Teeth, Soft Tissue Flashcards
Dentin and cementum are mainly comprised of ___ matrix reinforced with the calcium phosphate mineral called ___.
Dentin forms the bulk of the tooth and is joined to the enamel at the ___
Dentin is covered by ___ that provides connection of the tooth to the ___ via the ___.
- Collagen type 1
- Apatite
- Dentin-enamel junction (DEJ)
- Cementum
- Alveolar bone
- PDL
Enamel is formed by ___ starting at the DEj. They exchange signals with ___ located on the other side of the DEJ and move away from each other.
The structural arrangement of enamel forms keyhole-shaped structures known as ___ that are ~__ µm across.
- Ameloblasts
- Odontoblasts
- Enamel prisms
- 5 µm
Why is dentin more soluble/susceptible to acid than enamel? (Aka rapid spread of caries once it penetrates the DEJ) (Four reasons)
- Different carbonate content (3% for enamel to 5% for dentin) for their calcium-deficient carbonate-rich hydroxyapatite.
- Dentin apatite crystals are smaller than enamel crystals (more surface area to attacking acids)
- Dentin mineral occupies only 50% of dentin structure, so not as much apatite compared to enamel (85%)
- The dentin tubules provide a pathway for acid dissolution.
Dentin - percent volume composition?
50 vol% carbonate-rich, calcium-deficient apatite
30 vol% organic matter (mostly type 1 collagen with elastin)
20 vol% fluid
Dentin tubules represent the tracks taken by the ___ cells from the DEJ or cementum to the pulp chamber. Tubule density is lowest at the ___ and highest near the ___, where ___ cells in a close-packed array.
How does this affect dentin bonding?
- Odontoblastic cells
- DEJ
- Pulp chamber
- Odontoblastic cells
- Deep dentin has a higher density of tubules per unit area which means more moisture when deep dentin is cut. A wetter surface means possible interference with bonding procedures.
Why is the dentin-pulp complex considered vital tissue?
What’s differentiates primary from secondary dentin? How about from tertiary dentin?
- The odontoblasts rest inside the dentin and line the walls of the pulp chamber.
- Secondary dentin forms over time and has a change in orientation of the dentin tubules.
- Tertiary is in response to insults such as caries or tooth preparation and is less organized than either 1 or 2.
Why is bonding to dentin difficult? (Four reasons)
- Dentin collagen matrix is wetter than enamel.
- Cutting dentin results in smear layer formation. (Plugs up dental tubules)
- Dentin may be altered by caries (tertiary dentin) which may result in loss of mineral
- Lower mineral content
Why is the DEJ considered a crack-arresting interface?
Enamel is brittle and is not as tough as dentin. Dentin is needed to support and redistribute stresses to resist crack propagation from enamel to dentin. The gradual transition from dentin to enamel prevents an abrupt transition in mechanical properties which would lead to high stress at the junction.
Enamel - Percent volume composition?
How does that compare to most bones?
95% vol Hydroxyapatite (calcium phosphate mineral)
4-5% vol Water
1% vol Organic material
Most bones are 70% vol minerals and contains collagen (think bone marrow dishes)
At what pH does enamel start to dissolve?
How does this compare to stomach acid?
Soda?
Sparkling water?
Critical pH of 5.5
Stomach acid: 1.5 to 2
Soda: 2.5 to 3.5
Sparkling water: 3 to 6
Why is CEJ believed to be anti-resorptive?
Harder than bone and has anti-angiogenic properties (no blood vessels adjacent and no osteoclasts as a result)
The gingival mucosa can be divided into three components:
- Free gingival margin
- Attached gingiva
- Alveolar mucosa
Average biologic width and its three components?
Sulcular depth (.69)
JE (.97)
CT (1.07)
Eight gingival fibers
- Dentogingival fibers
- Dentoperiosteal fibers
- Alveologingival fibers
- Intergingival fibers
- Circumferential fibers
- Semicircular fibers
- Transgingival fibers
- Transeptal fibers
Sharpey’s fibers - Collagen fibers that anchor the PDL to the cementum of the tooth and the alveolar bone.
- Composition
- Structure
- Function
- Location
Type 1 collagen fibers that extend from PDL to insert into cementum and periosteum of bone. They help withstand forces.
- Composition - Type 1 Collagen
- Structure - These fibers extend from PDL into cementum and alveolar bone
- Function - Structural connector, anchoring tooth in place
- Location - Found all over, but highly concentrated at CEj where fibers insert into both cementum and bone
Which bacteria are associated with dental caries (2) and which with root caries (1)?
- Strep mutans and lactobacilli acidophilus
- Actinomyces
Primary function of PDL?
Specialized connective tissue fibers that attach the tooth to alveolus and withstand the compressive and tensile forces during mastication (“shock absorber”)
What are the six types of PDL’s?
Which is the most numerous? What kind of forces do they resist?
- Transseptal
- Alveolar crest
- Horizontal
- Oblique
- Apical
- Interradicular
B. Most numerous: Oblique fibers
C. Resist intrusion or occlusal forces
Which two of the eight gingival fibers are unique that they are present but orientated in a parallel or oblique orientation for implants unlike perpendicular like in teeth?
Alveologingival and circumferential
Which aspect of the mucosal complex forms the most crystal connection with a tooth or implant and functions as a physical barrier to the ingress of bacteria?
Junctional epithelium
Which of the eight gingival fibers maintains tooth approximation and proximal contacts?
Transeptal gingival fibers
