How are cementoblasts formed? 

After HERS disintigrates from the surface of the newly formed root, the mesenchymal cells of the dental follicle come into contact with the outer layer of root dentin (Hyalin layer of Hopewell Smith). This contact causes them to differentiate into cementoblasts. 

How are Sharpey's fibers formed? 

After the cementoblasts lay down the uncalcified cementoid, the fibroblasts of the adjacent developing PDL intertwine collagen fibers around the protruding cementoid fibers and deposit mineral onto the root surface (making Sharpey's fibers). 

The resulting cementum is known as Mixed Fiber Cementum and makes up the majority of secondary cementum. 

Where is cellular cementum found? 

Cellular (secondary) cementum contains cementocytes, and is found on the apical third of the root and in the interradicular areas of multi-rooted teeth. Unlike primary (acellular) cementum the collagen fibers of the cementoid are deposited parallel to the root. Cellular cementum is deposited after the tooth reaches occlusion, in response to trauma or wear.

What are the different zones of peripheral dental pulp? 

Odontoblastic zone - 1 cell layer thick, borders predentin and lines the pulp cavity.

Cell Poor Zone of Weil - Beneath the odontoblastic zone, thin layer of blood vessels and nerves, including the Nerve Plexus of Raschkow.

Cell Rich Zone (of Rinaggio) - 3-5 layers thick, under cell poor zone, mostly made up of fibroblasts. 

Match the activity to the stage of Amelogenesis in which it occurs:

A. hemidesmosomes are formed

B. modulation occurs

C. Tome's process is visible

D. IDE cells are cuboidal to low columnar

E. Nucleus is near the stratum intermedium 

A. hemidesmosomes and a basal lamina are secreted by ameloblasts during protective stage

B. modulation, the alternation of a ruffled and smooth ameloblast border, occurs during maturation phase, as water is removed and calcium absorbed.

C. Tome's process is visible during secretory stage.

D. IDE cells are not yet ameloblasts, small with a central nucleus during morphongenetic stage.

E. The nucleus moves to non-secreting end during differentiation stage (cells are now preameloblasts). 

What types of cells are found in (inner) dental pulp? 

Fibroblasts - numerous, secreted ground substance

Undiff. mesenchymal cells - can become fibroblasts or odontoblasts

Macrophages - toward pulp core

Lymphocytes - T more common than B when healthy

Dendritic Cells - antigen presenting, more common than macrophages 

What are the types of fibers found in the PDL? 

Alveolar Crest fibers - slightly apical to CEJ

horizontal group - just apical to alveolar crest group

oblique - most common, osseous attachment is coronal to origin in cementum

Apical - found in the apex, resist pulling

Interradicular - like apical near furcation of roots 

Where are neonatal lines found? 

Neonatal lines are incremental lines found in enamel and dentin. In enamel they are considered exaggerated Striae of Retzius. In dentin they run perpendicular to the dentinal tubules. 

These are found in mature dentin and represent 5-day cycles of dentinogenesis. 

Lines of Von Ebner 

What types of fibers compose the gingival ligament? 

Dentogingival group - most numerous

Alveologingival group

Circular group - holds free gingiva against the tooth

Dentoperiosteal group

Transseptal fibers - constitute interdental ligament, responsible for mesial drift 

What does the enamel organ give rise to?

The dental papilla?

The dental follicle? 

THE TOOTH GERM IS MADE UP OF: 

The enamel organ (epithelial) gives rise to (duh) the enamel.

The dental papilla (ectomesenchymal) component gives rise to the dentin and pulp.

The dental follicle (ectomesenchyme) surrounds the papilla and gives rise to the cementum, periodontal ligament, and alveolar bone.

(these 3 structures = periodontium) 

What is ectomesenchyme derived from? 

In the developing embryo ectomesenchyme is derived from neural crest cells. 

After what week of embryonic development would the primary epithelial band appear? 

After the fifth week.

What 2 structures does the primary epithelial band give rise to?

Which structure forms first? 

The dental lamina and the vestibular lamina come from the epithelial band. The dental lamina arises just before the vestibular lamina. 

What is the earliest sign of tooth development in embryogenesis?

When does it take place? 

On day 11 of embryogenesis there are thickenings of the future tooth bearing area on the first branchial arch. 

What are the 2 theories that attempt to explain the embryological patterning of dentition?

Which theory relies on both the ectomesenchyme and the epithelium? 

The 2 theories are the field model and the clone model.

The clone model says that there are specific ectomesenchymal cells that influence the epithelium to produce a certain patten.

(The field model says that different types of ectomesenchyme determine pattern.) 

Which parts of the tooth germ have their origin in neural crest cells?

A. dental papilla

B. enamel organ

C. dental follicle 

A. dental papilla

C. dental follicle

-both comprised of ectomesenchyme 

(B. enamel organ is derived from epithelium) 

In Bell Stage of tooth development the cells of the enamel organ adjacent to the dental papilla undergo histodifferentiation. 

Which eventual cell type shows increased alkaline phosphatase activity?

Which type becomes slightly columnar and has increased glycogen content? 

The Stratum Intermedium shows increased alkaline phosphatase activity, and is thought to be important for eventual mineralization of the tooth.

The IDE becomes slightly columnar with increased glycogen content. 

What transient structure sits between the stellate reticulum and the stratum intermedium and is thought to play a role in cusp development? 

Enamel knot

- the enamel cord is a continuation of this organ that intersects with the EDE 

During Bell Stage, what is the thick basement membrane that forms between the dental papilla and the IDE called? 

The Acellular Zone 

Where in the future tooth does differentiation of the IDE into pre-ameloblasts first begin? 

Differentiation begins along the incisal edge or cusp tips and proceeds down the cusp inclines.

What directly precedes (induces) the pre-ameloblasts to secrete enamel matrix (making them ameloblasts)? 

 A. odontoblasts secreting pre-dentin

B. odontoblasts secreting dentin

C. pre-odontoblasts secreting dentin

D. pre-odontoblasts secreting pre-dentin 

A. odontoblasts secreting pre-dentin 

The enamel organs of which 3 teeth are the last to form?

When does each begin to form? 

The permanent molars form by a continuing posterior growth of the dental lamina.

1st molars - 4 months in utero

2nd molars - 10 months postnatal

3rd molars - 5 years of age 

Which of the following takes placed during Crown Stage:

A. Amelogenesis and Dentinogenesis

B. Cementogenesis

C. Root Formation

D. A & C

E. All of the above 

E. All of the above 

The proliferation of what type of cell obliterates the acellular zone? 

The odontoblasts 

What is the first type of dentin formed?

How thick is it? 

Mantle dentin is formed first, and is 15-20 microns thick. 

What type of dentin is responsible for the narrowing of pulp canals seen in older dental patients? 

Secondary dentin 

What substance can penetrate the thinner epithelia  of the oral mucosa?

nitroglycerine or glucose paste

- used to treat hypoglycemic shock(?) 

What are the 3 types of oral mucosa within the oral cavity? 

Masticatory mucosa - on gingiva and hard palate, ortho/parakeratinized sse overlying mucoperiosteum.

Lining mucosa - on soft palate, ventral tongue, floor of mouth, lower alveolus, lips, buccal mucosa; thin non-keratinized (except lips) sse over loose irregular collagenous connective tissue.

Specialized mucosa - thick keratin/non-keratin sse; lingual papillae, rich nerve & blood supply.