牙根发育不良病因及分子机制的研究进展

牙根发育不良（HTR）是指发生于牙齿根部的先天性发育障碍的一种疾病,国外学者称其为短根异常疾病（SRA）,乳、恒牙列均可发生,其发生通常无任何临床症状,且牙冠色泽正常,但偶有牙齿异常的松动,影像学可见诸如短锥状牙根等。该病诊断具有一定的挑战性。本文就牙根发育不良的发病因素、分子机制作一简要综述。     

ADAM28反义核酸治疗牙根发育不良疾病的实验研究

目的:探讨金属蛋白酶解离素28(ADAM28)反义核酸(AS-ODN)治疗牙根发育不良疾病(CHTR)的可行性和效果。方法:应用反义核酸技术、基因重组、动物实验和酶联免疫吸附测定(ELISA)法检测ADAM28 AS-ODN、S-ODN和真核质粒对CHTR的不同效应。结果:用药后AS-ODN组患牙松动度明显减轻,牙周袋深度显著变浅,COL-Ⅱ、IL-1β、PGE2水平均显著下降,呈现炎症愈合趋势;S-ODN组和真核质粒组各项检测结果正相反,炎症呈显著上升趋势。结论:应用ADAM28 AS-ODN(200μmol/L)可有效治疗牙根发育不良疾病,但最佳药物浓度和用药时间还需进一步探讨。     

牙根短小的临床分类及致病因素的研究进展

牙根短小在临床上并不少见,一般分为先天性和后天性两大类,先天性牙根短小是指牙根发育不良,与遗传性因素、全身性疾病、医源性因素等有关,通常是牙根发育的调控基因出了问题;后天性牙根短小通常是由损伤和刺激导致的牙根吸收造成的。严重牙根短小者可造成牙齿过早脱落,从而影响美观和功能。     

先天性多数恒牙缺失伴牙根发育不良1例

<正>1病例报告患者,女,16岁。因前牙龋坏影响美观来院就诊。面部外观:上颌骨发育不良,下颌骨颏部前突。口内检查:多数恒牙缺失,遗留牙牙冠结构异常,并伴有不同程度的龋损。遗留牙除下前牙无松动度外,其余恒牙都有不同程度的松动,前牙反牙合。口腔黏膜正常,牙周组织未见异常。全口牙位曲面体层片示:上下颌第三磨牙、第二磨牙;下颌第二前磨牙;     

先天性牙根发育不良致病相关基因的筛选

目的:筛选先天性牙根发育不良的致病相关基因.方法:采用改良消减杂交技术,以先天性牙根发育不良患儿及其正常兄弟为研究对象,制备血液基因表达cDNA文库,构建两者的差异表达文库,采用反向点杂交技术剔除假性克隆,挑取部分克隆进行定性测序.结果:构建的差异表达基因文库浓度为4.0×102,反向点杂交检测发现基因文库质量较好:获得了11个与先天性牙根发育不良疾病相关的基因克隆.结论:成功构建了先天性牙根发育不良致病相关基因的消减cDNA文库,推测筛选出的ADAM28和MCPR1可能是牙根发育不良的致病相关基因.     

3例牙根发育不良患儿牙齿的病理学评估

目的：收集并检测3例牙根发育不良患儿的脱落牙齿，探讨该疾病的病理学表现。方法：采用X线透射和电镜检测，以及用HE染色和改良Mallor三色法染色观察患儿脱落牙齿标本，并分析其病理学变化进而对疾病进行定性诊断，初步筛选致病相关基因。结果：3例牙根发育不良患儿脱落牙齿分别展现不同的病理学变化。结论：本研究发现的3种不同临床表型的牙根发育不良患儿病理学诊断分别为牙根发育不良疾病、牙齿型低碱性磷酸酯酶症疾病和一种新型的综合征，进而按照功能克隆策略初步筛选ALPL、EDA基因为致病候选相关基因。     

