【作者】 王晶；

【导师】 徐平平； 黄建生；

【作者基本信息】 南方医科大学 ， 口腔临床医学， 2011， 硕士

【摘要】 研究背景：牙根病理性吸收是口腔科临床较常见的病变,常常在脱位牙再植、局部阻生牙或肿瘤压迫、严重感染等之后发生,部分牙根吸收在病理性因素去除后可停止,而亦有病变呈进行性发展。牙根吸收是一个复杂的病理过程,由破牙细胞与体内各种调解因子协同作用完成。然而,牙根吸收的确切机理到底是怎样的呢?牙根的自我修复与牙根吸收也有着复杂且紧密的关系,其机理又是怎样的呢?我们尚不得而知,这些均有待进一步的深入研究。由于牙根吸收其过程的不可逆性,针对人体牙根吸收的研究多为回顾性的研究,因而在人为控制下研究牙根吸收修复,动物模型的建立是必不可少的。然而,以往研究所建立的动物模型多采用正畸加力的方式导致牙根吸收,然后停止加力观察牙根有无修复,但因加力方式易受外界因素的干扰、力值衰减以及牙根吸收具有部位及程度的不可控性等因素的影响,所建立的动物模型具有不稳定性及难以重复性。目的：1.以Beagle犬为研究对象,对犬牙根在翻瓣去骨暴露法损伤和支抗种植钉植入法损伤后的牙根牙周损坏形态、术区愈合状态和牙骨质修复情况进行比较,观察犬牙根在自然状态下的修复再生过程,旨在建立一个基于此牙根损伤方法的牙根损伤修复动物模型,以期为下一步研究牙根吸收的修复机制打基础。2.对Beagle犬后牙进行相关应用解剖学测量研究,为模型中支抗种植钉植入部位的定位提供参考数据,以期解决支抗种植钉植入定位这一关键性的技术难题。方法：实验一：两种牙根损伤修复的实验动物模型比较选用合适的实验用Beagle犬4只制造牙根损伤：1.翻瓣去骨暴露法损伤牙根：以每只犬的上下颌两侧尖牙牙根远中面中下1/3交界处、尖牙牙根近中面中上1/3交界处及第三切牙的牙根近中面中部作为损伤位点,每只犬共12个位点,共48个位点。于犬上下颌牙相应牙根损伤点区切开黏膜、翻瓣,定位牙根,以小球钻去骨,并在根中部制造4.0mm(长)×1.2 mm(宽)×1.2 mm(深)缺损,冲洗,瓣复位,缝合。2.支抗种植钉植入法损伤：每只犬选取上颌第一、第二、第三、第四前磨牙和下颌第二、第三、第四前磨牙及下颌第一磨牙,其中上颌第二、第三前磨牙和下颌第二、第三、第四前磨牙及下颌第一磨牙选取近中根的远中面,上颌第一前磨牙则选取牙根远中面(上颌第一前磨牙为单根牙),上颌第四前磨牙选取远中根的近中面,每只犬16个位点,共计64个位点。在预先设计的植入部位垂直于牙长轴植入支抗种植钉(规格Φ1.5 mm×L 10.0 mm)约10mm,并立即旋出。术后1～3d给予肌肉注射青霉素预防感染。术后当天半流食,以后均为软食。术后拍摄CT,并定期观察伤口愈合情况,8周后过量麻醉处死实验动物,按牙位切取标本,EDTA脱钙8～10周,常规切片,HE染色,行组织形态学观察。观察和比较两种方法的牙根牙周损坏形态、术区愈合状态和牙骨质修复情况。实验二：牙根损伤修复实验支抗种植钉植入部位的犬后牙相关应用解剖学测量：选择全身发育良好的健康成年Beagle犬5只,过量麻醉处死后,去除颊侧的骨质暴露牙根,分取上下颌第二、第三、第四前磨牙(Pm2、Pm3、Pm4)及下颌第一磨牙(M1),并确保各牙冠外形完整,共70颗牙作为研究对象。观察各牙的解剖形态,分别测量各牙AB(与牙体长轴垂直的牙冠最大近远中径)、Dm(支抗种植钉植入的参照点至近中根的距离)、Dd(支抗种植钉植入的参照点至远中根的距离)和Df(支抗种植钉植入的参照点点至根分叉的距离),并进行统计学分析。结果：两种牙根损伤修复的实验动物模型比较：1.术后8周,两种方法所致的牙根缺损其损伤的牙根面及损伤区均有不等程度的修复反应,损伤的牙根面均可见到新生牙骨质形成及牙周膜的再附着。2.牙根牙周损坏形态：影像学检查显示,翻瓣去骨暴露法所致牙根及牙周组织缺损形状不规则,周围组织亦见破坏暗影,支抗种植钉法所致牙根及牙周组织缺损呈规则的圆形,周围组织未见明显破坏。3.术区愈合状态：4只实验犬均无死亡,饮食、活动正常。采用翻瓣去骨暴露法位点,术区伤口愈合较慢,术后1周伤口仍见红肿现象、未见溢脓,术后2周伤口愈合良好。采用支抗种植钉法位点,术后1周术区伤口未发现感染溢脓情况,愈合良好4.牙骨质修复情况：组织切片观察发现,翻瓣去骨暴露法所致牙根及牙周组织缺损形状不太规则,在根面缺损底部高低不平,4只犬口内共计48个牙根损伤位点中,21个位点成功观察到牙根损伤修复,占43.8%,余位点或未损伤牙根,或损伤过深达牙髓。有部分损伤的牙根未观察到牙骨质修复现象。支抗种植钉法所致牙根及牙周组织缺损呈规则的圆形,在根面缺损底部呈近似圆弧形。4只犬口内共计64个牙根损伤位点中,42个位点成功观察到牙根损伤修复,占65.6%。部分位点仅损伤牙槽骨、牙周膜或者损伤达牙髓。牙根损伤修复实验支抗种植钉植入部位的犬后牙相关应用解剖学测量：1. Beagle犬后牙解剖形态观察：上下颌第二、第三、第四前磨牙和第一磨牙都有各自特征和形态。2.左右侧同名牙特定位点间距Dm、Dd、Df差异均无统计学意义(t分别为0.466、-1.871、1.763,P分别为0.644、0.070、0.087)。上下颌各牙位各指标的测量值均服从正态分布,Dd值与Dm值基本相等,Df值均大于4.0 mm。3.Beagle犬后牙牙根之间的间隙较小,而根分叉区域相对较大。根分叉区域植入MIA相对较为理想,并初步确认D点可以作为MIA在根分叉区植入的参照点。在进行MIA植入定位时,笔者建议可参考如下公式计算：d=Dm(Dd)-Φ/2。结论：1.术后8周,两种方法所致的牙根缺损其损伤的牙根面及损伤区均有不等程度的修复反应,损伤的牙根面均可见到新生牙骨质形成及牙周膜的再附着,标志着牙根损伤修复研究动物模型成功建立。2.支抗种植钉法应用于牙根损伤修复研究动物模型的建立为更佳。3.通过对Beagle犬后牙实体标本的定量测量,本研究所选取的参照点较为理想,在此基础上的定位方法d=Dm(Dd)-Φ/2较为简便易行,可为牙根损伤修复研究中动物模型的建立提供有意义的参考。更多还原

【Abstract】 Background:Pathological root absorption, as common dental clinical phenomenon, often follows the replantation of evulsed tooth, impacted tooth, oncothlipsis and severe infection. It could be ceased by removal of the pathological factors in some cases, and still advances in other cases. Root resorption is a complex pathological process, involved by odontoclast and various other factors. However, it is still rare known regarding the mechanism and the relationship between root resorption and self-reparation.The relative experiments upon root resorption and repair are necessary for the exploration of the exact mechanism. Because of the irreversibility of the process, root resorption is primarily explored by retrospective clinical studies. Therefore, it is necessary to establish an animal model of root resorption/damage and repair in order to observe exactly the process and the involving factors. In most of previous studies, excessive orthodontic force was used to induce root resorption and the force was ceased until the occurrence of root resorption so as to observe the response of root reparation. However, the process of root resorption and repair is apt to be interferenced by various factors, such as modes of orthodontic force placed, force degradation and some locally non-controllable factors, so the established animal models is unstable and difficult to repeat. Objective:1. Beagle dogs’teeth are subjected to surgery expose and damage