Peridontium Flashcards
What is the periodontium?
The periodontium is the tissue that surrounds and supports the teeth.
What are the components of the periodontium?
The components include the gingiva, cementum, alveolar process, and periodontal ligament (PDL).
What is the primary function of the periodontium?
Its primary function is to support and surround the teeth.
What is the role of cementum in the periodontium?
Cementum attaches the teeth to the alveolar bone by anchoring the periodontal ligament (PDL).
Where is cementum located?
It forms the outermost layer of the root(s) of the tooth.
Is cementum clinically visible in healthy patients?
No, cementum is not clinically visible in healthy patients.
Where is cementum thickest and thinnest?
It is thickest at the tooth’s apex or apices and in interradicular areas of multirooted teeth, and thinnest at the cementoenamel junction (CEJ).
Does cementum have a nerve supply?
No, cementum does not have a nerve supply.
Is cementum vascular or avascular?
Cementum is avascular.
How does cementum receive its nutrition?
It receives nutrition through the surrounding periodontal ligament (PDL).
Can cementum form throughout the life of the tooth?
Yes, cementum can form throughout the life of the tooth, including after eruption.
What is the composition of mature cementum by weight?
Mature cementum consists of 65% inorganic or mineralized material, 23% organic material, and 12% water.
What crystalline material is found in mature cementum?
The crystalline material is mostly calcium hydroxyapatite.
From where does cementum develop?
Cementum develops from the dental sac.
What initiates the formation of cementum on the root dentin?
Cementum formation begins after the disintegration of Hertwig epithelial root sheath (HERS).
What happens when the dental sac cells contact the root dentin?
The contact induces the undifferentiated cells of the dental sac to become cementoblasts.
What do cementoblasts do during cementum formation?
Cementoblasts disperse to cover the root dentin area and undergo cementogenesis, laying down cementoid.
What are cementocytes, and how are they formed?
Cementocytes are cementoblasts that become entrapped by the cementum they produce.
When is cementoid considered mature cementum?
Cementoid becomes mature cementum when it reaches the full thickness needed and undergoes mineralization.
What are the primary components of cementum?
Cementum is composed of a mineralized fibrous matrix and cementocytes.
What are Sharpey fibers, and where are they located?
Sharpey fibers are collagen fibers from the PDL that are partially inserted into the outer surface of the cementum at a 90º angle and also insert into the alveolar process.
What are the three possible transitional interfaces at the CEJ?
Cementum may overlap enamel (<15%), meet enamel end-to-end (52%), or leave a gap between enamel and cementum, exposing dentin (33%).
What can result from a gap at the CEJ?
A gap can expose dentin, potentially leading to dentinal hypersensitivity.
Can these transitional interfaces vary in an individual’s oral cavity?
Yes, all three patterns can be present within the same individual, and variations can occur even around a single tooth.
What are the two types of cementum?
Acellular cementum and cellular cementum.
What is acellular cementum, and where is it found?
Also called primary cementum, it is the first layer deposited at the DCJ, formed slowly, and contains no embedded cementocytes. At least one layer covers the entire outer surface of the root, with many more layers covering the cervical one-third near the CEJ.
What is cellular cementum, and where is it located?
Also called secondary cementum, it consists of layers deposited over acellular cementum, mainly in the apical one-third of each root. It is formed quickly, capturing cementoblasts during production, resulting in embedded cementocytes.
Can cementum repair itself?
Yes, cementum repairs itself and maintains the tooth’s attachment to the bone through cementogenesis.
What causes the breakdown of cementum?
The breakdown involves resorption of cementum by odontoclasts.
How is cementum repaired?
Cementoblasts in the adjacent PDL produce new cementum through appositional growth.
What are cementicles, and where are they found?
Cementicles are mineralized spherical bodies of cementum found attached to the root surface or free in the PDL.
How do cementicles form?
They form from the appositional growth of cementum around cellular debris in the PDL, often due to microtrauma to Sharpey fibers.
Are cementicles a clinical problem?
Generally, they are not problematic unless they become numerous or large enough to interfere with the PDL, potentially causing tooth mobility or discomfort.
What are cemental spurs?
Cemental spurs are symmetrical spheres of cementum attached to the cemental root surface, similar to enamel pearls.
Where are cemental spurs typically located?
