Dental Tissues Flashcards
Label the diagram (including the white and yellow parts of the tooth)
What is the difference between the anatomical and clinical crown?
Anatomical crown = part of tooth that is covered by enamel
Clinical crown = part of the tooth that is visible in the patient’s mouth (clinical is what you can “C” see)
What is the cervical margin?
Where the crown meets the root (the enamel stops) = cervical margin (cervical means neck)
When is the anatomical crown bigger than the clinical crown (and vice versa)?
Erupting tooth: clinical crown < anatomical crown
Gingival recession: clinical crown > anatomical crown
Label the diagram
What is the function of cementum?
- Covers the root of teeth
- Part of what attaches the tooth to bone
What is pulp composed of? What does it contain?
Soft tissue which contains a lot of nerves (nerve is just part of the pulp)
What are the mineralised tissues of the body?
What is the mineral they contain?
What does it do?
- Enamel
- Dentine
- Cementum
- Bone
Mineral component in them (inorganic) is a calcium phosphate product - hydroxyapatite (apatite for short)
The mineral component makes them hard.
List the components and the % of components within mineralised tissues
Components of mineralised tissues:
- Mineral component: (inorganic) apatite
- Matrix component: (organic) e.g. collagen
- Water component
Enamel: 96% mineral, 1-2% matrix, 2% water
Dentine: 70% mineral, 20% matrix, 10% water (descending)
Cementum: 65% mineral, 23% matrix, 12% water (increments descending)
Bone: 60% mineral, 25% matrix, 15% water (rounding up increments to 5)
List the main features of enamel
- Almost a pure crystal structure (96% apatite crystals)
- Most mineralised, hardest tissue in the body
- Brittle: can be broken by hand if not supported by dentine
- Enamel prisms: apatite crystals are arranged in a prismic arrangement running from the ADJ to the surface
- Covers the anatomical crown
- About 2 mm thick layer
- Epithelial product: produced by epithelial cells
- Cells that make them disappear
- We cannot add enamel
- Non-vital: does not contain nerves
- Translucent: not transparent, but lets light in; grey material, not white
- Permanent teeth yellow since translucent enamel allows us to see through to the colour of dentine
- Deciduous teeth whiter since enamel not yet perfectly formed - more opaque
- Can only be cut by high speed air turbine (0.5 mio revs/min) with:
- Diamond burs
- Tungsten carbide coated burs
- (stainless steel drill will not cut through enamel)
Label all the features of the mineralised tisses
- Enamel Prisms
- Dentinal Tubules (from ADJ to pulp)
- Collagen Fibers (roughly paralled to ADJ)
What kind of a tissue is dentine? What does it contain?
Describe the important characteristics of dentine’s important component, as well as of dentinal tissue
Dentine is connective tissue.
It is connective tissue, being composed of 20% collagen matrix (organic). It also contains blood vessels and nerves (is vital)
Collagen is :
- a structural proten which exists in very strong fibers, tendons, and connective tissue: it gives dentine its strength
- collagen fibers in dentine run parallel to the ADJ
Dentinal tissue:
If we look at dentine through a microscope, we don’t see collagen fibers. What we see if a lot of dentinal tubules – dentine is full of holes.
- The tubules run from the ADJ right through to the pulpal aspect (continuous with the pulp)
- Dentine extremely tubular: 15-65k tubules per mm sq.
Between ADJ and predentine (next to pulp):
- Tubule density increases
- Tubules get closer together
- Tubule diameter increases
So dentine on the outside is quite different from dentine in the inside. it gets easier for bacteria deeper down
What is dentine formed from? Where is it located?
Dentine is formed from predentine, the non-mineralised tissue located beside the pulp
What do dentinal tubules contain?
How does sensodyne toothpaste work?
Tubules may contain:
- Cell processes: bits of cells (the dontoblasts that made them have their processes in the tubules). The cells that form dentine remain (unlike enamel)
- Nerves: this is the important bit. If we have exposed dentine, or if we drill dentine that is not anesthetized, it is ridiculously painful. Sensodyne toothpaste works by blocking the dentinal tubules that are exposed. Since it contains nerves, we describe dentine as a vital tissue – it is alive.
- Fluid
What are the 3 mechanisms for making sure fillings stay in?
- Mechanical mechanism: undercut - filling wider at bottom than at top, so wedged in
- Enamel bonding:
- by acid etching to roughen the surface of enamel
- makes filling bond better
- Dentine bonding
- acid used to demineralise dentine: dissolves away surface apatite, leaving collagen meshwork exposed
- resin bonding to collagen meshwork: infiltrates collagen fibers and locks filling in
- resin bonding to dentinal tubules: infiltrates tubules and locks filling in
What kind of tissue is dental pulp?
Where is it located? What is the disadvantage of its location?
Specialised connective tissue
Dentine is the calcified (mineralized) tissue of the pulp that encloses the pulp – remember that pre-dentine, the non-mineralized dentine is beside the pulp
Disadvantage: So pulp is effectively enclosed in a rigid chamber: no scope for tissue to swell when inflamed
Label the diagram
Which part of the pulp grows smaller with age?
Which part can have various anatomies?
- Coronal = crown
- Radicular = root
- Apical foramen: a hole, where the tissues enter and exit the space
Pulp horns – underneath the cusps of tooth, especially in young people. So big in young people, it is very easy to inadvertently drill into them. In an older person it is more difficult to find
Apical foramen can have various anatomies:
- Delta:more difficult to manage/clean in RCT
- Lateral canals:exit down the side
What are the functions of dental pulp?
Pulp functions:
- Dentine formation
- Defence cells (it can get infected) and repair
- Sensory function: Contains a lot of nerves. We only feel pain/cold – both unpleasant. Some of the worst pain you can get is acutely inflamed pulp.
Describe the relationship between dentine and pulp
Dentine-Pulp complex: both intricately linked
- Embryologically
- physically
- functionally
Dentine is porous: any material or procedure in dentine may lead to inflammation of pulp
- Pulp has no room to swell when inflamed (effectively enclosed in a rigid dentine chamber) = pressure builds up = no blood flow = pulp dies = bacteria city
- Some materials can be therapeutic: eg calcium hydroxide
Dentine is vital: can respond to insult to protect pulp
What type of tissue is cementum?
Describe its functions and characteristics
Mineralised specialized connective tissue
Functions:
- Covers the roots
- Supports tooth – tooth stays in bone because the collagen fibers around the tooth anchor in to cementum and bone
- Resistant to resorption: Bone resorbs, cementum does not easily resorb. This is vital in putting orthodontical appliances on teeth
What kinds of cementum-enamel relationships are found in people?
- 60% of people: cementum extends beyond the ADJ at the cervical margin onto the enamel on the crown
- 30% of people: cementum ends at the ADJ at the cervical margin
- 10% of people: cementum ends before the ADJ/cervical margin, leaving exposed dentine tubules
