口腔组织病理学03牙本质ppt课件

3/26/2019,1,Chapter 3 Dentin,主 讲 沈 丽 佳,Oral Histology & Embryology,3/26/2019,2,Pulp-dentinal complex-Dentine,I. Physical and Chemical properties II. Histological structure III. Innervation IV. Biological properties V. Clinical consideration Discussion,3/26/2019,3,I. Physical and chemical properties,Distribution of dentine Physical properties Chemical properties Comparative anatomy,3/26/2019,4,The distribution of dentine,3/26/2019,5,I. Physical and chemical properties,与骨的相似之处 与骨的不同之处,外加性生长 羟基磷灰石晶体大小相似 含有细胞突起的小管 存在含细胞外液的间隙 均有矿化机质小泡及胶性有机基质,牙本质内无血管 骨组织内富含细胞 胞体及突起,而牙本质内只有突起无胞体,3/26/2019,6,Physical properties of dentine,牙本质呈浅黄色,具有一定的弹性。 牙本质硬度平均68 KHN。 牙本质还具有丝绢状光泽，由于有牙本质小管存在，具有较高的透射度与通透性。,3/26/2019,7, Dentine is pale yellow in color It is harder than bone and cementum but softer and less brittle than enamel Dentine has greater compressive and tensile strengths than enamel Regional variations in tubule size and density are reflected in differences in permeability,Physical properties of dentine:,3/26/2019,8,Chemical composition of dentine:,by weight(%) by volume(%) Inorganic material 70% 45% Organic material 20% 33% Water 10% 22%,3/26/2019,9,Phosphoproteins -carboxyglutamate-containing proteins Acidic glycoproteins Plasma proteins,Other non-collagenous proteins in calcified dentine include:,3/26/2019,10,Chemical properties of dentine:,The non-mineral component is much higher than in enamel The principal inorganic component is hydroxyapatite, the crystals are smaller than those of enamel The main organic component is type I collagen with proteoglycans (dentin sialophosphoproteins, dentin matrix protein 1, glycosaminoglycans )between the fibers.,3/26/2019,11,Chemical properties of dentine:,无机物为羟基磷灰石晶体，但比釉质内的晶体小，还有少量磷酸盐、碳酸盐和硫酸盐。此外还有一些微量元素如：氟、铜、锌、铁。 有机成分中，胶原蛋白主要是I型胶原（约占18%)及牙本质基质蛋白、胺基多糖等。,3/26/2019,12,II. Histological structure,Regional differentiation of dentine: Mantle dentin (crown) Hyaline layer (root) Circumpulpal dentin Predentin,3/26/2019,13,Regional differentiation of dentine:,Primary dentin and secondary dentin (regular secondary dentine) Reparative dentin or irregular secondary dentine, (tertiary dentin , reaction dentin) osteodentine Transparent dentin (sclerotic dentin),3/26/2019,14,II. Histological structure,1. Dentinal tubules 2. Odontoblastic processes 3. Peritubular dentin 4. Intertubular dentin 5. Incremental lines 6. Globular dentin and interglobular dentin 7. Tomes granular layer,3/26/2019,15,Mantle dentine Ground section,The mantle dentine is a thin layer approximately 15-20m wide;it is the first dentine formed. The main distinguishing feature of the mantle dentine is the orientation of a large proportion of its collagen fibers (Korff fibers) perpendicular to the enamel-dentine junction.,16,Enamel-dentine junction in the cervical region, shown in polarized light Ground section 50,Mantle dentine appears as the orange layer immediately beneath the enamel-dentine junction. The use of polarized light allows a visible distinction to be made between the mantle dentine and the circumpulpal dentine, which here appears blue and the fibers in it are mainly parallel to the enamel-dentine junction.,17,Root dentine showing the granular(A) and hyaline layers(C).,The granular and hyaline layers in polarized light. Cementum (B),Ground section 160,18,3/26/2019,19, The hyaline layer is the clear and relatively structureless which is approximately 5-10m wide. Sometime the hyaline layer may be difficult to distinguish from the adjoining layer of acellular cementum. But in polarized light, the hyaline layer is sharply demarcated from the overlying acellular cementum. its purple color indicates a lack of birefringence due to the mixed orientation of its fibers.,19,3/26/2019,20,Decalcified section;H&E 3,Circumpulpal dentine The bulk of the dentine , termed circumpulpal dentine, differs in terms of structure and composition from the outer dentine