Dentinogenesis and Dentin Flashcards
Dentin Components
70% mineral - Ca++ hydroxyapatite and trace amount os Ca++ carbonate, fluoride, magnesium and zinc
20% Organic - T1Collagen with some 3 & 5, 50% of non collagenous proteins are phosphoprotein, sialoprotein and sialophosphoprotein, proteoglycoasminoglycans, osteronectin and osteropontin
10% water
Type 1 collagen of dentin is slightly different than that of
bone. Higher ratio of proline and hydroxyproline, higher prevalence of molecular cross-linking, higher level of bound water, random orientation of the hydroxyapatite crystals
Dentin matrix non-collagenous proteins include
Proteoglycans (biglycan and decorin)
Glycosaminoglycans (chrondroitin -4-sulfate and 6)
_-carboxyglutamate-containing protein (Gla-proteins)
Osteonectin
Osteropontin (contains the receptor binding sequence arginine-glycine-asparagine)
Life cycle stages
Pre-odontoblast
Secondary odontoblast
Transitional odontoblast
Resting odontoblast
Mantle dentin
50-100mm thick layer of first formed dentin. Contains both Type 1 and 3 collagen which are arranged perpendicular to the basal lamina of the IEE
Dentinal tubules are tapered
2.5 diameter at the pulpal surface. 1.2 diameter at midlength. 0.9 near the DEJ
Decreasing the volume of the pulp chamber
the number of dentinal tubules per unit area at the pulpal surface is 40,000 and about 1/2 that number of the DEJ
Demineralized sections of dentin demonstrating the
type 1 collagen matrix (SEM)
Positive impression of branching and anastomosis of dental tubules by flowing
composite bonding agent onto an acid etched surface of dentin as would be done in placement of a composite resin restoration
Interglobular dentin
A zone of globular, rather than linear, formed dentin in the crowns of teeth. Characterized by interlobular spaces that are unmineralized or hypomineralized dentin btw normal calcified dentinal layers
Tome’s Granular layer
A granular-appearing layer in the dentin of the root adjacent to the cementum Possibly comprised of hypo mineralized interglobular dentin
Primary dentin
All dentin (except mantle dentin) formed up to the time the tooth achieves functional occlusion
Secondary dentin
All dentin formed (except tertiary dentin) formed after tooth achieves functional occlusion
Dead tracts
Dentinal tubules that are void of the odontoblastic process. They are generally filled with air or organic debris and look black in transmitted light microscopy
Sclerotic Dentin
Dentin in which the tubules are occluded with mineral. The dentin is non-tubular and is nearly transparent. Incidence of occurrence increases with increasing age of the patient. May be tertiary (reparative) dentin
Incremental lines of von Ebner
The organic matrix of dentin is deposited in increments of 4mm to 8mm per 24 hrs. Occur after 4-20 days of matrix deposition and are thought to represent hesitations in matrix deposition and therefore altered mineralization.
Neonatal line and contour lines of Owen
Both represent exaggerated lines of con Ebner that occur during periods of altered cell metabolism
Tertiary Dentin
Dentin deposited by newly differentiated odontoblasts at the site of pulpal trauma. A defense reaction attempiting to wall off the pulp from the site of injury
Cells in the subodontoblastic layer once exposed to growth factors released by stimulated pulpal cells
differentiate and form the matrix of reparative dentin.
BMP, IGF, FGF, DMP
Dentinogenesis Imperfecta
Hereditart defect that results in bluish-gray teeth with an opalescent sheen. Enamel is normal but chips off due to lack of support by the abnormal dentin. Pulp chamber and canals are generally obliterated by defective dentin formation
Attrition
Loss by wear of surface caused by tooth to tooth contact during mastication or parafunction. Matching wear on occluding surfaces, and shiny facets on amalgam contacts are common. Enamel and dentin wear is at the same rate. Possible fracture of cusps and restorations
Erosion
Loss of hard dental tissue by chemical processes. Braod concavities with cupping of occlusion surfaces and dentin exposure. Incisal translucency with wear on non-occluding surfaces Amalgam restorations appear “raised” and have a non-tarnished appearance. Pt are hypersensitive. Common with GERD pts
Bacteria responsible for dental caries include
Strep. Mutans (enamel/dentin caries) Strep. sorbrinus ^^ Strep. Gordonii ^^ Lactobascillus acidophilus ^^ Actinomyces viscous (root caries)
Dentinal sensitivity
1 in 5 adults suffers from dentinal sensitivity. The teeth most commonly affected are cuspids and bicuspids. Stimuli associated with dentinal sensitivity include:
- cold and/or hot drinks
- sweet or sour (acidic) foods or drinks
- overly aggressive brushing
- acidogenic plaque bacteria
- cosmetic bleaching of teeth
- clenching or bruxism
Direct innervation theory
Direct stimulation of nerve endings in dentinal tubules
Transduction theory
Stimulation of odontoblasts that are coupled to nerves in the pulp
Brannstrom’s hydrodynamic theory
Stimulation of dentinal tubules or exposed odontoblastic cell processes causes movement of tissue fluids within dentinal tubules that stimulates nerve endings in close association with dentin at the dentin/pulpal interface
