Dkk-Wnt信号通路在牙齿发育中作用的研究进展

哺乳动物的牙齿发育是外胚层上皮与间充质间相互调控和信号交流的结果,其中Dkk-Wnt信号通路是近年来牙胚发育研究领域的热点。Dkk-Wnt信号通路已被证实在牙体形成细胞功能的发挥、牙齿模式化、形态发生、牙冠钙化过程中扮演重要作用。牙齿发生发育分子机制的深入研究,将为牙再生组织工程技术以及相关技术的临床转化提供理论基础。本文就近十年对Wnt信号通路在牙齿发育中所起作用的研究作一综述。     

Yes相关蛋白基因在牙发育中的作用

牙发育过程,包括胚胎早期预定成牙部位到发育形成完整的牙及牙周组织的发育成熟,是一个复杂的连续过程。牙发育实际上是牙源性上皮与脑神经嵴来源的牙源性间充质之间相互作用的结果,这一过程受到诸多信号的影响。Yes相关蛋白基因（YAP）是Hippo通路中的靶基因,在牙胚发育的初始阶段,可在不同部位检测到其表达。Hippo-YAP信号通路通过抑制YAP的活性,调控细胞增生和程序性细胞死亡间的平衡,从而调控器官的大小。本文就Hippo-YAP信号通路和YAP在牙发育过程中的表达等研究进展作一综述。     

Wnt信号通路与牙胚发育

牙齿的发生、分化是牙源性上皮与外胚间充质相互诱导、相互作用的结果。牙胚发育过程中复杂的信号调控体系是近年来口腔科学研究领域的难点和热点。现已初步证实Wnt信号通路是参与牙胚发育过程重要的分子信号调控因子。在牙胚发育过程中,随着Wnt信号通路调控机制的阐明,必将为牙再生的研究提供理论基础。该文就近几年对Wnt信号通路与牙胚发育关系的研究作一综述。     

初级纤毛在牙发育中的分布及相关信号通路的研究进展

初级纤毛是位于大多数哺乳动物细胞表面,感受外环境刺激并传导信息的一种细胞器,在组织发育过程中参与调控各种信号通路。本文就初级纤毛在牙发育中的分布及相关信号通路的研究进展作一综述。文献复习结果表明,在牙发育过程中,初级纤毛在上皮与间充质的相互诱导中发挥重要作用,且随细胞不断增殖分化,初级纤毛的分布呈现出时间和空间依赖性。尽管此分布特征的原因尚不明确,但部分实验证据表明其与初级纤毛所分布的细胞与组织的功能相适应。初级纤毛在牙发育过程中主要参与调控Hedgehog和Wnt两种重要的信号通路,编码纤毛蛋白的基因(如Kif3a、Evc/Evc2和Ift等)可通过对这两种信号通路的调控来影响牙齿的发育,并且两种信号通路之间存在交互作用。相关基因(如Ofd1,Bbs等)的缺失也可通过损害纤毛的结构或功能破坏上下游信号的传导,引起多种类型的牙齿发育不良,包括小牙、釉质发育不全、牙齿缺失或颅面部畸形。     

初级纤毛对牙发育的作用及相关机制的研究进展

初级纤毛是哺乳动物细胞表面特化的细胞突起,其内部存在大量调控细胞生命活动的信号分子,参与构成细胞内的信息传递系统。近年来研究发现,牙组织细胞有纤毛存在,并且纤毛病患者可同时伴有牙齿发育异常表现。说明细胞纤毛可能参与牙发育过程。本文旨在将近年来国内外有关初级纤毛在牙齿发育中的功能及作用机制研究进展作一综述,阐示细胞纤毛中信号分子的功能及作用通路,拓展对牙发育机制的了解。     

几种牙源性肿瘤及其相关病损的临床与病理研究现状

颌骨是人类骨骼中最好发上皮性囊肿和肿瘤的部位,这是由于牙和牙发育与颌骨关系密切,颌骨内的成牙组织常可作为囊肿和肿瘤的组织来源.这类多发于颌骨内的牙源性病损好发于年轻人,可造成颌骨及邻近软组织的破坏,导致口腔颌面部外形改变;某些侵袭性病损具有较高的复发倾向,可对患者的生存质量及心理健康造成严重影响.由于其发生与颌骨和牙的发育关系密切,故在发病过程、临床病理表现以及生物学行为等方面均具特殊性,是口腔颌面部特有的一类肿瘤.     