全口牙根短小1例报道

患者,女,23岁。因感觉前牙渐松动外突,影响美观就诊。幼时乳恒牙萌出及替换基本正常,无牙外伤及牙体治疗史,否认家族性遗传病史。自述父亲牙齿略不整齐,没有脱落;母亲在30岁左右大多数牙齿均已脱落,原因不明。     

3例中国牙根发育不良患儿的临床、实验室检查及分析

目的：收集、观察3例牙根发育不良患儿,探讨该疾病的实质病因。方法：采用临床、实验室检查方法对3例患儿进行详细的体检,并分析导致出现牙根发育不良表型的遗传学因素。结果：3例牙根发育不良患儿分别诊断为：病例1为一种新表型的牙根发育缺陷的低碱性磷酸酯酶症;病例2为儿童型低碱性磷酸酯酶症;病例3为一种新表型的综合征。结论：本研究发现的3种不同临床表型的牙根发育不良疾病初步认为可能是基因突变导致的遗传性疾病或发育异常疾病。     

1例先天性牙根发育不良患儿致病基因的筛选及突变分析

目的:收集及分析1例先天性牙根发育不良病例,探讨该疾病的实质病因.方法:采用临床、实验室检查和遗传学方法对患儿进行临床病理诊断及致病基因筛选,并通过基因测序方法探寻其突变位点.结果:该例牙根发育不良患儿诊断为伴发短根症的低碱性磷酸酯酶症,筛选致病候选基因为ALPL基因,基因突变型为583G＞A,R136H.结论:该例牙根发育不良病例初步认为是ALPL基因突变导致的遗传性疾病.     

牙根纵裂的病因学研究

牙根纵裂 ,是指发生于牙根的从根管延伸到牙周膜的纵向折裂 ,是一种病因复杂的非龋性牙体病。虽然其发病率不高 ,但因为目前对其诊断还有一定困难 ,且预后不佳 ,所以近年对其病因学方面的研究日益增多。本文综合国内外文献报道 ,对牙根纵裂的病因学研究进行综述。1　医源性因素是最常见的致病原因。最常累及进行过牙髓治疗的无髓牙[1] 。Ｍｏｒｆｉｓ(1990 )检查了 4 6 0个由其本人进行牙髓治疗后修复并壳冠保护 ,行使功能 3年以上的患牙 ,牙根纵裂发生率达 3.6 9% [2 ] 。其内因 :一是无髓牙牙体硬组织脱水 ,牙齿结构变脆 ;二是根管预备时…     

牙根发育不全疾病致病差异表达基因文库的建立

目的：建立先天性牙根发育不全疾病患儿与其正常兄弟间致病差异表达基因的cDNA文库。方法：采用改良消减杂交技术，以先天性牙根发育不全疾病患儿与其正常兄弟外周静脉血的总mRNA为对比材料，筛选出候选相关致病基因差异表达的cDNA，将其与pGEM-T载体进行T／A连接构建文库，然后转化高效感受态大肠杆菌进行文库扩增，随机挑取100个白色克隆进行酶切鉴定。结果：扩增消减cDNA文库获得400余个白色阳性克隆，随机挑取的100个白色克隆经酶切后90％有插入片段。结论：用改良消减杂交技术成功构建了先天性牙根发育不全疾病致病差异表达基因的消减cDNA文库，该文库的建立为进一步筛选、克隆该疾病的候选致病相关基因奠定了基础。     

The external and internal anatomy of human mandibular canine teeth with two roots

Abstract— This study investigated the internal anatomy of 65 human mandibular canines with two well-defined roots. The teeth were decalcified and injected with gelatin coloured with india ink. Diaphanization was carried out using clear resin to allow permanent preservation. It was found that all mandibular canines with two roots had two root canals. Lateral canals were found in 68.9% of teeth and 19.7% had lateral canals at the bifurcation. The results of the external measurements (cusp tip to root apex) showed that the average buccal root length was 23.0 mm and the average lingual root length was 22.7 mm. The maximum and minimum buccal lengths were 26.7 mm and 17.9 mm respectively and the maximum and minimum lingual lengths were 27.2 mm and 17.1 mm respectively. The buccal root was the larger of the two in 47.7% of teeth and 43.1% had roots of equal size. The lingual root was larger than the buccal root in 9.2% of cases. Clinicians should be aware of the anatomical variation that exists for mandibular canines.     

