clinical significance of tooth for operative dentistry

Question 1

where does enamel originate from ?

Answer 1

ectodrm embryonic germ layer

Question 2

composition of enamel :

Answer 2

92% hydroxyapatite , 2% organic matrix , 2-12% water by volume

Question 3

example of tooth surface that is not naturally cleaned by salive:

Answer 3

pit and fissure

Question 4

enamel is formed of enamel rods and cementing interrod substance to form :

Answer 4

incremental striae of retzius

Question 5

dentine and pulp are considered as one organ because they are related to eachother :
-embryologically :
-anatomically:
-physiologically:
explain these relations.

Answer 5

embryologically : derived from the same mesodermal origin (dental papilla)

anatomically: tome’s fibers , which constitute 1/3rd of the dentin structure, are protoplasmic processes of odontoblastic cells which are cells of the pulp

physiologically: dentine provides protection to the pulp while pulp provides nutrition to the dentine

-pulp-dentine complex responds together to pathologic challenge

Question 6

formative/ developmental functions of the pulp(-dentine complex) :

Answer 6

formation of primary and secondary dentine

Question 7

nutritive functions of pulp(-dentine complex):

Answer 7

supplies mineral ions , proteins , and water to dentin through blood supply to odontoblasts process

Question 8

sensory (protective)functions of pulp(-dentine complex):

Answer 8

provide nerve fibers within pulp that mediate the sensation of pain

Question 9

defensive / reparative functions of pulp(-dentine complex):

Answer 9

response to pathological challenges (caries)

Question 10

location of odontoblasts:

Answer 10

their cell bodies are in pulp while their cell processes extend into tubules in mineralized dentine

Question 11

how does the presence of enamel spindles affect cavity preparation ?

Answer 11

they can act as pain receptors as they extend past the DEJ

Question 12

largest part of tooth structure:

Answer 12

dentine

Question 13

pre-dentine :

Answer 13

unmineralized zone next to pulp

Question 14

primary dentin :

Answer 14

form the initial shape of tooth.secreted before root formation is complete

Question 15

sclerotic dentin

Answer 15

mature aged dentin–FIlld dead tracts

Question 16

how does dentin differ from enamel in regards to :
-color :
-reflection:

Answer 16

color : dentin is normally yellow-white and slightly darker than enamel (older patients or old restorations appear even darker)

reflection: dentine is more opaque, dull , and less reflective to light while enamel is shiny

Question 17

physical , thermal , chemical , bacterial , and traumatic stimuli are remote from the nerve fibers and are detected through :

Answer 17

dentinal tubule (hydrodynamic theory)

Question 18

transparent dentin:

Answer 18

early defense response in primary dentin to block the advancement of caries (less hard due to mineral loss)

Question 19

reactive dentin sclerosis :

Answer 19

calcification / increased overall remineralization of dentine tubules in carries affected primary dentine

Question 20

tertiary dentin formation occurs when :

Answer 20

simultaneously with pulpal inflammatory response at the pulp-dentine interface

Question 21

Reactionary tertiary dentin

Answer 21

in mild injury (caries lesion) primary
odontoblasts initiate increased formation of dentin along the internal aspect
of the dentin beneath the affected area

Question 22

when is reparative (secondary) tertiary dentin secreted?

Answer 22

severe injury(deep caries) cause death of primary odontoblast thus secondary odontoblast secretes reparative dentin

Question 23

area with most dentine tubules:

Answer 23

deep dentin near pulp

least : dentine in superficial root

Question 24

shape of dentine tubules in tooth crown :

Answer 24

gentle S shaped curve

• straighter in incisal edges , cusps and root area

Question 25

how is the number and the diametes of dentin tubules affected as you go from DEJ to pulp.

Answer 25

number increases from 15,000-20,000/mm2 at DEJ to 45,000-65,000/mm2 towards the pulp diameter increases from 0.5-0.9um at DEJ to 2-3um near the pulp

Question 26

how is pulp affected as age increases?

Answer 26

there is a reduction in pulp volume as you age due to. an increase in secondary dentine deposition -there is also a reduction in blood vessels and decrease in dentin permeability which decreases sensitivity and the possibility of reduced ability of pulp to react to irritants and repair itself

Question 27

convexity on cervical third of lingual surface is present on :

Answer 27

anterior teeth

Question 28

convexity on middle third of lingual surface is present on :

Answer 28

posterior teeth

Question 29

importance of proximal contact area;

Answer 29

stablize dental arch, prevent food impaction and provide adequate embrasures

Question 30

significance of marginal rdiges:

Answer 30

help balance teeth in both arches to improve efficiency of mastication and prevent food impaction

Question 31

enamel thickness:

Answer 31

covers anatomic crown usually 2-3mm

Question 32

convexity found on all teeth:

Answer 32

cervical third of facial surfaces

Question 33

protective contours of the teeth are most functional when ____

Answer 33

teeth are in proper alignment

Question 34

what's the function of normal tooth contours ?

Answer 34

act in deflecting food and passing food to stimulate (but not irritate) supporting soft tissue

Question 35

describe the location of proximal contact areas:

Answer 35

in anterior teeth its found more cervcally and centralized face-lingually in posterior teeth they are in the buccal 1/3rd

Question 36

improper proximal contact areas cause:

Answer 36

carious lesions , periodontal ligaments due to food impaction