AMELOGENESIS

A BRIEF DESCRIPTION TO THE PROCESS OF ENAMEL FORMATION.

1. AMELOGENESIS PROCESS BY WHICH ENAMEL IS LAID DOWN BY AMELOBALSTS DR.VIGNESH R, BDS

2. AMELOGENESIS CONSISTS MAINLY OF 3 STEPS: FORMATION OF ENAMEL MATRIX MINERALIZATION OF THE FORMED MATRIX MATURATION OF MINERALIZED MATRIX. BEGINS BY THE LATE BELL STAGE OF TOOTH FORMATION.

3. AMELOGENESIS REQUIRES A SMALL AMOUNT OF DENTIN TO BE LAID DOWN FIRST THIS PREDENTIN LAYER INDUCES AMELOBLASTS TO SECRETE THE FIRST LAYER OF ENAMEL EACH ROD IS FORMED FROM 4 AMELOBLAST CELLS

4. AMELOGENESIS At the late bell stage, the inner enamel epithelium has already differentiated into ameloblasts When the first layer of dentin is secreted by odontoblasts, the ameloblasts secrete the first layer of enamel

5. AMELOGENESIS THIS INITIAL LAYER OF ENAMEL DOES NOT CONTAIN RODS (PRISMS). CALLED RODLESS / APRISMATIC ENAMEL AS EACH INCREMENT OF ENAMEL IS FORMED, THE AMELOBLASTS MOVE AWAY FROM THE DENTIN SURFACE. THIS IS TO ACCOMMODATE SUBSEQUENT INCREMENTS OF ENAMEL.

6. AMELOGENESIS THE SURFACE OF THE AMELOBLASTS FACING THE DENTIN IS NOT SMOOTH CERTAIN FINGER LIKE THIN EXTENSIONS APPEAR ON THIS BORDER OF THE CELLS TOME’S PROCESSES / FIBERS INTERDIGITATE WITH THE ENAMEL RODS WHICH ARE BEING PRODUCED.

7. AMELOGENESIS TOME’S FIBERS HELP THE ENAMEL TO BE LAID DOWN PRECISELY AT THE REQUIRED POINT. THIS ARRANGEMENT OF TOME’S FIBERS ALONG THE SECRETORY BORDER GIVES A “PICKET FENCE” ARRANGEMENT.

8. AMELOGENESIS IN THE INITIAL STAGES OF TOOTH FORMATION, THE DENTAL PAPILLA SUPPLIES NUTRITION TO THE ENAMEL ORGAN. AS ENAMEL & DENTIN ARE FORMED, THE AMELOBLAST CELLS MOVE AWAY FROM THE DENTAL PAPILLA THE BLOOD SUPPLY IS THEN DERIVED FROM THE VESSELS INVAGINATING THROUGH THE OUTER E. E.

9. AMELOGENESIS ENAMEL FORMATION FIRST BEGINS IN THE TIP OF THE CUSPS THEN IT SLOPES DOWNWARDS GRADUALLY TO THE CERVICAL LOOP AREA. THIS AREA FORMS THE FUTURE CEJ .

10. LIFE CYCLE OF AMELOBLASTS DURING AMELOGENESIS, THE AMELOBLASTS UNDERGO CHANGES IN THEIR MORPHOLOGY, STARTING FROM PRE-SECRETORY STAGE TO POST-SECRETION PERIOD. AT EACH STAGE, THE CELL REARRANGES ITSELF TO SUIT THE FUNCTIONAL REQUIREMENTS.

11. LIFE CYCLE OF AMELOBLASTS BROADLY CLASSIFIED INTO 3 STAGES: PRE-SECRETORY STAGE SECRETORY STAGE POST-SECRETORY STAGE.

12. LIFE CYCLE OF AMELOBLASTS EACH IS AGAIN SUBCLASSIFIED: PRE-SECRETORY MORPHOGENETIC PHASE ORGANIZING / DIFFERENTIATING SECRETORY FORMATIVE PHASE POST- SECRETORY MATURATIVE PHASE PROTECTIVE PHASE DESMOLYTIC PHASE.

13. MORPHOGENETIC PHASE COINCIDES WITH EARLY BELL STAGE SHAPE OF THE TOOTH DETERMINED AT THIS STAGE CELLS OF THE DENTAL PAPILLA SEPARATED FROM IEE BY A BASEMENT MEMBRANE CELLS OF IEE SHORT COLUMNAR OTHER ORGANELLES ARE NOT FULLY DEVELOPED.

14. DIFFERENTIATING PHASE CELLS OF THE IEE BECOME TALL COLUMNAR HYPERCHROMATIC NUCLEUS SHIFTS TO PROXIMAL END (TOWARDS SI) ORGANELLES MOVE DISTALLY. THIS CELL IS “POLARIZED”, CALLED “PREAMELOBLASTS”

15. FORMATIVE STAGE ACTIVE SECRETION OF ENAMEL MATRIX TAKES PLACE TOME’S PROCESSES DEVELOPS FROM THE DISTAL END OF THE CELL ENAMEL FORMATION MOVES DOWN FROM THE CUSP TIP TO THE CERVICAL AREA. ORGANELLES ACTIVITY INTENSE.

16. MATURATION PHASE FULL MINERALIZATION (MATURATION) OCCURS AFTER FULL THICKNESS OF ENAMEL MATRIX HAS BEEN LAID DOWN IN THE OCCLUSAL / INCISAL AREA. WHEN MATURATION TAKES PLACE IN THE CUSP TIP, FORMATION OF MATRIX WILL STILL BE ON IN THE CERVICAL LOOP AREA. CELLS OF SI TAKE A SPINDLE SHAPE

17. PROTECTIVE PHASE WHEN ENAMEL HAS FULLY CALCIFIED, AMELOBLST LAYER LOOSES IDENTITY. CANNOT BE DIFFERENTIATED FROM SI & OEE. THESE CELLS OF THE OEE & IEE (AMELOBLSTS) TOGETHER FORM A EPITHELIAL COVERING OVER NEWLY FORMED ENAMEL  REDUCED ENAMEL EPITHELIUM. (REE) PROTECTS ENAMEL BY SEPARATING IT FROM CONNECTIVE TISSUE TILL IT ERUPTS.

18. DESMOLYTIC PHASE CELLS OF THE REE ELABORATE SOME ENZYMES WHICH CAUSE LYSIS OF THE CONNECTIVE TISSUE SO THAT THE TOOTH CAN ERUPT INTO THE ORAL CAVITY. THIS IS CALLED “DESMOLYSIS ”.