They are usually found at or near the CEJ.
What causes cemental spurs?
They result from irregular deposition of cementum on the root and may be visible on radiographs.
What is hypercementosis? What type of cementum is used acellular or cellular?
Hypercementosis is the excessive production of cellular cementum.
Where is hypercementosis most commonly seen?
It occurs mainly at the apex or apices of the tooth.
How does hypercementosis appear on radiographs?
It appears as a radiopaque mass at each root apex.
What causes hypercementosis?
It may result from occlusal trauma, chronic periapical inflammation, systemic conditions (e.g., Paget disease), or as a compensatory response to attrition to maintain occlusal tooth height.
What is root apex resorption, and what causes it?
It is the resorption of the apical root, often an unwanted side effect of rapid orthodontic therapy.
Which teeth are most commonly affected by root apex resorption?
Permanent maxillary incisors are especially noted for root apex resorption.
What is concrescence?
Concrescence is a rare condition where the cementum of two or more teeth fuses together at the roots.
Which teeth are most commonly affected by concrescence?
It mostly occurs in permanent maxillary molars.
How does concrescence develop?
It happens when excessive cementum deposition on one or more teeth causes the roots to fuse after eruption.
What is the alveolar process, and what is its function?
The alveolar process is the part of the periodontium that attaches cementum to the bone via the PDL. It supports and protects the teeth.
What type of tissue is the alveolar process?
It is a hard mineralized tissue with components similar to other bone tissue.
What is the composition of the mature alveolar process by weight?
It consists of 60% inorganic or mineralized material, 25% organic material, and 15% water.
What crystalline material is found in the alveolar process?
The crystalline material is mostly calcium hydroxyapatite.
What part of the jaws contains the roots of the teeth?
The alveolar process contains the roots of the teeth.
What is the basal bone, and how does it differ from the alveolar process?
The basal bone forms the body of the maxilla or mandible and is not part of the periodontium.
What are the two divisions of the alveolar process?
The two divisions are the alveolar bone proper and the supporting alveolar bone.
What components do the alveolar bone proper and supporting alveolar bone share microscopically?
They both contain fibers, cells, intercellular substances, nerves, blood vessels, and lymphatics.
What is the alveolar bone proper (ABP), and what is its function?
The ABP is the lining of the tooth socket (alveolus) and provides support for the tooth.
What type of bone forms the ABP?
It is composed of compact bone.
Why is the ABP also called the cribriform plate?
It contains numerous holes where Volkmann canals allow nerves and blood vessels to pass into the PDL.
What are Sharpey fibers, and how are they associated with the ABP?
Sharpey fibers are collagen fiber bundles that insert into the ABP and help anchor the teeth.
How do the sizes and depths of alveoli vary according to tooth type?
Canines have the deepest alveoli, molars have the widest, and incisors have single, deep, narrow alveoli.
What is the lamina dura, and how does it appear on radiographs?
The lamina dura is the part of the ABP visible on radiographs, appearing uniformly radiopaque.
What is the alveolar crest, and where is it located in a healthy jaw?
The alveolar crest is the most cervical rim of the ABP, located slightly apical to the CEJ, about 1 to 2 mm.
How should the alveolar crests appear in a healthy jaw?
They should be uniform in height along the jaw.
What are the two components of the supporting alveolar bone?
The supporting alveolar bone consists of cortical bone and trabecular bone.
What is cortical bone, and where is it located?
Cortical bone is a plate of compact bone found on the facial and lingual surfaces of the alveolar process.
What is the term used to describe cortical bone in the alveolar process?
It is also referred to as the cortical plate.
Can cortical bone be seen on standard radiographs?
No, it is visible only on occlusal radiographs as a uniformly radiopaque bony sheet.
What is trabecular bone, and where is it located?
Trabecular bone is cancellous (spongy) bone located between the alveolar bone proper and cortical plates.
How does trabecular bone appear on radiographs?
It appears less uniformly radiopaque and more porous than the lamina dura of the ABP.
What is the interdental septum, and where is it located?
The interdental septum is the alveolar process that separates neighboring teeth.
Is the interdental septum visible on radiographs?
Yes, it is visible on both periapical and bitewing radiographs.
What is the interradicular septum, and where is it found?
The interradicular septum separates the roots of the same tooth and is found in multirooted teeth.
