W7 Enamel Flashcards
What are the chemical properties of enamel?
Inorganic mineral: hydroxyapatite
Organic matter: Enamelin protein
Water 2%
What are the physical properties of enamel?
Thickest over cusp tips and incisal edge, thinnest over the cervical margin. Low tensile strength. Core is more soliable
How many ameloblasts form the enamel rod?
4, 1 ameloblast in head, 2 neck, 1 tail
What are Hunter-Schreger bands? (HSB)
Alternating light and dark lines seen in enamel that begin at the DEJ and each before they meet the enamel surface. Function: strengthen enamel and prevent cracks
What are Incremental lines?
Stria of Retzius: recurrent depositation. Two types: short period - cross-striations
Long period - enamel striae
What are Cross-striations?
Short period: Rods alternate between thin and thick segments exhibit cross-striation
What are Enamel Striae (of retzius)
Long period: Structural lines running obliquely across the prisims in longitudinal section, reflect weekly intervals. Neonatal line is marked stria formed at birth
What are Perikymata grooves and ridges
Occur as enamel striae reach enamel surface. Appear as a series of fine grooves and ridges alternatively running circumferentially
What is the DEJ?
DentinoEnamelJunction refelcts the boundry between enamel and dentine. 2 patters scalloped and smooth. Structures visible: Enamel spindles Enamel tufts Enamel lamellae
What are enamel spindles?
Odontoblastic process that remained between ameloblasts
What are enamel tufts?
Hypomineralised area
What are enamel lamellae?
Sheet like structural fault, run through entire thickness of enamel, hypomineralised. Developmental incomplete maturation of groups of prisims.
What is gnarled enamel?
Near DEJ mostly in cusp areas the enamel rods form intertwining bundles
What clinical findings affect enamel wear?
Abrasion, Erosion, Attrition
What happens in age to enamel?
Darkening in colour due to thinness, acquired stains.
