteoblasts proliferate and differentiate,and bone deposit and calcify in the palatal suture.Consequently,the width of dental arch increase,and dentition crowding is relieved.Although rapid expansion is feasible in theory,there are many problems in clinical practice,such as root damage,periodontal tissue retraction and recurrence after expansion,etc.The treatment cycle is relatively long,and the effect is not ideal.At present,accelerating bone remodeling in the mid-palatal suture can enhance the effect of arch expansion in RME,which has become one of the hotspots among many orthodontists.Objective:The rat model of RME was established and quercetin suspension was given to the rats.The maxilla was obtained after the experiment.By histological observation and detecting bone morphogenetic protein-2(BMP-2),we investigated the effect and mechanism of quercetin on palatal suture reconstruction after RME,so as to provide valuable experimental basis for clinical application of quercetin in accelerating the remodeling of palatal suture,enhancing the effect of arch expansion and shortening the treatment duration of RME.Method:Eighteen SPF male Wistar rats(6w old)were randomly divided into three groups with an average of six rats in each group:group A(blank control group),group B(simple expansion group),and group C(arch expansion+quercetin group).Group A was not treated at all;group B and group C were implanted with double ring spring arch expander with force value of 0.98 N(100 g);group C was given quercetin solutionere given the same dose of normal saline according to their body weight.On the 14th(100 mg/kg)every day at the same time of arch expansion,while group A and B w day,the rats were killed,and the maxillary tissues were dissected to make specimens.After embedding and dewaxing,Hematoxylin-eosin(HE)staining was used to observe the changes of bone histomorphology in the rat palatal suture.Masson staining was used to observe the changes of collagen fibers in the rat palatal suture.Immunohistochemistry staining was used to detect the expression of BMP-2 in the rat palatal suture.Image-pro Plus software was used to analyze the section absorbance,and SPSS19.0 software package was used for statistical analysis of the data.Result:1.General condition:During the experiment,both the arch expansion device and all signs of the rats in the three groups were normal.The weight of rats in group A increased steadily every day.The weight of rats in groups B and C showed a decreasing trend from the 2nd day,and then began to increase again from the 4th day.Finally,the weight of rats in the three groups was almost equal after the 11th day.2.HE staining:The palatal suture tissue of the maxilla includes fibrous tissue intermediate zone,secondary cartilage tissue located on both sides and bone plate tissue near the edge.Group A showed red-stained fibrous tissue in the middle,a few mesenchymal cells,chondrocytes,osteoblasts on both sides,and occasional osteoclasts on the edge.At the edge of the bone plate,osteoblasts with different number and cuboidal shape were scattered,even some areas showed uneven appearance.Group B and C showed red-stained fibrous tissue in the center of the palatal raphe,and secondary cartilage tissue on both sides extended to the central red-stained band,with obvious chondrocyte differentiation and proliferation.At this point,a large number of osteoblasts accumulated at the edge of the palatal raphe to generate new bone.In group C,osteoblasts were denser at the palatal raphe to mineralize bone deposition,which suggested more active bone remodeling in the palatal raphe.3.Masson staining:Group B and C were generally darker stained than group A,showing a large number of blue-stained collagen fibers in the palatal raphe after RME.The width of the palatal raphe increased significantly,with a large number of osteoblasts and chondrocytes on both sides proliferating and osteoid formation.Group C had more active bone action than group B,with deeper staining of collagen fibers and deposition of new bone calcification.4.Immunohistochemical staining:BMP-2 cells in the raphe area of the rat palate were stained brownish yellow.In group A,the number of BMP-2 cells was very small,with the small volume and the light-colored.In group B and C,new bone and BMP-2 positive cells were found on the inner side of the chondrocyte layer of the two sides of the middle palatal suture area,both quantity and coloration were superior to group A.In group C,the number of brownish yellow particles was more than those in group B,indicating the enhanced expression of BMP-2 cells.Some BMP-2 positive cells were diffusely distributed and gradually extended to both sides of the palatal raphe.The MOD value of BMP-2 in group B was significantly higher than that in group A(P<0.01),and the MOD value of BMP-2 at the palatal raphe in group C was higher than that of BMP-2 in group B(P<0.05),the difference was statistically significant.Conclusion:1.Rapid maxillary expansion applied force value of 100 g(0.98N)could enlarge the palatal raphe in growing rats.2.Compared with the simple rapid maxillary expansion,quercetin assisted rapid maxillary expansion can promote the osteogenesis of the palatal suture,and the deposition and calcification of bone are more obvious.3.Compared with the simple rapid maxillary expansion,quercetin assisted rapid maxillary expansion can promote the expression of BMP-2 in the palatal suture,and the remodeling of bone is active.