Tooth development, eruption & applied aspects

TOOTH DEVELOPMENT, ERUPTION & APPLIED ASPECTSSaurabh Roy09.03.2016

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CONTENTS :■ Introduction■ Initiation

– Dental lamina, Its fate– Vestibular Lamina– Defects

■ Proliferation – Bud stage– Cap stage– Defects

■ Histodifferentiation – Early bell■ Morphodifferentiation – Advanced bell

– Defects

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CONTENTS :■ Apposition :

– Defects■ Root formation :

– Defects■ Eruption

– Phases– Mechanism – Defects

■ Conclusion■ References

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INTRODUCTION :

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INTRODUCTION :■ As an oral diagnostician it is worth learning about Tooth

developmental stages and eruption for the following reasons :– Check for developmental milestones– Co relate dental with skeletal maturity– To anticipate developing malocclusion and prevent it

before it happens– To check for dental anomalies in syndromic and non -

syndromic patients– In case of premature deciduous tooth loss or delayed

eruption of permanent teeth (patient guardian re assurance)

– Age estimation in neonates and children may be deduced by pinpointing the stage of tooth development (forensic odontology)

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Initiation in IUL :■ Tooth formation occurs in the 6th week of intrauterine life with

the formation of primary epithelial band■ The primitive oral cavity, or stomodeum, is lined by stratified

squamous epithelium called the oral ectoderm■ The oral ectoderm contacts the endoderm of the foregut to

form the buccopharyngeal membrane

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Initiation in IUL :■ At about 7th week the primary epithelial band divides into a

lingual process called dental lamina & a buccal process called vestibular lamina

■ All deciduous teeth arises from dental lamina, later the permanent successors arise from its lingual extension & permanent molars from its distal extension

■ Post 37 days of development, a horseshoe shaped band of thickened epithelium is formed at the presumptive upper & lower jaws

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Timeline of tooth development :

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Stages of Tooth Development :

Formation of Dental lamina Initiation

Bud & Cap Stage

Early bell stage

Proliferation

Formation of enamel & dentin matrix

Advanced bell stage Morphodifferentiation

Histodifferentiation

Apposition

MORPHOLOGICAL PHYSIOLOGICAL

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INITIATION :

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INITIATION :

• The dental lamina serves as the primordium for the ectodermal portion of the deciduous teeth

• The successors of the deciduous teeth develop from a lingual extension of the free end of the dental lamina opposite to the enamel organ of each deciduous teeth.

• The lingual extension of the dental lamina is named the successional lamina & develops from the 5th month in utero ( permanent central incisor) to the 10th month of age (second premolar)

• Total activity of the dental lamina exceed atleast 5 years

Dental Lamina :

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Fate of Dental Lamina :

As the teeth continue to

develop, they loose their

connection with the dental lamina

They later break up by

mesenchymal invasion, which is at first incomplete

and does not perforate the total thickness of the

lamina

Fragmentation of the dental lamina progresses toward

the developing enamel organ

Any particular portion of the dental lamina functions for a much briefer

period since only a relatively short time elapses after initiation of tooth

development before the dental lamina begins to

degenerate

However the dental lamina

may still be active in the third molar region after it has

disappeared elsewhere, except

for occasional epithelial remnants

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Vestibular Lamina :• Labial and buccal to the dental lamina

in each dental arch, another epithelial thickening develops independently

• It is Vestibular Lamina also termed as lip furrow band

• Subsequently hollows and form the oral vestibule between the alveolar portion of the jaws and the lips and cheeks

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DEFECTS IN INITIATION:

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Defects :■ Anodontia vera■ Rare genetic disorder characterized by the

congential absence of all primary or permanent teeth

Initiation

COMPLETE

PARTIAL

FORM

S True False

Pseudo MUTATION OF PAX9 MSX1 AND AXIN2

Anodontia :

Mokhtari et al; Christ-Siemens-Touraine Syndrome: A Case Report and Review of the Literature; Case Reports in Dentistry ; Hindawi Publishing Corporation; Article ID 586418

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Defects :■ Anodontia :

Initiation

Multiple developmentally missing permanent teeth and several retained deciduous teeth in a female adult.

