dental embry, histo, and anatomy ch 5-6 quiz

pharyngeal arches/ branchial apparatus

• consists of arches 1-6, negating arch 5 as it goes away

• begins development in week four due to embryonic folding

• consists of arches, grooves, membranes, and pouches

• each arch has its own cartilage, muscle, vascular, and cranial nerves

first pharyngeal arch

• also known as the mandibular arch

• both mandibular processes fuse to form mandible, lower lip, and mandibular teeth

• contains meckel cartilage

• innervated by the trigeminal nerve (mandibular branch)

• muscles and structures needed for chewing

second pharyngeal arch

• known as hyoid arch

• contains reinchert cartilage

• innervated by facial nerve

• develops horns of hyoid bone and muscles/ facial features designated to creating facial movements and expressions

third pharyngeal arch

• creates the rest of the hyoid bone

• contains unnamed cartilage

• innervated by the glossopharyngeal cranial nerve

fourth and sixth pharyngeal arch

• contain unnamed cartilage

• innervated by the vagus nerve

• create the laryngeal cartilages

the development of the orofacial structures including the palate, nasal septum, nasal cavity, and tongue, occurs during the _ to _week of prenatal development, spanning the later part of the embryonic period and early part of fetal period

• fourth to twelfth week

the formation of the palate begins during the __ week of prenatal development within the embryonic period

• fifth week

the palate is then completed during the __ week within the fetal period

• twelfth

fifth to sixth week of palatal development

• The primary palate is formed from the inferior growth of the intermaxillary segment

• triangular shape, anterior 1/3 of the hard palate

• gives rise to the 4 anterior maxillary incisors

• served only as a partial separation between the developing oral cavity proper and the nasal cavity

sixth to twelfth week of palatal development

• Bilateral maxillary processes will give rise to palatal shelves

• secondary palate begins to form and migrate as palatal shelves grow inferiorly and deep on the inside of the stomodeum in a vertical direction towards each other

• tongue forming on the floor of the primitive pharynx initially fills the cavity, but will contract and move inferiorly

• because of an unknown elevating force, palatal shelves will begin to “flip” up and grow in a superior direction after movement of tongue

• two palatal sheleves elongate and move medially, joining in the middle and fusing to form secondary palate

• posterior 2/3rds of hard palate, soft palate, uvula is the last thing to fuse

intermaxillary segment arises as a result of the fusion between the two __ nasal processes internally

• medial

• inferior growth and fusion of the medial nasal processes internally forms the intermaxillary segment that will eventually give rise to the anterior 1/3 of the hard palate and the 4 anterior maxillary incisors

palatal shelves

• also known as lateral palatine processes

• will grow horizontally towards each other after flipping in superior direction to form secondary palate

• will fuse with nasal septum

median palatine raphe

• indicate the line of fusion of the palatal shelves

• suture located in the middle of the mucosa lining of the hard palate

twelfth week of palatal development

• final palate takes form

• palate undergoes fusion of all three processes (primary palate and two palatal shelves that have created secondary palate)

• posterior part of primary palate meets the secondary palate due to increased growth, structures gradually fuse in an anterior to posterior direction (primary palate to median raphe to uvula)

• mature oral cavity becomes completely separated from the nasal cavity

failure of fusion of the palatal shelves with the primary palate and/or with each other results in __ __ with varying degrees of disability

• cleft palate

cleft uvula

• is the least complicated form of cleft palate

• may still cause velopharyngeal insufficiency (VPI)

velopharyngeal insufficiency (VPI)

• a disorder that prevents the velum or soft palate from closing against the posterior pharyngeal wall during speech in order to close off the nasal cavity, which is needed for the production of most speech sounds

Epstein pearl

• small white papule seen in the midline of the palate of an infant

• represents epithelial tissue that becomes trapped during palatal fusion

nasal cavity formation

• forms in the same time frame as palate from the fifth to twelfth week of prenatal development

• later serve as part of respiratory system

• nasal septum is a growth from the fused medial nasal processes

• vertical nasal septum then fuses with the horizontally oriented final palate after it has formed

deviated septum

• occurs when the thin wall that makes up the nasal septum inside the nose is displaced to one side

• nasal septum separates the right and left nasal cavities

the tongue begins to develop during the __ to __week of prenatal development

• fourth to eighth

the body of the tongue develops from the __ pharyngeal arch

• first pharyngeal arch

the base of the tongue originates from the _,_, and _ pharyngeal or bracnhial arches

• the base of the tongue originates from the

• second

• third

• and fourth pharyngeal arches

fourth week to eighth week of the body of the tongue development

• The body begins to form as a triangular median swelling called the tuberculum impar is formed on the mandibular arch, and lateral lingual swellings appear on either side of the tuberculum impar

