Dental Histology - ABone/PDL Flashcards

Terms Definitions
Alveolar Bone
-Osseous tissue of maxilla + mandible that surrounds and supports the teeth
-Partially derived from Dential Follicle

-Formed during cementogenisis when additional osteogenesis occurs along surface of bony crypts that partially enclose developing teeth
Alveolar Bone Anatomy
-The structure composed of alveolar bone is know as the Alveolar Process

-Consists of an outer cortical plate, central spongy bone, and bone lining the tooth socket (bundle bone)
-Is able to deform slightly to accommodate the biting forces/minor trauma placed upon it
-PDL fiber bundles within A bone and cementum are called Sharpey's Fibers
Bundle Bone
-Bundle Bone is the bone which collagen bundles of PDL insert.

-Also known as the Alveolar Bone Proper

-Has numerous foramina that transmit nerves and vessels to the PDL, so it is also known as the Cribiform Plate

-Radiographically, it is known as the Lamina Dura
PDL Development
-Derived from Dental Follicle

-At onset of development, PDL consists of disorganized CT which has protruding collagen fibers from cementum and alveolar bone
-Then PDL fibroblasts synthesize collagen, forming fibrous bridge between cemental and alveolar bone collagen, anchoring tooth into mouth
-At eruption, PDL fibers organizie and thicken via fibroblast remodeling
PDL Function
-Supports tooth inside socket
-Helps withstand occlusal forces, shoch absorber
-Serves as sensory organ
-0.15-0.38mm and Thinnest at middle 1/3 of Root

- PDL gets thinner with age due to production of secondary dentin
Cells in PDL
1. Fibroblasts
2. Epithelial Cells
3. Undifferentiated Mesenchymal Cells
4. Cementoblasts
5. Osteoblasts
6. Osteoclasts
PDL Fibroblasts
-Most Common cell of PDL
-Very active and continuosly degrading and synthesizing collagen
PDL Epithelial Cells
-Remnants of Hertwig's Rooth Sheath, also known as The epithelial Rests of Malassez

-Have no function other than to give people cancer! WOO!
PDL Undiff. Mesenchymal Cells
-Tend to cluster around blood vessels
-Provide a cellular pool for the recruitment of new fibroblasts, cementoblasts and osteoblasts
PDL Cementoblasts
-Found within the PDL
-Also associated with surface of cementum
PDL Osteoblasts
-Found within the PDL
-Also associated with surface of alveolar bone
-Are either actively producing osteoid or resting
PDL Osteoclasts
-Found in areas where the alveolar bone is undergoing resorption
Fiber Groups in the PDL
-Fibers are Type I, III and XII
-Arranged in bundles with well defined orientation:
1. Alveolar Crest Group
2. Horizontal Group
3. Oblique Group
4. Apical Group
5. Interradicular Group
PDL Alveolar Crest Group
-Attached to tooth slightly apicla to CEJ
-Insert into crest of alveolus
PDL Horizontal Group
-Found JUST apical to the alveoalr crest group
-Fibers oriented at Right Angles to long axis of tooth
PDL Oblique Group
-Most Common fiber group in PDL
-Largest role in anchoring teeth
-Alveolar bon attachment is coronal to their origination on the cementum
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PDL Apical Group
-Run between the apical cementum directly to the apicla alveolar bone
-Resist forces that would pull teeth straight out
PDL Interradicular Group
-Found in the interradicular/bifurcation regions of multi-rooted teeth
PDL Elastic Fibers
-Mature elastic fibers NOT found in PDL
-BUT immature Oxytalan Fibers can sometimes be found
-Run vertically along surface of cementum to root apices where they end at vascular/nerve supply
-Thought to play a role in lympahtic flow
-Most numerous in cervical region of PDL
PDL Ground Substance
-PDL ground substances acts as shock absorber against occlusal forces
-Mostly Water (70%) and Dermatan Sulfate (glycosaminoglycan)
PDL Blood Supply
1. Superior Alveolar Artery - Maxilla
2. Inferior Alveolar Artery - Mandible
-Branches run through A bone and enter PDL through Cribiform Plate

-The Perforating Arteries are more numerous in posterior teeth and more common in the mandible
-Arteries reside between fiber bundles
-Arterial blood runs apical to crestal, venous and lymph run the opposite
PDL Nerve Supply
Has a Dual Nerve Supply:

1. Sympatheitc nerve fibers of ANS that regulate blood flow through PDL (No PNS)
2. Afferent, mostly myelinated, Sensory branches of 2nd and 3rd divisions of Trigeminal Nerve

-Fibers enter via apical regions and run to gingival margin or via cribiform plate running up and down PDL
More PDL Nerve Supply
Apical Region contains the greatest # of nerve endings With One Exception:
-The upper incisors have nerve endings concentrated in the coronal half of the labial portion fo the PDL
-Posterior teeth have the most nerve fibers
4 Types of Nerve Endings in PDL
1. Free Nerve endings
2. Ruffini-like Corpuscles
3. Coiled Nerve Endings
4. Spindle-like Endings
PDL Free Nerve endings
-Most Common

-Serve are Nociceptors  and Mechanpreceptors

-Found evenly distributed along length of PDL
PDL Ruffini-like Corpuscles
-Mechanoreceptors that are found among the PDL fibers
PDL Coiled Nerve Endings
-Unknown function
-Found in Mid-portion of the PDL
PDL Spindle-like Endings
-Unkown function
-Least common, seen around Root Apex
Functions of the Periodontium
Periodontium = Alveolar bone, PDL and cementum complex
1. Attachment - PDL keeps tooth anchored in jaw and helps dampen occlusal forces
2. Sensation - Pain, touch, pressure
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