Histow Flashcards
(162 cards)
% composition of enamel? What is the main mineral component?
96% inorganic
Calcium phosphate aka Hydroxyapatite arranged in prisms
1% amelogenins (main protein) and enamelins contained in enamel tuft
3% water
*Dentin: 70% inorg
*cementum: 55% inorg (calcium salts)
Enamel prisms are arranged…
Approximately PERPENDICULAR to the dentin at the dentinoenamel junction following a wavy course towards enamel surface
Gnarled enamel vs straight enamel
Gnarled enamel - prisms are twisted in a random manner, located over cusps and ridges of premolars and molars, rarely fractures
Shallow, transverse, wavelike grooves visible under reflected light parallel to the CEJ, surface manifestation of the lines of Retzius
Perikymata / imbrication line of Pickerill
- encircles the surface of enamel on anatomic crown
Some sources: perikymata - cervical ridges
Imbrication lines - grooves between
Brown lines seen in ground sections at the enamel
Incremental striae (lines of Retzius)
-indicate variations in deposition of organic matter in enamel which later calcifies
Hypomineralized area
Line where enamel is being deposited at birth
Neonatal line
- represents accentuated lines of Retzius
- reflects metabolif changes at birth
-present in dentin
Enamel Internal to it: formed before birth and has fewer defects
Enamel External to it: formed after birth
Alternating light and dark bands seen under oblique reflected light in longitudinal ground sections
Hunter-Schreger bands - DEJ to external surface of enamel / inner 2/3 of enamel (due to periodic changes in the enamel prism direction)
LIGHT ZONE: PARAZONE
DARK ZONE: DIAZONE
Area of poorly calcified enamel that extend from outer surface into the tissue for variable distances
Enamel lamellae - sometimes completely through underlying dentin
Extension of adjacent odontoblastic processes that continue into enamel (left behind kasi)
Enamel spindles - various terminations (pointed, sharp, rounded)
Areas of hypocalcification in prisms and interprismatic material (calcification imperfections in enamel prisms) that starts at DEJ and penetrates into enamel
Enamel tufts - start at DEJ and penetrate into enamel about 1/3 of its thickness
Enamelin: organic material in enamel tufts
Some patients experience pain on tooth may be due to:
A. Enamel Tufts
B. Enamel lamellae
C. Enamel spindles
D. Striae of Retzius
C
Cause of sclerosis in dentinal tubules
Increase formation of peritubular dentin = decrease permeability
Optical phenomenon due to cyclic activity of the odontoblasts during dentin formation
Incremental lines of von Ebner (perpendicular to the dentinal tubules)
Sa DENTIN TO!!
Completion of radicular dentin formation
(closure of apex)
Primary: 18months after eruption
Permanent: 2-3yrs after eruption
Tomes fiber vs tomes process
Odontoblastic process: tomes fiber
Ameloblast extension: tomes process (responsible for enamel secretion)
Main bulk of dentin?
Intertubular dentin
Immediate wall material which is the peritubular dentin was previously called?
Sheath of Neumann
Type of dentin that lines the pulp?
Secondary dentin -can sometimes obliterate the pulp
Type of dentin that develops at localized sites stimulated by local irritation
Tertiary or reparative or irregular dentin
Type of dentin resulting from stimuli that causes calcification of the odontoblastic process
Sclerotic or transparent dentin - hypercalcification = harder and denser dentin
Seen where tome’s process has disintegrated
Dead tracts in dentin - black in transmitted light, white in reflected light
Location of cellular and acellular cementum
Acellular deposited slowly from CEJ to 2/3 of root
Cellular rapidly forms and predominantly in apical 3rd and furcations
Two types mingle in the apical 3rd of the root
Most common type of CEJ
Acellular cementum overlaps the cervical enamel (60%)
Cementum and enamel meet at a sharpt point (30%)
No direct connection (10%)
Involved in dentin formation that originates in the pulp
First sign of mantle dentin formation
Von Korff’s fibers - type 3 collagen fibers (reticular) + fibronectin