• paired swellings grow and merge, growing over the top of the tuberculum impar

• These swellings form the anterior 2/3rds of the body of the tongue, and around swellings, the cells degenerate, forming a sulcus and freeing the body of the tongue from the floor except for the midline lingual frenum

tuberculum impar

• median tongue bud

• triangular median swelling that appears during the body of the tongues development

• appears in the midline and formed on mandibular arch (first pharyngeal arch)

median lingual sulcus

• is a superficial demarcation of the line of fusion of the two lateral lingual swellings, as well as of a deeper fibrous structures

fourth week to eighth week of the base of the tongue development

• posterior to the fused anterior swellings, a pair of swellings, the copula, becomes evident

• gradually overgrows the hyoid arch (second pharyngeal arch) and this overgrowth will form the posterior one-third of the mature tongue, the base

• farther posterior to copula is a projection of a third median swelling, the epiglottic swelling and marks the development of the most posterior region of tongue and site of epiglottis

eighth week of tongue development

• completed tongue: merging of anterior swellings of body and copula of base after copula overgrows hyoid arch (2nd pharyngeal arch) during eighth week of prenatal development

• fusion is superficially demarcated by the sulcus terminalis on the mature dorsal surface of tongue

• sulcus terminalis points backwards toward a small pit-like depression, the foramen cecum, which is the beginning of the thyroglossal duct

the thyroglossal duct shows the origin of the __ gland and the migration pathway of the __ gland into the neck region

• thyroid gland

• later this duct will close off and become obliterated before birth

ankyloglossia

• “tongue-tied”

• tongue is “anchored down”

• results from a short attachment of the lingual frenum that extends to the tongue apex

incisive foramen

• important structure in the hard palate that allows nerves to sprout through

• formed due to the merging and fusion of primary palate and secondary palatal shelves

• when the triangular primary palate and elongated secondary palatal shelves meet, it leaves a hole that we know as the __ __

odontogenesis

• is the process of tooth development

• starts between weeks 6-7 of prenatal development

• typically includes 6 stages

  • initiation, and then the initial identifiable stages are:

  • bud

  • cap

  • bell

  • progresses to the apposition

  • maturation

dentition

• used to describe the natural teeth in the jaws

• primary (deciduous) and permanent

initiation stage (weeks 6-7)

• the first stage of odontogenesis

• at the beginning of the sixth week, the embryo’s stomodeum (primitive mouth) is lined by ectoderm that gives rise to oral epithelium

• in the oral epithelium ectomesenchyme interacts with dental lamina but is seperated by an acellular structure known as the basement membrane

• during the later part of seventh week oral epithelium thickens to form dental lamina and vestibular lamina

• dental placodes form

oral epithelium

• consists of two horse-shoe shaped bands of tissue at the surface of the stomodeum

• one band for each future dental arch

ectomesenchyme

• a tissue derived from neural crest cells that have migrated to the region

• in this instance it is located deep to the forming oral epithelium

basement membrane

• an important acellular structure that separates the oral epithelium and the ectomesenchyme within the stomodeum

dental lamina

• 2 u-shaped bands of thickened epithelium formed during induction

• occurs in each developing jaw where the two future curved dental arches of the primary dentition will form

dental placodes

• resemble the other placodes developing

• each placode consist of plate-like thickened epithelium associated with an underlying neural crest derived mesenchyme (neuroectoderm)

• function as first signalling centers of the tooth

anodontia

• lack of initiation within the dental lamina results in the absence of a single tooth, multiple teeth, or even an entire dentition

• also known as hypo (less) dontia

• hereditary

most common teeth for partial anodontia

1. permanent third molar

2. maxillary lateral incisor

3. mandibular second premolar (because it is the only premolar to have 3 cusps)

ectodermal dysplasia

• can be associated with anodontia

• many of the components of the tooth germ are indirectly or directly of ectodermal origin

• dysplasia- displaced

• displaced ectoderm

supernumerary teeth

• known as hyperdontia

• extra teeth initiation from persisting clusters of the dental lamina

• have a hereditary etiology

• commonly between the maxillary central incisors, distal to the maxillary thid molar, and premolar region of both dental arches

mesiodens

• term for a supernumerary tooth located between the maxillary central incisors

bud stage (week 8)

• second stage of odontogenesis

• extensive proliferation of the dental lamina into 10 buds per arch that penetrate the ectomesenchyme

• basement membrane remains between the dental lamina bud and the surrounding growing and condensing ectomesenchyme

• each bud will later form the tooth germ

distomolar

• supernumerary tooth located distal to the maxillary third molar

perimolar

• supernumerary tooth located in the premolar region of both dental arches

macrodontia

• abnormally large teeth

• result of abnormal proliferation during bud stage

• most commonly affects maxillary lateral incisors and third molars

microdontia

• abnormally small teeth

• result of abnormal proliferation during bud stage

• most commonly affects maxillary lateral incisors and third molars

cap stage (weeks 9-10)

