Alveolar Bone & Cementum

Question 1

What is alveolar bone?

Answer 1

Mineralised tooth support

Boundary at level of root apices of teeth

Question 2

What is alveolar bone necessary for? (4)

Answer 2

Muscle attachment

Bone marrow

Reservoir for ions

Plasticity and remodelling

Question 3

What does alveolar bone depend on? (3)

Answer 3

Tooth eruption for development

Tooth retention for maintenance

Functional stimuli to maintain bone mass

Question 4

When does alveolar bone start to develop?

Answer 4

Second month i.u. (but major portions at root formation/tooth eruption)

Question 5

What are the two layers of cortical alveolar bone called?

Answer 5

Labial and lingual cortical plates

Question 6

Why is there a lot of spongy bone in alveolar bone? (3)

Answer 6

Low mass

Allows vessels and nerves to pass through

Allows cellular interactions

Question 7

What is the layer of alveolar bone which is in contact with the tooth?

Answer 7

Bundle bone/cribriform plate

Question 8

What is the bundle bone referred to radiographically?

Answer 8

Lamina dura

Question 9

Where are the outer cortical plates thicker?

Answer 9

In mandible

In premolar-molar regions

Question 10

What is bundle bone?

Answer 10

Part of alveolar bone where PDL fibres are inserted

Question 11

What are the principal fibres of the PDL?

Answer 11

Sharpey’s fibres

Question 12

What orientation are the Sharpey’s fibres?

Answer 12

Perpendicular to the bundle bone and tooth

Question 13

What orientation are the fibres of the PDL (not Sharpey’s fibres)?

Answer 13

Parallel to bundle bone and tooth

Question 14

What is another name for lamina dura?

Answer 14

Dental lamina

Question 15

Why is the bundle bone often referred to as a cribriform plate?

Answer 15

Has many openings/perforations for blood vessels and nerves

Question 16

What is the interradicular septum?

Answer 16

Alveolar bone separating roots (of multi-rooted teeth)

Question 17

What is the interdental septum?

Answer 17

Alveolar bone separating adjacent teeth

Question 18

Why do the maxillary teeth tend to have more roots?

Answer 18

Maxilla is more spongous so teeth need more stability

Question 19

What are the three blood sources for the tooth/gingiva?

Answer 19

Periodontal

Alveolar

Mucogingival/supraperiostal

Question 20

What do the blood supplies of the tooth anastomose as?

Answer 20

Post-capillary venous plexus

Sub-epithelial capillary loops

Question 21

Describe the innervation of the jaw area. (3)

Answer 21

Spinal sensory trigeminal nucleus and trigeminal sensory nucleus give rise to mesencephalic sensory neurons of CNV

Masticatory musculature = motor nucleus of CNV

Teeth and gums = maxillary and mandibular branches formed via Gasserian/trigeminal ganglion

Question 22

What are the three branches of the trigeminal nerve?

Answer 22

Ophthalmic

Maxillary

Mandibular

Question 23

What is the role of the canals in alveolar bone?

Answer 23

Pathways for nerves and vessels

Question 24

What is type I spongy bone and where is it mostly found?

Answer 24

Regular trabeculae, heavier, more compact

Mandible

Question 25

What is type II spongy bone and where is it mostly found?

Answer 25

Irregularly arranged, delicate and numerous trabeculae Maxilla

Question 26

Where is spongy bone most and least dense?

Answer 26

Most - alveolar crest; next to teeth (cribriform plate) Least - apex

Question 27

How does tooth and alveolar bone loss affect the face?

Answer 27

Shortening of lower third of face

Question 28

Why does periodontal disease cause tooth loss?

Answer 28

Loss of alveolar bone (support)

Question 29

What do bone-lining cells do?

Answer 29

Regulate movement of calcium and phosphate into and out of bone

Question 30

What is the difference between resting and reversal lines?

Answer 30

Resting = osteoblast deposition temporarily halted, smooth contour Reversal = osteoclast resorption, scalloped edge

Question 31

What is cementum?

Answer 31

Bone-like tissue which covers roots of teeth

Question 32

What are the functions of cementum? (3)

Answer 32

Anchor teeth to alveolus Anchors gingival and periodontal fibres Protects dentin

Question 33

What cell type forms cementum?

Answer 33

Cementoblasts

Question 34

Why is cementum formed continuously?

Answer 34

Compensates for tooth wear

Question 35

Where is cementum thickest?

Answer 35

At apex

Question 36

What are the possible origins of cementoblasts?

Answer 36

Pulp cells - from odontoblasts HERS cells - epithelial to mesenchymal transformation Dental follicle cells - fragmentation of HERS cells allows dental follicle to contact dentin to trigger differentiation

Question 37

What is the composition of cementum?

Answer 37

65% inorganic 23% organic 12% water

Question 38

What is the organic component of cementum comprised of?

Answer 38

Collagens (mainly type I) Proteoglycans (chondroitin sulphate) Glycoproteins (osteopontin, bone sialoprotein)

Question 39

Which of cementum or bone is harder and why?

Answer 39

Cementum Higher mineral content

Question 40

What are the four types of cementum?

Answer 40

Acellular, afibrillar cementum AAC Acellular, extrinsic-fibre cementum AEC Cellular, intrinsic-fibre cementum CIC Cellular, mixed-fibre cementum CMC

Question 41

Describe the differences between cellular and acellular cementum.

Answer 41

Cellular = cementocytes (and canaliculi) due to faster deposition, incremental lines are far apart, thick precementum

Question 42

Which way do the canaliculi usually point in cementum?

Answer 42

Towards tooth surface

Question 43

What are extrinsic fibres and their function?

Answer 43

Fibres which are not produced by cementoblasts - Sharpey's fibres Anchor teeth

Question 44

What are intrinsic fibres and where are they found?

Answer 44

Fibres produced by cementoblasts Do not anchor teeth, found at site undergoing repair after resorption

Question 45

Where is mixed-fibre cementum found?

Answer 45

Apical portion of root and in furcation region

Question 46

Describe the areas of cementum repair.

Answer 46

No remodelling in cementum Reversal lines Cellular, intrinsic-fibre cementum CIC laid down

Question 47

Describe the characteristics of hypercementosis. (3)

Answer 47

Lamina dura intact Occlusal forces increase cementum formation Chronic periapical inflammation