Dentinogenesis and Dentin

Question 1

Dentin Components

Answer 1

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

Question 2

Type 1 collagen of dentin is slightly different than that of

Answer 2

bone. Higher ratio of proline and hydroxyproline, higher prevalence of molecular cross-linking, higher level of bound water, random orientation of the hydroxyapatite crystals

Question 3

Dentin matrix non-collagenous proteins include

Answer 3

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)

Question 4

Life cycle stages

Answer 4

Pre-odontoblast
Secondary odontoblast
Transitional odontoblast
Resting odontoblast

Question 5

Mantle dentin

Answer 5

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

Question 6

Dentinal tubules are tapered

Answer 6

2.5 diameter at the pulpal surface. 1.2 diameter at midlength. 0.9 near the DEJ

Question 7

Decreasing the volume of the pulp chamber

Answer 7

the number of dentinal tubules per unit area at the pulpal surface is 40,000 and about 1/2 that number of the DEJ

Question 8

Demineralized sections of dentin demonstrating the

Answer 8

type 1 collagen matrix (SEM)

Question 9

Positive impression of branching and anastomosis of dental tubules by flowing

Answer 9

composite bonding agent onto an acid etched surface of dentin as would be done in placement of a composite resin restoration

Question 10

Interglobular dentin

Answer 10

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

Question 11

Tome’s Granular layer

Answer 11

A granular-appearing layer in the dentin of the root adjacent to the cementum Possibly comprised of hypo mineralized interglobular dentin

Question 12

Primary dentin

Answer 12

All dentin (except mantle dentin) formed up to the time the tooth achieves functional occlusion

Question 13

Secondary dentin

Answer 13

All dentin formed (except tertiary dentin) formed after tooth achieves functional occlusion

Question 14

Dead tracts

Answer 14

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

Question 15

Sclerotic Dentin

Answer 15

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

Question 16

Incremental lines of von Ebner

Answer 16

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.

Question 17

Neonatal line and contour lines of Owen

Answer 17

Both represent exaggerated lines of con Ebner that occur during periods of altered cell metabolism

Question 18

Tertiary Dentin

Answer 18

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

Question 19

Cells in the subodontoblastic layer once exposed to growth factors released by stimulated pulpal cells

Answer 19

differentiate and form the matrix of reparative dentin.

BMP, IGF, FGF, DMP

Question 20

Dentinogenesis Imperfecta

Answer 20

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

Question 21

Attrition

Answer 21

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

Question 22

Erosion

Answer 22

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

Question 23

Bacteria responsible for dental caries include

Answer 23

Strep. Mutans (enamel/dentin caries)
Strep. sorbrinus ^^
Strep. Gordonii ^^
Lactobascillus acidophilus ^^
Actinomyces viscous (root caries)

Question 24

Dentinal sensitivity

Answer 24

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

Question 25

Direct innervation theory

Answer 25

Direct stimulation of nerve endings in dentinal tubules

Question 26

Transduction theory

Answer 26

Stimulation of odontoblasts that are coupled to nerves in the pulp

Question 27

Brannstrom’s hydrodynamic theory

Answer 27

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