11/7: Teeth Flashcards
What are teeth grossly divided into?
Root and crown
What is the portion of the tooth embedded in bone?
Tooth root
What is the pat of jaw that a tooth is embedded in?
Alveolar ridge
What is the tooth socket called?
Alveolus
What is the portion of tooth that projects into oral cavity?
Crown
What are teeth protected by?
A layer of highly mineralized enamel, covers crown
What is enamel?
a hard, translucent substance, containing < 1% organic material & 96-98% hydroxyapatite
What is enamel secreted by?
Tall, columnar ameloblasts of enamel organ
When do ameloblasts degenerate?
When the tooth erupts, after which enamel cannot be replaced by new synthesis
What do secretory ends of ameloblasts form?
Single, large process, Tome’s process (microtubules and secretory vesicles)
Explain enamel mineralization
Non-uniform, resulting in highly calcified enamel rods or prisms - roughly hexagonal
What is enamel separated by?
Interprismatic material
Where do enamel rods extend from?
Ameloblasts at enamel surface to dentino-enamel junction
What is the bulk of tooth composed of?
Less mineralized dentine
What is dentine secreted by?
Odontoblasts of dental papilla as non-mineralized pre-dentine
Explain the components of dentine?
Chemically similar to bone, but more mineralized; ~70-80% hydroxyapatite crystals
What plays a key role in mineralization of dentine matrix (like odontoblasts)?
Matrix vacuoles (Ca2+ and PO4-)
What else does dentine contain?
Type I collagen and GAG’s
How is dentine arranged?
In dentine tubules
What are dentine tubules?
Hollow, parallel tubes radiating from pulp cavity
What do dentine tubules contain?
Long, rod-like cytoplasmic process of odontoblasts (aka Tome’s fibers)
What does the central pulp cavity contain?
Support structures - sensory nerves and blood vessels
What is dentine innervated by?
Myelinated nerves
Describe dental pulps origin
Mesodermal in origin
What does dental pulp resemble?
Primitive mesenchyme
What does dental pulp contain?
Sellate 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?
Cementum
What is cementum manufactured by?
cementoblasts
What do cementoblasts mature into?
Cementocytes
What do cementocytes that lie against the surface of the periodontal ligament produce?
New cementum by appositional growth
What is similar to osteoblasts/cytes structurally and functionally?
Cementocytes
What is the region of the tooth between root and crown?
Neck of tooth
What is the neck of tooth protected by?
Masticatory oral mucosa called gingiva
What does the gingiva cover?
Upper portion of alveolar ridge
What is gingiva sometimes divided into/
Attached gingiba
What does attached gingiva cover?
Upper alveolar bone and free gingiva (forms cuff ~ neck of tooth)
What is the spave between free gingiva and crown called?
Gingival sulcus or crevice
What is the gingiva lined by?
Cervicular epithelium
What is crevicular epithelium easily breached by?
Bacteria -> periodontal disease, gingivitis
What is tissue that surround and support tooth referred to as?
Periodontium
What is included in periodontium?
Epithelium, cementum, peridontal ligament, and alveolar bone
How is cementum layer anchored to bone of alveolus?
With gibers of periodontal ligament or membrane
What is periodontal ligament composed of?
Dense, collagenous fibers, called Sharpey’s fibers
How do Sharpey’s fibers run?
At oblique angle, support tooth in socket
What do Sharpey’s fibers allow?
Slight movement of tooth during mastication
What are clusters of epithelial cells within periodontal ligament?
Vestigial epithelial rests (of Malassez)
Where is tooth formed in relation to epithelial cells?
Between opposing layers of epithelial cells
ameloblasts of enamel organ &
odontoblasts of dental papilla
What is the ectodermal origin?
Enamel
What are mesodermal origin?
Dentine, cementum, pulp, and periodontal ligament
When does odontogenesis occur?
6th week of fetal development
What does the epitheloium look like during the early bell stage of odontogenesis?
Horseshoe-shaped epithelial ridge arises from oral epithelium
What does the horeshoe epithelial form?