牙源性肿瘤的WHO(2005)新分类

由于牙源性肿瘤的发生与颌骨和牙发育关系密切,故在其发病、临床病理表现以及生物学行为等方面均具特殊性,是口腔颌面部特有的一类肿瘤,一直备受关注。上世纪40年代以前,几乎所有的牙源性肿瘤被统称为“牙瘤（odontome）”。1946年,Thoma和Goldmann按组织来源将牙源性肿瘤分为上皮性、间叶性和混合性三类,取消了笼统“牙瘤”的概念。基于牙源性肿瘤中可能存在类似于牙发育过程中上皮和间叶组织之间的相互诱导作用,     

报告基因及其在牙发育和牙再生研究中的应用

报告基因可通过基因产物的表达来"报告"目的 基因的表达调控,是细胞和组织内监测基因表达与蛋白定位的理想标记.报告基因种类多样,可根据不同需要选择应用.报告基因广泛用于牙发育及牙再生机制的研究,包括研究基因表达和调控、作为基因转染对照、细胞分化和定位的示踪等.为揭示牙发育的启动、细胞分化和形态调控各阶段的分子机制,探索牙组织工程与牙再生的有效方法 提供了较好的研究平台.     

控制间充质干细胞牙向分化功能是促进牙齿组织再生的关键

牙齿组织缺损、缺失是人类的常见病、多发病,严重影响患者的咀嚼、言语、消化等口颌功能和身心健康。现有的牙齿组织缺失修复方法属于非生物性的修复,难以完全恢复天然牙的结构与功能。随着生物技术的发展,利用间充质干细胞结合组织工程技术再生牙齿组织是牙齿组织生物性再生修复研究的前沿及关键课题。但目前在牙齿组织再生过程中,间充质干细胞如何进行牙向分化,其功能、调控作用与机制仍未完全明确,限制了其研究及临床转化应用。因此,阐明间充质干细胞牙向分化功能及调控是促进间充质干细胞介导的牙齿组织再生的关键,具有重要的科学意义及临床应用价值。     

孕期健康和环境暴露对牙发育的影响

牙发育是复杂信号网络调控的牙源性上皮和神经嵴来源牙源性间充质之间交互作用的结果,遗传因素及环境因素在此过程中均发挥重要作用。母体是胎儿生长发育的主要载体,孕期母体健康和环境暴露对胎儿和儿童牙发育具有较大影响。本文根据不同类型的孕期母体环境因素,重点从环境内分泌干扰物、多种化学物质的联合作用及母体健康等三个方面对胎儿和儿童牙发育的关键问题进行综述,探讨了孕期环境因素在釉质发育缺陷、磨牙切牙矿化不全、氟牙症、多生牙及先天性缺牙等牙发育异常中的作用,为从生命早期预防牙发育异常、评估牙发育异常风险、进行牙发育相关咨询、促进儿童口腔健康管理提供理论依据。     

牙齿再生研究的现状和展望

牙齿再生为临床牙齿缺失的修复开辟了新的途径，而研究牙齿再生的前提是必须明确牙齿自然发育过程本文在简述牙齿形成的基本模式基础上，对，才齿再生研究的现状和展望作一综述。     