Is the interradicular septum visible on radiographs?
Only a part of the interradicular septum is visible on bitewing radiographs.
How does orthodontic therapy affect the alveolar process?
Orthodontic therapy forces bone remodeling, producing tooth movement by creating compression and tension zones in the PDL.
What happens in the compression zone during orthodontic therapy?
Compression in the PDL leads to bone resorption.
What happens in the tension zone during orthodontic therapy?
Tension in the PDL leads to the deposition of new bone.
Does the width of the space between alveoli and roots change during orthodontic therapy?
No, the width remains approximately the same as the tooth is repositioned.
What is mesial drift?
Mesial drift, or physiologic drift, is the natural movement of teeth slightly toward the midline over time.
What can mesial drift cause in adulthood?
It can cause crowding in a previously well-aligned dentition.
What factors influence the degree of mesial drift?
The degree of wear on contact points between adjacent teeth and the number of missing teeth affect mesial drift.
How much movement occurs due to mesial drift over a lifetime?
The total movement may amount to no more than 1 cm over a lifetime.
What is supraeruption?
Supraeruption, also called overeruption or supereruption, is the physiologic movement of a tooth lacking an opposing partner within the occlusion.
Which teeth are most commonly affected by supraeruption?
It commonly occurs in permanent posterior teeth.
What are some consequences of supraeruption?
It may expose root surfaces, leading to dentinal hypersensitivity, root caries, esthetic compromise, and periodontal health issues.
What happens to the alveolus after a tooth is extracted?
The clot in the alveolus fills with primary bone, which is later remodeled into mature secondary bone.
What occurs to the alveolar process when a patient becomes edentulous?
The surrounding alveolar process progressively undergoes resorption.
How does the loss of teeth affect the bony trabeculae in the alveolar process?
The number and thickness of bony trabeculae decrease, and the alveolar process becomes thinner.
Does the basal bone remain affected by tooth loss?
The basal bone is less affected because it does not depend on teeth to remain viable.
What stimulates the alveolar process to maintain its structure?
Functional stimulation from teeth during mastication and speech preserves the alveolar process.
What causes the loss of vertical dimension in the face?
The loss of alveolar process height, coupled with tooth attrition, leads to a reduction in the lower third of the vertical dimension when the teeth are in maximum intercuspation.
Why is bone loss in the alveolar process more significant in postmenopausal women?
Postmenopausal women often experience a shortage of estrogen, which helps maintain bone density.
What condition can exacerbate alveolar bone loss in postmenopausal women?
Severe bone loss may occur with the onset of osteoporosis.
How can the structural integrity of the alveolar process be preserved in postmenopausal women?
Placing dentures, bridges, or dental implants can provide stimulation to maintain the bone’s structure.
How does a dental implant benefit an edentulous area?
A dental implant preserves the integrity of the bone by providing adequate stimulation.
What purpose does a dental implant serve?
It acts as a permanent replacement for a lost tooth or teeth and helps prevent further loss of vertical dimension.
What is required for a dental implant to be successful?
A sufficient level of alveolar process must be present.
Why is functional stimulation important in implant placement?
Stimulation from the implant helps maintain the alveolar bone structure.
What happens to the alveolar process during periodontitis?
The localized alveolar process is lost at varying levels depending on the progression and severity of the disease.
What causes tissue destruction in periodontitis?
Hard and soft tissue destruction occurs due to collagen and extracellular matrix (ECM) degradation, primarily by protein-degrading enzymes like matrix metalloproteinase (MMP).
Where does bone loss first occur during periodontitis?
Bone loss is first evident in the most coronal part of the alveolar bone proper (ABP), the alveolar crest.
How does bone loss appear in periodontitis radiographically and microscopically?
The alveolar crest appears ‘moth-eaten’ both microscopically and radiographically.
What happens to the tooth as the alveolar process loss progresses apically?
The tooth becomes increasingly mobile, increasing the risk of future tooth loss.
What causes mobility in teeth affected by periodontitis?
Mobility results from the loss of support by the periodontium.
What is furcation involvement?
Furcation involvement is the loss of the interradicular septum on multirooted teeth.
How is furcation involvement suspected?
It is suspected when a 4-mm probe depth is recorded on a multirooted tooth with normal gingival contour.
How is furcation involvement classified?