• third stage in odontogenesis

• differentiation and morphogenesis begin

• unequal growth in different parts of tooth bud, leads to the formation of cap shape overlying the ectomesenchyme

• primordium of the tooth (tooth germ) forms containing tissue

  • enamel organ

  • dental papilla

  • dental sac

• innermost margin of cap consists of enamel knot

• during later part, site of origin called the successional dental lamina begins to form lingual to developing primary tooth germs

enamel organ

• forms enamel

• tooth germ

• formation of tooth bud in cap shape with deep central depression

dental papilla

• forms dentin and pulp (DP)

• tooth germ

• condensed mass of ectomesenchyme within concavity of enamel organ

dental sac (follicle)

• forms cementum, periodontal ligament, alveolar process

• tooth germ

• condensed mass of ectomesenchyme surrounding the outside of enamel organ

successional dental lamina

• appears during the 10th week

• each primordiym for these initially formed permamnent teeth appears as an extension of the dental lamina into the ectomesenchyme that grows lingually to developing primary tooth germs

• start to form permanent dentition

succedaneous teeth

• permanent teeth formed with primary predecessors

• anterior teeth and premolars

• crown of each permanent succedaneous tooth will reupt lingual to roots of its primary predecessor

nonsuccedaneous

• have no primary predecessors

• the six permanent molars per dental arch

dens in dente

• translates to tooth inside a tooth

• during cap stage enamel organ may abnormally invaginate by growth into the dental papilla

• (enamel folds into crown)

• commonly found in permanent maxillary incisors (lateral)

gemination

• occurs as the single tooth germ tries unsuccessfully to divide into two tooth germs, resulting in a notably large, single-rooted tooth with common pulp cavity

• developmental disturbance during cap stage

• gemini (two heads, two germs)

• root is one but the head is two

• normal number of teeth

fusion

• union of two adjacent tooth germs, possibly resulting from pressure in the area

• a different head and root, but are joined together

• Two tooth buds merge as a result of pressure

• fewer teeth in the arch

tubercles

• small, round enamel extensions forming extra cusps

• results from an enamel knot malformation

• common on molars

bell stage (weeks 11-12)

• fourth stage of odontogenesis

• continuation of ongoing process of proliferation, differentiation, and morphogenesis

• four different types of cells are now formed within the enamel organ

• (from outer to inner)

  • outer enamel epithelium (OEE)

  • stellate reticulum

  • stratum intermedium

  • inner enamel epithelium (IEE)

• assumes a three dimensional bell shape

• dental papilla cell differentiation

  • outer cells → become odontoblasts

  • inner cells → become pulp tissue

• dental sac increases amount of collogen fibers forming around enamel organ

• dental lamina is disintegrating so tooth continues development divorced from oral epithelium

outer enamel epithelium (OEE)

• outer cuboidal cells of the enamel organ

• serves as a protective barrier for the rest of the enamel organ during production

inner enamel epithelium (IEE)

• innermost tall columnar cells of the enamel organ

• will differentiate into enamel-secreting cells known as ameloblasts

• basement membrane still remains between the IEE and adjacent dental papilla during bell stage

• establishes crown pattern of tooth by ways of folding

ameloblasts

• enamel secreting cells that will form enamel matrix

stellate reticulum

• consists of star-shaped cells in many layers, primarily located in the center of the enamel organ, and forms a network

• synthesize glycosaminoglycans, in which water is drawn in between the cells and stretches them apart

• even though they are being stretched, they remain in contact with each other through cell junctions by way of desmosomes

• located between the outer and inner enamel epithelium

• help support future production of enamel

stratum intermedium

• made up of a compressed layer of flat to cuboidal cells

• help support the future production of enamel

• is a layer of two or three cells like a layer cake between IEE and stellate reticulum

outer cells of dental papilla

• become odontoblasts during the bell stage

• form dentin

central cells (inner cells) of dental papilla

• become primordium of the pulp tissue during the bell stage

apposition stage (secretory stage)

• one of the final stages of odontogenesis

• enamel, dentin, and cementum are secreted in successive layers upon those already present

• originally secreted as a matrix

• odontoblasts secrete pre-dentin → triggers ameloblasts to form enamel matrix

• basement membrane disintegrates, forming the dentinoenamel junction (DEJ)

matrix

• an extracellular substance or surrounding medium

• serve as frameworks

maturation stage

• the final stage of odontogenesis

• reached when the matrices of the hard dental tissue types subsequently fully mineralize to their correct levels

• enamel, dentin, and cementum fully mineralize

apposition

• add

• adding layers on top of one another

pre-ameloblasts

• after the formation of IEE

• “baby” or “learning” version of enamel makers

• innermost cells grow even more columnar as they elongate and differentiate into __