The panoramic radiograph shows no unerupted teeth in either jaw.

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Defects :■ Associated syndromes :

– Ectodermal dysplasia– Cleft lip & palate– Ellis van creveld– Ehlers danlos– Goldenhar – Hurler– Gorlin goltz– Lipoid proteinosis– Progeria– Sturge weber’– Turners

Initiation

Anodontia :

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Supernumerary tooth :■ Results from continued proliferation of primary dental lamina

to form 3rd tooth germ

Initiation

Upper distomolars

Mesiodens

Premolars

Lower distomolars

Canines Garvey et al; Supernumerary Teeth -An Overview of

Classification, Diagnosis and Management; J Can Dent Assoc 1999; 65:612-6

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Supernumerary tooth :■ Associated syndromes :

– Apert– Cleido cranial dysplasia– Crouzon – Down – Ehlers danlos– Gardner– Sturge weber– Curtius – Fabry anderson

Initiation

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Supernumerary tooth :■ Post permanent dentition :

– The rare appearance of supernumerary teeth after loss of permanent teeth

– Most teeth that appear after extraction of permanent teeth are due to eruption of previously impacted teeth

Initiation

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Ectopic initiation :■ Dermoid cyst :

– An example of a teratoma– Teratoma is a true neoplasm arising

from totipotent cells made up cell types representative of more than 1 germ layer; usually all 3

– Containing ectodermal cells have been known to appear in■ Ovary■ Spinal cord tumours■ Periorbital areas

– The common factor is the presence of a solitary or multiple hamartomous tumour

Initiation

Yashwant Ingale et al; Ectopic Teeth in Ovarian Teratoma: A Rare Appearance; Hindawi Publishing Corporation;Case Reports in Dentistry;Volume 2013, Article ID 970464, 3 pages

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PROLIFERATION :

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PROLIFERATION :

• This is the initial stage of tooth formation where enamel organ resembles a small bud

• During the bud stage, the enamel organ consists of peripherally located low columnar cells & centrally located polygonal cells

• The surrounding mesenchymal cells proliferate, which results in their condensation in two areas

• The area of condensation immediately below the enamel organ is the dental papilla

• The ectomesenchymal condensation that surrounds the tooth bud & the dental papilla is the dental sac

Bud stage : Early bud

Late bud

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Bud stage :• The dental papilla as well as the

dental sac are not well defined during the bud stage, they become more defined during the subsequent cap & bell stages

• The cells of the dental papilla form the dentin and pulp while the dental sac forms cementum & periodontal ligament

Proliferation

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Cap stage :■ Unequal growth in different parts of the tooth bud leads to

the cap stage, which is characterized by a shallow invagination on the deep surface of the bud

Proliferation

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Cap stage :■ Outer & inner enamel

epithelium :– Peripheral cells of the cap

stage are cuboidal, cover the convexity of the “cap” called Outer Enamel Epithelium

– The cells in the concavity of the “cap” become tall, columnar cells represent Inner Enamel Epithelium

– The OEE is separated from the dental sac and IEE from the dental follicle by a delicate basement membrane

– Hemidesmosomes anchor the cells to the basal lamina

Proliferation

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Cap stage :■ Stellate reticulum :

– Initially Polygonal cells– Between the OEE and IEE– Endosmosis of water into enamel organ results in cells

being star shaped with inter connected processes– As the enamel formation starts., the Stellate reticulum

collapses to a narrow zone thereby reducing the distance between the outer & inner enamel epithelium

Proliferation

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Cap stage :■ Dental sac(follicle) :

– Concomitant with the development of the enamel organ and the dental papilla, there is marginal condensation in the ectomesenchyme surrounding both

– Gradually, a denser and more fibrous layer develops, which is the primitive dental sac

Proliferation

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Cap stage :■ Dental papilla :

– Partial enclosure of ectomesenchyme by the invaginated portion of IEE results in its proliferation and condensation into dental papilla

– Formative organ of the dentin & pulp primordium– It shows active budding of capillaries and mitotic figures,

& its peripheral cells adjacent to the inner enamel epithelium enlarge and later differentiate into odontoblasts

Proliferation

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DEFECTS :

