def of enamel
DESCRIPTION
ENAMEL STRUCTURETRANSCRIPT
Enamel
Enamel ENAMEL is epithelialy deried protecticve covering of teeth, the cells responsible for formation of the enamel ameloblast. Enamel is a most highly mineralized tissue consisting of 96% inorganic and 4% organic material and water.
Enamel rodit is the basic unit of the enamel with a highly organized pattern of the crystal orientation (hydroxy apitite crystalls).Incremental lines of enamel:
Bands of hunter and shreger : it is a optical phenomenon produced by the changes in the direction of rods .Appears as alternating dark and light strips of varying widths , the starts from dentinoenamel junction and end at some distance away from surface.
Incremental lines of retzius In a groud section they appears as series of dark bands illustrating the incremental pattern or succesive opposition of enamel during its formation .In cross section they appears as concentric rings . ENAMEL LAMELLAE:These are hypomineralized lef like sructures that exend from enamel surface towards the DEJ or may extend into the dentine,Consist of linear longitudinally oriented defects filled with organic materialEnamel tufts It is a hypo mineralized structure arises from DEJ for a short distance ino enamel. They appear to be branched and contain greater concentration of enamel proteins than the rest of the enamel.Tufts are believed to occur developmentally because o abrupt changes in the direction of group of rods that arise from different regions of the scalloped DEJ.
Enamel spindles Occasionally odontoblastic process passes across the DEJ into the enamel they have been termed enamel spindles.They originate from odontoblastic process that extend into the enamel epithelium before hard substance are formed, the direction of enamel spindles crossponds to the orignal direction of ameloblast ,i.e at right angle to dentine.Gnarled enamelOver the cusps tips of the tooth the rods appear twisted arround each other in a complex manner known as gnarled enamel.The twisted arrangement creats an optical appearance . this also provides strength to the incisal and cuspal region .Perikymata
It is a external manifestation of incremental lines of retzius appears as a wave like grooves on external surface of enamel. They are continous around the tooth and usually lie parallel to each other and to the CEJ.