• The nucleus of each cell moves away from the center of the cell to the position furthest away from the basement membrane during cellular repolarization

• will induce dental papilla cells to differentiate into dentin-forming cells (odontoblasts) and then will themsleves differentiate into ameloblasts after contacting predentin

odontoblasts

• dentin building cells

• located in the outer cells of the dental papilla

• induced by the pre-ameloblasts

repolarization of cells

• nuclei moves from the center of the cell to a position in the cell that is farthest from the basement membrane

dentinogenesis

• The appositional growth of the dentin matrix that will form dentin

amelogenesis

• the appositional growth of the enamel matrix

• begun by the ameloblasts

• laying it down on their side of the now disintegrating basement membrane

tomes process

• the enamel matrix is directly secreted from the __ __

• an angled distal part of each ameloblast that faces the fully disintegrated basement membrane

dentinoenamel junction

• enamel matrix comes in contact with predentin and mineralizes the disintegrating basement membrane

• inner junction between the dentin and enamel tissue

odontoblastic process

• odontoblasts leave attached cellular extensions in the length of the predentin called __ __ as they move away from DEJ

• each process is contained in a mineralized cylinder, the dentinal tubule

enamel dysplasia

• local or systemic

• faulty (defective) development of enamel

local enamel dysplasia

• may result from trauma or infection occurring to a small group of ameloblasts

systemic enamel dysplasia

• involves larger numbers of ameloblasts that may result from traumatic birth, systemic infections, nutritional deficiencies, or dental flurosis

dental fluorosis

• may occur alongside enamel hypoplasia or hypocalcification

• hypomineralization occurs due to excessive systemic fluoride level that causes white spots or brown putting

• may occur due to oxidative stress to the ameloblast from excess fluroide

enamel hypoplasia

• a type of enamel dysplasia

• develops during apposition stage

• results from a reduction in the quantity of the enamel matrix

• teeth appear with pitting and grooves in the enamel surface or in the development of horizontal lines across the enamel of the crown

• noted in the presence of Hutchinson incisors and mulberry molars

enamel hypocalcification

• A disturbance developed in the apposition stage that results in a reduction in the quality of the enamel maturation

• teeth appear more opaque, yellower, or even browner within because of an intrinsic staining of enamel

• could have “turner spots” that are single affected areas, or could affect the entire crown

amelogenesis imperfecta

• a type of enamel dysplasia

• has a hereditary etiology and can affect all teeth of both dentitions

• teeth either have no enamel or very thin enamel that chups off, leaving yellow crowns of dentin

dentin dysplasia

• faulty development of dentin

• result of interference with the metabolic processes of odontoblasts during dentinogenesis

• more rare than enamel dysplasia but can be caused by systemic factors

dentinogenesis imperfecta

• a type of dentin dysplasia

• a hereditary basis

• blue-gray or brown teeth with opalescent sheen

root development begins long after __

• the crown is completely shaped and the tooth is starting to erupt into the oral cavity

• tooth is formed starting from crown then moving to apex of root

cervical loop

• structure responsible for root development

• the most cervical part of enamel organ

• bilayer rim that consists of only inner enamel epithelium (IEE) and outer enamel epithelium (OEE)

• grows deeper into surrounding ectomesenchyme of dental sac and forms the Hertwig epithelial root sheath (HER)

Hertwig epithelial root sheath

• __

• function is to shape the root(s) by inducing dentin formation in the root area, so that it is continuous with coronal dentin

• will determine if the root will be curved or straight, short or long as well as single or multiple

  • there is differential growth of __ that causes the root trunk of each multirooted tooth to divide into two or three roots

• induces odontoblastic differentiation but fails to differentiate into enamel-forming ameloblasts (no enamel in roots)

epithelial rests of Malassez (ERM)

• After the disintegration of Hertwig epithelial root sheaths, these cells may possibly form

cementogenesis

• The process of forming the cementum that surrounds the root area of a tooth

• occurs when HERS disintegrates

cementoblasts

• cells that build the cemetum

• form after contact of dental sac cells with dentin surface

cementocytes

• many cementoblasts become entrapped by the cementum they produce and become mature __

• surrounded and entrapped by cementoid, and once they mineralize, they make cementum

cementoid

• cementoblasts move to cover the root dentin area and undergo cementogenesis, laying down cementum matrix, also known as __

dentinocemental junction (DEJ)

• basement membrane disintegrates and _ is formed where the membrane was located

• a result of the apposition of cementum over the dentin

concrescence

• excess cementum formation that rarely occurs

• con man produced too much cementum

enamel pearl

• misplaced ameloblasts migrated to the surface of root by localized failure of HERs to separate from dentin

• enamel ectopically forms over cemental root surface

• small spherical enamel projection on root especially at CEJ