lining and the innermost dentine lining.,3/26/2019,21,Decalcified section of the pulp and dentine;H 200, The innermost, uncalcified layer of dentin lining the pulp is termed the predentine. The width of predentine varies from 10-12m. Its thickness varies according to the rate of dentine formation, being thick in young teeth where dentine forms rapidly.,21,3/26/2019,22,Decalcified section of pulp and inner regions of dentin H&E 500,The border between the circumpulpal dentine and predentine is the mineralizing front, predentine being unmineralized. The predentine layer is always present.,A: odontoblasts B: circumpulpal dentine C: predentine,22,3/26/2019,23, The term primary dentine is used to describe the first formed dentine which produces the typical form of the tooth. Secondary dentine is deposited during the later functional life of the tooth inside the primary dentine. Secondary dentine may be subdivided into regular and irregular varieties, depending upon its structure.,23,3/26/2019,24,Regular secondary dentine may not be easily distinguished from primary dentine. There are usually fewer tubules in secondary dentine. There is often a sudden change in tubule direction from that taken by the tubules of primary dentine ,thus forming a pronounced contour line. The color differences illustrate the change in direction of the matrix and tubules from primary to secondary dentine.,Ground section 80, ( R) in polarized light Primary dentine(A) and regular secondary dentine(B),24,Decalcified section of dentine,Silver stain; 32 The contour line of Owen (arrowed) separating the primary (A) and secondary dentine (B),1. Dentinal tubules Summary: General condition of the dentinal tubules:,牙本质小管 髓 腔 端 釉 质 端 数目 30,0007,500条/mm2 1,500条/mm2 管径 34 m 1 m 分支小管 较少 1m 较多 1 m 形弯曲 突面朝向牙根 突面朝向牙冠 管壁厚度 400 nm 750 nm,26,3/26/2019,27,The dentinal tubules,Ground,longitu-dinal section; 25,Dentine is permeated by tubules which run from the pulpal surface towards the enamel-dentine junctions. The tubules taper from about 4m in diameter at their pulpal ends to 1 m or less peripherally.,27,3/26/2019,28,The tubules follow a curved , sigmoid course-the primary curvatures. The convexity of the primary curvatures nearest the pulp chamber faces rootward. In the root and beneath the cusps, the primary curvatures are less pronounced, the tubules running a straighter course.,28,3/26/2019,29,The dentinal tubules Ground section; 320,The tubules also show smaller changes in direction every few micrometres (m ) the secondary curvatures. Where these secondary curvatures coincide in direction, they produce the appearance of a line crossing the dentine-a contour line of Owen.,P11 P14,29,3/26/2019,30,Dentinal tubules in regular secondary dentine. Ground section; 125,primary,secondary,30,3/26/2019,31,The walls of the dentinal tubules SEM; 1,750,In predentine, the wall of a tubule consists of collagen fibers embedded in organic matrix with a thin, amorphous layer on the pulpal surface. In calcified dentine, an apparently proteinaceous membrane (the lamina limitans) overlies the mineralized collagen.,P12,31,3/26/2019,32,Branching of the dentinal tubules near the enamel-dentin junction (Ground section; Picrothionin 320,The dentinal tubules are not single discrete tubes running through the dentine,but give off narrow branches along their course.,32,3/26/2019,33,Transverse ground section showing dentinal tubules. Partially demineralized and stained with eosin; 1,500,A: The dentinal tubules B: Intertubular dentine C: Peritubular dentine,33,3/26/2019,34,Transverse decalcified section of dentinal tubules,Harris heamatoxylin; 1,000,Compared with ground section,tow basic differences are seen in a decalcified transverse section through the tubules. An odontoblast process may be seen within the lumen of the tubule, and the peritubular dentine is lost so that the lumen of the tubule appears larger.,34,3/26/2019,35,Dentinal