1. Kharkov National Medical University Department of Histology, cytology and embryology LECTURE for dentistry students

2. TEETH AND THEIR DEVELOPMENT

3. TOOTH HAS 4 PARTS: 4. PULP 2. DENTINE 1. ENAMEL 3. CEMENTUM PERIODONTAL LIGAMENT/ PDL ALVEOLAR BONE GINGIVA WABeresford

4. TOOTH DERIVES FROM ECTODERMAL ENAMEL ORGAN (ENAMEL) AND MESENCHYME (REST) DENTAL LAMINA DENTAL PAPILLA DENTAL SAC/FOLLICLE ENAMEL ORGAN MESENCHYME ALVEOLAR BONE PULP DENTINE ENAMEL CEMENTUM PDL A BONE

5. Oral ectoderm Oral ectoderm thickens and grows down to the mesenchyme forming Dental lamina Mesenchyme

6. Formation of a BUD from the dental lamina ON THE INTERNAL SURFACE OF DENTAL LAMINA IS FORMED Bud Odontogenic mesenchyme Next step - formation of enamel organ from the bud

7. BUD EXPANDS AND BECOMES ENAMEL ORGAN DENTAL LAMINA 1. DENTAL PAPILLA 2. DENTAL SAC ENAMEL ORGAN UNDERLIING IT MESENCHYME FORMS: 3. ALVEOLAR BONE

8. Tooth development Enamel organ Dental lamina Dental papilla Dental sac Odontoblasts Dentine Ameloblasts Enamel Sheath of Hertwig

9. TOOTH GERM: next steps DENTAL LAMINA - upper degenerates, lower forms 2nd bud DENTAL PAPILLA becomes pulp DENTAL SAC FORMS CEMENTUM outermost papilla cells have become Odontoblasts, producing dentine Ingrowing pulp vessels

10. TOOTH GERM: next steps 2.Inner cells of enamel organ become ameloblasts, producing enamel DENTAL SAC still quiescent 1.Dentine is produced by odontoblasts Ingrowing pulp vessels become

11. TOOTH GERM: all crown-forming elements present

12. Ameloblas t Tomes’ process ENAMEL FORMATION - AMELOGENESIS Organic first deposits, + 30% mineral organic materials digested; replaced by mineral to 96% - maturation DEJ Ameloblasts are pushed up by thikening enamel and reduced by tooth eruption

13. ENAMEL REDUCED enamel organ HERTWIG’S ROOT SHEATH = = DENTINE PULP Epithelial end of enamel organ CROWN odontoblasts ROOT FORMATION H. Root sheath breaks up, allowing sac mesenchymal cells to contact dentine and to produce cementum

14. TOOTH & MANDIBLE DEVELOPMENT 1 0 TOOTH 2 0 TOOTH GERM MECKEL’S CARTILAGE TONGUE ALVEOLAR BONE DENTAL SAC ALVEOLAR NERVE Oral ectoderm

15. ENAMEL REDUCED DENTAL EPITHELIUM TOOTH ERUPTION GINGIVAL EPITHELIUM still fusing with CUTICLE will wear away

16. H. ROOT SHEATH LATE ERUPTING TOOTH DENTINE ENAMEL BONE GINGIVA CEMENTUM PDL PULP Rests of Mallasser’s – en.organ remnants of Root sheath Cementum starting as sheath breaks down!!

17. Deciduous tooth Gingiva BODY of MANDIBLE ALVEOLAR BONE FROM MESENCHYME PDL FROM MESENCHYME Permanent tooth MANDIBULAR CENTRAL INCISORS at 2 y

18. Deciduous tooth Cortical plate dense bone Permanent tooth MANDIBULAR CENTRAL INCISORS at 2 y - Bone Spongy/ cancellous bone Resorption of bone & deciduous root will start here

19. 13254760 YEARS YOUNG CHILD’S ERUPTION SEQUENCE Time of emergence Root formingCrown forming KEY 1 0 2nd Molar 2 0 Incisor 2 0 Cuspid 2 0 2nd PreMolar Deciduous Permanent

20. 1 0 Incisor 1 0 Cuspid 13254760 YEARS YOUNG CHILD’S ERUPTION SEQUENCE 1 0 2nd Molar 2 0 Incisor 2 0 Cuspid 2 0 2nd PreMolar

21. PULP DENTINE CEMENTUM TOOTH STRUCTURE (decidious, permanent) ENAMEL CROWN Cervix ROOT } }

22. ENAMEL: Boundaries Dentino-enamel junction DEJ Cemento-enamel junction - CEJ

23. ENAMEL: Nature Enamel is the dead, very hard The dense packing, curved units = prisms composed of densely arranged mineral crystals, RODROD RODROD Mineral is hydroxyapatite, with Ca 2+, OH -, PO 4 --, etc, ions Cross-section of rods

24. ENAMEL DEJ PRISMS/ RODS between prisms is organic Enamel is: 96% mineral, 3% water, 1% organic material First enamel is NON-PRISMATIC Last enamel is NON-PRISMATIC