at the root surfaces or insert anchorage miniscrew implants and spin out at the root sites for the purpose of generatation of root damage and observation of repair. One of the aims of the study is to explore the better experimental animal model of root damage and repair based on the comparison of both of the above procedures.2. By the relevant measurement of anatomy regarding the Beagle dogs’teeth root, the other aim of the study is to to provide the data for the location of the insertion site of the implant in the experimental animal model of root damage and repair.Methods:Experiment I:Comparison of two experimental animal models of root damage and repair.Four experimental Beagle dogs were selected in this study to made root damage:1. Root surface exposed and damaged:There were three damaged sites in each quadrant. They were the junction of apical 1/3 and middle 1/3 on the distal root surface of canine, the junction of cervical 1/3 and middle 1/3 on the mesial root surface of canine and the middle 1/3 on the mesial root surface of the third incisor. A total of 48 sites, as 12 sites for each dog were included in this study. The mucoperiosteal incision was made near the scheduled damaged sites, the mucoperiosteal flap elevated, the root positioned, the bone removed by the ball drills, and defect made in the sites of root surface with 4.0 mm long,1.2 mm wide and 1.2 mm deep. The operation area was rinsed, and the mucoperiosteal flap was reset and sutured. 2. Root damaged by MIA implanted:There were four damaged sites in each quadrant. The teeth included left and right first, second, third and fourth premolars in maxilla and second, third, fourth premolar and first molar in mandible of each dog. In details, the damaged sites were selected at the distal surface of the mesial roots of upper second and third premolars, and lower second, third, fourth premolar and first molar. The mesial surface of the distal roots of upper fourth premolars and the distal root surface of upper first premolar (as the upper first premolar was of single root) were selected as the damaged sites. A total of 64 sites, as 16 sites for each dog were included in this study. Anchorage miniscrew implants (MIA) with 1.5 mm in diameter were inserted perpendicularly to the long axis of the teeth at the pre-designed sites at about 10 mm deep, and spinned out immediately.The situation of the root damage was evaluated by CT right after operation. Penicillin was injected intramuscularly for 1—3d to prevent infection after operation. Semi-liquid food is given in postoperative day and all soft food after that. The wound healing was observed regularly. Animals were sacrificed by excessive anesthetic 8 weeks later. Specimens of each damage site were harvested and decalcificated by EDTA for 8 to 10 weeks, then proceeded routine section, HE staining and morphological observation. The morphology of periodontal and root damage was observed and the surgical healing and cementum repair by two procedures were compared.Experiment II:The applied anatomical survey of dog’s posterior teeth as the guide for MIA implanting in the experiment of root damage and repair:Five well-developed and healthy adult Beagle dogs were selected and sacrificed by excessive anesthetic. The buccal bone of upper and lower second, third, fourth premolar (Pm2, Pm3, Pm4) and lower first molar (M1) was removed to expose their roots. The crowns of the teeth were kept intact carefully during the operation. A total of 70 teeth, as 14 teeth for each dog were included in this study. The anatomy of the each teeth was observed, and the indices such as AB (the greatest mesiodistal diameter of the crown which is perpendicular to the long axis), Dm (the distance from the point D to the mesial root surface), Dd (the distance from the point D to the distal root surface) and Df (the distance from the point D to the root furcation) of each teeth were measured and analyzed statistically.Results:Comparison of two experimental animal model of root