Exam 2 Flashcards
What material forms the bulk of the tooth and has elasticity?
Dentin
What other tissues are dentin protected by?
Enamel and cementum
Predentin and dentin are similar to what other tissue type in the body?
Osteoid and bone
T or F. Dentin contains dentinal tubules.
True
T or F. Odontoblasts are present in pulp.
True
What is the in/organic content of mature dentin?
70% inorganic
20% organic
10% water
What type(s) of collagen are present in dentin?
Type 1 (56%) Small amounts of type III, V
Name some common dentin proteins.
DPP DSP DGP DMP1 osteocalcin ostepotin
How can dentin proteins impact mineralization?
Dentin proteins can be promoters or inhibitors of mineralization.
What are the three classes of dentin?
Primary (circumpulpal)
Secondary
Tertiary
Describe primary dentin.
AKA circumpulpal dentin.
Makes up most of tooth’s dentin
Mantle dentin (first dentin) within primary dentin
What is mantel dentin?
Aka First dentin
outer layer of coronal dentin
-has different properties, collagen distribution and orientation in the crown compared to the root
Describe secondary dentin.
- after root formation
- form by odontoblasts that form primary dentin
- can be seen by demarcation line
- continuous but slower odontoblastic activity
- reduction of pulpal chamber size over time (recession)
Describe tertiary dentin.
- refractionary (preexisting odontoblasts) or reparative (newly differentiated cells) dentin
- reaction to attrition, caries or restorative procedure
- site specific
- produced only by those cells directly stimulated
- tubular or atubular osteodentin
- (DSP upregulated)
How is tertiary dentin related to degree of injury?
- rate of tertiary dentin depends on the degree of injury
- more severe injury= more rapid rate of deposition
- cells can get trapped in the newly formed matrix, reason why tubular pattern becomes grossly distorted.
When and where does dentin formation begin?
- begins in bell stage
- forms from cusp tips and down the slope
When is root dentin completed?
After tooth eruption occurs. open apex before formation
- Primary: 18 mo after eruption
- permanent: 2-3 yrs after eruption
How does rate of deposition of dentin vary.
It can vary both within different regions of the tooth, also among different teeth
T or F. Dentin formation continues throughout life.
True. Result is a progressive reduction of size of the pulp cavity.
What is the first product of dentinogenesis?
Type III collagen fibrils with fibronectin (Von Kroff’s fibers)
Then type 1 collagen parallel to the DEJ
Describe mineralization of dentin.
- occurs by formation of matrix vesicles
- mineralization first appears as single crystals seeded by phospholipids in vesicle membrane
- crystals grow, rupture from vesicle and fuse with adjacent clusters to form a continuous layer of mineralized matrix
- deposition of mineral lags behind formation of organic matrix so that a layer of predentin is always present between odontoblasts and mineralization front.
- noncollagenous protein secreted by odontoblasts will now regulate mineral deposition
What are the two patterns of dentin mineralization?
Linear and globular- depends on the rate of dentin formation
What pattern is mantle dentin?
predominantly globular
What pattern is circumpulpal dentin?
both linear and globular
When does a globular pattern of dentin occur?
When mineralization is fastest.
When does a linear pattern of dentin occur?
When the rate of formation and mineralization is slow.
Describe dentinal tubules.
- contain cytoplasmic processes
- extend through the entire thickness of dentin
- have s-shaped path due to crowding in crown
- strait in incisal area and root dentin
- tapered (largest diameter near pulp)
- branches are found from odontoblastic processes. (frequently in roots)
What surrounds odontoblastic processes in predentin?
meshwork of collagen
What surrounds odontoblastic processes in dentin?
Odontoblastic process is within dentinal tubule surrounded by peritublar dentin that is poor in collagen and more mineralized.
What is intratubular dentin?
AKA intratubular dentin
- collar of hypermineralized dentin
- has little cartilage but increased DSP, DMP1
- forms between tubules
- primary secretory product of odontoblasts.
Describe sclerotic dentin.
- occluded dentinal tubules
- increases w/ age
- happens in root and middle of crown
- reduces dentin permeability–> prolonged pulp vitality
Describe interglobular dentin.
Areas of undermineralization or hypomineralized dentin.
- defect in mineralization
- occurs in primary teeth
- No defect in matrix formation, tubules normal
- lack peritubular dentin
- purely a mineralization defect
- prevalent in patients w/ vit D deficency or exposed to high levels of F during dentin formation.
What are incremental growth lines and why do they form?