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Microdontia :1. True generalized microdontia :

■ All teeth smaller than normal

2. Relative microdontia : (misnomer?)■ Normal or slightly smaller than normal

teeth■ Normal sized teeth may appear small when

present in widely spaced jaw larger than normal (macrognathia)

3. Focal or localized microdontia :■ Common condition■ Most affected – maxillary lateral incisor &

3rd molar■ Most common form – Peg shaped lateral

Proliferation

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Macrodontia :– Appiled only when teeth are physically larger than usual

and should NOT include normal-sized teeth crowded within a small jaw (relative macrodontia)

– Additionally, this term should NOT be used to describe teeth altered by fusion or gemination

Proliferation

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HISTODIFFERENTIATION :

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HISTODIFFERENTIATION :

■ Deepening of epithelial invagination and growth of its margins, leads to assumption of bell shape

■ The folding of enamel organ to cause different crown shapes is shown to be due to differential rates of mitosis & differences in cell differentiation time

■ Determination of crown shapes is under the control of genes and their signalling molecules and growth factors

Early bell stage :

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Early bell stage :■ Inner enamel epithelium :

– Single layer of cells differentiate into tall columnar cells – Ameloblasts

■ Stratum intermedium :– Few layers of squamous cells between the inner enamel

epithelium and stellate reticulum■ Stellate reticulum ;

– This stage leads to further expansion, with an increase in the amount of intercellular fluid

– Before enamel formation begins, the stellate reticulum collapses, reducing distance between ameloblasts and nutrient capillaries near outer enamel epithelium


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Early bell stage :■ Outer enamel epithelium : flattening to a low cuboidal form■ Dental lamina :

– Extends lingually and gives rise to successional lamina– Gives rise to enamel organs of permanent successors of

deciduous teeth■ Dental papilla :

– Enclosed in the invaginated portion of the enamel organ– The basement membrane that separates the enamel organ

and dental papilla just prior to dentin formation is called membrana preformativa

■ Dental sac :– Shows a circular arrangement of its fibres & resembles a

capsular structure


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MORPHODIFFERENTIATION :

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MORPHODIFFERENTIATION :

■ Characterized by the commencement of mineralization & root formation

■ The boundary between the inner enamel epithelium & odontoblasts outline the future dentinoenamel junction

■ Formation of dentin occurs first as a layer along the future dentinoenamel junction in the region of future cusps & proceeds pulpally & apically

■ After the first layer of dentin is formed, the ameloblasts lay down enamel over the dentin in the future incisal & cuspal areas

Advanced bell stage :

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Advanced bell stage :■ The enamel formation then proceeds coronally & cervically in all

the regions from the dentinoenamel junction toward the surface■ The cervical portion of enamel organ gives rise to Hertwig

Epithelial Root Sheath (HERS)■ This HERS outlines the future root & thus responsible for the size,

shape , length & number of roots

Morphodifferentiation

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DEFECTS :

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Gemination :– Single enlarged tooth or joined(double)

tooth in which tooth count is normal when anomalous tooth is counted as 1

– Partial or complete cleavage of single tooth germ

– Large single rooted tooth with one pulp cavity exhibits “twinning” in crown area

– The etiology of geminated teeth remains unknown

– Possible cause-nutritional deficiency, endocrinal disturbance, infectious/inflammatory processes, hereditary or congenital diseases, and local traumas and by ionizing radiation is also considered


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Fusion :

– Defined as a single enlarged tooth or joined(double) tooth in which the tooth count reveals a missing tooth when the anomalous tooth is counted as 1

– Either complete or incomplete union of two normally separated tooth germs

– The dentin always confluent in cases of true fusion


If this contact occurs

Before calcification

begins

The 2 teeth may be completely

united to form a single large tooth

Later, when a portion of tooth

crown has completed formation

The may be union of the roots

only

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APPOSITION :

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APPOSITION :■ Appositional growth of enamel and dentin is a layer like

deposition of an extracellular matrix■ Hence, this type of growth is additive■ It signifies fulfilment of the plans outlined at the stages of

histodifferentiation and morphodifferentiation■ Appositional growth is characterized by regular and rhythmic

deposition of the extracellular matrix, which is by itself incapable of further growth

■ Periods of activity and rest alternate at definite intervals during tooth formation

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DEFECTS :

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Dens invaginatus (Dens-in-dente) :■ Represents a defect of tooth in which a

focal area on the tooth surface is folded or invaginated pulpally to a variable extent.