It is classified based on the extent of bone destruction.
What tool is used to measure furcation involvement?
A Nabers probe is used.
How does furcation involvement appear radiographically?
It appears as a triangular radiolucency in the bifurcation areas of molars.
What is a fenestration defect in the bone?
A fenestration is a window-like defect in the bone or soft tissue over a tooth, implant, or alveolar ridge.
What is a dehiscence defect in the bone?
A dehiscence is a cleft-like defect in the bone or soft tissue over a tooth, implant, or alveolar ridge.
What is the purpose of bone grafting in periodontal therapy?
Bone grafting is used to regenerate bone, particularly during implant placement.
What are the possible sources of bone graft material?
Bone graft material may come from the patient’s alveolar process, other bone sources (like the chin), cadavers, or synthetic materials.
What is guided tissue regeneration (GTR)?
GTR is a surgical procedure using barrier membranes to direct the growth of new bone and soft tissue in areas with insufficient volume or dimensions.
What cells are involved in re-creating the original periodontal attachment during GTR?
Fibroblasts from the PDL and undifferentiated mesenchyme cells contribute to the regeneration process.
What is the role of the periodontal ligament (PDL)?
The PDL provides attachment of the teeth (via cementum) to the surrounding alveolar bone proper (ABP).
How does the PDL appear on radiographs?
It appears as a radiolucent area between the radiopaque lamina dura and the cementum.
What forces does the PDL transmit?
The PDL transmits occlusal forces from the teeth to the bone, allowing for a small amount of movement.
What are the additional functions of the PDL?
It acts as a shock absorber, serves as the periosteum for cementum and alveolar process, and participates in the development and resorption of the periodontium.
How does the PDL receive nutrition?
The PDL contains blood vessels that provide nutrition for the ligament cells, cementum, and alveolar process.
What sensory functions does the PDL provide?
The PDL provides a proprioceptive mechanism, detecting delicate forces, touch, pressure, and temperature sensations.
Does the PDL transmit pain sensations?
Yes, it transmits pain as well as sensations of touch and pressure.
What types of nerves are found in the PDL?
The PDL contains afferent (sensory) myelinated nerves for sensation and autonomic sympathetic nerves to regulate blood vessels.
What are the primary components of the periodontal ligament (PDL)?
The PDL is made up of connective tissue, which includes cells, fibers, intercellular substances, blood vessels, and nerves.
What is the primary type of protein fiber found in the PDL?
The primary fibers are collagen fibers, specifically Type I collagen.
What is the most important group of fibers in the PDL?
The most important group is the principal fibers, which are organized into bundles.
What are Sharpey fibers, and what is their role?
Sharpey fibers are the ends of the principal fibers that are embedded into the cementum and alveolar bone, anchoring the tooth.
How are the principal fiber groups in the PDL organized?
They are organized based on their orientation to the tooth and alveolar bone.
What is the function of the alveolar crest group of fibers?
These fibers resist tilting, intrusive, extrusive, and rotational forces.
What is the function of the horizontal group of fibers?
They resist tilting forces and rotational forces.
What is the role of the oblique group of fibers?
These fibers resist intrusive forces and rotational forces.
What is the function of the apical group of fibers?
They resist extrusive forces and rotational forces.
What do the interradicular fibers in multirooted teeth do?
They resist intrusive, extrusive, tilting, and rotational forces.
What are the gingival fiber groups, and where are they located?
These fibers are located in the lamina propria of the marginal gingiva and support the gingiva.
What is the role of circular ligament fibers?
They help maintain gingival integrity by encircling the tooth.
What is the function of dentogingival ligament fibers?
They maintain gingival integrity and insert into the cementum on the root and the free gingiva.
What do the alveologingival ligament fibers do?
They help attach the gingiva to the bone.
What is the role of the dentoperiosteal ligament fibers?
These fibers anchor the tooth to the bone and protect the deeper PDL.
What is the interdental ligament, and where is it located?
It is located in the interdental area, connecting the cementum of one tooth to the cementum of an adjacent tooth.
What is the function of the interdental ligament?
It helps maintain the alignment of teeth in the dental arch.
interdental ligament function
It resists rotational forces and maintains interproximal contact.
What is the most common cell in the PDL?
The most common cells are fibroblasts.
What is the function of fibroblasts in the PDL?
