Day 1 Lecture 2 Flashcards
Periodontium
Gums and jaw
TMJ
Temperomandibular joint
Restorative + Prosthetic Dentistry
Repair and replace teeth
Baby teeth
Deciduous - 20
Incisors
Cut/shear food, phonetics function and aesthetics
Canines
Shear, tear, pierce food, longest roots and strategic position in arch, key to occlusion (protection) - allow lateral guidance
Premolars
Grinding, fine chewing
Molars
Multi-rooted, strong, grinding, crushing, chewing.
Clinical Crown
What you can see
Anatomical crown
where DEJ is and on
DEJ
dentin enamal juncture
Dentin strength
1/10 strength - second hardest bone in body
Enamel comp.
90-95% inorganic HA, 4-8% H20, 1-2% protein
HA
hydroxyapatite -a calcium phosphate
Enamel structure
striated - rods from ameloblasts
Ameloblasts
form enamel from DEJ, extinct after deposition. Epithelial origin
Dentin/pulp complex
Mesenchymal in origin, odontoblasts in pulp
Odontoblasts
Form dentin, still can make dentin throughout life - cell bodies line wall of pulp chamber
Enamel organization
teardrops, rods are 4-8 microns, rods surrounded by organic sheath (easily sheared). Head region and tail region are 5 microns wide/long respectively
Enamel crystals with fluoride
Fluorapatite
Crystalite direction in/around rods
parallel in rods, up to 65deg fro prism direction in periphery/tail
Gnarled enamel
Occurs at cervical (visible base) and incisal/occlusal (pointed, valley) areas
Enamel properties
Hard brittle parallel to rod direction, rarely follows straight path. Low tensile strength perpendicular to rod direction (dentin is stronger in terms of tensile)
Enamel fracture lines
interprismatic - don’t go into dentin. dentin acts as a cushion and the tooth doesn’t shatter as a result
Isotropic
same in all directions
Anisotropic
depends on direction (tooth)
When is enamel subject to fracture
When unsupported by dentin
Dentin comp.
50% vol HA (75% wt), 25% vol collagen (20% wt), 25% vol H20 (5%wt)
Dentin tubules
extend from pulp chamber to DEJ. Related to cells that line pulpal wall
Peritubular dentin
denser, has had a longer time to deposit (larger and near DEJ)
Intertubular dentin
located between tubules, hasnt had much time to deposit
Dentin tubules
channel for odontoblastic process, allows fluid movement and ion transport. Allows remineralization, apposition of p. dentin, pain perception (perceived by nerves in pulp)
Odontoblastic process
extension of odontoblast into dentin - cytoplasmic, aka tomes fibers
Dentin structure
not uniformly mineralized (peritubular more than intertubular), principle organic component = collagen (toughness). HA crystals in collagen (smaller than enamel). 20% less hard than enamel, higher tensile strength, lower stiffness (more elastic). isotropic, cushion
Predentin
Unmineralized zone of dentin immediately adjacent to cell bodies of odontoblasts
Primary dentin
First dentin formed - forms up to 3 years after eruption
Secondary dentin
Without any obvious stimulus, dentin direction changes and deposition slows.
Reparative dentin (tertiary)
pulp fills in cavity in case of injury.
Sclerotic dentin
Doesnt follow rules, like gnarled enamel, especially down in cervical area
Dentin differ from Enamel
Less mineral content, small tubules for fluid (pain reception) and ion transport. Ability to repair or regenerate to physical or chemical response until pulp dies.
Radiopaque
White on x-ray (enamel)
Cementum
Periodontum - borders tooth. Slightly ligher in color than dentin. Lost as periodontium is lost (rarely seen in clinic, often brushed away).
Periodontal Ligament - hold
Sharpeys fibers holds
Cementum composition
5-10% mineral content. 45-50% inorganic (HA) by weight, 50-55% organic matter and water by weight (mainly collagen and protein polysaccharides). highest fluoride content of all mineralized tissue.
Cementum structure
hard, avascular on anatomic roots. Formed continually throughout life, repair is limited as it is based on surrounding tissue (once it’s gone it is gone). Slightly softer than dentin, but permeable.
Cementum origin
Formed by cementoblasts which develop from mesenchymal cells in connective tissue of dental follicle.
Cementodentinal Junction (CDJ)
Attachment of cementum to dentin
Cementoenamel Junction (CEJ)
Cervical line, where cementum joins enamel
Dental Pulp functions
Formative/developmental, Nutritive, Sensory/Protective, Defensive/reparative
Formative/developmental (pulp)
Production of primary and secondary dentin by odontoblasts
Nutritive (pulp)
Supplies moisture and nutrients through blood to odontoblasts and their processes
Sensory/Protective (pulp)
Provides nerve fibers to mediate pain (only response).
Defensive/reparative (pulp)
Deposition of reparative dentin in response to stimuli. Inflammatory reaction to severe irritation - this can cause pulp death.
