Ch. 6: Tooth Development and Eruption Review Questions

Cap stage

- Dental lamina holds on growing and a cap is formed around the bud. - Unequal growth in different parts of the tooth bud, leading to formation of a cap shape attached to the dental lamina. - A lot of differentiation is going on. Enamel organ is formed (produced from ectoderm). - Ectomessenchyme produces a dental papilla (future dentin and pulp). - Ectomessenchyme condenses producing dental sac which becomes cementum, alveolar bone and periodontal ligament - primordium of the tooth (tooth germ) forms, containing each of the primordial types of tissue necessary to develop the future tooth. - tooth germ is formed - the enamel organ and the dental papilla, being the site of the future dentinoenamel junction - 10th week: Primary initiation occurs in the anterior teeth of the permanent dentition and then later for the premolars of the permanent dentition

10. What is the successional dental lamina and what does it provide?

- Dental lamina that will provide a space for succedaneous permanent teeth. - It is the extension of dental lamina into ectomesenchyme forming succedaneous permanent teeth. It provides permanent teeth.

Bell stage

- Four different types of cells are now found within the enamel organ. These cell types include the: 1) outer enamel epithelium 2) stellate reticulum 3) stratum intermedium 4) inner enamel epithelium (from outer to inner)

What do of the inner enamel epithelium (IEE) become in the future?

- In future development, theIEE will differentiate by phases into enamel secreting cells (ameloblasts).

What is the function of the inner enamel epithelium (IEE).

- The innermost tall columnar cells of the enamel organ are the inner enamel epithelium (IEE). - However, a basement membrane still remains between the IEE and the adjacent dental papilla

What is the function of the outer enamel epithelium (OEE)?

- The outer cuboidal cells of the enamel organ are the outer enamel epithelium (OEE) - The OEE serves as a protective barrier for the rest of the enamel organ during enamel production

What two layers are between the outer and inner enamel epithelium?

- The stellate reticulum and the stratum intermedium. - The stellate reticulum consists of star-shaped cells in many layers, forming a network

15. What does the enamel organ consist of and what is the function of each layer?

-OEE: Outer cuboidal cells of enamel organ. Serves as protective barrier for enamel organ - IEE: Inner most tall, columnar cells of enamel organ . Will differentiate into ameloblasts that form enamel matrix. Produce enamel - Stellate reticulum: More outer star-shaped cells in many layers, forming a network within the enamel organ. Supports the production of enamel matrix. Do not produce enamel but provide the material to produce enamel - Stratum intermedium: Most inner compressed layer of flat to cuboidal cells. Supports the production of enamel matrix Do not produce enamel but provide the material to produce enamel appears during the 14th week ? notably high alkaline phosphatase activity.

1. Discuss and explain the two dentitions and when they occur.

1) Primary Dentition - develop during prenatal (20 teeth. Eventually lost. 2) Permanent - 32 teeth replaces primary and is permanent.

28. What is the Hertwig epithelial root sheath, and what is its function?

A membrane that shapes the roots by inducing dentin formation in the root area so that it is continuous with coronal dentition.

5. What developmental disturbances can occur during the initiation stage?

Anodontia: Absence of single tooth or multiple teeth owing to lack of initiation. - associated with the syndrome of ectodermal dysplasia because many of the components of the tooth germ are indirectly or directly of ectodermal origin. Supernumerary (or hyperdontia): Developmental disturbance characterized by one or more extra teeth. - caused buy multiple dental laminas

In what stage does the enamel organ start to form

Cap stage

What is the stratum intermedium made up of?

Compressed layer of flat to cuboidal cells.

12. What developmental disturbances can occur during the cap stage?

Dens in dente- A tooth forming within a tooth Germination- Two crowns and one root Fusion- Two roots but one crown. tubercles- Appear as small, round enamel extensions forming extra cusps.

A part of the ectomesenchyme has condensed into a mass within the concavity of the cap. The inner mass of ectomesenchyme is now considered the?

Dental papilla

The dental papilla will produce the future?

Dentin and pulp

Describe the pirmordium

Each primordium for these initially-formed permanent teeth appears as an extension of the dental lamina into the ectomesenchyme lingual to the developing primary tooth germs. Its site of origin is called the successional dental lamina

The dental papilla and dental sac is originally derived from?

