Alveolar bone

Question 1

what is the alveolar process

Answer 1

• gross structure
• organ and tissue (connective tissue)
• compact bone (surface bone – outside wall)
• trabecular/spongy bone: inside of bone, surrounds bone marrow

Question 2

what is the anatomy of a flat bone

Answer 2

• outer compact bone
• spongy bone
• trabeculae
• inner compact bone

Question 3

what is compact bone

Answer 3

• gives strong structure

Question 4

what is spongy bone

Answer 4

• lightweight

- rich blood/nutrient supply

Question 5

what does bone marrow do

Answer 5

• provides rich nutrient supply to bone tissue

- rich circulatory blood supply inside/outside bone

Question 6

what is the periosteum

Answer 6

• thin (but touch) layer of connective tissue -> outside covering of all bones

Question 7

what is the endosteum

Answer 7

• delicate layer of connective tissue -> inside covering of trabeculae
• both periosteum and endosteum contain osteoblasts and osteoclasts (most in the endosteum)

Question 8

what is the bone matrix

Answer 8

• 50% mineralized
• 50% organic (collagen fibers) and water
• hydroxyapatite matrix
• about the same hardness as cementum

Question 9

what are the 3 major types of cells in bones

Answer 9

1. osteoblasts: bone producing cells (in periosteum and endosteum). as they become entrapped in their secretions, they become osteocytes
2. osteocytes: in lacunae connected by canaliculi
3. osteoclasts: bone destroying cells, just beneath periosteum and endosteum

Question 10

what is the Haversian system

Answer 10

• Haversian canals are a series of tubes around narrow channels formed by lamellae
• the Haversian canals surround blood vessels and nerve fibers throughout the bone and communicate with osteocytes
• the canals and the surrounding lamellae are called a Haversian system (or an osteon)

Question 11

what is the microscopic structure of compact bone

Answer 11

• Haversian system (canals) = osteons
• thin layers (lamellae)
• arranged in circles
• central canal = haverian canal -> blood vessels and nerves go within these
• lacunae = found between lamellae, contains osteocytes
• canaliculi = small canal contains projections of osteocytes, connects lacunae together. all connected with Haversian canal to transport nutrients

Question 12

what is the microscopic structure of spongy bone

Answer 12

• arranged in trabeculae
• lamellar system for spongy bone: not arranged in circular pattern, follows shape of trabecullae
• bone still arranged in thin layers
• but, don’t surround Haversian canal
• transport nutrients by canaliculus only
• both systems (Haversian and lamellar) found in mature bones
• lamellar system also outside and inside layer cortical (compact) bone

Question 13

what do both spongy and compact bone have

Answer 13

• osteocytes
• lacunaes
• canaliculi

Question 14

what is the vascularity like in bones

Answer 14

• bone is very vascular
• arteries and veins enter and leave in various places
• Haversian calan: center canal and bone, up and down
• volkmann’s canal: transverse passageway blood vessels in bone, from side

Question 15

what are canaliculi

Answer 15

• high communication from one cell to the other

- forms a system of connected bone cells by which nutrients are distributed throughout bone tissue

Question 16

where is bone marrow found and what are the 2 types

Answer 16

• centre of bones
  1. red bone marrow
  2. yellow bone marrow

Question 17

what is red bone marrow

Answer 17

• mostly young individuals

- RBC and WBC production

Question 18

what is yellow bone marrow

Answer 18

• fat marrow
• triglycerides storage – fact, increase in older bones (RBM becomes YBM)
• red in adults converts to yellow

Question 19

what do both the periosteum and endosteum function in

Answer 19

• resorption and formaiton
• osteoclasts and osteoblasts
• in the PDL
• it is a specialized periosteum -> functions formation/destruction of bone on one side and cementum on the other side

Question 20

what is ossification and what are the 2 steps

Answer 20

• formation of bone
• involves 2 steps:
• conversion of unspecialized connective tissue cells -> osteoblasts, into bone matrix, and
• mineralization of the bone matrix

Question 21

what are the 2 types of ossification and when does this occur

Answer 21

• embryonic development of bone (ossification)
• 2 types of ossification:
  1. intramembraneous ossification
  2. endochondral ossification

Question 22

what is intramembraneous ossification

Answer 22

• simplest method of ossification
• bone tissue forms directly within mesenchyme
• mesenchyme cells in fibrous connective tissue cluster together and transform into osteoblasts
• osteoblasts secrete bone matrix, become osteocytes,… calcification
• ex: flat bones, mandible and maxilla

Question 23

what is endochondral ossification

Answer 23

• bone tissue formation is preceded by cartilage formation (chondrocytes)
• bone tissue is formed within a cartilage model in shape of bone that is to be formed
• then, cartilage is resorbed and replaced by bone
• most bones (long bones of arms and legs)

Question 24

are bones formed through intramembraneous vs endochondral ossification any different

Answer 24

• no, microscopically, they are the same, just the process of formation is different

Question 25

what is bone remodelling

Answer 25

- continual formation and resorption of bones - bone is not a permanent and unchanging tissue -> bone is in a constant state of change - continues throughout the life of bone - orthodontics: successful in all ages - formation of bone is compensated for resorption, therefore same mass - in growing bone, the connective tissue that forms new bone is either periosteum or endosteum (depends if bone is added to outside or inside of organ) - bones are formed by osteoblasts

Question 26

where does bone resorption occur

Answer 26

- beneath periosteum or endosteum in cells called osteoclasts - in bone resorption, both the organic matrix and the mineral material are removed - osteoclasts breakdown partially/completely the Haversian system or lamellar systems, osteoblasts reform system

Question 27

what is the structure of the alveolar process like

Answer 27

- mx and mn support teeth (alveolar process) - alveolar crest: portion near tooth crown - cortical plates (on outside of mx and mn) - trabecular bone: in between plates and lamina our - lamina dura: lines tooth socket, cortical like bone

Question 28

what is medial drifting

Answer 28

- natural physiological process - slow movement teeth medially throughout life - may cause overlapping later in life - missing tooth: adjacent posterior tooth will move toward midline

Question 29

what is occlusal drifting

Answer 29

- supereruption - slow movement tooth vertically when no occlusion is present - missing 4-6: may cause 1-6 to supererupt

Question 30

what is orthodontics

Answer 30

- tooth subjected to horizontal pressure - destruction and formation of bone during tooth movement - but only is pressure is continued

Question 31

what are some irreversible damages that can be caused by orthodontics

Answer 31

- pull/pressure tensions on PDL are excessive - too fast movement - root resorption

Question 32

what is the significance of periodontal disease in bone

Answer 32

- plaque/calculus in sulcus - inflammation of surrounding tissues - destruction of PDL and attaching bone - destruction of lamina dura - possible eventual tooth loss - limited repair: lower alveolar crest, lower attachment of the PDL or JE