quiz 4: topic 5 alveolar bone & cementum

Macroscopic level of AB

What you can see with the naked eye

Microscopic level of AB

• specialized CT; mineralized → osseous tissue

• Dynamic tissue: bone apposition vs bone resorption

Osseous

Bony, composed of, containing or resembling bone

Compact bone structure

• layers of dense solid bone

• Lamellae tightly arranged w/ no spaces

• Contains longitudinal and concentric lamellae

• Acts as a protective armor

Synonym for Compact bone

Cortical bone

Cortical bone location

External aspect of the bone seems only on Bu/Li view

Spongy bone structure:

Latticework arrangement made of trabeculae that is separated by marrow spaces

Trabecula(e)

Spicules of bone

Spicule

Small, pointed fragments of bone

Marrow spaces

Spaces in spongy bone that contains blood-forming cells, fat cells, mesenchymal cells, and bone marrow

Hemopoietic

Blood forming tissue in RBCs

Synonym for spongy bone

Cancellous/trabecular bone

Cancellous bone location

Internal aspect of bone that is bounded by compact bone

Basal bone

Foundation of the jawbone, apical to the roots of the tooth

Alveolar Bone/Process

Part of the jawbone that surrounds and supports the teeth

No tooth =

No alveolar process

Components of Alveolar Process:

• Alveolar Bone Proper (ABP)

• Supporting Alveolar Bone (SAB)

ABP:

• thin plate of compact bone that lines/forms the tooth socket

• Where sharpey’s fibers insert into

SAB two components:

• compact SAB

• Spongy SAB

Cortical SAB

• Found on the external aspects of the AP consisting of dense solid bone

Spongy SAB

Found on the internal aspects of the alveolar process consisting of a latticework of bony spicules separated by marrow spaces

SAB

Alveolar bone that surrounds the tooth socket and provides additional support to the teeth

Different terms for ABP:

• cribiform plate

• Lamina dura

• Bundle bone

Cribiform plate

gross anatomical term for ABP

Cribiform plate

Lamina Dura

Lamina Dura

• radiologic term for ABP

• Appears as a thing radio plaque (white) line

Bundle Bone

Bundle Bone

• microscopic term for ABP

• Where sharpey’s fibers insert into

Which type of lamellae are found in the alveolar bone proper?

Longitudinal and Concentric

Alveolar Crest

• most coronal portion of the ABP

• Aka Crestal Bone

Interdental septum

Alveolar bone that is located between two adjacent teeth

Interradicular septum

Alveolar bone located between the roots of multi-rooted tooth

Lamellae

Layers of bone; Latin “little plate”

Interdental AND Interradicular septum are composed of:

• ABP

• Cortical SAB

• Spongy SAB

• light blue - crestal bone

• Indigo - interdental septum

• Green - Interradicular septum

Factors that influence the contour of the AB in health: 4

• shape of the teeth + CEJ

• Position of teeth

• Tooth contact

• Normal occlusal forces

Festooning

Wavy contour of AB related to the prominences of the roots w/ the depressions in between them

Festooning is most prominent in what region?

Anterior region

Why is festooning more prominent in the anterior region?

The bone is thinner, making the root prominences more apparent

Shape of interdental septum in Anterior teeth

Conical, triangular

Shape of interdental septum in Posterior teeth

Rectangular/ box-shaped

Width of interdental septum when there is lesser contact of the enamel

Board

Width of interdental septum when there is greater contact of the enamel

Narrow

1. Lesser enamel contact = boarder interdental septum

2. Greater enamel contact = narrow interdental septum

General contour of alveolar crest in health

Scalloped following the outline of the CEJ

“___” following the “___” of the “___”

“Scalloped” following the “outline” of the “CEJ”

General contour of the Interdental Septum to the Alveolar Crest in health

Parallel to the imagine line drawn between the CEJ’s of two adjacent teeth

General Height of Alveolar Crest in health

1-2 mm apical to the CEJ

Horizontal bone loss

Alveolar crest is lower than normal but its level remains roughly parallel to the line between the CEJs, crest is 3mm or more apical to the CEJ

Vertical/angular bone loss

Bone drops unevenly or diagonally beside a tooth → crest is not parallel to the CEJ reference line

Factor to determine bone height

Distance between crest and CEJ reference line

Normal distance between crest and CEJ in health

Crest should be 1-2 mm a pick to the CEJs

Factor to determine between horizontal or vertical bone loss

Angle

Alveolar bone and cementum are what type of CT?