■ Malformation of teeth probably resulting from an infolding of the dental papilla before calcification.

■ Maxillary lateral incisors, central incisors, premolars, canines and molars are affected in the order of fashion

Apposition :

M. Hülsmann, “Dens invaginatus: aetiology, classification, prevalence, diagnosis, and treatment considerations,” International Endodontic Journal, vol. 30, no. 2, 79–90, 1997.

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Dens invaginatus (Dens-in-dente) :■ Dens invaginatus (Dens-in-dente) :

Apposition :

Coronal dens invaginatus

Type I - Invagination

confined to the crown

Type II – extends past the CEJ but does not involve

the periapical tissues

Type III – extends past the CEJ & may result in

formation of a 2nd apical foramen

Oehler’s classification

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Dens evaginatus :■ central tubercle, tuberculated cusp,

accessory tubercle, occlusal pearl, evaginated odontome,Leong premolar, tuberculated premolar

■ Cusp like elevation of enamel located in the central groove or lingual ridge of the buccal cusp of premolar or molar teeth

■ Accessory cusps are frequently associated with occlusal interferences and pulpal pathoses

Apposition :

result of outward folding of inner enamel epithelial cells and transient

focalhyperplasia of the peripheral cells of

mesenchymal dental papilla

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Enamel pearl :■ The formation of ectopic enamel requires the presence of

differentiated ameloblasts apical to the CEJ. In humans, Hertwig's epithelial root sheath (HERS) or its residues, the epithelial rests of Malassez have been implicated as the likely sources of ectopic ameloblasts

Apposition :

Shivani sharma et al Enamel pearl on an unusual location associated with localized periodontal disease: A clinical report, J Indian Soc Periodontol. 2013 Nov-Dec; 17(6): 796–800

Radiopaque nodule on the mesial surface of the root of the maxillary third molar.

Another less distinct enamel pearl is present on the distal root of the second

molar

Mass of ectopic enamel located in

the furcation area of a molar tooth

Enamel pearls are found most frequently

on the roots of maxillary molars

(mandibular molars are the second most

frequent site)

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Talon’s cusp :■ Well delineated additional cusp located on the surface of an

anterior tooth and extends at least half the distance from the CEJ to the incisal edge

Apposition :

Normal cingulum

Enlarged cingulum

Small accessory

cusp

Full fledged Talon’s cusp

As a result of outward folding of inner enamel epithelial cells and transient

focalhyperplasia of the cells of mesenchymal

dental papilla

Permanent lateral incisors(55%), central (33%), mandibular incisors (6%),

maxillary canines (4%)

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Talon’s cusp :■ Hattab et al classified talons cusps as :

– Type 1, major talon: A morphologically well delineated additional cusp that prominently projects from the facial or palatal/lingual surface of an anterior tooth and extends at least half the distance from the CEJ to the incisal edge.

– Type 2, minor talon: A morphologically well-defined additional cusp that projects from the facial or palatal/lingual surface of an anterior tooth and extends more than onefourth, but less than half the distance from the CEJ to the incisal edge.

– Type 3, trace talon: Enlarged or prominent cingula and their variations, which occupy less than one-fourth the distance from the CEJ to the incisal edge

Apposition :

Hattab FN, Yassin OM, Al-Nimri KS. Talon cusp in the permanent dentition associated with other dental anomalies: Review of literature and reports of seven cases. J Dent Child 1996;63:368-76

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Taurodontism :■ Enlargement of the body and pulp chamber of a multirooted

tooth, with apical displacement of the pulpal floor and bifurcation of the roots

■ Failure of Hertwig's epithelial sheath diaphragm to invaginate at the proper horizontal level

■ Shape of the taurodont resembles that of the molar teeth of cud-chewing animals (tauro = bull; dont = tooth)

Apposition :

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Taurodontism : :

Apposition :

Illustration exhibiting the classification of taurodontism according to the degree of apical displacement of the pulpal floor

