Tooth Development And Eruption Part 2 Flashcards
What is enamel hypoplasia?
Enamel hypoplasia is a type of enamel dysplasia resulting from a reduction in the quantity of enamel matrix.
How do teeth appear with enamel hypoplasia?
Teeth appear with pitting and grooves in the enamel surface or horizontal lines across the enamel of the crown.
What dental conditions are associated with enamel hypoplasia caused by syphilis?
Hutchinson incisors and mulberry molars are associated with enamel hypoplasia caused by syphilis.
What causes hutchinsons incisors and mulberry molars?
They are caused by the teratogenic effects of syphilis during development.
What is enamel hypocalcification?
Enamel hypocalcification is a type of enamel dysplasia that results in a reduction in the quality of enamel maturation.
How do teeth with enamel hypocalcification appear?
Teeth appear more opaque, yellower, or browner due to intrinsic staining of the enamel.
What is a Turner spot?
A Turner spot is a single affected area of enamel hypocalcification.
What is a Turner tooth?
A Turner tooth refers to a permanent crown entirely affected by hypocalcification.
How can the discoloration in Turner teeth vary?
The discoloration can range from white spots to darker overall staining.
What can cause both enamel hypoplasia and hypocalcification?
These conditions can occur together and are commonly seen in dental fluorosis.
What is dental fluorosis?
Dental fluorosis is a form of enamel hypomineralization caused by excessive systemic fluoride exposure.
What factors influence the severity of dental fluorosis?
The severity depends on the dose, duration, and age of the individual during fluoride exposure.
How does excessive fluoride affect ameloblasts?
Excess fluoride can cause oxidative stress to ameloblasts, disrupting enamel formation.
How does mild fluorosis appear on enamel?
Mild fluorosis appears as opaque white patches on the enamel.
What are the characteristics of severe fluorosis?
Severe fluorosis causes dark brown stains, rough pitted enamel, and difficulty in cleaning the teeth.
What is the cause of amelogenesis imperfecta and which dentitions does it affect?
Amelogenesis imperfecta is a hereditary condition affecting all teeth in both dentitions.
How does amelogenesis imperfecta affect enamel?
It results in very thin enamel, which may chip off easily or be absent entirely.
How do crowns appear in teeth affected by amelogenesis imperfecta?
The crowns are yellow because they consist mostly of softer dentin.
What problem arises from the soft dentin in amelogenesis imperfecta?
The softer dentin undergoes extreme attrition (wear).
What treatment is recommended for amelogenesis imperfecta?
Full-coverage crowns are recommended to improve esthetics and prevent further attrition.
What is dentin dysplasia?
Dentin dysplasia is the faulty development of dentin.
What causes dentin dysplasia?
It results from an interference with the metabolic processes of odontoblasts during dentinogenesis.
Is dentin dysplasia more common than enamel dysplasia?
No, dentin dysplasia is much rarer than enamel dysplasia.
Can dentin dysplasia result from local or systemic factors?
Yes, it can result from both local and systemic factors, similar to enamel dysplasia.
What disturbances can dentin dysplasia involve?
It can involve dentin hypoplasia, hypocalcification, or both disturbances simultaneously.
What is dentinogenesis imperfecta?
Dentinogenesis imperfecta is a type of dentin dysplasia with a hereditary basis.
How do teeth affected by dentinogenesis imperfecta appear color wise?
They appear blue-gray or brown with an opalescent sheen.
What happens to the enamel in teeth affected by dentinogenesis imperfecta?
The enamel chips off due to lack of support from the abnormal underlying dentin, leaving crowns composed mostly of dentin.
When does the process of root development take place?
Root development takes place after the crown is completely shaped and the tooth is starting to erupt into the oral cavity.
What structure is responsible for root development?
The structure responsible for root development is the cervical loop.
Where is the cervical loop located?
The cervical loop is the most cervical part of the enamel organ.
What does the cervical loop consist of?
It consists of a bilayer rim made up of the inner enamel epithelium (IEE) and outer enamel epithelium (OEE).
What role does the cervical loop play in root formation?
The cervical loop begins to grow deeper into the surrounding ectomesenchyme of the dental sac to form the Hertwig epithelial root sheath (HERS).
What is the function of Hertwig Epithelial Root Sheath (HERS)?
HERS shapes the root(s) of the tooth and induces dentin formation in the root area, so it is continuous with coronal dentin.
What does HERS determine about the tooth root?
HERS determines if the root will be curved or straight, short or long, and whether it will be single or multiple.