tubules in peripheral dentine.,TEM; 8,000,35,In the inner third of calcified dentine, a variety of intratubu- lar appearances are seen. Some tubules clearly contain cell processes, others are apparently empty and others contain non-cellular material.,TEM; 3,000,Dentinal tubules in intermediate dentine.,36,3/26/2019,37,TEM; 10,000,Dentinal tubules in inner calcified dentine.,All tubules in inner dentine are occupied by odontoblast processes and most of the tubules also contain sensory nerve terminals.,37,3/26/2019,38,2. Odontoblastic processes,（1）光镜结构： （2）电镜结构： 在胞浆突起内，胞浆较少，细胞器也较少，主要为微管（Microtubules）、微丝 （filaments）、线粒体 （Mitochondria）致密小体 （densebodies）、包裹小泡。前期牙本质处的胞突可见有线粒体，但无核糖体和内质网,Each dentinal tubule is occupied by a protoplasmatic extension of the odontoblast cell of the pulp the odontoblast process. It is bounded by a cell membrane. In calcified dentine, the process contains micro-tubules, microfilaments and vesicles responsible for the transport and discharge of materials into the periodontoblastic space.,39,The process occupies the full length of the tubule during the early stages It remains along the full length of the tubule It reaches a predetermined ,finite length and retreats bodily It shortens at its distal end, becoming incorporated into the matrix of the peritubular dentine.,The odontoblast process in the maturing tooth. There are three possible fates for the odontoblastic process.,40,3/26/2019,41,The odontoblast process in transverse section. TEM; 80,000,Many of the elements included in the preceding diagram are found in this process, sectioned here in the unmineralised predentine, including microtubules, microfilaments, vesicles and mitochondria.,38,3/26/2019,42,3. Peritubular dentin,管周牙本质是围绕成牙本质细胞突起周围的一层钙化度较高的牙本质, 构成小管的管壁。 管周牙本质可连续缓慢地外加性生长，使管腔直径减小。 管周牙本质的沉积、小管矿化形成硬化牙本质。,3/26/2019,43,A,B,Peritubular dentine(A) can be distinguished from intertubular dentine (B) as a zone of increased electron density lining the internal surface of the dentine tubule.,Demineralized section; TEM 6,000,43,The relationship between peritubular dentine formation and tubule diameter at various levels within the dentine. A: Near the EDJ the tubule may be filled or nearly filled with peritubular dentine. B: Towards the middle of the dentine a distinctive zone of peritubular dentine is seen. C: Near the pulp where the tubule is newly formed,there may be little or no peritubular dentine.,A,B,C,44,3/26/2019,45,A: Near the EDJ. SEM; 1,200,45,B: Middle of the dentine.SEM; 1,200,Neumann sheath,P14,46,3/26/2019,47,C: Near the pulp. SEM; 540,47,3/26/2019,48,4. Intertubular dentin,管间牙本质是位于牙本质小管之间的牙本质基质，是成牙本质细胞的分泌产物。 钙化程度较管周牙本质低，含有较多有机物质。 胶原纤维较多主要为I 型胶原蛋白。,3/26/2019,49,Intertubular dentine,49,3/26/2019,50,Intertubular dentine, collagen type I, SEM,50,3/26/2019,51,5. Incremental lines,Incremental line; Incremental zone Major incremental line (Owen line) Minor incremental line (Von Ebner) Neonatal line,3/26/2019,52,The contour lines of Owen (arrowed) Ground section,polarized light; 120,The most consistent Owens line is seen at the junction of the primary and secondary dentine.,52,3/26/2019,53,Von Ebners lines -Incremental line,Ground section 12,The Ebners lines run at right angles to the dentinal tubules and are approximately 20m apart. Dentine matrix is laid down at a rate of 4m per day. With each increment, the orientation of the deposited collagen fibers changes slightly.,53,3/26/2019,54,Mineralizing lines,(A) periodontal ligament (B) Pulp Decalcified ,transverse section of root dentine. H&E 80,Mineralizing lines are incremental lines due to variations in mineralization. They may be seen microradiographically in ground section,and in demineralized sections with certain stains.,54,3/26/2019,55,Neonatal lines(arrowed) in dentine and enamel.,In the deciduous teeth and the first permanent molar, an accentuated incremental line is seen separating the pre-(A) and