Dentin

Dentin

• 1.
  Dentin
• 2.
  Contour lines ofOwen • During development of dentin, variations in the metabolism of the organism cause variations in the amount of organic material deposited in the dentin, just as occurs in the enamel. • Changes in the coloration of the dentin are called contour lines of Owen. • The first dentin that is layed down (at the DEJ) forms the mantle layer while subsequent dentin forms the circumpulpal layer. • In the crown of tooth, dentinal tubules from S-shaped primary A, Contour line of Owen; curves. B, Mantle layer of dentin; C, Circumpulpal layer of dentin; D, DEJ
• 3.
  Contour lines ofOwen and Stria of Retzius • The contour lines of Owen intercept the dentino-enamel junction and meet an accompanying Stria of Retzius that was formed at the same time. A, Contour line of Owen; B, Stria of Retzius
• 4.
  Lines of vonEbner •Daily alterations in the formation of dentin produce imbrication lines of von Ebner that are approximately 5 µm in length, are seen as banding along the dentinal tubules and are comparable to the cross-striations in enamel. • Arrow indicates the direction of the lines of von Ebner that are perpendicular to the dentinal tubules.
• 5.
  Dentinal tubules • Eachodontoblast has a long process that projects through the dentin to the DEJ. • The hole or tube in the dentin through which this process projects is called the dentinal tubule. • The course of the dentinal tubules in the crown of the tooth is S-shaped due to the crowding of the odontoblasts as they get squeezed into a smaller and smaller space within the pulp cavity. A, Primary curve of dentinal tubule; • This curve is called a primary B, DEJ; C, Mantle dentin; curve. D, Circumpulpal dentin
• 6.
  Odontoblasts in anerupted tooth • As the dentin layer forms, the odontoblast become increasingly crowded as they are squeezed into a smaller area. • The single layer of odontoblasts (as occurs in early development) has now changed to stacks of odontoblasts. A, Odontoblasts; B, Predentin; C, Pulp cavity; D, Dentinal tubules
• 7.
  Secondary curves • Duringthe deposition of dentin, the odontoblast makes slight undulations that creates wavy dentinal tubules. • This waviness of the dentinal tubules is called secondary curves. A, Secondary curve of dentinal tubule
• 8.
  Mantle dentin • Whenviewed in polarized light, mantle dentin (red band), which is about 10 µm wide, can be differentiated from circumpulpal dentin (purple with black dentinal tubules). • This is due to a difference in the collagen fibers in mantle dentin. A, Enamel; B, Circumpulpal dentin; C, Mantle dentin
• 9.
  Globular calcification ofdentin • Dentin is calcified after it is formed. • The calcification begins in small spherical areas. • These become larger and fuse with one another to form a calcification front (row of calcification sheres along the A, Odontoblasts; B, Predentin; C, Calcification front; predentin edge). D, Calcified dentin
• 10.
  Calcification pattern ofdentin - decalcified section • In mature dentin, globules of well- calcified dentin are apparent (arrow) along with areas of less calcified dentin (white areas). A, Globule of well-calcified dentin
• 11.
  Interglobular dentin inglobular layer - ground section • Between the mantle and circumpulpal layers is a layer of dentin in which the calcified globules do not fuse evenly. • This is called the globular layer. • In a ground section of dentin, the less-calcified areas of dentin appear as irregularly shaped crescents called interglobular dentin. A, Interglobular dentin
• 12.
  Globular layer andgranular layer • In the root of the tooth, the peripheral border of mantle dentin adjacent to the cementum has a granular appearance and is called the granular layer of Tomes. • The granular layer is a less calcified layer like that of the globular layer. • Generally, interglobular dentin is seen only in the crown, but in this specimen it extends into the root. A, Circumpulpal layer; B, Globular layer; C, Mantle layer; D, Granular layer; E, CEJ; F, Enamel; G, Cementum
• 13.
  Dentinal tubules • Dentinaltubules are the hollow tubes that run through the dentin in which are located the odontoblastic processes. • During formation of dentin, intertubular dentin is layed down between the odontoblastic processes. • Then a second layer of more mineralized dentin is added to "coat" the inside of the tubules. • This layer of dentin is called peritubular dentin or intratubular dentin. A, Peritubular dentin; • In this scanning electron micrograph, B, Intertubular dentin; the peritubular dentin appears white. C, Dentinal tubule
• 14.
