Enamel

Question 1

What’s enamel prisms /rods and from where originate ?

Answer 1

The enamel prisms or rods are the basic structural component of enamel.

They originate at the dentino-enamel junction and extend through the thickness of the enamel surface.

The prisms appear cylindrical in longitudinal sections and take up key-hole or fish-scale pattern in cross-sections

Question 2

What’s Striae of Retzius ? They have another name what’s called ?

Answer 2

These appear as brownish bands in ground sections and illustrate incremental pattern of enamel.

Striae of Retzius represent the rest periods of ameloblast during enamel formation, therefore, also called as growth circles, similar to annual rings on a tree

Question 3

we could definitely identify striae of retzius, debris, and cracks under under how much magnification ?

Answer 3

×50

Question 4

What’s the three morphological patterns of prism arrangement ?

Answer 4

Type 1 - shallow prisms
Type 2 - well-defined prisms
Type 3 - microporosities in *3000 magnification

Question 5

When prisms were measured under ×6000 magnification and the results showed larger prisms in ?

Answer 5

posterior than in anterior teeth

Question 6

What’s the most common prisms structure On the mesial and distal surfaces, of Posteriors and anteriors ?

Answer 6

Type 2 well defined

Question 7

What’s the most common prisms in mesial structure ?

Answer 7

Type 2 well defined

Question 8

Which type of prisms prodeminate in mesial Incisal edge of posterior ?

Answer 8

Type 1 shallow

Question 9

Which type of prisms prodeminant in mesial Incisal edge of anterior ?

Answer 9

Type 2

Question 10

Which type The incisal third of distal surface showed predominant pattern in the anterior teeth?

Answer 10

Type 1, shallow prism

Question 11

Which type The incisal third of distal surface showed predominant pattern in the anterior teeth?

Answer 11

Type 1, shallow prism

Question 12

Which surface showed equal distribution between Type 1 and 2 prism patterns ?

Answer 12

The labial surface of anterior teeth

Question 13

Which surface showed predominant Type 1 shallow prism pattern ?

Answer 13

lingual surface of anterior teeth

Question 14

Which surface showed predominant Type 1 shallow prism pattern ?

Answer 14

lingual surface of anterior teeth

Question 15

Which surface showed predominant Type 2 prism pattern ?

Answer 15

Lingual surface posterior teeth

Question 16

Occlusal surface of posteriors showed predominant ?

Answer 16

Type 2 prism pattern

Question 17

Which teeth have more big and small prisms ?

Answer 17

Anteriors 5.0microns
Posteriors 5.35 microns

Question 18

What does The surface enamel is composed of ?

Answer 18

enamel prisms or rods, rod sheaths, and cementing interprismatic substance.

Question 19

What does The surface enamel is composed of ?

Answer 19

enamel prisms or rods, rod sheaths, and cementing interprismatic substance.

Question 20

What’s enamel rods / prisms ? From where does they originate ?

Answer 20

the basic structural component of enamel.

They originate at the dentino-enamel junction and extend through the thickness of the enamel surface.

The prisms appear cylindrical in longitudinal sections and take up key-hole or fish-scale pattern in cross-sections.

Question 21

What’s 2 pattern of prisms ?

Answer 21

Majority of the prisms were smooth with some grooves, and few showed abundant microporosities.

Another secondary pattern seen only in the incisal third was the exposed prisms.

Question 22

Explain the arrragment of enamel rods ?

Answer 22

The rods are oriented so that the heads face toward the cusp tip and the tails toward the cervical margin.

Question 23

What’s the composition of each rod ?

Answer 23

The enamel crystallites that compose each rod exhibit differing orient-ation within these two regions.

The crystallites are composed of hydroxyapatite (90% of the inorganic component of mature enamel).

The space between the crystallites is occupied by the organic matrix (2%) and water (12%).

Question 24

Rods oriention ? And were they in clockwise and vertical ?

Answer 24

Rods are oriented perpendicular to dentinoenamel junction and follow a wavy course in clockwise and anticlockwise direction.

Toward incisal/occlusal surface, these become almost vertical

Question 25

What’s the inclination of Cervical enamel rods of deciduous and permanent teeth ? And clinical significant ?

Answer 25

incisally or occlusally, while in permanent teeth these are inclined apically.

avoid unsupported enamel rods at gingival floor, cavosurface bevel (15 to 20°) at gingival margin is given by using gingival margin trimmer

Question 26

What’s the inclination of Cervical enamel rods of deciduous and permanent teeth ? And clinical significant ?

Answer 26

incisally or occlusally, while in permanent teeth these are inclined apically.

avoid unsupported enamel rods at gingival floor, cavosurface bevel (15 to 20°) at gingival margin is given by using gingival margin trimmer

Question 27

Where is the thinnest enamel ?

Answer 27

CEJ KNIFE EDGE , cervical area

Question 28

Where is the thinnest enamel ?

Answer 28

CEJ KNIFE EDGE , cervical area

Question 29

Enamel in nature is translucent which factors affect its color ?

Answer 29

i. Thickness of enamel; young anterior teeth appear translucent gray or bluish near incisal edges. It appears yellowish in cervical areas due to thin enamel from which color of underlying dentin is visible (Fig. 3.3A).

ii. Shade of underlying dentin.

iii. Presence of stains in enamel.

iv. Anomalies occurring during developmental and mineralization stage, antibiotic usage and fluorosis, etc. affect the color of teeth

Question 30

Why all all enamel rods should be supported by healthy dentin base ?

Answer 30

Because of more compressive strength of dentin than enamel, dentin acts as a cushion for enamel when masticatory forces are applied on it.

Therefore, during tooth preparation, to have maximum strength of underlying remaining tooth structure all enamel rods should be supported by healthy dentin base .