- organic matrix deposited at 4microm/day
- changes in the orientation from day to day
- at the 5th day there is a more exaggerated change in orientation (lines of von Ebner) occur 20micom apart.
- occur at right angles to tubles, inward and rootward direction
- 2microm/hr
- mineralization is an a 12 hr cycle
What are contour lines of owen?
- another type of incremental pattern
- characterize areas of deficient mineralization due to trauma
- neonatal lines
What are neonatal lines?
- defines the disturbance of mineralization during birth
- a contour line of owen ?
Describe the granular layer of Tomes.
- root
- ground secretions
- progressive increase from CEJ to apex of tooth
- hypomineralization of interglobular dentin
- sections made through loops of dentinal tubules, and an optical phenomenon?
- special arrangement of collagen and noncollagen matrix proteins at the interface between dentin and cementum.
What are changes dentin experiences with age?
- dentinal tubule complete closure
- sclerotic dentin
- dead tracts of dentin
What are dead tracts of dentin?
- retracted processes from tubules
- entrapped air in ground sections
- coronal dentin
- bound by sclerotic dentin
Name 3 hereditary abnormalities of dentin.
1) dentinogenesis imperfecta
2) dentin dysplasia
3) vitamin D resistant rickets
What type of fiberous joint does the periodontium form?
Gomphosis
What does the periodontium include?
cementum
PDL
Alveolar bone
Gingiva facing the tooth
Describe cementum.
A hard avascular connective tissue that covers the roots of teeth.
What is the biggest difference between cementum and bone?
Cementum is avascular, bone is not.
What are the three main roles of cementum?
1) covers and protects the root dentin (covers the openings of the tubules)
2) provides attachment to the periodontal fibers
3) compensates for tooth resorption
Where is cementum the thickest?
apex and inter-radicular areas of multirooted teeth.
Where is cementum thinnest?
The cervical area
How does cementum simulate bone?
- has organic fibrous framework, ground substance, crystal type, development
- lacunae
- Canaliculi
- cellular component
- incremental lines (aka resting lines)
What are the main differences between bone and cementum?
cementum is…
- non vascularized, thus resistant to resorption
- only has a minor ability to remodel (bone easily remodeled)
- lacks neural component
- is 45-50% inorganic, (bone 70%)
- cementum attachment protein (CAP) and IGF
Where does cementum formation occur?
along the entire tooth
Hertwig’s epithelial root sheeth is an extension of ___ and ___.
inner and outer dental epithelium.
Describe HERS involvement in development in cementum.
- HERS sends inductive signals to ectomesenchymal pulp cells to secrete predentin by differentiating into odontoblasts
- HERS becomes interrupted
- Ectomesenchymal cells from the inner portion of the dental follicle come in contact with predentin by differentiating into cementoblasts.
- cementoblasts lay down cementum
What type of cells lay down cementum?
cementoblasts which differentiate from the ectomesenchymal cells from the inner portion of the dental follicle.
What are the three theories about how cementoblasts get activated?
1) infiltrating dental follicle cells recieve reciprocal signals from the dentin or the surrounding HERS cells and differentiate into cementoblasts
2) HERS cells directly differentiate into cementoblasts
3) Epithelial cell rests of malassez?
What cells are cementoblast cells derived from?
transformation of epithelial cells in the dental follicle
What are the proteins associated with cementogenesis?
Growth factors -TGF -PDGF -FGF Adhesion molecules -bone sialoprotein -osteopontin Epithelial enamel-like factors Gollagens Gla proteins (matrix and bone) Transcription factors (Cbfa1 (Runx2) and osterix) Alkaline phosphatase
What is intermediate cementum and how is it formed?
AKA Hayline layer of hopewell-smith
- first layer of cementum layed down by inner cells of HERS
- deposited on root’s surface
- seals dentinal tubules
- located between granular dentin layer of tomes and the secondary cementum that is formed by cementoblasts
- aprox 10microm thick
- more mineralized than secondary cementum
- deposited before HERS desintegrates
List the physical properties of cementum.
- pale yellow with a dull surface
- more permeable than other dental tissues
- relative softness and thinness at the cervical portion (easily removed by abrasion if gingiva recedes)
List the chemical properties of cementum.
45-50% hydroxyapatite (inorganic)
50-55% collagenous and noncollagenous matrix proteins (organic)
What are the collagenous components of cementum?
- Type 1 (mostly)
- Type III, XII, V, XIV
How is cementum classified?
- presence or absence of cells
- origin of collagenous fibers of the matrix
- prefunctional and functional
Compare cellular and acellular cementum.
