Periodontium histology Flashcards
What are the components of the periodontium?
Cementum
Alveolar bone
Periodontal ligament
Lamina propria of the gingiva
What common illnesses are assoicated with periodontitis?
Alzheimer’s disease and cardiovascular disease
What is the periodontal ligament?
Specialized connective Tissue situated between cementum and alveolar bone proper
How thick is the periodontal ligament? What happens to its thickness with age?
Ranges between 0.15 and 0.38mm and is thinnest in the middle portion of the root.
Its width decreases with age
What kind of turnover rate does the periodontal ligament have? What does this mean?
Periodontal ligament has a high turnover rate.
This is why they need a large blood supply.
What is the embryological origin of the PDL and how does that affect the anatomy?
Dense fibrous connective tissue . It is derived from the dental follicle. Above the alveolar crest the periodontal ligament is continuous with the connective tissues of the gingiva; at the apical foramen it is continuous with the dental pulp .
What factors affect the width of the periodontal ligament?
Width of the periodontal space considerable
variation between teeth, according to several factors:
The functional state, non-functional and unerupted
teeth,
Permanent and deciduous teeth.
What are the functions of the PDL?
Tooth support
Shock absorption (masticatory forces)
Sensory receptor for proper jaw positioning
Nutrition (blood vessels provide essential nutrients to vitality of the PDL and cementum)
Attachment
Important for tooth eruption and drift.
Its cells form, maintain, and repair alveolar bone and cementum
Its mechanoreceptors are involved in the neurological control of mastication.
What fibers is the periodontal ligament made up of?
Collagenous (90%) [mostly type 1 - >70% and about 20% type 3]
Oxytalan
Elastin
Reticulin
What structure do teeth develop in?
Teeth are formed within the bone
What are the 5 groups of fibers of the periodontal ligament?
Dentoalveolar crest fibers
Horizontal fibers
Oblique fibers
Apical fibers (formed when the whole root is completed)
Interradicular fibers
What are Sharpey’s fibers?
Sharpey’s fibers are the fibers that go from cementum to the alveolar bone
What are the types of gingival ligament fibers?
Dentogingival: most numerous; cervical cementum to f/a gingiva
Alveologingival: bone of the alveolar crest to f/a gingiva
Circular: around neck of teeth, free gingiva
Dentoperiosteal: runs apically from the cementum over the outer cortical plate to alv. process or vestibule (muscle) or floor of mouth
Transseptal: cementum between adjacent teeth, over the alveolar crest
Where does the dentogingival fibers of the PDLigament go?
Cervical cementum to the free and attached gingiva
Where does the alvelogingival fibers of the PDLigament go?
Bone to to the free and attached gingiva
Where are the circular fibers of the PDL locaed?
Around neck of the teeth and free gingiva
What happens when the PDL is destroyed?
Destruction of the PDL leads to loose and sometimes disconnected teeth
Where are principal fibers of the PDL smallest?
At the cementum (Sharpey’s fibers)
What is teh function of hyaluronate GAG?
Fiber orientation and calcification of the fibers.
Water binding and exchange, control of collagen fibrillogenesis and
fiber orientation
Which part of the tooth has a large number of stem cells?
Dental pulp has lots of stem cells
What cells of the PDL do most of the synthesis?
Fibroblasts and fibroclasts
Cementoblasts and cementoclasts
Osteoblasts and osteoclasts
Progenitor cells
What do fibroblasts do?
Regenerate tooth support apparatus
Adaptive response to mechanical loading
Protein synthesis and secretion
secrete
metalloproteinases-1 (which
degrades extracellular matrix collagen at physiological conditions )
Secrete Tissue Inhibitors of MetalloProteinases - 1 (TIMPs)
Collagenase production and phagocytosis
Have cilia and many intercellular contacts, the cilium differs from those seen in other cell types
What structures join fibroblasts to each other?
Gap junctions (for cell communication and
What motility features do fibroblasts have?
They have chemotactic abilities and motile-contractile features
What are cementoblasts?
Cement-forming cells
Cuboidal cells
Protein synthesis and secretion
What do osteoblasts do?
Form bone
Protein synthesis and secretion
What do osteoblasts look like on histology?
Cuboidal cells with basophilic cytoplasm
Desmosomes and tight junctions, some tight junctions with osteocytes
Where do osteoclasts and cementoclasts arise from?
From blood cells such as macrophages
What do epithelial cell rests of malassaez do?
Chrnic inflammation
Direct cellular events during cementogenesis
Inhibit cementogenesis in mature teeth
Capable of phagocytosing collagen and synthesizing metalloproteinases and prostaglandins
How are cells lost and gained in the PDL?
Periodontal fibroblasts comprise a renewal cell system
– balance between newly generated cells and cells lost by apoptosis and migration out of the tissue.
Progenitor cell population are located adjacent to the blood vessels near the surface of the alveolar bone .
The rate of cell generation (mitotic index ) is modest (0,5 – 3%)
Where does the PDL get its blood supply?
From perforating arteries (cribiform plate of the bundle bone)
The small capillaries derive from the superior and inferior alveolar arteries
The blood supply is rich because the PDL has a very high turnover rate
Posterior blood supply is more prominent than he anterior blood supply.
Mandibular blood supply is more prominent than the maxillary.
What kind of nerve endings are in the PDL?
Nerve endings are mechanosensors which respond to pressure
What are the types of bone seen in the oral cavity?
Developmentally:
Endochondral bone
Intramembranous bone
Histologically:
Compact bone
Cancellous bone
Lamellar bone
Woven bone
Where are bones located relative to the teeth? (Classification based on location)
Internally: Thin layer of compact bone lines the tooth socket and gives attachment to the principal fibers of the periodontal ligament
Externally: On the buccal/labial and lingual/palatal surfaces are thicker layers of compact bone, forming the external and internal alveolar plates
What is bundle bone?
Bone that is perforated by many foramina that transmit nerves and vessels
What does bundle bone look like radiographically?
Radiodense because inreased mineral content around the fiber bundles.
The bundle bone is the lamina durea the lining of the alveolus is fairly smooth in the young but rougher in the adults.
Where is the alveolar crest located?
It is found 1.5 - 2mm below the level of the CEJ.
What does it mean if the line connecting the CEJ of adjacent teeth is not parallel to the alveolar crest?
Then there is a high probability of periodontal disease
What is bone remodelling?
Bone remodeling involves independent
sites of resorption and formation that
change the size and shape of bone
What are the stages of bone remodelling?
Activation
Resorption (osteoclasts)
Reversal
Formation (osteoblasts)
Termination
How does bone resorption take place?
Ruffled border with microenvironment of low pH and lysosomal enzymes is formed which breaks down the bone.
What is osseointegration?
Integration of structures in the bone and soft tisse to the prosthetics and teeth (as seen in dental implants).
What clinical consideration does the remodelling of bone have on movement of teeth?
This process can occur during orthodontic
movement of teeth. Bone is resorbed on the side of
pressure and opposed on the site of tension.
What happens at tensile site during orthodontic treatment?
Dilatation of blood vessels
More O2 demand
Active metabolism
New bone formation
