Oral Cavity and Tooth development -Part 2 Flashcards
what are teeth grossly divided into
root and crown
what is the tooth root
portion of tooth embedded in bone
where is the tooth root located
in part of the jaw called alveolar ridge, in the tooth socket called the alveolus
what is the crown
the portion of the tooth that projects into oral cavity
what is the enamel
a highly mineralized layer that protects the crown
describe enamel
hard, translucent substance, containing less than 1% organic material and 96-98% hydroxyapatite
what does enamel derive from embryologically
ectoderm
what is enamel secreted by
tall, columnar ameloblasts of enamel organ
what are tome’s processes
apical, secretory end of ameloblast
what is the formation of enamel rods due to
enamel mineralization not being uniform
what are enamel rods separated by
interprismatic material
where do enamel rods extend from
ameloblasts at enamel surface to dentino-enamel junction
what is dentin embryologically derived from
mesoderm
what is the bulk of the tooth composed of
dentin
what secretes dentin
odontoblasts of dental papilla as non-mineralized pre-dentin
what is dentin chemically similar to
bone but more mineralized ~70% hydroxyapatite crystals
what does dentin contain
type 1 collagen and GAGs
what is dentin arranged in
dentin tubules
what do dentin tubules radiate from
pulp cavity
what do dentine tubules contain
long rod-like cytoplasmic processes of odontoblasts (Tome’s processes)
what does the pulp cavity contain
support structures such as sensory nerves and blood vessels
what is dentin innervated by
myelinated nerves
what is dental pulp embryologically derived from
mesoderm
what does dental pulp resemble
primitive mesenchyme
what does dental pulp contain
stellate fibroblasts, reticular fibers, collagen and ground substance
what is dental pulp supplied by
capillaries from arterioles running with periodontal ligament
what is the tooth root covered by
a thin layer of cementum
what is cementum embryologically derived from
mesoderm
what is cementum
amorphous, collagen-based, calcified tissue ~45-50% hydroxyapatite, similar to bone
what makes cementum
cementoblasts that mature into cementocytes
what are cementoblasts/cementocytes similar to
osteoblasts/osteocytes
what anchors the cementum layer to bone of alveolus
fibers of periodontal ligament or membrane
what is the periodontal ligament composed of
dense, collagenous fibers called sharpeys fibers
what do sharpeys fibers do
run at an oblique angle to support tooth in socket and allow slight movement of tooth during mastication
what are epithelial rests of Malassez
occasional clusters of epithelial cells within periodontal ligament
what is the neck of the tooth
the region of tooth between root and crown
what protects the gingiva
masticatory oral mucosa
what does the gingiva cover
upper portion of alveolar ridge
what does attached gingiva cover
upper alveolar bone
what does free gingiva form
cuff or neck of tooth
what is the space between the free gingiva and crown called
gingival sulcus or crevice
what the gingival sulcus lined by
crevicular epithelium
what is the periodontium
tissues that surround and support tooth
what does the periodontium include
epithelium, cementum, periodontal ligament and alveolar bone
what 2 opposing layers form the tooth and what is their origin
ameloblasts of enamel organ and odontoblasts of dental papilla
what tooth structures are derived from ectoderm
enamel
what tooth structures are derived from mesoderm
dentin, cementum, pulp, and periodontal ligament
what happens in the 6th week of fetal development
a horseshoe shaped epithelial ridge arises from oral epithelium which forms the dental lamina in position of future jaws
what forms in each quadrant
lamina develops globular, ectodermal swellings ( one for each deciduous tooth) -> superficial half forms enamel organs and deep half forms dental papilla
what happens in the cap stage
enamel organ initially cup shaped
what do the cells of enamel organ progressively differentiate into
stellate reticulum with ECM of GAGs
what comes after the cap stage
bell stage
what do the cells lining the outer convex surface of the enamel organ become in the bell stage
external enamel epithelium
what do the cells lining concave surfaces of the enamel organ form in the bell stage
internal enamel epithelium that differentiate into tall columnar ameloblasts
what is amelogenesis
enamel formation
where is the dental papilla located
deep to developing enamel organs
what do cells lining convex surface of dental papilla develop into
odontoblasts
what is dentinogenesis
dentin formation
what does the development of ameloblasts induce
differentiaition of odontoblasts
what does calcification of dentin induce
deposition of enamel
what is tooth formation initiated by
deposition of organic pre-dentin by odontoblasts on surface of dental papilla that is later calcified into dentin
what does the calcification of dentin matrix secondarily induce
enamel production by ameloblasts
where are odontoblasts processes located
embedded in dentin matrix to form dentin tubules
what does enamel form in and what is it separated by
forms in mineralized columns of enamel rods separated by less mineralized interprismatic material
what happens after the deposit of dentin and enamel
dental lamina fragments and atrophies
what happens at tooth eruption to enamel organ and ameloblasts
they degenerate
what separates as the tooth erupts
overlying mucosa
what does the dental papilla become as it shrinks
dental pulp surrounded by dentin
what continues to be produced after tooth formation is complete
small amounts of secondary dentin
what determines the 3D shape of the tooth crown
overall shape of enamel organ
what is the epithelial sheath of Hertwig
outer rim of enamel organ
what does the epithelial sheath of Hertwig determine
cross sectional outline of tooth
what does the surrounding mesenchyme form
dental follicle -> periodontal ligament
what do enamel organs of permanent teeth develop as buds from
dental lamina and deciduous enamel organ
what does the dental lamina proliferate as in molars
caudally to form enamel organs of secondary dentition
when does tooth development begin
at 6th week of fetal development
how many roots do incisors and canines have
1 root
how many roots do premolars usually have
2 roots
how many roots do molars usually have
2-4 roots
when should you not prescribe tetracycline and why
during development of permanent dentition because it causes yellow discoloration of teeth
do molars have precursors
no
what is the human dental formula
I 2/2, C 1/1, P 2/2, M 3/3
what are incisors function
cutting and biting
what is canine function
puncturing and holding
what are premolars and molars used for
grinding
what does TMJ allow for
lateral and anterior-posterior motion important for chewing and grinding
what are cusps
raised points on occlusal surfaces of molars and premolars
what are the types of cusps
protocone, metacone and paracone
what is talonid
flattened posterior surface of lower molars
what is bunodont
low crowned premolars and molars in omnivores
what is hypsodont
tall and high crowned premolars and molars in herbivores
what is orthodontia accomplished by
osteoblast and osteoclast activity in alveolus
what are dental caries
results when weak acids in food and drink erode calcified enamel augmented by bacterial infection
what does fluoride do
hardens enamel and kills bacteria
what is a root canal
when caries extend into dentin or pulp cavity to produce abscesses or death of tooth
what is periodontal disease caused by
accumulation of calcified food and bacterial debris (plaque) in gingival sulcus that results in widening of gingival sulcus, possible inflammation and destruction of periodontal ligament
what is gingivitis
inflammation of gums
what is periodontitis
inflammation of periodontal ligament