Acellular cementum: (primary) covers the root adjacent to dentin. Thin cervical layer requires no cells to maintain viability (nourished by fluids at surface near pdl)
Cellular: (aka secondary) apical area and overlying acellular cementum. Common in inter-radicular areas. More cellular as thickness increases to maintain viability.
Cellular cementum usually overlies acellular cementum.
What are canaliculi in regards to cementum?
Cementocytes in lacunae and the channels that their processes extend
Define cementoid.
Young matrix that becomes secondarily mineralized.
How is cementum deposited?
In increments similar to bone and dentin.
Describe one theory of why there are structural differences between acellular and cellular cementum.
-structural differences related to the faster matirx formation for cellular cementum. Cementoblasts get incorporated and embedded in the tissue as cementocytes.
What type of cementum has lacunae and canaliculi containing cementocytes and thier processes?
Cellular
Which type of cementum has clearly defined border with dentin?
Cellular
Acellular- not clearly demarcated border
What type of cementum forms relatively slowly?
Acellular.
What type of cementum has incremental lines relatively close together?
Acellular
Which type of cementum has a precementum layer present?
Cellular
The organic matrix of cementum is derived from what two sources?
1) PDL (sharpey’s fibers)
2) cementoblasts
What are extrinsic fibers and what direction are they oriented?
- derived from the PDL
- same direction of the PDL principal fibers (perpendicular or oblique to root surface)
What are intrinsic fibers derived from and how are they oriented?
- derived from cementoblasts
- run parallel to the root surface at right angles to the extrinsic fibers
What is mixed fiber cementum?
The area where both extrinsic and intrinsic fibers are together.
Describe Acellular Extrinsic Fiber Cementum.
- AEFC primary cementum
- located in cervical half of the root and constitutes bulk of cementum
- collagen fibers derived from sharpey’s fibers and ground substance from cementoblasts
- covers 2/3rds of root corresponding with the distribution of primary acellular cementum
- principal tissue of attachment
- function in anchoring of tooth
- fibers are well mineralized
Describe Cellular Intrinsic fiber cementum CIFC (Secondary cementum)
- starts forming after the tooth in in occlusion
- incorporated cells with majority of fibers organized parallel to root surface
- cells have phenotype of bone forming cells
- very minor role in attachment (absent in canine and incisors)
- corresponds to cellular cementum and is seen in middle to apical 3rd and interradicular
- adaptaion
- repair
Describe secondary cellular mixed fiber cementum.
- both intrinsic and extrinsic fibers
- bulk of secondary cementum
- cementocytes
- laminated structure
- cementoid on the surface
- apical portion and interradicular
- adaptation
- intrinsic fibers are uniformly mineralized but extrinisc fibers are variable mineralized with some central unmineralized cores.
Describe acellular afibrillar cementum.
- limited to enamel surface
- close to the CEJ
- lacks collagen os plays no role in attachment
- developmental anomaly vs. true product of epithelial cells
Describe the distribution of cementum on the root.
- Acellular afibrillar: cervical enamel
- Acellular extrinsic: cervix to pratically the whole root, increasing in thickness
- Cellular: apical third, furcations
What is the OMG rule?
Cementum Overlaps enamel -60%
Cementum just Meets enamel- 30%
Small Gap between cementum and enamel- 10%
Oral Mucosa
Oral Mucosa flash cards
Define mucous membrane.
moist lining of the gastrointestinal tract, nasal passages, and other body cavities that communicate with the exterior. In the oral cavity the linin is called oral mucous membrane or oral mucosa.
What are 4 functions of the oral mucosa?
1) protection: barrier for mechanical trauma and microbiological insults
2) Sensation: temperature, touch, pain, taste buds, thirst, reflexes such as swallowing, itching, gagging and salivating
3) secration: salivary secretion
4) thermal regulation: important in dogs, not in humans.
What are the three functional types of oral mucosa?
1) masticatory
2) lining
3) specialized
Describe masticatory mucosa.
- 25% of total mucosa
- gingiva (free, attached and interdental) and hard palate
- primary mucosa to be in contact with food during mastication
- usually keratinized
Describe Lining mucosa.
- 60% of total mucosa
- covers floor of mouth, ventral tongue, alveolar mucosa, cheeks, lips and soft palate.
- does not function in mastication, has minimal attrition
- non keratinized
- soft, pliable
Describe specialized mucosa.
- 15% of total mucosa
- covers ventral tongue
- composed of cornified epithelial papillae