Ectomesenchyme

In the future the enamel organ will produce?

Enamel

The tooth's future crown form , such as cusps occur through non dividing cells in the ?

Enamel Knot

What originally derived from ectoderm, making enamel an ectodermal product?

Enamel organ

21. How do odontoblasts form, and what do they produce?

Odonoblasts are formed after the outer cells of the dental papilla are induced by the preameloblasts. Produce dentin

2. Name and explain each of the three dentition periods.

Primary - Baby teeth Permanent - Adult teeth Mixed - Permanent and mixed

6. What occurs during the bud stage and what tissue types are involved?

Time span: 8th week Main process: Proliferation Histologic features: - Growth of dental dental placodes into the bud shape that penetrates growing ectomesenchyme - Extensive proliferation of the dental lamina into buds, with these three-dimensional oval masses penetrating into the surrounding ectomesenchyme - At the end of the proliferation process involving the dental lamina of the primary dentition, both the future maxillary arch and the future mandibular arch will each have 10 buds.

8. What occurs during the cap stage and what tissue types are involved?

Time span: 9th-10th week Main process: Proliferation, differentiation, morphogenesis Histologic features: Formation of tooth germ as enamel organ forms into cap shape that surrounds inside mass of dental papilla, with outside mass of dental sac, both from ectomesenchyme

3. What is odontogenesis and does it generally occur for the primary dentition?

Tooth development, in stages - initiation - bud - cap - bell - apposition - maturation

24. What occurs during the process of amelogenesis?

amelogenesis is the enamel process. Apposition of enamel matrix by ameloblasts.

23. How do ameloblasts form, and what do they produce?

cells that differentiate from preameloblasts and that will form during amelogenesis.

33. What developmental disturbances can occur with cementum formation?

concrescence can occur. Which is the union of the root structure of two or more teeth through the cementum only. It mainly occurs with permanent maxillary molars.

27. Describe the process of root development.

crown forms from the root down to the apex. The cervical loop (cervical part of enamel matrix that consists of IEE and OEE) grows deeper into ectomesenchyme of dental sac, elongating and moving away from the newly completed crown area to enclose more of the dental papilla, forming Hertwig's epithelial root sheaths (HERS)

What does the tooth germ consist of?

dental papilla, enamel organ and dental sac

26. Describe the developmental disturbances that can occur during the apposition and maturation stages of tooth development.

enamel dysplasia- faulty enamel local enamel dysplasia- may result in trauma or infection in a small group of ameloblasts. Systemic enamel dysplasia- large number of ameloblasts. Enamel hypoplasia- reduction in the quantity of enamel matrix. Teeth appear with pitting and grooves. Hutchinson's incisors and mulberry molars: caused by syphillis Hutchinson's incisors: have a crown with a screwdriver shape and notched incised edge. Mullberry molars: enamel tubercules on occlusal surface enamel hypocalcification: reduction in the quality of the enamel maturation. Teeth appear more opaque, yellower or browner. Dental flourosis: enamel hypoplasia and ypocalcification occurring together. Amelogenesis imperfecta: certain types of enamel dysplasia, very thin enamel that chips off, no enamel at all.

20. How do preameloblasts form, and what will they produce in the future?

form by the innermost cells of the bell shaped enamel organ, growing and elongating. In the future, the preameloblasts will fist induce dental papilla cells to differentiate into cells that secrete enamel.

29. How does root dentin form?

it forms when outer cells of dental papilla in the root area undergo induction and then differentiate and become odontoblasts. Influence of IEE on HERS lacking stellate reticulum and stratum intermedium creates antiballistic differentiation.

32. Where is the dentinocemental junction located, and what is its relationship to the pulp and other types of dental tissue?

located in the area where the disintegrating basement membrane between the two tissue types was located. Dentinocemental junction is apposition of cementum over the dentin. Central cells of dental papilla are forming pulp at the same time, which later becomes surrounded by the newly formed dentin.

14. What developmental disturbances can occur during the bell stage?

none?

25. Explain the dentinoenamel junction and its relationship to the Tomes process, odontoblasts, and ameloblasts.

odontoblasts and ameloblasts. Preameloblasts are induced to differentiate into ameloblasts and beginning amelogenesis from tomes process, with the apposition of enamel matrix on their side of basement membrane. Later, this membrane will disintegrate and mineralize to form the dentinoenamel junction. The prevention is thicker than the enamel matrix because the odontoblast differentiate and start matrix production earlier than the ameloblasts.