25. AT GROWTH. On section Contour lines of Retzius; rhytmic mineralisation S-shaped prisms form Hunter- Schreder bands

26. DEJ DEJ is actually a little irregular, ENAMEL SPINDLE Odontoblast process stuck into enamel matrix and form nonmineralised spindles E D

27. Plates, bunches (tuft) ENAMEL: plates, bunches, spindles – low mineralised sites for infection SPINDLE

28. DENTINE is the major part of the tooth, The inner d. is not calcified called predentine

29. DENTINE: Boundaries Dentino-enamel junction DEJ Dentino-cemental junction DCJ Pulp surface APICAL FORAMEN Orally exposed - pathological

30. Odontoblasts DENTINE consists of: 1. MATRIX of collagen fibrils, mineral crystals, Penetrated by 2. DENTINAL TUBULES containing processes of cells - ODONTOBLASTS -whose bodies lie in the pulp Tomes fiber

31. DENTINE: Composition MATRIX collagen fibrils and glycoproteins & proteoglycans 28% - Organic mineral crystals 72% - Inorganic MATRIX TUBULE

32. DENTINE: MATRIX subdivided into TUBULES 1-3  m wide 1. Peritubular d. (without organic) 2. Inter-tubular d. (mineralised collagen fibrils)

33. PULPPULP MATURE DENTINE: Varieties MANTLE D. just below DEJ = radial Korff fibrils CIRCUMPULPAL D.- main mass of dentine = perpendicular to tulules fibers- Ebner Predentine - UNCALSIFIED { REPARATIVE D. - response to caries/erosion * * Response relies on the pulp and the odontoblasts staying alive & active

34. PULPPULP MATURE DENTINE: Sites for defects INTERGLOBULAR SPACES uncalcified DEAD TRACT - wide, empty dentinal tubules easily colonized by bacteria TOMES’ GRANULAR LAYER – the largest interglobular spaces SCLEROTIC DENTINE - tubules filled with mineral

35. CEMENTUM: Boundaries Cemento-enamel junction CEJ Dentino-cemental junction DCJ Ligamento-cemental junction APICAL FORAMEN

36. CEMENTUM: Role Cementum is the hard covering of the root that can: CONNECTS TO periodontal- ligament BY fibers, and thus attach the tooth to the alveolar bone. It is itself a kind of bone

37. CEMENTUM: types The cervical half is thin and acellular - no cementocytes At top cementum is cellular

38. PERIODONTAL LIGAMENT fibers (extrinsic) become imbedded in newly formed cementum CEMENTUM MATRIX Fine collagen fibrils - intrinsic MATRIX PROPORTIONS collagen fibrils and glycoproteins & proteoglycans – 30% Organic mineral crystals -- 70% Inorganic = Sharpey’s fibers

39. PULPPULP CEMENTUM: Defects CORONAL CEMENTUM spurs, etc, on enamel HYPERCEMENTOSI S -excess deposition CEMENTOCLASIA - eroded cementum (occurs normally in decidual-tooth shedding) CEMENTICLES IN PDL

40. PULPPULP CEMENTICLES Hard mineralized bodies found in the periodontal ligament or partially imbedded in cementum

41. PULP DENTINE ENAMEL CEMENTUM PERIODONTAL LIGAMENT/ PDL ALVEOLAR BONE GINGIVA Its Odontoblasts alive for slow renewal of the dentine Provides antimicrobial defense for the dentine and itself Provides sensory feedback from the dentine WABeresford TOOTH TISSUES: Pulp & its role

42. PULP CHAMBER CORONAL ACCESSORY CANAL ROOT CANAL APICAL FORAMEN

43. PULP REGIONS Outer layer - ODONTOBLASTS Inner layer - loose c.t. with vessels and nerves

44. PULP MATRIX - Ground substance, fibers Blood vessels, Nerves Lymphatics CELLS – Odontoblasts, Fibroblasts Macrophages, Mast cells Leukocytes

45. PULP ODONTOBLASTS Nerves 1. PULP 2. ODONTOBLASTS 3. DENTINAL TUBULES 4. TOMES PROCESS Blood vessels Nerves: 12 4343 Sub-odontoblastic plexus in cell- poor zone of Weil

46. PU LP DENTICLES/ PULP STONES Hard mineralized bodies found in the pulp TWO TYPES: Both may show layering/lamellar patterns from incremental growth

47. ENAMEL 1. PERIODONTAL LIGAMENT/ PDL 2. ALVEOLAR BONE 3. GINGIVA 1- contains Scharpey’s perforating fibers from cementum to bone 2. Compact bone external, spongy - internal 3. Stratified slightly keratinized E, c.t. WABeresford PERIODONTIUM –supportive apparatus

48. Gingiva BODY of MANDIBLE ALVEOLAR BONE FROM MESENCHYME PDL FROM MESENCHYME PERIODONTIUM – supportive apparatus

49. RESTS OF HERTWIG’S ROOT SHEATH Sites for pathology – Cysts, tumors DENTINE ENAMEL BONE GINGIVA CEMENTUM PDL PULP Rests of Mallasser’s – en.organ Root sheath Cementum starting as