不同时期大鼠牙齿胚基各部分组织发育能力的研究

目的：比较不同发育时期牙胚各部分异位环境下的发育能力,为牙齿再生重组实验提供参考。方法：分离获取SD大鼠帽状期和钟状末期牙胚,分离成釉上皮与牙乳头间充质,分别将完整牙胚、牙间充质、成釉上皮剪碎后异位移植至同种异体大鼠肾被膜下。4周后取材,对移植物进行组织学观察。结果：帽状期牙胚碎组织块移植物中可见部分不规则的牙齿样结构形成。钟状末期牙问充质碎组织块移植组中既有牙本质牙髓复合体样结构形成,还能观察到大量骨样基质形成。而钟状末期成釉上皮碎组织块移植物生成的组织均为骨样的结构。结论：发育早期牙胚的碎组织较发育末期的牙胚碎组织具有更强的牙齿形成能力,所形成的牙齿结构完整包括釉质、牙本质以及牙髓且顺序正确,提示这个时期牙上皮和间充质之间信号网络所提供的微环境可以更加完善和充分地指导牙齿的发育。     

Patterns of tooth agenesis in patients with orofacial clefts

Orofacial clefts are a common oral disorder associated with tooth agenesis. As information on the simultaneous absence of teeth can be an aid in treatment planning, a large sample of orofacial cleft patients was examined. The sample consisted of 910 patients with cleft lip and palate. Tooth agenesis was assessed on the basis of at least two panoramic radiographs and patient records. Third‐molar agenesis was determined in 474 patients. Patterns of tooth agenesis were analysed using Tooth Agenesis Code (TAC) values, according to van Wijk & Tan . Per quadrant, at least 90% of patients could be described according to three different patterns. In the maxilla, 85% of patients with tooth agenesis had a TAC‐value of 2, 16, or 18 on either the left side, right side or bilaterally. In the mandible, 90% of patients with tooth agenesis had a TAC‐value of 16, 1 or 2 on either the left side, right side or bilaterally. In patients with tooth agenesis, patterns were symmetrical in the maxilla in 18.8% and in the mandible in 51%. More extended cleft types were associated with a higher prevalence of tooth agenesis. Third‐molar agenesis (prevalence = 22.4%) was significantly related to the prevalence of other absent teeth. These results show which patterns of tooth agenesis can be expected to occur in most orofacial cleft patients.     

Tooth survivial in institutionalized elderly Cape Coloreds from the Cape Peninsula of South Africa

An investigation has been conducted in order to assess the oral health status and need for dental treatment among Cape Coloreds resident in homes for the aged in the Cape Peninsula of South Africa. Tooth loss was greater in females than in males (P less than 0.002) but a statistically significantly greater proportion of surviving teeth were grossly carious in men than in women (P less than 0.002). More teeth had survived in the mandible than in the maxilla (P less than 0.002) and proportionately more teeth were grossly carious in the maxilla than in the mandible (P less than 0.002). The distribution pattern of the remaining dentition according to tooth type was similar for both jaws, the canines being the most persistent teeth.     

Preservation of ridge dimensions following grafting with coral granules of 48 post-traumatic and post-extraction dento-alveolar defects