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Enamel hypoplasia :■ occurs in the form of pits, grooves, or larger areas of missing

enamel

Apposition :

Factors producing injury to ameloblasts during tooth formation:

Nutritional deficiency (vit. A,C,D)Diseases like measles, chicken pox,

scarlet feverCongenital syphilis

HypocalcaemiaBirth injury

Local infection or traumaIngestion of chemicals

Tissue irradiationBilaterally symmetrical pattern of horizontal enamel hypoplasia of the anterior dentition. Maxillary

central incisors have been restored previously

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Amelogenesis imperfecta :■ Encompasses a complicated group of conditions that

demonstrate developmental alterations in the structure of enamel in the absence of a systemic disorder

Apposition :

The DLX3 gene is in a group of genes that code for a number of proteins that are critical for craniofacial , Tooth, hair, brain, and neural development

Elaboration of organic matrix• Hypoplastic Mineralization of the matrix• Hypocalcified Maturation of the enamel• Hypomaturation

Related gene Protein VariantsAMLEX AMELOGENI

Nsmooth hypoplastic and hypomaturation

ENAM ENAMELIN Hypoplastic (minor pitting to diffuse generalized thin enamel)

MMP-20 ENAMELYSIN

pigmented hypomaturation

KLK4 KALLIKREIN

Hypomaturation

DLX3 hypoplastic-hypomaturation

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Amelogenesis imperfecta :Apposition :

Hypoplastic amelogenesis imperfecta, generalized pitted pattern

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Dentinogenesis imperfecta :■ Hereditary opalescent dentin, capdepont’s teeth■ Hereditary developmental disturbance of the dentin the

absence of any systemic disorder■ Dentitions have a blue to brown discoloration, often with a

distinctive transluscence■ Teeth are constitutionally weaker, prone to rapid wear,

breakage, caries and ultimately loss

Apposition :

A B

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Dentinogenesis imperfecta :Apposition :

Aswathy Raj,Deepa.M.S, Ahmed Hasan Farooqi GENETICS AND TOOTH ANOMALIES - AN UPDATE

Oral & Maxillofacial Pathology Journal Vol. 4 No. 1 Jan - June 2013

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■ Classified into 3 basic types :Shields Type I (associated with Osteogenesis Imperfecta)-

Features- periapical radiolucencies, bulbous crowns, obliteration of pulp chambers, root fractures and amber translucent tooth color

Shields Type II (Hereditary Opalescent Dentin) Features are same as Shields Type I apart from Osteogenesis Imperfecta

Shields Type III (Brandywine Type)Teeth have a shell-like appearance with bell-shaped crowns.

Occurs exclusively in a isolated group in Maryland called Brandywine population

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SHELL TEETH

■ :

NORMAL TEETH

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Regional odontodysplasia : Apposition :

Posterior mandibular dentition exhibiting enlarged

pulps and extremely thin enamel and dentin

■ Localized, nonhereditary developmental abnormality of teeth with extensive adverse effects on the formation of enamel, dentin, and pulp

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Dentin dysplasia : Apposition :

2 types :

Type I (radicular

dentin dysplasia)

Type II (coronal dentin

dysplasia)

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■ Dentin dysplasia type I (radicular dentin dysplasia) :– has been referred to as rootless teeth, because the

loss of organization of the root dentin often leads to a shortened root length

FEATURES- Because of the shortened roots, the initial clinical signs are extreme tooth mobility and premature exfoliation, spontaneously or secondary to minor trauma. Less frequently, delayed eruption is the presenting symptom

Posterior dentition exhibiting shortened roots, absence of pulp canals, and small, crescent-shaped pulp chambers.

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■ Dentin dysplasia type I (radicular dentin dysplasia) :

Subclassifcation of Dentin DysplasiaType IDDIa: No pulp chambers, no root formation, DDIb: A single small horizontally oriented and crescent-shaped pulp, roots only a few millimeters in length,DDIc: Two horizontally oriented and crescent-shaped pulpal remnants surrounding a central island of dentin, significant but shortened root length,DDId: Visible pulp chambers and canals, near normal root length, enlarged pulp stones that are located in the coronal portion of the canal and create a localized bulging of the canal and root, constriction of the pulp canal apical to the stone.