What do the outer cells of the dental papilla in the root area do when induced by the HERS?
They are induced by HERS to undergo differentiation into odontoblasts.
Why is enamel absent in the root area?
Enamel is absent in the root area because HERS lacks the stellate reticulum and stratum intermedium, which are necessary for enamel formation.
What happens after odontoblast differentiation in the root area?
These odontoblasts begin dentinogenesis, producing predentin.
What happens when root dentin formation is completed?
The basement membrane disintegrates, as does the entire Hertwig epithelial root sheath (HERS).
What can the disintegrated cells of HERS become?
They may become the epithelial rests of Malassez (ERM).
When does cementogenesis begin?
Cementogenesis begins when HERS disintegrates.
What happens after the disintegration of HERS during cementogenesis?
The disintegration allows the dental sac cells to come into contact with the dentin surface.
What is the result of this contact between dental sac cells and dentin?
The contact induces these cells to become immature cementoblasts.
What do cementoblasts produce?
Cementoblasts lay down cementoid, a matrix of cementum.
What happens to cementoblasts during appositional growth?
Some cementoblasts become trapped in the cementoid and mature into cementocytes.
When does cementoid become cementum?
Cementoid becomes cementum when it is fully mineralized.
What junction is the result of the apposition of cementum over the dentin?
The dentinocemental junction (DCJ) is formed.
What is concrescence?
Concrescence is a rare condition where the cementum of two or more teeth fuses together at their roots.
In which teeth does concrescence most commonly occur?
It most commonly occurs with permanent maxillary molars.
What causes concrescence?
It occurs due to excessive cementum deposition on one or more teeth after eruption.
How do the teeth involved in concrescence start?
The teeth are originally separate but become joined by their cementum.
How do multirooted premolars and molars begin their development?
They originate as a single root on the base of the crown.
What is the part of these posterior teeth at the base of the crown called?
It is called the root trunk.
What happens to the root trunk during the development of a multirooted tooth?
The root trunk divides into the correct number of root branches for the tooth type.
What causes the division of the root trunk into multiple roots?
Differential growth of Hertwig epithelial root sheath (HERS) causes the root trunk to divide into two or three roots.
What happens during the formation of the enamel organ in a multirooted tooth?
The cervical loop elongates, allowing the development of long, horizontal extensions or flaps within it.
How is the cervical opening divided in a multirooted tooth?
Horizontal extensions divide the cervical opening into two or three openings.
What forms on the pulpal surfaces of the openings formed by horizontal extentions?
Dentin formation starts after the induction of odontoblasts.
What do cementoblasts do in multirooted teeth?
Cementoblasts form cementum on the newly formed dentin only at the periphery of each opening.
How does root development proceed in multirooted teeth?
It proceeds in the same way as described for a single-rooted tooth.
What is an enamel pearl?
An enamel pearl is a small, spherical enamel projection on the root surface.
What causes an enamel pearl?
It is caused by misplaced ameloblasts.
Where do enamel pearls most commonly occur?
They most commonly occur at the cementoenamel junction (CEJ) or in the furcation areas of molars where roots divide.
What is the appearance of an enamel pearl?
It appears as a small, rounded enamel projection that can sometimes include dentin and pulp.
How do enamel pearls appear on radiographs?
They appear radiopaque (light) on radiographs.
What can occur if amelogenesis is not turned off after crown formation?
The enamel organ may continue to produce enamel over the root dentin.
What is the shape of additional enamel formed in cases where the ameloblasts of the crown are not turned off a proceed to root dentin?
It often takes the shape of enamel projections or enamel spurs.
Where are enamel projections or spurs typically located?
They project into the furcation areas of multirooted teeth.
What is a potential complication of enamel projections or spurs?
They may increase the risk of periodontal lesions in the affected furcation areas.
What is dilaceration?
Dilaceration is a disturbance during root development that results in distorted roots or severe crown angulation in a formed tooth.
What causes dilaceration?
It is caused by distortion of Hertwig epithelial root sheath (HERS) due to injury or pressure.
Which teeth can be affected by dilaceration?
Dilaceration can affect any tooth or group of teeth during development.
What are accessory roots?
Accessory roots, also known as supernumerary roots, are extra roots on a tooth.
What causes accessory roots to form?
They may form due to trauma, pressure, or metabolic disease affecting Hertwig epithelial root sheath (HERS).
Which teeth are most commonly affected by accessory roots?
Accessory roots occur most commonly in permanent third molars.
Are accessory roots common in incisors?
No, they are rare in incisors.
Can accessory roots occur in any tooth?