Abstract – This prospective clinical analysis reports on the use of coral granules in alveolar ridge preservation procedures in a population of young, growing patients. The sample consisted of 21 patients, 12 females and 9 males, with a mean age of 13.6 years. These 21 patients had 48 dento‐alveolar defects suitable for augmentation with coral granules, and were followed clinically and radiographically for 3–7 years after augmentation. There were two areas of augmentation: 17 defects in the anterior maxilla resulted from traumatic tooth loss, and 31 defects in the posterior maxilla and mandible resulted from the extraction of ankylosed retained primary molars with no permanent succedaneous teeth. Between 1–2 ml of coral granules were implanted into the alveolar bone defects left by the extraction of teeth in both the areas. This was in order to preserve the remaining edentulous ridge from further alveolar ridge resorption. The goal of the procedure was to preserve the alveolus so that in the future, a dental implant could be placed to replace the missing tooth, after jaw growth had stopped, without the need for a bone graft. The coral granules appeared to be totally replaced by the host bone on follow‐up clinical and radiographic examinations. The two areas of the jaws behaved quite differently. In the anterior maxilla, where tooth loss was secondary to trauma, the coral granules restored the alveolar ridges temporarily. However, over the years of follow‐up in this study, the coral granules failed to provide sufficient bone to support the placement of a dental implant without using a bone graft in 14 of the 17 defects or 82.4% of sites. In the posterior maxilla and mandible, where tooth loss was due to the elective removal of ankylosed primary molars, 29 of the 31 defects or 93.5% of sites were successful as they were able to support the placement of an osseo‐integrated dental implant without the use of a bone graft. The alveolar sparing technique was more successful in maintaining an alveolar ridge sufficient for the placement of a dental implant without bone grafting in the posterior maxilla and mandible, where tooth loss was secondary to the elective removal of ankylosed deciduous molars than in the anterior maxilla, where tooth loss was secondary to trauma. Coral granules seem to be more suitable in the posterior maxilla and mandible where there were ankylosed deciduous teeth and congenitally absent permanent teeth than in the traumatized anterior maxilla. In successful sites, coral granules can spare the alveolus from residual ridge atrophy or resorption, obviating the need for a bone graft. This reduces patient morbidity, as a second surgical donor site is avoided because bone graft harvesting is made unnecessary.     

Agenesis of permanent incisors in a mediaeval maxilla and mandible: aetiological aspects

A paleopathological maxilla and mandible with tooth agenesis were analyzed, focussing on the aetiology of the condition. The jaw material, derived from an adult mediaeval male, was examined by standard anthropological analyses, including radiography. In the maxilla there was agenesis of three permanent incisors and one premolar, and in the mandible of one permanent incisor and two permanent molars. Absence or marked reduction of the incisive foramen and the nasopalatine canal was found. The pattern of tooth agenesis was similar to the pattern observed in contemporary individuals, except for the agenesis of one permanent maxillary centreal insisor. It is suggested that the pronounced lack of the premaxillary area of the nasopalatine canals and the incisive foramen. As the condition can be ascribed to deviations in the prenatal developments, this investigation shows that embryological developmental patterns, which form the basis for the pattern of tooth agenesis, should be taken into account when evaluation dry bonde patholgy.     

New standards for permanent tooth emergence in Australian children

BACKGROUND: Published standards for permanent tooth emergence in Australian children are 40 years old. The aim of this study was to present new data on the timing and sequence of permanent tooth emergence in a large sample of Australian children and to compare the findings with those of earlier studies. METHODS: Records of a randomly selected sample of 8676 children, aged between 4 to 16 years, who had attended the clinics of the South Australian Dental Service were scanned optically and coded to provide the data for this study. A logistic regression analysis enabled median times of emergence, together with percentile ranges, to be calculated for each tooth, except third molars, in boys and girls. Comparisons were made between the sexes and with previously published values. The frequencies of occurrence of emergence polymorphisms for different tooth pairs were also computed. RESULTS: The earliest teeth to emerge in both boys and girls were the central incisors and first molars, whereas the second premolars and molars and maxillary canines tended to be last to emerge. The mandibular teeth tended to precede the corresponding maxillary teeth in emergence in both sexes. Tooth emergence was advanced in girls compared with boys, averaging 4.5 months in the maxilla and 5.3 months in the mandible. In general, emergence times of children in the present sample were later than those reported previously for Australian children. The most common emergence polymorphism in the maxilla involved the canine and second premolar, whereas common polymorphisms in the mandible were noted for the central incisor and first molar, canine and first premolar, and the second premolar and second molar. CONCLUSIONS: Given that they have been collected relatively recently from a large sample of children, the new data reported in this paper can now be used as standards when assessing permanent tooth emergence of Australian children.