| Objective: Appropriate occlusal stimuli can maintain the stability of internal environment of periodontal tissues,and regulate the morphology and function of periodontal tissues.However,in clinical practice,excessive masticatory forces are often observed.When the occlusal forces changed,the structure of periodontal tissues would also change accordingly to adapt to the change of forces.The shape,color,and position of gingival tissues are critical to the health of periodontal tissue and smile aesthetics,and gingival remodeling is also an important factor that affecting the effect of orthodontics.In this study,hyperocclusion animal models were established by tooth extraction to observe the effect of hyperocclusion on gingival tissues,and to preliminarily explore the mechanism.Methods : 4-week-old male Kunming mice without caries and periodontal diseases were used.They were randomly divided into control group and experimental group,with fifteen mice in each group.The experiment began after 1 week of adaptive feeding.The right maxillary molars of mice were successively extracted under local anesthesia.Three mice in each group were randomly selected and sacrificed on postextraction day 3(PED3),postextraction day 7(PED7),postextraction day 14(PED14),postextraction day 28(PED28),and postextraction day 56(PED56).And the left mandible was taken after 4%paraformaldehyde internal fixation,and then decalcified and embedded.Continuous tissue sections were made along the sagittal direction of the left mandibular first molar.Hematoxylin eosin(HE)staining and Matson staining were performed for histological observation;apoptosis cells were detected by Terminal deoxynucleotidyl Transferase Biotin-d UTP Nick End Labeling(TUNEL)staining;and the expressions of proliferating cell nuclear antigen(PCNA),p65,Interleukin-1β(IL-1β),Tumor necrosis factor-α(TNF-α),vascular endothelial growth factor(VEGF)and β-catenin were detected by immunohistochemical staining.The reconstruction of gingival tissues was observed under a microscope,and the image analysis software was used for quantitative calculation.Result: 1.HE staining results: Well-oriented collagen fiber bundles were observed in the intact dentition.Collagen fiber bundles were obviously disordered on PED14.On PED28,the collagen fiber bundles became thicker and regular,and vascular hyperplasia were obvious.Masson’s trichrome staining results: An increase in the amount of new collagen fiber deposition was observed in the gingiva on PED28.2.TUNEL staining results: Hyperloading increased the number of apoptotic cells in gingival tissues rapidly.TUNEL-positive cells reached the peak on PED3,and then decreased until PED14,which was similar to the control group.3.Immunohistochemical results: The increased occlusal force resulted in the enhanced expression of PCNA,IL-1β,TNF-α,VEGF and β-catenin.PCNA immunohistochemical staining analysis indicated that the cell proliferation reached the peak on PED7,and then the number of positive cells remained at a high level although decreased to some extent,and there was still a significant difference between PED56 group and the control group(P< 0.05).VEGF staining results showed a similar trend,and the number of positive cells reached the peak on PED14,which indicated tissue regeneration.The number of TNF-αpositive cells reached the peak on PED7 and decreased to the initial level on PED28.The number of p65,IL-1β and β-catenin positive cells reached the peak on PED14,and there was no significant difference between PED28、PED28、PED56 group and the control group(P > 0.05).Conclusions:Hyperocclusion induced a series of cellular and molecular reactions in the gingival tissues,including apoptosis and proliferation,which leaded to gingival modification to adapt to the new occlusal state.NF-κB and Wnt/β-catenin signaling pathways might play a regulatory role in this process. |
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