Fibroblasts produce fibers and intercellular substances and also help in the breakdown of worn-out fibers.
What are cementoblasts, and what do they do in the PDL?
Cementoblasts are cells that produce cementum.
What role do osteoblasts play in the PDL?
Osteoblasts are involved in bone formation and repair.
What are osteoclasts and odontoclasts responsible for in the PDL?
Osteoclasts resorb bone, and odontoclasts resorb cementum and dentin.
What are epithelial rests of Malassez (ERM), and what is their significance?
The ERM are remnants of Hertwig epithelial root sheath (HERS) and can participate in the formation of periodontal cysts if activated.
What type of collagen is primarily found in the PDL?
The PDL is comprised mostly of Type I collagen, along with lesser amounts of other types.
The PDL has____, which enter the apical foramen of the tooth to supply the pulp
vascular supply, lymphatics, and nerve supply
What types of nerves are found within the PDL?
There are two types of nerves: afferent (or sensory) and autonomic sympathetic nerves.
What is the function of afferent nerves in the PDL?
Afferent nerves are myelinated and transmit sensations that occur within the PDL.
What is the role of autonomic sympathetic nerves in the PDL?
Autonomic sympathetic nerves regulate the blood vessels.
What type of fibers are found in the periodontal ligament (PDL)?
All the fibers in the PDL are collagen in structure.
What are most of the fibers in the PDL classified as?
Most of the fibers in the PDL are considered principal fibers.
How are principal fibers in the PDL organized?
Principal fibers are organized into groups or bundles according to their orientation to the mature tooth and related function.
What do the bundles of principal fibers resemble?
These bundles overall resemble spliced ropes working together.
What forces are exerted on a tooth during mastication and speech?
The forces exerted on a tooth include rotational, tilting, extrusive, and intrusive forces.
How do the principal fibers of the PDL respond to these forces?
Principal fibers of the PDL distribute these forces, protecting its soft tissue and allowing some give when they occur.
What are the ends of the principal fibers that are embedded in either cementum or alveolar bone proper called?
These ends are called Sharpey fibers.
What are the specific functions of the alveolar crest group of fibers in the PDL?
The alveolar crest group resists tilting, intrusive, extrusive, and rotational forces.
Where is the alveolar crest group attached?
It is attached to the cementum just below the cementoenamel junction (CEJ) and runs in an inferior and outward direction to insert into the alveolar crest of the alveolar bone proper (ABP).
What is the function of the horizontal group of fibers in the PDL?
The horizontal group resists tilting and rotational forces.
Where is the horizontal group located?
It is located just apical to the alveolar crest group and runs at a 90° angle to the long axis of the tooth, from the cementum to the ABP, just inferior to the alveolar crest.
What is the function of the oblique group of fibers in the PDL?
The oblique group resists intrusive and rotational forces.
Where is the oblique group found, and what is its orientation?
It is the most numerous fiber group, covering the apical two-thirds of the root, and runs from the cementum in an oblique direction to insert into the ABP more coronally.
What is the function of the apical group of fibers in the PDL?
The apical group resists extrusive and rotational forces.
Where does the apical group radiate from and insert into?
It radiates from the cementum around the apex of the root to the surrounding ABP, forming the base of the alveolus.
What is the function of the interradicular group of fibers in the PDL?
The interradicular group resists intrusive, extrusive, tilting, and rotational forces.
Where is the interradicular group found?
It is found only between the roots of multirooted teeth, running from the cementum of one root to the cementum of the other root(s), superficial to the interradicular septum, with no bony attachment.
What is another principal fiber group in the periodontal ligament?
The interdental ligament, also known as the transseptal ligament.
Where does the interdental ligament insert?
It inserts mesiodistally or interdentally into the cervical cementum of neighboring teeth.
At what height does the interdental ligament insert?
It inserts at a height coronal to the alveolar crest of the alveolar bone proper (ABP), apical to the base of the junctional epithelium.
Does the interdental ligament have bony attachment?
No, the fibers traverse from cementum to cementum without any bony attachment, connecting all the teeth of the arch.
What is the function of the interdental ligament?
Its function is to resist rotational forces and to hold the teeth in interproximal contact.
What do some histologists consider the gingival fiber group to be part of?
