Clinical And Experimental Research On The Regeneration Of Alveolar Dehiscence And Fenestration

Objects:In this study,the etiology of alveolar dehiscence and fenestration was explored preliminarily in clinic.The bone regeneration effect of the mandibular anterior ridge after using periodontal accelerated osteogenic orthodontics(PAOO)and three techniques were quantitatively evaluated.In the dog dehiscence model,the regenerative capability of the PLGA/ATT,Bio-Gide and the periosteum as barriers in GBR were evaluated.Furthermore,the biological effect of poly(lactic-co-glycolic acid)(PLGA),the laponite--doped PLGA(PLGA/LAP)and the attapulgite-doped PLGA(PLGA/ATT)nanofibers as scaffolds of bone tissue engineering materials on bone marrow mesenchymal stem cells(BMSCs)were investigated in vitro.Materials and methods:1.Three-dimensional cone-beam computed tomogram(CBCT)was taken to investigate the prevalence and the distribution of alveolar bone dehiscence and fenestration in lower anterior region of class Ⅰ,Ⅱ and Ⅲ malocclusions.Morphologic changes of the mandibular anterior ridge were compared among different malocclusions.2.Non-idiopathic condylar resorption(ICR)of class Ⅱ malocclusions were chosen as control,CBCT was used to analyze the craniofacial and alveolar morphology in ICR3.Traditional orthodontics were chosen as control,CBCT was applied to observe alveolar bone changes before treatment(T0),immediately after PAOO(T1)and at least 6 month(T2)after PAOO.The modified technique,grafting fixed with the periosteum and traditional technique were analyzed to detect the bone regeneration.4.The cytocompatibility of three different nanofibers was evaluated by CCk-8 assay and scanning electron microscopy(SEM)morphology observation of BMSCs cultured onto the prepared three different fibrous scaffolds.The osteogenic differentiation of BMSCs cultured onto three nanofibers was quantitatively investigated by measuring alizarin red-S(ARS)staining,the alkaline phosphatase(ALP)activity and Real-time PCR.5.Establishing a model of alveolar dehiscence in dogs,then PLGA/ATT,Bio-Gide and the periosteum were used as barriers in GBR procedure for alveolar defect.Twelve weeks after defects repaired,Micro-CT,sequencal fluorescent labeling and histological observation were adopted to detect new bone formation.Results:1.For skeletal Class Ⅰ,Ⅱ,and Ⅲ malocclusions,the Class Ⅱ group had a greater prevalence of dehiscence(class I,32.96%;class Ⅱ,64.47%;class Ⅲ,58.43%)and fenestration(class I,13.41%;class Ⅱ,14.72%;class Ⅲ,13.86%)than the other groups.The lower middle incisor in class Ⅱ malocclusion was the most associated with dehiscence(74.24%)while the canine was more related with fenestration(27.27%).2.There was a significant difference in SNB,ANB,FMA and FMIA between ICR group and non-ICR in class Ⅱ group.Compared with non-ICR,a significant higher incidence of dehiscence for the lower lateral incisor occurred in the ICR group(67.74%).Thin alveolar bone and decreased alveolar bone height on lingual surface was associated with ICR.3.Compared with the control group,the vertical alveolar height and horizontal bone thickness were significantly increased in PAOO group.The vertical alveolar height and the horizontal bone thickness from T0 to T1 increase significantly.However,there is a significantly decrease from T1 to T2.Compare to T0,Significant bone augmentation was still observed in T2.The alveolar bone thickness increased buccally at the coronal portion of the root with the modified technique.The modified technique and the periosteum technique had a significant bone augmentation at midroot level,which were superior to the traditional PAOO.No significant differences were found among different techniques in bone augmentation at apex level.The modified technique showed a predominant effect on vertical alveolar bone augmentation,followed by the periosteum technique,and traditional technique was last.4.Three materials can guide bone regeneration in the dog dehiscence defect.The new bone percentage(%)was highest in the periosteum group and there was no significant difference between Bio-Gide and PLGA/ATT group.5.PLGA/ATT nanofiber exerted promotion effect on the proliferation of BMSCs.PLGA/ATT could promote the expression of osteogenic genes of BMSCs such as Runt-related transcription factor 2(Runx-2),ALP,collagen type I(Col-I),osteopontin(OPN)and osteocalcin(OCN)as well as the ALP activity.Conclusions:1.Class Ⅱ malocclusion has a highest prevalence of dehiscence among different malocclusions,which become a predisposing factor to the alveolar bone defect.2.ICR with retruded mandible,steep mandibular plane and thin alveolar ridge,which become a predisposing factor to the alveolar bone defect.3.Compared to traditional orthodontics,PAOO has a therapeutic effect on dehiscence and fenestration.Traditional PAOO is suitable for apical third bone defect and the periosteum technique is suitable for fenestration and thin alvelus.The modified technique shows a predominant effect on coronal alveolar bone augmentation.4.Bio-Gide membrane,PLGA/ATT nanofiber and the periosteum can guide bone regeneration at dehiscence defect,especially for the periosteum.5.Among three different nanofibers,the osteogenic differentiation of BMSCs was enhanced most by the PLGA/ATT with good biocompatibility.