Specialized

Alveolar bone and cementum components:

• associated cells

• Organic ExtraCellular Matrix

• HydroApatite crystals

ECM is composed of:

• fibers/fibrous matrix

• Ground substance

-blasts

Produce/appose the tissue

-clasts

Destroy/resorbs the tissue

Mesenchymal stem cells

Osteogenic cells

-cytes

Tells blast and clast what to do

Where are osteocytes found?

Within the tissue itself; the bone

Where are cementocytes found?

In cementum, the cellular portion

When do cementoblasts function?

Always in health

When do cementoclast function?

Only in health in exfoliation or pathology

Osteogenesis

Formation of bone

Cementogenesis

Formation of cementum

Name of organic matrix for bone and cementum:

• Osteoid

• Cementoid/precementum

Percentage of osteoid/cementoid

50-55%

Percentage of inorganic component

45-50%

Name of inorganic component in bone and cementum

Mineralized/calcified HA crystals

Fibrous matrix is made up of ___

Type I collagen fibers → mechanical support

Ground substance consist of ___

Protein-carbohydrate complexes → metalloproteinases → mechanical & biological support

Which tissue is vascular?

Alveolar bone

Which tissue is avascular?

Cementum

Functions of osteocytes:

• regulate bone remodeling

• Maintain bone tissue

• Communicate with osteo blast and clasts

Alveolar bone and cementum contain ___ produced by fibroblast

Sharpey’s fibers

The two steps of apposition of bone/cementum:

1. Formation of the organic matrix

2. Mineralization of the organic matrix

Apposition

Forming a layer

Osteogenesis

Development of bone

Resorption

Destruction of mineralized tissue

Step 1: Formation of Organic matrix

-blast produce Type I Collagen fibers and Ground Substance

Step 2: Mineralization of Organic Matrix

• blasts pump out Ca & PO4 ions

• Ions combine in the organic matrix → forms HA crystals

• Occurs as another layer of organic matrix that is laid down next to -blasts

the two steps to resorption of bone/cementum:

1. Resorption of the mineral (inorganic) component

2. Destruction of the organic component

Step 1: Resorption of the Mineral(inorganic) component

-clasts dissolve the HA crystals

Step 2: Destruction of the Organic Component

-clast break down the Type I collagen fibers and ground substance

How is resorption of cementum different from resorption of alveolar bone?

Cementum is more resistant to resorption

Resorptive cells of cementum

Cementoclasts

What stimulates cementoclasts?

Eruption or deciduous teeth or pathology

Primary function of cementum

Serves as the attachment medium by which the PDL fibers attach the tooth to its surrounding bony socket (sharpey’s fibers)

Additional functions of the cementum:

• protect underlying root dentin

• Continue deposition at apex, serves to maintain the tooth in functional occlusion by compensating for occlusal wear (active eruption)

• Repairs root fractures by formation of new cementum - to a degree

-cytic lacunae

Space occupied by cell bodies (-cytes)

Howship’s lacunae

Ditch formed by resorptive cell of bone

Resorptive cell of bone

Osteoclasts

Canaliculi

Small, radiating channels that contain cell processes of -cytes

Osteocytic lacunae characteristics:

• dense, more numerous

• Neat arrangement

• Canaliculi radiate uniformly around the lacunae

Cementocytic lacunae characteristics:

• not as dense, fewer in numbers

• Less regular arrangement, scattered

• Canaliculi are oriented preferentially on the PDL isde

Resting lines

Lines separating the lamellae

Synonyms for resting lines

Arrest, incremental, appositional lines

What do resting lines represent?

The periods of rest between periods of activity by the osteoblasts; diurnal/nocturnal