Some histologists consider the gingival fiber group to be part of the principal fibers of the PDL.
Where is the gingival fiber group located?
It is found within the lamina propria of the marginal gingiva.
What are the subgroups of the gingival fiber group?
The subgroups include the circular ligament, dentogingival ligament, alveologingival ligament, and dentoperiosteal ligament.
Do gingival fiber groups support the tooth in relation to the jaws?
No, they do not support the tooth in relation to the jaws like the principal fibers of the PDL.
What is the function of the gingival fiber group?
The gingival fiber group supports only the marginal gingiva in maintaining its relationship to the tooth.
What is the function of the circular ligament?
The circular ligament encircles the tooth and helps maintain gingival integrity.
Which gingival fiber subgroup is the most extensive?
The dentogingival ligament is the most extensive subgroup.
Where does the dentogingival ligament insert?
It inserts in the cementum on the root, apical to the epithelial attachment, and extends into the lamina propria of the marginal and attached gingiva.
What is unique about the dentogingival ligament?
It has only one mineralized attachment to the cementum.
What is the function of the alveologingival ligament?
It helps attach the gingiva to the ABP (alveolar bone proper) through its single mineralized attachment to bone.
Where does the dentoperiosteal ligament run?
It runs from the cementum near the CEJ, across the alveolar crest.
What is the function of the dentoperiosteal ligament?
It anchors the tooth to the bone and protects the deeper PDL.
How does orthodontic therapy affect the PDL?
Orthodontic therapy affects the PDL similarly to the alveolar process.
What happens to the PDL on the side under tension?
The PDL space becomes wider on the side under tension.
What happens to the PDL space on the side under pressure?
The PDL space becomes narrower on the side under pressure.
What role does the interdental ligament play in orthodontic therapy?
The interdental ligament is responsible for the memory of tooth positioning within each dental arch.
Why is a prolonged retention period necessary after orthodontic therapy?
It allows the interdental ligament to fully reattach in its new position, ensuring clinical stability of the tooth.
Why does the interdental ligament require more time to adapt?
Its turnover time is slower compared to the alveolodental ligament.
What is used to maintain alignment after orthodontic therapy?
Retainers, both removable and permanent, are used to maintain alignment.
What does occlusal trauma involve?
Occlusal trauma involves trauma to the periodontium caused by occlusal disharmony.
Does occlusal trauma cause periodontal disease?
No, it does not cause periodontal disease but can accelerate its progression.
What happens to the PDL when traumatic occlusal forces are applied?
The PDL widens to accommodate the extra forces.
How does the PDL respond to increased forces?
The width of the ligament can double, and the principal fiber bundles become thicker.
How can early occlusal trauma be identified radiographically?
It appears as a widening of the radiolucent PDL space.
What happens to the lamina dura in response to occlusal trauma?
The lamina dura may thicken in response to the overall loss of the alveolar process.
What are the late signs of advanced occlusal trauma?
Increased tooth mobility and pathologic tooth migration (PTM).
How does the periodontium compensate for advanced occlusal trauma?
The widened PDL space is compensated by the deposition of cementum.
What happens to the PDL during advanced periodontitis?
The PDL undergoes drastic changes with chronic advanced periodontitis, involving the deeper structures of the periodontium.
What happens to the fiber groups of the PDL in periodontitis?
The fiber groups become disorganized, and their attachments to the ABP or cementum through Sharpey fibers are lost due to the resorption of these two hard dental tissue types.
Which fiber group is the first affected by periodontitis?
The alveolar crest group of the alveolodental ligament, which are the most coronal fibers, is the first to be affected.
How does destruction of the PDL progress in periodontitis?
Destruction progresses in an apical manner, affecting (in order) the horizontal, oblique, apical, and then the interradicular subgroups, if present.
What happens to the teeth as periodontal disease advances?
The teeth become increasingly mobile as the disease progresses.
Which fiber group remains the longest during active periodontitis?
The interdental ligament remains the longest, despite the destruction of the adjacent alveolodental ligament.
What does the interdental ligament do as periodontitis progresses?
The interdental ligament reattaches itself in a more apical manner, maintaining interproximal contact as the periodontitis advances apically.
What is the prognosis when teeth become severely mobile interproximally?
The prognosis is poor because destruction has affected the interdental ligament, especially when mobility in other directions is already present.
