Alveolar bone Flashcards
what is the alveolar process
- gross structure
- organ and tissue (connective tissue)
- compact bone (surface bone – outside wall)
- trabecular/spongy bone: inside of bone, surrounds bone marrow
what is the anatomy of a flat bone
- outer compact bone
- spongy bone
- trabeculae
- inner compact bone
what is compact bone
- gives strong structure
what is spongy bone
- lightweight
- rich blood/nutrient supply
what does bone marrow do
- provides rich nutrient supply to bone tissue
- rich circulatory blood supply inside/outside bone
what is the periosteum
- thin (but touch) layer of connective tissue -> outside covering of all bones
what is the endosteum
- delicate layer of connective tissue -> inside covering of trabeculae
- both periosteum and endosteum contain osteoblasts and osteoclasts (most in the endosteum)
what is the bone matrix
- 50% mineralized
- 50% organic (collagen fibers) and water
- hydroxyapatite matrix
- about the same hardness as cementum
what are the 3 major types of cells in bones
- osteoblasts: bone producing cells (in periosteum and endosteum). as they become entrapped in their secretions, they become osteocytes
- osteocytes: in lacunae connected by canaliculi
- osteoclasts: bone destroying cells, just beneath periosteum and endosteum
what is the Haversian system
- 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)
what is the microscopic structure of compact bone
- 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
what is the microscopic structure of spongy bone
- 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
what do both spongy and compact bone have
- osteocytes
- lacunaes
- canaliculi
what is the vascularity like in bones
- 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
what are canaliculi
- high communication from one cell to the other
- forms a system of connected bone cells by which nutrients are distributed throughout bone tissue
where is bone marrow found and what are the 2 types
- centre of bones
1. red bone marrow
2. yellow bone marrow
what is red bone marrow
- mostly young individuals
- RBC and WBC production
what is yellow bone marrow
- fat marrow
- triglycerides storage – fact, increase in older bones (RBM becomes YBM)
- red in adults converts to yellow
what do both the periosteum and endosteum function in
- 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
what is ossification and what are the 2 steps
- formation of bone
- involves 2 steps:
- conversion of unspecialized connective tissue cells -> osteoblasts, into bone matrix, and
- mineralization of the bone matrix
what are the 2 types of ossification and when does this occur
- embryonic development of bone (ossification)
- 2 types of ossification:
1. intramembraneous ossification
2. endochondral ossification
what is intramembraneous ossification
- 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
what is endochondral ossification
- 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)
are bones formed through intramembraneous vs endochondral ossification any different
- no, microscopically, they are the same, just the process of formation is different
what is bone remodelling
- 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
where does bone resorption occur
- 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
what is the structure of the alveolar process like
- 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
what is medial drifting
- natural physiological process
- slow movement teeth medially throughout life
- may cause overlapping later in life
- missing tooth: adjacent posterior tooth will move toward midline
what is occlusal drifting
- supereruption
- slow movement tooth vertically when no occlusion is present
- missing 4-6: may cause 1-6 to supererupt
what is orthodontics
- tooth subjected to horizontal pressure
- destruction and formation of bone during tooth movement
- but only is pressure is continued
what are some irreversible damages that can be caused by orthodontics
- pull/pressure tensions on PDL are excessive
- too fast movement
- root resorption
what is the significance of periodontal disease in bone
- 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
