clinical significance of tooth for operative dentistry Flashcards
where does enamel originate from ?
ectodrm embryonic germ layer
composition of enamel :
92% hydroxyapatite , 2% organic matrix , 2-12% water by volume
example of tooth surface that is not naturally cleaned by salive:
pit and fissure
enamel is formed of enamel rods and cementing interrod substance to form :
incremental striae of retzius
dentine and pulp are considered as one organ because they are related to eachother :
-embryologically :
-anatomically:
-physiologically:
explain these relations.
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
formative/ developmental functions of the pulp(-dentine complex) :
formation of primary and secondary dentine
nutritive functions of pulp(-dentine complex):
supplies mineral ions , proteins , and water to dentin through blood supply to odontoblasts process
sensory (protective)functions of pulp(-dentine complex):
provide nerve fibers within pulp that mediate the sensation of pain
defensive / reparative functions of pulp(-dentine complex):
response to pathological challenges (caries)
location of odontoblasts:
their cell bodies are in pulp while their cell processes extend into tubules in mineralized dentine
how does the presence of enamel spindles affect cavity preparation ?
they can act as pain receptors as they extend past the DEJ
largest part of tooth structure:
dentine
pre-dentine :
unmineralized zone next to pulp
primary dentin :
form the initial shape of tooth.secreted before root formation is complete
sclerotic dentin
mature aged dentin–FIlld dead tracts
how does dentin differ from enamel in regards to :
-color :
-reflection:
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
physical , thermal , chemical , bacterial , and traumatic stimuli are remote from the nerve fibers and are detected through :
dentinal tubule (hydrodynamic theory)
transparent dentin:
early defense response in primary dentin to block the advancement of caries (less hard due to mineral loss)
reactive dentin sclerosis :
calcification / increased overall remineralization of dentine tubules in carries affected primary dentine
tertiary dentin formation occurs when :
simultaneously with pulpal inflammatory response at the pulp-dentine interface
Reactionary tertiary dentin
in mild injury (caries lesion) primary
odontoblasts initiate increased formation of dentin along the internal aspect
of the dentin beneath the affected area
when is reparative (secondary) tertiary dentin secreted?
severe injury(deep caries) cause death of primary odontoblast thus secondary odontoblast secretes reparative dentin
area with most dentine tubules:
deep dentin near pulp
least : dentine in superficial root
shape of dentine tubules in tooth crown :
gentle S shaped curve
- straighter in incisal edges , cusps and root area
how is the number and the diametes of dentin tubules affected as you go from DEJ to pulp.
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
how is pulp affected as age increases?
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
convexity on cervical third of lingual surface is present on :
anterior teeth
convexity on middle third of lingual surface is present on :
posterior teeth
importance of proximal contact area;
stablize dental arch, prevent food impaction and provide adequate embrasures
significance of marginal rdiges:
help balance teeth in both arches to improve efficiency of mastication and prevent food impaction
enamel thickness:
covers anatomic crown usually 2-3mm
convexity found on all teeth:
cervical third of facial surfaces
protective contours of the teeth are most functional when ____
teeth are in proper alignment
what’s the function of normal tooth contours ?
act in deflecting food and passing food to stimulate (but not irritate) supporting soft tissue
describe the location of proximal contact areas:
in anterior teeth its found more cervcally and centralized face-lingually
in posterior teeth they are in the buccal 1/3rd
improper proximal contact areas cause:
carious lesions , periodontal ligaments due to food impaction
