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Trans-sutural Maxillary Distraction and Tissue Regeneration: Experimental Studies in Growing Dogs

Author: YaoYuSheng
Tutor: LiuChunMing
School: PLA Postgraduate Medical School
Course: Clinical Stomatology
Keywords: Midfacial displasia SDO Ni-Ti shape memory alloy transmission electron microscopic ultrastructure transverse palatine suture Alkaline Phosphatase BMP immunohistochemistry
CLC: R782.2
Type: PhD thesis
Year: 2008
Downloads: 67
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Abstract


Midfacial hypoplasia is a common deformity of craniofacial surgery.The current technique for this deformity include orthopedic protraction,orthognathic surgery and distraction osteogenesis.Sutural distraction osteogenesis is a new emerging technology,in the past 10 years it had been applied to the craniofacial and has beconing a viable option in the correction of craniofacial deformities.But there are still some critical questions we do not know.Such as bone reneneration and fine distraction force.In order to understand these questions we performed this study on the technique of sutural distraction osteogenesis in growing mongrel dogs.PartⅠTrans-sutural maxillary distraction and histological observation of the maxillary sutures in growing dogsobjective The tissue regeneration mechanism of sutural distraction osteogenesis in maxilla has not been fully understood.In this research we study the mechanism of bone formation and sutural tissue restoration during sutural distraction osteogenesis and the histology change of transverse palatine suture.Methods 3~4 months mongrel dogs were used as experimental animals,mean weight 3.5 kg and divided into 4 groups randomly.One as normal control,three being experimental, and six dogs in each group.New designed internal nickel-titanium shape memory alloy distractors with three initial force level were inserted in the palatal and facial bones across the transverse palatine suture and frontomaxillary suture in all three group experimental dogs.one dog in each group was sacrificed at different time points of 5.10.15.20.30.40 days after distraction respectively.Tissue was taken from the transverse palatine suture,and stained whth HE,Toluidine Blue and Sirius red.Histological changes were evaluated under Olympus microscope and polarization microscope.Results Maxillary complex was successfully advanced in experimental dogs.Histologically,there are no significant difference between three experimental dogs.Under Olympus the width of the palatine suture were found broadened dramatically,the number of osteoblast and fibroblast increased.Ⅰtype collagen in sutural tissue and new bone increased,theⅡandⅢtype collagen decreased little by little,at last,it is made up ofⅠtype collagen.We didn’t find cartilage cells in histology during the whole distraction stage.Conclusion SDO is a kind of simple.convenience.reliability.effective operative method to extend the maxillary bone of dogs in growing period.More distraction force better result below 1500g.During distraction stage we found activated bone formation.PartⅡThe ultrastructure observation of transverse palatine suture induced by SDO in growing dogsObjective To observe the ultrastructure changes of transverse palatine suture during distraction stage in growing mongrel dogs.Methods 3~4 months mongrel dogs were used as experimental animals,mean weight 3.5 kg and divided into 4 groups randomly.One as normal control,three being experimental,and 3 dogs in each group.New designed internal nickel-titanium shape memory alloy distractors with three initial force level were inserted in the palatal and facial bones across the transverse palatine suture and frontomaxillary suture in all three group experimental dogs.one dog in each group was sacrificed at different time points of 10.20.40 days after distraction respectively.Tissue was harvested from the transverse palatine suture and chipping into 1mm~3,then processed for transmission electron microscopic observation.Results There are no difference between three experimental dogs under transmission electron microscopic.In the early stage we found break gap and loose fiber in TPS,subsequently repaired in the later stage.Sutural tissue accumulated a great many of osteoblast cells and fibroblast like cells.There are dilated rough endoplasmic reticulum and low electron density floccule in osteoblast.Later stage we found new bone formation. Conclusion Through TEM detection.We believe 1500g distraction force can’t damage osteoblasts enormously,however improve their biologic activity on the technique of SDO.During distraction stage there no cartilage cell was found.PartⅢBone Alkaline Phosphatase study of transverse palatine suture induced by SDO in growing dogsObjective To evaluate the influence of three different distraction force on TPS with the content of AKP.Methods animal experiment and operation were identical with partⅠ.one dog in each group was sacrificed at different time points of 5.10.15.20.30.40 days after distraction respectively.Tissue was taken from the transverse palatine suture,and processed for AKP detection.The content of AKP in new bone was semiquantiative analyzed with spectrophotometer.Results The AKP content of experiment group was increased obviously.A group: 14.01±4.84 U/gprot,B group:14.2±4.78 U/gprot,C group:15.63±10.22U/gprot, normal control:7.47±0.09U/gprot.The statistical results showed there are significant difference between the experimental and normal control(p<0.01).Conclusion The force of internal nickel-titanium SMA distractor had manifest influence on AKP content of transverse palatine suture.Reinforce cytoactive of osteoblast.The optimization force of SDO is 1200g.PartⅣThe expression of BMP-2,-4,-7 induced by SDO in growing dogsObjective The purpose of this study was to investigate the response and change of bone morphogenetic protein(BMP-2,-4,-7)induced by sutural distraction osteogenesis in growing mongrel dogs.Methods animal experiment and operation were identical with partⅠ.one dog in each group was sacrificed at different time points of 5.10.15.20.30.40 days after distraction respectively. Tissue was taken from the transverse palatine suture,and processed for immunohistochemistry examination to evaluate BMP-2,-4,-7 expression. Image-pro plus calculate the value of integrated optical density(IOD).Results Immunohistochemistry studies showed that the Buffy color of BMP-2,-4,-7 positive signals were mainly seen in osteoblasts,fibroblasts,osseous cell and mesenchymal.These cells showed cytoplasmic staining.At 10 day after distraction,distractied zone showed very intense signals for BMP-2 and BMP-4 in TPS during distraction stage of osteoblasts.Subsequently,these signals decreased considerably.But increased again after 15 day of distraction.However the expression of BMP-7 in low expression.Conclusion These data indicate that the change in mechanical environment created by distraction leads to increased BMP-2,-4 expression.Thus BMP-2,-4 may play important role in the the signaling pathways that link the mechanical forces created by distraction to cellular responses.They may have promote function on undifferentiated mesenchymal cells and osteoblast cells.From a more clinical perspective,our observations suggest that future attempts to accelerate the distraction process with exogenous BMPs administration should focus on the consolidation period,when endogenous BMPs production declined in the bone-forming osteoblast cells.

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CLC: > Medicine, health > Oral Sciences > Oral and maxillofacial surgery > Oral and maxillofacial plastic surgery
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