damage:1. After 8 weeks, various repair response could be found at the root surface and defect area prepared by both of the damage procedures, the formation of new cementum and periodontal ligament reattached can be seen at the surface of root damage.2. The form of root and periodontal damage:CT showed that the shape of root defects prepared by the method of surface exposed and damaged was irregular, and the damage shadow can be seen in the surrounding tissue. The defects of root and periodontal tissue prepared by MIA implanted were uniformly round, and no significant damage was found at the surrounding tissue.3. Situation of the surgical healing:four dogs kept alive after the operation and their diet and activity is normal. The healing of surgical wound left by the method of surface exposed and damaged was delayed, and the wound was still red or swelling a week postoperatively. However, no overflow pus was found, and the wounds healed 2 weeks later. By contrast, the surgical wound prepared by the method of MIA implanted has not been found infected or pus overflow, and healed well a week postoperatively.4. Repair of cementum:The histological observation showed that the shape of periodontal defects prepared by the method of surface exposed and damaged was irregular. it was rugged on the bottom of the defect of root surface. Twenty one sites were observed repair of root damage successfully, as total 48 sites of root damage of four dogs, accounting for 43.8%. The remaining sites were left not damage at the roots or damage too deep to injure the pulp. No cementum repair was observed at some root damage. The defects of root and periodontal tissue prepared by MIA implanted was uniformly round. It appeared approximate arc on the bottom of the defect of root surface. Forty two sites were observed repair of root damage successfully, as total 64 sites of root damage of four dogs, accounting for 65.6%. A few sites were found damage just limited to alveolar bone, periodontal ligament or the pulp.The applied anatomical survey of dog’s posterior teeth that MIA implanted in the experiment of root damage and repair:1. The observation of anatomic form of the posterior teeth of Beagle dogs:the second, third, fourth premolar and first molar of upper and lower jaws had their own characteristics and morphology.2. The value of specific sites Dm, Dd, Df of the teeth on both sides with the same name had no significant difference (t values equal to 0.466,-1.871,1.763 respectively; P values equal to 0.644,0.070,0.087 respectively). The measured values of index of teeth in upper and lower jaws were normally distributing, Dd and Dm values were almost equal, the average of Df value was more than 4.0 mm.3. The interspace between the posterior tooth root of Beagle dogs was small relatively, while the interspace of root furcation area was large. This area between the furcation was relatively satisfactory for implanting MIA, and it was initially recognised that D points can be used as point of reference for MIA implanted here. During positioning MIA implantation, the author suggests that the following formula can be refered to:d=Dm (Dd)-Φ/2.Conclusion: 1. Eight weeks after operation, various repair response appeared at the root surface and defects prepared by both the method of surface exposed and damaged and the method of MIA implanted. The formation of new cementum and periodontal ligament reattached can be seen at the surface of root damage. It seems that the animal model of root damage and repair has been established successfully.2. The method of MIA imlplanted is better for the animal model of root damage and repair than the method of surface exposed and damaged.3. By achieving the quantitative measurement of real specimens of posterior tooth root of Beagle dogs, the reference point that the study selected is ideal. The location method d=Dm (Dd)-Φ/2 that based on this is more simple. It can be a meaningful reference for the establishing of the animal model of root damage and repair.更多还原