postnatally formed dentine(B).,51,3/26/2019,56,6. Globular dentin and interglobular dentin,The mineral in dentine is laid down in the form of globules, the calcospherites. There the calcospherites do not completely fuse, hypocalcified areas between the globules occur. Interglobular dentine may persist in mature dentine(particularly in the coronal, circumpulpal dentine close to the enamel-dentin junction.,3/26/2019,57,Globular and interglobular dentine,57,3/26/2019,58,Interglobular dentine (arrowed),58,3/26/2019,59,Note that dentine tubules are not interrupted by the interglobular areas but pass through them.,59,3/26/2019,60,7. Tomes granular layer,The granular layer is seen as a thin, dark, granular region just beneath the cementum. It lying along the whole length of the root. It is hypomineralized compared with the circumpulpal dentine. This layer is not seen in demineraized sections.,3/26/2019,61,Granular layer,3/26/2019,62,3/26/2019,63,III. Innervation,解释牙本质感觉的三种学说： A/ 外界刺激直接刺激牙本质小管内的神经末梢，传递至中枢。(神经传导学说 direct innervation theory) B/ 外界刺激使成牙本质细胞胞浆突发生组织化学变化，使小管内液体流动，刺激了牙髓中的感受器。（液体动力学说 hydrodynamic theory) C/ 成牙本质细胞本身作为感受器与牙髓神经相连接，传导痛觉。（传导学说 transduction theory),3/26/2019,64,64,Sensory mechanisms in dentine: A stimuli applied to dentine cause fluid movement through the tubules, and this movement is sufficient to depolarize nerve endings in the inner parts of tubules,at the pulp-predentine junction and in the sub-odontoblastic neural plexus. B heat, osmotic pressure and drying would tend to cause fluid movement outwards. C cold would cause movement inwards.,65,3/26/2019,66,The position of nerve endings in dentine is demonstrated by the black silver grains.,A,B,C,A: sub- odontoblastic plexus B: odontobalst layer C: tubules in the inner circumpulpal dentin,66,3/26/2019,67,Sensory nerves terminating in the dentine tubules. TEM; 70,000,It shows a single tubule containing both an odontoblastic process(B) and a sensory nerve terminal(A),67,IV. Biological properties,1. Metabolism of dentin 2. Reactionary change of dentin,back,IV. Biological properties,Metabolism of dentin Reactionary change of dentin,68,3/26/2019,69,1. Metabolism of dentin,牙本质的代谢主要有二个途径： (1) 通过牙髓进行代谢 (2) 通过牙骨质、牙周膜进行代谢，主要在牙根部。,3/26/2019,70,2. Reactionary change of dentin,Vitality of dentin Dead tracts Reparative dentin or irregular secondary dentine, (tertiary dentin , reaction dentin) osteodentine Transparent dentin (sclerotic dentin),3/26/2019,71, Vitality of dentin,The odontoblast, as well as its process, is an integral part of the dentine , so dentine is a vital tissue. If vitality is understood to be the capacity of the tissue to react to physiologic and pathologic stimuli, dentine must be consider a vital tissue. Dentine is laid down throughout life.,3/26/2019,72,A: Dead tract The dead tract shown has been produced in response to attrition. Its dark appearance is said to be related to the retention of air in the emptied tubules which have not been penetrated by the mounting medium.,72,3/26/2019,73,Ground section 15 Reparative dentine (C) has been produced in response to attrition,Decalcified section,H 50 Reparative dentine (A) (irregular secondary dentine) filling a pulp horn,73,3/26/2019,74,Ground section 20,Primary dentine and irregular secondary dentine (reparative dentine),This is a section of dentin in the floor of the pulp chamber. Where is subjected to acute damage, some of the underlying odontoblasts die, while others lay down a form of repair tissue called reparative dentine,in which the tubules are few in number and irregularly arranged.,74,3/26/2019,75,Reparative dentine,75,3/26/2019,76,Reparative dentine,76,3/26/2019,77, Translucent dentine,The dentinal tubules,especially in root dentine, become completely occluded by mineral in a process similar to that of peritubular dentine formation. The amount of translucent dentine increases linearly with age and is not affected b