Yes, any tooth may be affected by accessory roots.
What happens as the crown and root develop?
The surrounding supporting tissue types of the tooth also develop from the dental sac.
From where does the periodontal ligament (PDL) form?
The PDL forms from ectomesenchyme within the dental sac.
What occurs during PDL formation?
The ectomesenchymal cells in the dental sac begin to differentiate into fibroblasts.
What do fibroblasts produce during PDL formation?
They produce collagen fibers that become organized into bundles.
How do the collagen fibers produces by fibroblasts during periodontium development become structured?
They thicken and mature, becoming arranged in a structured manner to support the tooth.
What do the ends of these collagen fibers become embedded in?
They become embedded in the outer layers of the cementum and surrounding alveolar bone.
What are these embedded fibers called?
They are called Sharpey fibers.
What does the ectomesenchyme of the dental sac form in addition to forming the PDL?
It mineralizes to form the tooth sockets or alveoli of each alveolar process.
How does the eruption of primary and permanent teeth occur?
Eruption occurs in chronological order for both primary and permanent dentitions.
What is active eruption?
Active eruption is the actual vertical movement of the tooth.
How is passive eruption different from active eruption?
Passive eruption occurs with aging when the gingival tissue recedes, uncovering more of the clinical crown.
What is more important than the dates of eruption?
The sequence of eruption is more important than the actual dates.
Why are the actual dates of eruption less significant?
Because there can be a great deal of variation in the actual eruption dates, but the sequence tends to be uniform.
What happens after enamel appositional growth ceases in the crown?
The ameloblasts place an acellular dental cuticle on the newly formed outer enamel surface.
What do the layers of the enamel organ become compressed into?
They become compressed into the reduced enamel epithelium (REE).
How does the reduced enamel epithelium (REE) appear?
The REE appears as a few layers of flattened cells overlying the new enamel surface.
When does the primary tooth begin to erupt into the oral cavity?
It begins to erupt after the formation of the REE.
What must the REE first do to allow for eruption?
The REE must fuse with the oral epithelium lining the oral cavity.
What enzymes do cells from the REE release during eruption?
They release enzymes that disintegrate the central part of the fused tissue.
What does disintegration of the central part of the fused tissue of the REE and OE create?
It creates a protective epithelial-lined eruption tunnel for the tooth.
What inflammatory response may accompany tissue disintegration during eruption?
The response is known as ‘teething,’ which may include tenderness and swelling of the local tissue.
What happens to the fused epithelial tissue as the tooth erupts?
The coronal part of the tissue peels back from the crown, leaving the cervical part attached to the neck of the tooth.
What happens to the fused tissue that remains near the CEJ after eruption?
It serves as the initial junctional epithelium of the tooth.
What is the role of the initial junctional epithelium?
It creates a seal between the tissue and the tooth surface.
What happens to the initial junctional epithelium over time?
It is later replaced by a definitive junctional epithelium as the root becomes fully formed.
What happens to a primary tooth as the succedaneous permanent tooth develops?
The primary tooth is shed, also known as exfoliation.
Where does the succedaneous permanent tooth develop relative to the primary tooth?
It develops lingual to the roots of the primary tooth.
What process causes the shedding of a primary tooth?
Shedding involves the differentiation of multinucleated osteoclasts.
From where are osteoclasts derived?
Osteoclasts are derived from the fusion of macrophages in the surrounding area.
What do osteoclasts do during shedding?
They absorb the alveolar process between the roots of the primary tooth and the developing permanent tooth.
What other type of resorption occurs during shedding?
Odontoclasts resorb the roots of the primary tooth, removing dentin and cementum.
What role do fibroblasts play during the shedding process?
Fibroblasts destroy any remaining collagen fibers connecting the primary tooth to the PDL.
How do succedaneous permanent teeth erupt in relation to the primary teeth?
They erupt in a position lingual to the roots of the shedding primary teeth.
What is the exception to the usual lingual eruption pattern?
The exception is permanent maxillary incisors, which move to a more facial position as they erupt.
What process is the same for permanent and primary teeth during eruption?
The process of eruption is the same, beginning with the widening of the gubernacular canal (GC).
What happens after the reduced enamel epithelium (REE) fuses with the oral epithelium?
The REE degenerates, leaving an epithelial-lined eruption tunnel.
How does the eruption of nonsuccedaneous teeth compare to succedaneous teeth?
The process is similar for nonsuccedaneous teeth.
What teeth are classified as nonsuccedaneous?
Nonsuccedaneous teeth include the permanent molars.