  Dentinal tubular branchesin root - transmitted and differential interface contrast microscopy • Dentinal tubules generally have lateral branches where odontoblastic processes can communicate with one another. • These branches, as seen here, are most numerous A, Odontoblastic process; in the root of the tooth B, Lateral branches of dentinal tubules
• 15.
  Terminal branching ofdentinal tubules • Dentinal tubules are closely spaced but have a large diameter close to the pulp cavity. • Dentinal tubules become more widely spaced in the dentin but have a narrower diameter as they approach the DEJ. • At the DEJ, dentinal tubules branch. • This causes an increased dentity of dentinal tubules in cross-sections of dentin in this region. • In this micrograph, note the scalloped appearance of the DEJ. A, Dentinal tubule; B, DEJ; • The peaks of the scallops point C, Enamel; D, Enamel spindle toward the enamel.
• 16.
  Peritubular and intertubulardentin • In this scanning micrograph of dentin, the dentinal tubules can be seen surrounded by a somewhat loosely packed intertubular dentin and a more dense peritubular dentin. A, Intertubular dentin; B, Peritubular dentin; C, Dentinal tubule
• 17.
  Forms of dentin •Primary dentin, with straight tubules, is laid down before completion of the apical foramen. • Regular secondary dentin is characterized by a slower rate of deposition and an abrupt change in the direction of the dentinal tubules. • Tertiary or irregular secondary (also called irritation, reparative or reactive) dentin is laid down in response to an irritation or damage to the overlying dentin and/or enamel. • This dentin has irregularly arranged and few dentinal tubules. With aging or severe damage, tertiary dentin can totally obliterate the pulp cavity. A, Primary dentin; B, Secondary (regular) dentin; C, Reactive dentin
• 18.
  Dead tracts andblind tracts • When dentin is damaged, odontoblastic processes die or retract leaving empty dentinal tubules. • Areas with empty dentinal tubules are called dead tracts and appear as dark areas in ground sections of tooth. • With time, these dead tracts can become completely filled in mineral. • This region is called blind tracts and appears white in sections of ground tooth. • The dentin in blind tracts is called sclerotic dentin. • The adaptive advantage of blind tracts is the sealing off of the dentinal tubules to prevent bacteria from A, Dead tract; entering the pulp cavity. B, Blind tract (containing sclerotic dentin)
• 20.
  This slide from: SharifaAbdulla Alhaj
• 21.
  This slide from: Dalia.
• 22.
  Good Luck All Done by: Bedour Al-Arfaj.
• 23.
  ‫أدعيه قبل المذاكرهوبعدها...‬ ‫قبل المذاكرة‬ ‫اللهم أنً اسألك فهم النبٌٌن و حفظ المرسلٌن و المالئكة المقربٌن ، اللهم أجعل ألسنتنا عامرة بذكرك و قلوبنا بخشٌتك و أسرارنا‬ ‫بطاعتك أنك على كل شًء قدٌر .. حسبنا هللا و نعم الوكٌل‬ ‫بعد المذاكرة‬ ‫اللهم أنً استودعتك ما قرأت و ما حفظت و ما تعلمت فرده عند حاجتً الٌه انك على كل شًء قدٌر ، حسبنا هللا و نعم الوكٌل‬ ‫يوم اإلمتحان‬ ‫اللهم أنً توكلت علٌك و سلمت امري الٌك ال ملجأ و منجا منك إال الٌك‬ ‫دخول القاعة‬ ‫رب أدخلنً مدخل صدق و أخرجنً مخرج صدق و أجعل لً من لدنك سلطانا نصٌرا‬ ‫قبل البدء بالحل‬ ‫رب أشرح لً صدري و ٌسر لً أمري و احلل عقدة من لسانً ٌفقه قولً بسم هللا الفتاح ، اللهم ال سهل أال ما جعلته سهال و انت تجعل الحزن اذا‬ ‫شئت سهال ٌا ارحم الراحمٌن‬ ‫أثناء األمتحان‬ ‫ال إله اال انت سبحانك أنً كنت من الظالمٌن ٌا حً ٌا قٌوم برحمتك أستغٌث ، رب ان مسنً الضر أنك أرحم الراحمٌن‬ ‫عند النسيان‬ ‫اللهم ٌا جامع الناس فً ٌوم ال رٌب فٌه أجمعنً و ضالتً‬ ‫بعد األنتهاء‬ ‫الحمد هلل الذي هدانا لهذا و ما كنا لنهتدي لوال أن هدانا هللا‬