Mineralization defects of primary teeth in children born pre-term

abstract — Investigation of 82 2- to 3-year-old children born pre-term and 39 healthy full-term controls showed that enamel mineralization defects were significantly more common in the pre-term group than among the controls. Pre-term delivery per se does not seem to be the direct cause of enamel mineralization defects, but rather it seems that common complications such as asphyxia and/or hyperbilirubinemia explain the increased incidence in children born pre-term.     

Enamel changes in permanent teeth after trauma to their primary predecessors

abstract – The frequency of developmental disturbances in the permanent dentition due to traumatic injuries to primary teeth was examined in a Danish population sample consisting of 487 schoolchildren 9–17 years old. Of these children, 147 (30%) had a history of traumatic injuries to the primary dentition. Frequencies of 57.8% and 45.3% of developmental disturbances were found in the trauma and in the non-trauma group, respectively. The folloing types of developmental disturbances were more frequent in the trauma group than in the non-trauma group: (1) internal white enamel hypoplasia with a diameter of 0.5 mm or more, (2) internal and external white and yellow-brown enamel hypoplasia, (3) white and yellow-brown enamel hypoplasia and horizontal enamel hypoplasia. Internal white enamel hypoplasia with a diameter of less than 0.5 mm, and generalized internal and external white enamel hypoplasias were found with the same frequency in the two groups. About 10% of enamel hypoplasias in anterior teeth are due to trauma.     

内镜辅助取出下颌骨舌侧软组织间隙内残留牙根

目的：探讨内镜辅助取出下颌骨舌侧软组织间隙内残留牙根的可行性。方法：对5例因行下颌智牙拔除术致残根落入下颌骨舌侧软组织间隙内的病例,利用Karl Storz-Endoskope内镜系统辅助行下颌骨舌侧软组织间隙内残留牙根取出术。结果：残留于下颌骨舌侧软组织间隙内的牙根均在内镜辅助下顺利取出,平均用时约12min,手术过程顺利。术后均无严重并发症。结论：相对于传统手术方法,通过内镜辅助行下颌骨舌侧软组织间隙内残留牙根取出术具有损伤小、安全、快速等优点,值得临床推广应用。     

Mechanical properties across hypomineralized/hypoplastic enamel of first permanent molar teeth

The aims of the present study were to investigate the mechanical properties of first permanent molars affected with enamel hypomineralization or hypoplasia, and to describe the appearance of these lesions under scanning electron microscopy. Eight first permanent molar test teeth and two unaffected premolars (controls) were enclosed in resin, then sectioned axially and polished. The hardness and modulus of elasticity was determined from a single array of indentations made parallel to the amelo-dentinal junction using an Ultra-Micro-Indentation system. The teeth were then examined using the scanning electron microscope. The mechanical properties of the test teeth in the unaffected cervical region (hardness and modulus range, 2.03-4.99 GPa and 50.39-96.87 GPa, respectively) were similar to those of the control enamel (hardness and modulus range, 2.71-4.15 GPa and 62.06-95.77 GPa, respectively). Between the unaffected cervical enamel and the hypomineralized region there was a transitional area of 500-600 microm where the mechanical properties in the experimental teeth decreased linearly. The mechanical properties of the hypomineralized region of each experimental tooth were significantly lower than those of the control or cervical regions (hardness and modulus range, 0.07-1.74 GPa and 3.26-40.96 GPa, respectively). The scanning electron microscopy views revealed disorganized enamel with poorly demarcated prism boundaries in the affected regions. In conclusion, the hardness and modulus of elasticity of hypomineralized enamel in first permanent molars is significantly less than in unaffected areas of the same tooth. The reason for this is unclear but may be related to the lack of organization of the enamel crystals.