Exam 3 - Periodontium Davenport Flashcards
Periodontium - define
tissues supporting and investing the tooth
Periodontium consists of:
- cementum
- periodontal ligament
- bone lining the alveolus socket
- part of the gingiva facing the tooth
The periodontium tissues form a specialized fibrous joint called ____ and are thought to be of ____ origin
Gomphosis; ectomesenchymal
Cementum - define
Hard, avascular connective tissue that covers the roots of teeth
Cementum is classified according to:
Presence or absence of cells within its matrix
Acellular cementum
Provides attachment for the tooth
Cellular cementum
Adaptive role in response to tooth wear and movement and is associated with repair and regeneration of periodontal tissues
The composition of cementum is similar to that of __________, where proteins unique to cementum have yet to be confirmed
Bone
Cementum is made up of ___% hydroxyapatite and ___% collagen/noncollagenous matrix?
45-50% hydroxyapatite (inorganic); 50% collagen and noncollagenous matrix proteins (organic)
_____ constitutes up to 90% of the organic components of cementum
Type I collagen
What are the other types of collagen that are associated with cementum (besides type 1 collagen)?
- type III
- type XII collagen
- Trace amounts of other collagens, including type V and type XIV
What are the two apparently different/unique cementum molecules?
- an adhesion molecule (cementum attachment protein)
- a growth factor (insulin-like growth factor) have been identified
functions of both unknown
Bone sialoprotein and osteocalcin appear to be specific to mineralized tissues, except for _____
Enamel
Noncollagenous proteins identified in cementum also are associated with _________
Bone
During cementum formation, _______ is believed to send an inductive message, possibly by secreting some enamel proteins, to the facing ______ cells
HERS; Ectomesenchymal pulp (dental papilla)
Ectomesenchymal cells that receive inductive messages from HERS differentiate into odontoblasts and produce a layer of ___________ which comes into contact with ______
(in cementum formation)
Predentin; Ectomesenchymal cells from the inner portion of the dental follicle
What type of cementum is formed first?
Acellular
Acellular cementum covers approximately the _________________ of the root
Cervical 1/3-1/2
The acellular cementum is formed before the tooth reaches _____
The occlusal plane
What is the range of thickness of the acellular cementum?
30-230 microns
What comprises most of the structure of acellular cementum?
Sharpey’s fibers
When is cellular cementum formed?
After tooth reaches occlusal plane
Which is more irregular, acellular or cellular cementum?
Cellular cementum
Cellular cementum contains cells in lacunae that communicate with each other through a system of __________________
Anastomosing canaliculi
What type of cementum is less calcified?
Cellular cementum
Both acellular cementum and cellular cementum are arranged in lamellae separated by _____ parallel to the long axis of the root
Incremental lines
Incremental lines in cementum are also known as:
Resting lines
Resting lines of cementum represent:
rest periods in cementum formation
Resting lines of cementum are more or less mineralized than adjacent cementum?
More
Loss of the ____________ of the reduced enamel epithelium at the time of tooth eruption may place portions of mature enamel in contact with the connective tissue
cervical part
(will deposit over it an acellular afibrillar type of cementum)
What are the two sources of collagen fibers in cementum?
- Sharpey’s (extrinsic) fibers
- fibers that belong to the cementum matrix per se (intrinsic) and are produced by the cementoblasts
Sharpey’s (extrinsic) fibers, which are the embedded portion of the principal fibers of the PDL, are formed by _______
Fibroblasts
fibers that belong to the cementum matrix per se (intrinsic), are produced by the ________
Cementoblasts
Cementocytes dwell in __________
Lacunae
Cementocytes connect together by _____ extending through a system of interconnected canals within the cementum.
Cytoplasmic processes
Cementum is thicker towards the __________
Root apex (150-200 µm)
Cementum is thinner near the ______________
Enamel (20-50 microns)
acellular afibrillar cementum is limited to the ___________ enamel surface
Cervical (occurs as spurs extending from acellular extrinsic fiber cementum)
___________________, which becomes the principal tissue of attachment, extends from the cervical margin of the tooth and covers two thirds of the root and often more
Acellular extrinsic fiber cementum
Cellular cementum is confined to what areas or what teeth?
Apical third and interradicular regions of premolar and molar teeth
True/False: Cellular cementum is often absent from single-rooted teeth, which suggests its presence is not essential for tooth support.
True
Can fibrillar cementum varieties overlap?
Yes
Cementum formed during periodontal wound healing appears to be __________ in nature
Cellular
Is cementum deposited throughout life?
Yes, it is a continuous process that occurs at varying rates throughout life
Cementum formation is most rapid in the _______________, where it compensates for _____ which itself compensates for attrition.
Apical regions; tooth eruption
Cementum terminates at the commencement of the _____________ portion of the tooth
Enamel
What are the different ways in which the cementum and enamel can meet in the CEJ?
- butt joint (30%)
- gap between cementum and enamel (10%)
- cementum overlaps enamel (60%)
The _____ is the part of the jaw bone/mandible that houses the teeth
Alveolar process
Inner lining of tooth socket is called:
Alveolar bone proper
Alveolar process consists of:
- external plate of cortical bone
- alveolar bone proper
- Cancellous trabeculae, between these two compact layers, which act as supporting alveolar bone
Portion of jaw located apically but unrelated to the teeth
Basal bone
The bone __________ in the mandible in general are much thicker than in the maxillary bone
Lamellae
In areas where bone is very thin, the _____ of the supporting alveolar bone are in contact with the alveolar bone proper with no intervening spongy bone. _____ in these areas are common.
