Unit 12 - Periodontium Flashcards
The supporting structure for the teeth, consists of periodontal ligament, cementum, gingiva, and alveolar bone
Periodontium
A matrix of connective tissue consisting of bundles of strong predominantly type I collagen fibres connecting periosteum to bone
Sharpey’s fibers
A minute canal in a bodily structure
Canaliculi
The direct conversion of mesenchymal tissue into bone is called
Intramembranous ossification
The most coronal portion, or the top, of the alveolar process
Alveolar crest
This is a cross section through the roots of two adjacent teeth
Interdental septum
The bone structure located between dental sockets that separates the tooth roots from furcation line to the apical limit of the roots
Interradicular septum
The periodontium includes
Cementum
Alveolar process
Periodontium ligament
The part of the periodontium that attaches the teeth to the alveolar bone by anchoring the PDL
Cementum
Where is the cementum thickest?
At the tooth apex
Where is the cementum thinnest?
at the CEJ
What is the main function of cementum?
Tooth support or anchorage
Chemical characteristics of cementum
65% inorganic
23% organic
12% water
Does cementum have innervation or is it neutral to sensitivity?
Neutral to sensitivity
Is cementum vascular or avascular?
Avascular
When can cementum form?
Throughout the life of the tooth
How does cementum show up radiographically?
Darker than enamel, lighter than pulp
Colour of cementum
Lighter yellow than dentin
How does cementum feel with explorer?
Tacky
Why does controversy surround the root scaling?
Due to removal of root structure with removal of calculus or impregnanted tissue
Cementum forms on the root dentin after
The disintegration of Hertwig epithelial root sheath (HERS)
During matrix production of cementum, cementoblasts then disperse to
Cover the root dentin area and undergo cementogenesis, laying down cementoid.
How is cementoid laid down?
In lamallar layers that consist of ground substance and intrinsic fibers
What posseses canaliculi which are oriented towards the peridontal ligament?
Cementocytes
Collagen fibers from the PDL that are partially inserted into the outer surface of the cementum at 90% or perpendicular.
Sharpey fibers
Describe mineralization of cementum
Intial layer is mineralized from the hydroxyappetite crystals of dentin and then mineralization continues by the crystals growing and spilling over into the cementum matrix. The last layer of cementoid (uncalcified cementum) remains adjacent to the cementoblast.
When HERS break down it distrupts the REE. This allows a bit to remain uncovered. At the cervical loop area cementum spills over onto the enamel. What is this called and occurs how often?
Overlap <15%
When the REE stays in position while the HERS break down at the cervical area. This allows dentin to be deposited immediately adjacent to the enamel. What is this called and occurs how often?
Edge to edge 52%
Likely, the most cervical portion of HERS does not break down adjacent to the REE at the cervical loop area. What is this called and occurs how often?
Gap 33%
Which type of cementum is considered primary cementum?
Acellular
Which type of cementum is formed slower than other types?
Acellular
Which type of cementum is called secondary cementum?
Cellular
Which type of cementum is the last layer deposited?
Cellular
Which type of cementum contains no embedded cementocytes?
Acellular
Which type of cementum is found at the apical 1/3 of the root?
Cellular
Which type of cementum functions to adapt and repair throughout the life of the tooth?
Cellular
Which type of cementum has many layers covered the cervical 1/3 near the CEJ?
Acellular
Which type of cementum covered the entire outer surface of each root?
Acellular
Which type of cementum has perio fibers that are higher in numbered embedded in it?
Acellular
Mineralized spherical bodies of cementum found either attached to the cemental root surface or lying free in the PDL or embedded in cementum
Cementicles
The excessive production of cellular cementum, which mainly occurs at the apex or apices of the tooth
Hypercementosis
An overgrowth of cementum due to an increased function put on the tooth/teeth-
This allows a larger area for periodontal fiber attachment, therefore increases anchorage
Hypertrophy
Occurs on non-functioning teeth or on teeth with no increased function. Also occurs where there has been a chronic apical infection. Results in a decrease in embedded sharpey’s fibers. Cementum appears circumscribed (restricted) at the apical area
Hyperplasia
Type of cementum repair that
- only a thin layer of cementum is laid in an area of resorbed cementum
RESULT = leaves an area of cementum that is
recessed - Does not re-establish the original contour
- A bony projection may form to close the perio
- ligament space, this results in reducing
Functional
Type of cementum repair that:
Trauma may cause cementum resorption
*
* excessive occl. forces may leave a weak ligament
*
attachment & an area of resorbed cementum
RESULT: acellular or cellular cementum is deposited in the resorbed area = “re-establishing” the former outline of the root
Anatomic
Chemical properties of the alveolar process
60% inorganic
25% organic
15% water