19. Describe the process of induction during tooth development.

oral epithelium and dental lamina develop form ectoderm lining the stomodeum. Also, oral epithelium is separated from the underlying ectomesechyme by a basement membrane.

Describe the process of induction during tooth development

oral epithelium and dental lamina develop form ectoderm lining the stomodeum. Also, oral epithelium is separated from the underlying ectomesechyme by a basement membrane.

what two inter mediately-placed layers of the enamel organ help support the future production of enamel

stellate reticulum and the stratum intermedium

31. Discuss the process of cementogenesis.

the cells in dental sac come in contact with newly formed root dentin. This contact induces these cells to come cementoblasts. They move to cover root dentin area and undergo cementogenesis.

22. What occurs during the process of odontogenesis?

tooth development and it takes place in many stages; its a continuous process. Stages: initiation, bud stage, cap stage, bell stage, apposition and maturation.

30. What are the epithelial rests of Malassez, and what complication is associated with them?

when groups of cells of epithelium become located in mature periodontal ligament. They can become cystic presenting future periodontal infections.

Supernumerary (or hyperdontia):

Most common between the maxillary central incisors (mesiodens),distal to the maxillary third molars (distomolar or "fourth molar"), and in the premolar region (perimolar) of both dental arches (listed in order of occurrence)

What is the stellate reticulum?

- A cellular group located in the center of the enamel organ of a developing tooth. - These cells are sar shaped and synthesize glycosaminoglycans .As glycosaminoglycans are produced, water is drawn in between the cells which stretches them apart. - As they are moved farther away from one another with the production of glycosaminoglycans, the stellate reticula maintain contact with one another through cell junctions by way of desmosomes, resulting in their unique star-shaped appearance

Partial microdontia

Hereditary factors are involved, and teeth commonly affected are the permanent maxillary lateral incisor (peg lateral) and permanent third molar (peg molar) - Larger dental lamina= larger teeth

The the future the dental sac will produce?

Increasing amount of collagen fibers forming around the enamel organ. Will differentiate into cementum, periodontal ligament and alveolar process.

Partial endodontia

Is more common and most commonly occurs with the permanent third molar, maxillary lateral incisor, and mandibular second premolar (listed in order of occurrence)

7. What developmental disturbances can occur during the bud stage?

Macrodontia: Abnormally large teeth. Microdontia: Abnormally small teeth.

The predominant physiological process during the cap stage is?

Morphogenesis; proliferation

16. Describe the layers of the dental papilla and the function of each layer.

The dental papilla consists of two types of tissues in layers: - Outer cells of dental papilla: The outer layer of cells of the dental papilla, nearest the inner enamel epithelium of the enamel organ. A basement membrane is between this outer layer and this inner enamel epithelium. Will differentiate into odontoblasts that form dentin matrix - Central cells of dental papilla: Central mass of the dental papilla. will differentiate into pulp tissue.

17. Describe the dental sac and its function.

The dental sac is the tooth germ part consisting of ectomesenchyme surrounding outside of the enamel organ. It will differentiate into cementum, periodontal ligament, and alveolar bone.

18. Explain the stages of apposition and maturation during tooth development.

The stages of apposition and maturation are the final stages of odontogenesis. The enamel, dentin, and cementum are secreted in successive layers that will serve as a framework for later mineralization. Complete mineralization of enamel, dentin, and cementum.

11. What is the difference between succedaneous and nonsuccedanous teeth and which permanent teeth fall into which category?

The succedaneous teeth are the permanent teeth that replace the deciduous teeth. Permanent molars are not succedaneous teeth because they do not replace any primary teeth.

13. What occurs during the bell stage and what tissue types are involved?

Time span: 11-12th week Main process: Proliferation, differentiation, morphogenesis Histologic features: Differentiation of enamel organ into bell shape with four cell types and dental papilla into two cells

4. What occurs during the initiation stage and what tissue types are involved?

Time span: 6th-7th week Main process: Induction Histologic features: Ectoderm lining stomodeum gives rise to oral epithelium and then to dental lamina with its dental palcodes; adjacent to deeper ectomesenchyme, which derived from neural crest cells. Both tissues types are separated by basement layer.