Alveolar bone and pathologies Flashcards
cribriform plate
The cribriform plate is formed as a result of attachment of the PDL fibers and passage of vessels and nerves into and out of the PDL.
bone lining the alveolar socket
bundle bone
The term bundle bone refers to that bone in
which Sharpey’s fibers (PDL) are embedded.
Woven Bone
cells?
non-collagenous proteins?
rate of formation?
Woven Bone
• Immature bone in which the collagen fiber matrix is randomly oriented. This type of bone is generally newly formed (embryologic development) or associated with healing wounds.
§ More cells per unit area than mature bone
§ Greater volume of non-collagenous protein
§ Forms more rapidly than mature bone
Spongiosa (a.k.a. Cancellous)
• Trabecular bone that lies between the cortical plates and
within the marrow spaces
lining cells of trabeculae
osteoblasts
Structural Organization of the Alveolar Process
Supporting Alveolar Bone
• Facial and lingual cortical plates
Made of:
§ Lamellar bone
§ Haversian bone
§ Interstitial bone
spongy bone between the plates
Structural Organization of the Alveolar Process, composition of bone
see attatched
Cells Associated With Bone/cartilage
Ø Osteoblasts Ø Osteocytes Ø Osteoclasts Ø Bone Lining Cells Ø Chondroblasts Ø Chondrocytes Ø Mesenchymal Cells
Osteocyte
Osteocyte is an osteoblast that has been entrapped by it’s own osteoid matrix
Canaliculi
radiate in all directions, and allow diffusion of substances
throughout bone. Processes of the osteocytes travel within the canaliculi,
and connect to other osteocytes/osteoblasts, allowing cell-to-cell
communication. May have some mechanoreception properties, as well
Periosteum
contents? layers?
A dense connective tissue, bound to bone by Sharpey’s fibers, that contains blood vessels, nerves,
three cell layers:
§ Peripheral cell layer of fibroblasts
§ Intermediate cell layer of undifferentiated
mesenchymal cells
§ Proximal cell layer of osteoblasts
Endosteum
Lines the meduallary cavity and cancellous bone (trabeculae).
Generally has the same composition as periosteum but is
significantly thinner
collagens associated with bone
types 1,2,3,5,10
type 1 collagen in bone
Fibrillar: ubiquitous in distribution
type 2 collagen in bone
Fibrillar: primarily a cartilage protein
type 3 collagen in bone
Fibrillar: granulation and mesenchymal tissues
type 5 collagen in bone
fibrillar: stromal connective tissue and promotes cellular
attachment and migration
type 10 cartilage in bone
Growth Plate: facilitates conversion of cartilage to bone
Non-collagenous proteins associated
with bone matrix include:
Ø Osteonectin Ø Osteopontin Ø Osteocalcin Ø Sialoprotein Ø Phosphoprotein Ø Glycoprotein Ø Proteoglycan Ø Bone Specific Protein Ø Bone morphogenetic protein (BMP) Ø Carboxyglutamic acid containing protein
The non-collagenous matrix proteins of bone
are characterized by their:
Ø highly acidic nature
Ø high aggregation tendencies
Ø calcium binding properties
In-Situ Remodelling, commonly seen where in dentistry?
A process of osteoclast resorption, and bone replacement by osteoblast activity.
Mostly seen in areas of alveolar bone affected by orthodontics.
Intramembranous Bone Formation
Bone formation within or between connective tissue
membranes consisting of Type I collagen. Bone does
not replace cartilage as does endochondral bone.
This type of bone formation is found in the inner spongy layers of bone, as well as sutures. It is an extremely rapid and disorganized method of bone deposition, and allows for growth of the tissues surrounding it. Woven bone is an example of intramembranous bone growth.
Osteoblasts secrete matrix vesicles that mineralize surrounding collagen fibres. The osteoblasts usually become trapped themselves,
becoming osteocytes.
contents of osteoblasts secretory vesicles
Ø Pyrophosphatase Ø Alkaline phosphatase Ø Glycoproteins Ø Phosphoproteins Ø Phospholipids
Endochondral Bone Formation
Bone formation within hyaline cartilage that involves a
concomitant replacement of the cartilage framework by
bone
Mostly seen in the vertebrae, long bones, base of the skull, and
head of the mandible.
Mesenchymal cells make the general outline of the final bone
shape. The cells differentiate into cartilage cells
(chondroblasts), which increase in size, secrete collagen and
mineralize it with matrix vesicles. The newly formed
chondrocytes eventually die. Vascular tissue from the
surrounding perichondrium invades the cartilage, allowing
chondrocytes and mesenchymal cells to enter the area. The
chondrocytes eat away the cartilage, and newly differentiated
osteoblasts deposit osteoid onto the cartilage. The osteoid is
mineralized by osteocytes, and bone is made.