How do nonsuccedaneous and succedaneous teeth erupt?
Both erupt in chronological order.
What happens if a permanent tooth starts to erupt before the primary tooth is fully shed?
This can create challenges with spacing.
What can be done to address the spacing issues caused when permanent teeth erupt before primary teeth shed?
Interceptive orthodontic therapy can help prevent or manage these situations.
What should be done if a child has prolonged retention of primary teeth?
Early dental consultation is important for managing such cases.
What is the Nasmyth membrane?
The Nasmyth membrane is a residue that may form on newly erupted teeth of both dentitions.
How does the Nasmyth membrane appear?
It appears as a green-gray residue on the teeth.
What does the Nasmyth membrane consist of?
It consists of fused tissue from the reduced enamel epithelium (REE) and oral epithelium, as well as the dental cuticle placed by ameloblasts.
How does the Nasmyth membrane pick up stains?
It easily picks up coloring from food debris.
Can the Nasmyth membrane be removed?
Yes, it can be removed by selective polishing.
Why is it important to prevent traumatic injury to developing permanent teeth?
Because the crown forms before the root, permanent teeth are vulnerable until they are fully anchored in the jaws.
What is recommended to prevent traumatic injury in children?
Mouthguards are recommended for children active in all types of sports.
What is an avulsed tooth?
An avulsed tooth is a tooth that has been completely removed from its socket due to trauma.
What should be done immediately if a tooth is avulsed?
The patient should seek immediate examination by a dental professional in a dental setting or emergency hospital unit.
How should the avulsed tooth be transported?
It should be placed in a wet handkerchief, milk, water, or in the buccal vestibule (preferred for hydration with saliva).
Should primary teeth be replanted after avulsion?
No, primary teeth will not be placed back in the mouth.
What is the prognosis for an avulsed tooth?
The prognosis is better when there is a short time between avulsion and reimplantation.
What treatments might be required for an avulsed tooth?
Treatments may include pulp canal therapy, splint placement, and observation for other trauma.
What additional medical care might be needed for an avulsed tooth?
A tetanus booster may be indicated in some cases.
What is a dentigerous cyst?
A dentigerous cyst is an odontogenic cyst that forms from the reduced enamel epithelium (REE) after the crown has fully formed and matured.
What is another name for a dentigerous cyst?
It is also called a follicular cyst.
dentigerous cyst typically present initially with what symptoms?
It is initially asymptomatic.
Where does a dentigerous cyst form?
It forms around the crown of a nonerupted or developing tooth.
Which teeth are most commonly associated with dentigerous cysts?
The permanent third molars are most commonly affected.
What complications can arise from a large dentigerous cyst?
It may cause displaced teeth, jaw fractures, and pain.
How is a dentigerous cyst treated?
It must be completely removed surgically to prevent it from becoming neoplastic.
What is an eruption cyst?
An eruption cyst is a type of dentigerous cyst that forms on a partially erupted tooth.
How does an eruption cyst appear clinically?
It appears as a fluctuant blue vesicle-like gingival lesion.
What happens to an eruption cyst during tooth eruption?
The eruption cyst disintegrates as the tooth erupts.
Is treatment needed for an eruption cyst?
No further treatment is usually needed as it resolves naturally.
What results from the disintegration of the dental lamina after eruption?
Disintegration results in the formation of discrete clusters of epithelial cells that usually degenerate.
What can some clusters of epithelial cells form if they persist?
They may form epithelial pearls.
What can epithelial pearls give rise to?
They can form small cysts or eruption cysts over a developing tooth, delaying eruption.
What are other potential outcomes of epithelial pearls?
They may give rise to odontomas or be activated to form supernumerary teeth.
What is an odontoma?
An odontoma is a benign neoplasm of odontogenic origin, linked to tooth development.
What may odontomas arise from?
They may arise from the presence of epithelial pearls.
What tissues make up an odontoma?
An odontoma consists of dental tissues like enamel, dentin, cementum, and pulp.
How does an odontoma appear?
It may look like an oddly shaped tooth or a calcified tumor.
What is the recommended treatment for an odontoma?
It should be surgically removed before it interferes with tooth eruption in the area.
What are Bohn nodules?
Bohn nodules are large, sometimes multiple, white bumps present on the maxillary alveolar ridge.
What is the exact cause of Bohn nodules?
The exact etiology is unknown.
From what are Bohn nodules thought to arise?
They are thought to arise from remnants of the dental lamina.
Are Bohn nodules harmful?
No, they are a benign finding.
What happens to Bohn nodules over time?
They will disappear with time.