Cortical plates; Bone defects
What is the soft, specialized connective tissue situated between the cementum covering the root of the tooth and the bone forming the socket wall?
Periodontal ligament
As you age, the PDL becomes:
Thinner
Function of PDL
- support teeth in sockets
- withstand considerable forces of mastication (adapt to lifestyle)
Besides the attachment of teeth to bone, what other function of the PDL is important?
Acting as sensory receptor
The PDL acts as a sensory receptor, which is necessary for:
proper positioning of the jaws during normal function.
All 4 functions of PDL
- physical (holding tooth)
- formative and remodeling
- nutritional
- sensory
Cells of the periodontal ligament participate in the formation and resorption of _____ and _____
Cementum and bone
The periodontal ligament is constantly undergoing _______
remodeling
There is a very high turnover rate of ____ in the PDL
Collagen
(x2 faster turnover of collagen than gingiva and x4 faster than the skin)
What do cells of the periodontal ligament participate in the formation/resorption of?
cementum and bone
How does the periodontal ligament supply nutrients to the cementum, bone, and gingiva?
by way of the blood vessels and provides lymphatic drainage
What are the 4 types of neural termination in the PDL?
- free endings
- Ruffini-like mechanoreceptors
- Meissner’s corpuscles
- Spindle-like pressure and vibration endings
What theory of tooth support ascribes the principal fibers of the periodontal ligament the major responsibility in supporting the tooth and transmitting forces to the bone?
Tensional theory
What theory of tooth support considers the displacement of the tooth to be largely controlled by fluid movements, with fibers having only a secondary role?
Viscoelastic system theory
What are the predominant collagen types found in the PDL?
- Type I
- Type III
- Type XII
What do collagen fibrils in the PDL arranged in bundles resemble?
resembles a spliced rope
(individual strands can be remodeled continually, whereas the overall fiber maintains its architecture and function)
What allows for fiber bundles in the PDL to adapt to the continual stresses placed on them?
individual strands can be remodeled continually, whereas the overall fiber maintains its architecture and function
What collagen fibril bundles in the PDL represent the principal fiber bundles?
Bundles running between the tooth and bone
Where are the alveolar crest group of principal fiber bundles attached?
attached to the cementum just below the cementoenamel junction and running downward and outward to insert into the rim of the alveolus
Where are the horizontal group of principal fiber bundles attached?
just apical to the alveolar crest group and running at right angles to the long axis of the tooth from cementum to bone just below the alveolar crest
Where are the oblique group of principal fiber bundles attached?
Running from the cementum in an oblique direction to insert into bone coronally
What are the most numerous type of principal fiber bundles in the PDL?
Oblique group of principal fiber bundles
Where are the apical group of principal fiber bundles attached?
radiating from the cementum around the apex of the root to the bone, forming the base of the socket
Where are interradicular group of principal fiber bundles attached?
only between the roots of multirooted teeth and running from the cementum into the bone, forming the crest of the interradicular septum
Where are the transseptal group of principal fiber bundles attached?
extends from the cementum of one tooth across the interdental septum to the cementum of an adjacent tooth
What are the three types of “elastic fibers”?
- Elastin
- Oxytalan
- Elaunin
What is the only “elastic fiber” type present in the PDL?
Oxytalan
In addition to oxytalan, ____ also may be found within fibers of the gingival ligament
Elaunin fibers
The PDL is highly ____ and ____
Vascularized and innervated
PDL ground substance contains ____ water which has a significant effect on the ability of the tooth to ____
70%; withstand stress loads
The width of the PDL can increase by as much as:
50%
If the width of the PDL increases, what also increases?
- principal fiber bundles increase greatly in thickness
- alveolar bone becomes thicker
Healing of extraction wounds depends on:
Blood clot (loss of which leads to dry socket, very painful)
The blood supply of the PDL involves many ____
Arteriovenous anastomoses
Lymphatic vessels follow ____ in the PDL
Venous drainage
What type of cementum contains no cells and no extrinsic or intrinsic collagen fibers apart from mineralized ground substance?
Acellular afibrillar cementum
Acellular afibrillar cementum is a product of:
Cementoblasts
What type of cementum is almost entirely densely packed with bundles of Sharpey’s fibers and lacks cells?
Acellular Extrinsic Fiber Cementum (AEFC)
Acellular Extrinsic Fiber Cementum (AEFC) is found at:
Cervical third of roots and may extend further apically
Principal tissue of attachment (cementum)
Acellular Extrinsic Fiber Cementum (AEFC)
What is the cementum found on incisors and canines?
Acellular Extrinsic Fiber Cementum (AEFC) - extends to apical foramen
_____ cementum contains extrinsic and intrinsic fibers, and may contain cells
Cellular mixed stratified cementum (CMSC)
_____ is a co-product of fibroblasts and cementoblasts
Cellular mixed stratified cementum (CMSC)
____ cementum is found in the apical third of roots, apices, and furcation areas
Cellular mixed stratified cementum (CMSC)
What cementum contains cells but no extrinsic collagen fibers?
Cellular intrinsic fiber cementum (CIFC)
Cellular intrinsic fiber cementum (CIFC) is formed by _____ and fills _____
Cementoblasts; resorption lacunae
Ill defined zone near CDJ of certain teeth that contains remnants of HERS embedded in calcified ground substance
Intermediate cementum
Alveolar bone proper is seen as the ____ in radiographs
Lamina dura
The alveolar bone proper contains _____ through which neurovascular bundles link the PDL with the cancellous bone (alveolar bone)
Cribriform plate
_____ is necessary for successful implant placement
Adequate bone and soft tissue health
Bone lamellae is thicker in:
Mandible (compared to maxilla)