The growth of these bones is dependant on the growth of the
cartilage, and stops once the cartilage is been completely
removed
zones of activity in endochondral ossification
Ø Reserve or resting chondrocytes Ø Proliferation Ø Maturation Ø Hypertrophy and calcification Ø Cartilage degeneration Ø Osteogenesis
label this endochondral slide
control of bone metabolism, levels?
hormones?
Bone metabolism is controlled systemically by hormones and locally by mechanical factors, growth factors, and cytokines.
Hormones important to bone metabolism include: Ø Parathyroid hormone (PTH) Ø 1,25-dihydroxyvitamin D Ø Calcitonin Ø Estrogen Ø Glucocorticoids
Cytokines and growth factors important to bone metabolism include, important one?
Ø Interlukin-1 (IL-1)
Ø Interlukin-6 (IL-6): made by blasts to stimulate clast differentiation=resorbtion occurs
Ø BMP-2 and BMP-7
Ø Transforming Growth Factor (TGF-)
Ø Insulin-like growth factor (IGF-I and IGF-II)
Ø Platelet-derived growth factor (PDGF)
Ø Fibroblast growth factor-beta (FGF-)
what stimulates IL-6 production?
Under conditions that favor bone resorption,
osteoblasts can be stimulated by cytokines and
hormones to produce IL-6 which, in turn, promotes
differentiation of osteoclasts. Examples of such
stimulating cytokines include:
Ø Interleukin-11 (IL-11)
Ø Tumor necrosis factor-alpha (TNF-)
Ø Prostaglandins E2 (PGE2)
Ø Parathyroid hormone (PTH)
Ø 1,25-dihydroxyvitamin D
how osteoclasts resorb bone, rxn, enzymes?
Osteoclastic resorption of bone involves the creation of a localized acidic pH to demineralize hydroxyapatite, and a variety of enzymes that degrade the organic bone matrix: carbonic anhydrase Ø Lactic acid Ø Citric acid Ø Free protons (H+) Ø Acid phosphatase Ø Aryl sulfatase Ø Collagenase (MMP) Ø Gelatinase (MMP)
Architecture (shape) of the tooth-associated
facial and lingual cortical bone is dictated by:
Ø Facial-lingual alignment of teeth
Ø Mesial to distal contour of the CEJ
Ø Facial-lingual width of teeth
Ø Presence of enamel pearls or cervical enamel projections
Architecture (shape) of the interproximal
alveolar bone is dictated by:
Ø Facial to lingual contour of the CEJ Ø Mesial or distal tilt of the tooth Ø Root proximity Ø Presence of enamel pearls Ø State of tooth eruption
Fenestration
An isolated “port-hole” in the cortical bone that
allows exposure of the underlying root surface
only part of root exposed
Dehiscence
A denuded area of cortical bone that extends
through the marginal bone creating a “cleft-like”
defect
can see the whole root
Exostosis
An area of bone formation that exceeds the average for a given anatomical area.
The term is generally used in reference to the maxillary facial and lingual and mandibular facial
Torus /Tori
An area of bone formation that exceeds the
average for a given anatomical area.
The term is used in reference to the mandibular lingual or midline of the palate
Giant Cell Tumor symptoms? locular? confused with? histologically characterized by?
Ø Generally asymptomatic causing a painless expansion of bone
Ø Usually a single lesion that can be either unilocular or multilocular
Ø Often confused with ameloblastoma or periapical granuloma or periapical cyst
Ø Histology characterized by presence of numerous multinucleated giant cells in a stroma of ovoid & spindle shaped mesenchymal cells
Multiple Myeloma
accounts for what % of malignancies involving what tissue?
origin of the cells?
frequent complication?
Ø Malignancy of plasma cell origin that accounts for nearly 50% of all malignancies involving bone
Ø The abnormal plasma cells are typically monoclonal (arise from a single cell)
Ø Patients frequently suffer kidney failure due to overload of circulating light chain protein (Bence Jones Protein) produced by the abnormal plasma cells
Multiple Myeloma histology and radiology
Ø Histology shows monotonous sheets of neoplastic, variably differentiated, plasmacytoid cells that invade and replace normal host tissue
Ø Radiographically, patients may exhibit “punched out” areas in the cranium. Such areas are filled with the neoplastic plasmacytoid cells
Osteogenic Sarcoma
incidence?
common symptoms?
radiographs?
Ø A malignancy of mesenchymal cells that have the ability to produce osteoid or immature bone
Ø Excluding hematopoietic neoplasms, osteogenic sarcoma is the most common type of malignancy to originate within bone
Ø Pain and swelling are the most common symptoms
Ø Radiographic findings vary from dense sclerosis to a mixed sclerotic-radiolucent lesion. About 25% of lesions exhibit a “sunburst” patter
Comparison of the Four Mineralized Tissues chart
origin, matrix-forming cell, mech of growth, % mineral, organic matrix, blood?, inn? intracellular space?
