Alveolar Bone

Alveolar Bone is composed to two parts

Alveolar Bone Proper
And
Supporting Bone

Alveolar Bone Proper

Also know as Lamina Dura, Cribiform Plate, and Bundle Bone

Supporting Bone

Consists of an external supporting cortical plate of bone (lamellar bone) and underlying cancellous bone

Anatomy of Bone Socket

1.Outer cortical plate
2. Inner cortical plate
3. Spongiosa
4. Alveolar crest

Outer Cortical plate

(Compact lamellar bone)
faces cheeks and lips

Inner Cortical plate

(Compact lamellar bone)
faces tongue and palate

Spongiosa

Cancellous bone sandwiched btw cortical plates

Alveolar crest

Coronal border of alveolar process; 1.5mm below DEJ

What must be present to have an Alveolar Bone?

TEETH.
They must be in function to maintain alveolar bone health.
Alveolar Bone is constantly being remodeled in response to normal function.

Patients who do not have an Alveolar Bone

Edentulous Patients

Bundle Bone

Part of the alveolar bone where Sharpey's fibers of the PDL attach.

Lamellar Bone

Sheet-like bone that composes the rest of supporting bone

Cribiform Plate

Descriptive term-Cluster of perforations to allow nutrients and nerves to extend btw bone and PDL
*Also known as Lamina Dura, Alveolar Bone Proper, and Bundle Bone!

Orthodontic tooth Movement

Causes remodeling of the alveolar Bone. Includes: Compression and Tension

Compression

Placed on bone in the direction that the tooth is being guided to move. Pressure causes osteoclastic activity and bone resorption.

Tension

Placed on opposite side of the movement of the tooth and bone formation occurs.

Tissue Components of Bone:

(same as other connective tissues)
1. Cells
2. Fibrous Matrix
3. Ground Substance

Cells

Osteoclasts-develop from circulating monocytes
Osteoblasts- form bone
Osteocytes- mature bone cells present in a lucuna
Fibroblasts- produce collagen matrix

Fibrous Matrix

Mostly collage fibers that have been calcified by calcium and hydroxyapite.

Ground Substance

Gel-like substance made of proteoglycans.

Tooth movement can be a result of:

Growth, an Adaptation to a changing occlusion, or an Orthodontic force.

Mesial Drift

Shift toward Mid-line.
Occurs during mixed dendition phase.
Its a result of occlusal forces during clenching that produces anterior force.
Results in repositioning of teeth during growth phase.

Bone and Cementum

Cementum of bone is attached to bundle bone by collagen fibers (Sharpey's fibers)
Bone resorbs first during orthodontic movement, but both cementum and bone are able to resorb and rebuild hard tissue. If cementum does resorb also..it may result in tooth loss.

Cementum does not have:

A blood supply.
But Bone Does have a blood Supply.

____is more resistant to resorption than____

Cementum is more resistant to resorption than Bone.

Alveolar Bone Loss-

Can be a result of tooth extraction, normal aging, or osteoporosis.

Periodontal Ligament (PDL)

Suspends the tooth within its bony socket.
A specialized form of CT
**Develops from the dental follicle.

PDL consists of:

Gingival fiber bundles,
Dentoalveolar (principal) fiber bundles,
Loose CT,
Blood vessels,
nerves.

CT compoents:

Cells-
Fibrous Matrix-
Ground Substance-

Cells

Primarily fibroblasts which produce collagen at a rapid rate. Also found: osteoblasts, osteoclasts, macrophages, and cementoblasts.

**PDL is constantly being remodeled and has a rapid turnover rate.

Fibrous Matrix

*The dominant component of PDL*

Ground Substance

Gel-like substance made of proteoglycan

Shape of PDL

Slight hourglass shape.
thin in middle
surrounds all sides of tooth

Overall width _____ with age.

Decreases

Width is related to____

the amount of function.
Actively functioning tooth will have a slightly wider PDL.
Occlusal trauma can cause a widened PDL

Gingival fibers of PDL:

1. Free Gingival Fibers
2. Attached Gingival Fibers
3. Circumferential Fibers
4. Transseptal Fibers

Free Gingival Fibers-

Arise from the cementum and pass into the free gingiva.

Attached Gingival Fibers-

Arise from alveolar crest and pass into attached gingiva

Circumferential Fibers-

Continuous around neck of tooth.
(no attachment to cementum)

>First three fiber types all help resist gingival displacement.

Transseptal Fibers-

Attaches from one crown to another.
(resist tooth seperation)

Principal Fibers of the PDL:
(Dentoalveolar Fiber Group)

1. Alveolar Crest fibers
2. Horizontal fibers
3. Oblique Fibers
4. Apical Fibers
5. Interradicular Fibers

Alveolar Crest Fibers-

Begin in the cementum and end in the alveolar crest.
(curve shape)
>Resist vertical force.

Horizontal Fibers-

Extend horizontally from cemtentum at midroot to alveolar bone.
>Resists horizontal and tipping forces.
(Narrowest part of PDL)

Oblique Fibers-

Slant occlusally from cementum to alveolar bone in apical 2/3 of root.
>Resists vertical and intrusive force.
*Attaches high on bone and low on cementum*
**Most abundant type of fibers

Apical Fibers-

From surface of root apex to alveolar bone.
>Resist vertical force

Interradicular Fibers-

From cementum to alveolar bone in the furcation area.
*Multiple rooted molars only*
>Resist vertical and lateral movement.

Vascular System of the PDL:

Interstital spaces are found btw fiber bundles. THis contains the bv and nerves surrounded by collagen fibers of the PDL for protection against masticatory forces.

Blood Vessels of the PDL and Alveolar Bone are connected via_______

openings in the cribiform plate.

Nerual System

Nerves found in the interstitial spaces sometimes seem longitudinal to the tooth surface.

2 types of nerves:

1. Autonomic-Sympathetic
2. Afferent sensory

Autonomic-Sympathetic

Travel with the blood vessels and regulate blood flow

Afferent sensory

Pain & Pressure!

2 types of nerve endings in the PDL:

1. Free, unmyelinated nerve endings
2. Encapsulated nerve endings

Free, unmyelinated nerve endings-

Naked fibers; sense pain

Encapsulated nerve endings-

Sense pressure changes

Dentogingival Junction

Defined as the area on the tooth where the enamel and epithelium form a junction.

The type of epithlium present at the Dentogingival Junction:

Nonkeratinized stratified squamous epithelium

The dentoginginval junction is often the site where _______ begins.

Periodontal Disease.
It is easily invaded by microbs.

Developing Tooth is covered By:

Reduced Enamel Epithelium
(REE)

The formation of the dentogingival junction begins when the basal cells of the _______

oral epithelium that covers the emerging tooth and the outer cells of the reduced enamel epithelium MERGE AND PROLIFERATE just as the tooth being to erupt.

Dentogingival Junction is established when____

The tooth first erupts, and continues to migrate apically as tooth fully erupts.

Dentogingival junction is divided into:

1. Gingivalepithelium
(sulcular epithelium)
Not attached-sulcus-keratinized

2. Junctional Epithelium
(epithelium attachment)

Junctional Epithelium

Band of stratified squamous epithelium that is attached to the tooth and is continuous with the epithelium of the gingival sulcus.