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Dental Histology - Mature Enam
Exam 4
17
Medical
Professional
11/27/2008

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Cards

Term
Physical and Chemical Characteristics of Enamel
Definition
-most mineralized biological tissue (96% inorganic)
-translucent
-semipermiable to water and low-MW compounds
-inarganic = hydroxyapatie crystals (crystalline                                                        calcium phosphate)
-organic = amelogenin (TRAP) and other proteins 
Term

Structure of Enamel

 

(7) 

Definition
1. Enamel rods
2. Incremental lines
3. Hunter-Schreger bands
4. Gnarled enamel
5. Enamel tufts
6. Enamel lamellae
7. Enamel Spindles 
Term

Structure of Enamel

 

Enamel Rods 

Definition
-basic structural unit
-densly packed hydroxyapatite crystals
-interrod = area surrounding rod where crystals oriented in                 different direction from those of the rod
-rod sheath = interface between rod and interrod contains                 HIGHEST protein content
-no rod structure adjacent to dentin
-no rod structure at enamel surface (sometimes) due to lack of         Tomes' process at begining + end of amelogenisis
-diameter increases towards enamel surface
-rods mantain undulating coarse through enamel
-arranged perpendicular to dentinal surface
-bend toward cusp tip
-mechanically locked into dentin 
Term

Structure of Enamel

 

Incremental Lines 

 

(4 types) 

Definition
-due to variations in secretory activity, strucutre, and             mineralization
-visible on ground sections 
 
1. Striae of Retzius
2. neonatal line
3. cross striation
4. perikymata 
Term

Structure of Enamel

 

Incremental Lines

 

Striae of Retzius 

Definition
-primarily in perminent teeth (less evident in primary)
 
-represent constriction of Tomes' process coupled             with increased production of interrod enamel  
 
-result = prominent alteration alonf entire front
           =roughly parallel
           =no clinical sig
Term

Structure of Enamel

 

Incremental Lines

 

neonatal lines 

Definition
-exaggerated stria of Retzius
 
-reflects physiologic changes that occur at birth 
Term

Structure of Enamel

 

Incremental Lines

 

cross striations 

Definition
-represent either daily changes in secretory activity
            by ameloblasts
 
or
 
-differing orientations by hydroxyapatite crystals                     within a single rod 
Term

Structure of Enamel

 

Incremental Lines

 

Perikymata 

Definition
-surface irregularities
-represent termination of striae of Retzius
-horizontal bands encircle crown of tooth; absent on         occlusal surface 
 
Imbercation Lines pf Pickerel = troughs inbetween crests of enemel 
Term

Structure of Enamel

 

Hunter-Shreger bands

Definition
-optical phenomenon
-changes in rod orientation
-appear as alternating broad light and dark bands 
Term

Structure of Enamel

 

Gnarled enamel

Definition
-disarrayed enamel rods
-present at the cusp tips
-due to crowding anf twisting of rods in a small area 
Term

Structure of Enamel

 

Enamel  Tufts

Definition
-small, branchinf defects at DEJ
-projecting into enamel
-contain lareger % of enamel protein 
-short flame shaped 
-no clinical sig 
Term

Structure of Enamel

 

Enamel lamellae

Definition
-prominent linear enalem defects
-start at tooth surface
-sometimes penetrate DEJ
-high concentration of enamel protein
-sometimes contain material from oral cavity
-no clinical sig 
Term

Structure of Enamel

 

Enamel Spindles

Definition
-short, linear defects
-found at DEJ
-extend into the enamel
-more prevalent at cusp tip
-formed by entrapment of odonoblast processes b/w         ameloblasts prior to and during amelogenesis
-no clinical sig 
Term
Age Changes
Definition
1. Attrition
2. Discoloration
3. Reduced permeability
        -tooth most porus whrn youn 
        -less permeable over time as you add Ca+
4. Changes in surface structure
        -imbercation lines wear away
5. Modification of the surface layer
        -often due to dental procedures
 
Term

Clinical Implications

 

Fluoridation 

Definition
-enamel can become resistant to acid dissolution
-facilitates calcium phosphate percipitation 
 
fluoride ions incorporated into hydroxyapatite                 crystals 
Term

Clinical Implications

 

Acid Etching 

 

 

Definition
-used to increase mechanical retention of restoritives
-makes enamel surface irregular
-removes plaque, organic debris, and surface enamel
-increased porosity of exposed enamel
-rod orientation at enamel determines specific pattern
            of etching

 
Term

Clinical Implications

 

Acid Etching

 

(3 types) 

Definition

       Type I = removal of rod core
       Type II = removal of rod periphery
       Type II = irregular removal of enamel structure
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