Dental lamina in position of future jaws
In each quadrant, what does lamina develop
Several globular, ectodermal swellings (one for each diciduous tooth)
What does the superficial half of the cap stage form?
Enamel organs
What does the deep half of the cap stage form?
Dental papilla
What are cells involved in the early bell stage?
loosely arranged stellate cells and peripheral alyer of cuboidal/low columnar eoithelium
Where do the cells of the early bell shape meet?
Cervical loop
What does the internal enamel epithelium differentiate into?
Layer of amelobalsts and 2-3 cells (think stratum intermedium)
What does mesenchyme condense to form?
Dental papillae
What develops at the junction with ameloblasts?
Row of odontoblasts
What does permanent teeth arise from?
Side-growth of dental lamina
What is the initial shape of enamel?
Cup shaped (Cap stage)
What becomes stellate reticulum?
Cells of enamel organ differentiate with extracellular matrix of GAG’s
What does the outer part of the bell-shaped structure become?
External enamel epithelium
What do cells lining the concave surface of enamel organ form?
Internal enamel epithelium
What does internal enamel epithelium differentiate into?
Tall, columnar ameloblasts
What is enamel formation?
Amelogenesis
What are deep developing enamel organs?
Primitive mesenchyme
What does primitive mesenchyme develop into?
Dental papilla
Cells lining convex surface of dental papilla develop into?
Odontoblasts
What is dentine formation?
Dentinogenesis
What occurs to two cell layers in apposition?
Tooth forms between
What do the two cell layers form together?
Future incisors, canine and molars of primary dentition
What does development of ameloblasts induce?
Differentiation of odontoblasts
What does calcification of dentine induce?
Deposition of enamel
What is tooth formation initiated by?
Deposition of organic pre-dentine by odontoblasts on surface of dental papilla
What is pre-dentine layer calcified into?
Dentine
What does calcification of dentine matrix secondarily induce?
Enamel production by ameloblasats
What do odontoblasts have embedded into dentine matrix and what do they form?
Odontoblast processes; dentine tubules
What is enamel formed by?
Mineralized columns of enamel rods
What are enamel rods separated by?
Less mineralized inter prismatic material
What occurs to dental lamina?
Fragments and atrophies
What happens at the time of tooth eruption?
Enamel organ and ameloblasts degenerate
What happens to overlying mucosa as tooth erupts?
Separates as tooth erupts, exposing crown
What happens to the dental papilla as tooth erupts?
Shrinks, becomes dental pulp, surrounded by dentine
What is papillae enclosed by and become?
Dentine; pulp cavity
What is a proliferation of epithelial cells located at the cervical loop of the enamel organ?
Hertwig’s root sheath
What does hertwig’s root sheath initiate?
Formation of dentine in the root by causing the differentiation of odontoblasts from the dental papilla
When does the root sheath disintegrate?
With the periodontal ligament
What do residual pieces that do not completely disappear seen as?
Epithelial cell rests
What occurs after tooth formation if compelte?
Small amounts of secondary dentine continue to be produced
What is the outer rim of enamel organ known as?
Epithelial sheath of hertwig
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 in the case of molars?
Caudally to form enamel organs of secondary dentition
When does tooth eruption occur?
6-30 months after birth
How many deciduous teeth?
20 - 2I, 1C, 2M/quadrant
How many roots in I and C?
1
How many roots in P?
2
How many roots in M?
2-4
What occurs between ages of 6-12?
Deciduous teeth replaced by permanent
What causes yellow discoloration of teeth?
Tetracycline administered during development of permanent dentition
What is orthodontia accomplished by?
osteoblast & osteoclast activity in alveolus
When do dental caries result?
When weak acids in food and drink erode calcified enamel, augmented by bacterial action
What does fluoride do to enamel?
Harden and kill bacteria
Where can caries extend into?
Dentine or pulp cavity, produce abscesses or death of tooth
What is caused by
accumulation of calcified food & bacterial debris (plaque) in gingival sulcus?
Periodontal disease
What does periodontal disease cause?
widening of gingival sulcus, possible inflammation & destruction of periodontal ligament
What is inflammation of gums?
Gingivitis
What is inflammation of periodontal ligament?
Periodontitis