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■ Dentin dysplasia type II (coronal dentin dysplasia) :– The root length is normal in both dentitions. – Radiographically, the dental changes include bulbous crowns,

cervical constriction, thin roots, and early obliteration of the pulp.– The pulp chamber exhibit significant enlargement and apical

extension which is described as thistle tube–shaped or flame-shaped

Permanent dentition that does not exhibit translucence, as noted in the deciduous teeth.The patient also exhibits mild fluorosis of the enamel

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ROOT FORMATION :

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ROOT FORMATION :• The development of roots begin

after enamel & dentin formation has reached the future cementoenamel junction

• The enamel organ plays an important role in root development by forming HERS, which models the shape of the root

• HERS consists of outer & inner enamel epithelium only

• As the first layer of the dentin has been laid down, the epithelial root sheath loses its structural continuity and is close relation to the surface of the roots

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ROOT FORMATION :■ The rim of this root

sheath, the epithelial diaphragm, encloses the primary apical foramen

■ These cells eventually form dentin of the tooth leading to formation of a single root

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ROOT FORMATION :■ Remnants of HERS persists as an

epithelial network of strands or clumps near the external surface of the root

■ These epithelial remnants are found in the periodontal ligament of erupted teeth and are called as rests of mallasez

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DEFECTS :

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Concrescence : Root formation :

■ Two fully formed teeth, adhered along the root surface by cementum.■ 2nd molar is frequently involved.■ Clinically radiographic diagnosis is mandatory before attempting tooth

extraction.■ Deciduous dentition can result in crowding, abnormal spacing, and

delayed or ectopic eruption of the underlying permanent teethThe space restriction during development, local trauma, excessive occlusal force or

local infection after development may be the

suspected causative factors

Concrescence. Union by cementum of adjacent

Molars and it’s RadiographJyoti S. Khedgikar, Shirish B. Khedgikar Concrescence of a Maxillary First and Second Molar: A Case Report, Journal of Medical and Dental Science Research Volume 2 Issue

1 (2015)

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Dilaceration : Root formation :

• Dilaceration refers to an abnormal angulation or a sharp bend or curve anywhere along the root portion of a tooth

• Occurs due to trauma that displaces the calcified portion of the tooth germ which alters the angulation of the tooth during root formation

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Supernumerary roots :■ The term supernumerary roots refers to the development of

an increased number of roots on a tooth compared with that classically described in dental anatomy

■ These supernumerary roots may be due to the disturbances of the Hertwig's epithelial root sheath forming the root

Apposition :

A, Gross photograph showing a mandibular molar with a

supernumerary root.B, Periapical radiograph of the

extracted tooth

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ERUPTION :

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ERUPTION :■ The axial or occlusal movement of the tooth from its

developmental position within the jaw to its functional position in the occlusal plane

■ Maurya , massler & schour (1941) defined it asProcess whereby forming tooth migrates from its intra osseous location within the jaw to its functional position within the oral cavity

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Phases of tooth movements :Pre – eruptive

• Made by deciduous and permanent tooth germs intra-osseously before eruption

• This phase occurs in concordance with jaw growth for compensation

Eruptive • Tooth moves

from its position within the bone to its functional position in occlusion

• However, since jaw growth is still occurring, movement in planes other than axial movement supersedes eruptive phase

Post – eruptive • Maintains the

position of the erupted tooth while the jaw continues to grow

• Also compensates for occlusal and proximal wear

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Mechanism of tooth movements :■ Still debatable but is likely to be a combination of several

factors

Root growth

Bone remodelling

Vascular pressure

PDL traction

ERUPTION

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Mechanism of tooth movements :■ Bone remodelling :

– The end result of bone remodelling is a considerable bone deposition at the bottom of the socket

– Selective formation & resorption of bone brings about eruption

– Dental follicle provides the source for new bone forming cells and is the conduit for osteoclasts through its vascular supply, establishing its absolute requirement

– Fallacies :■ Alveolar bone remodelling which occurs around the root,

concluding by bone deposition is the outcome and NOT the cause of axial tooth movement

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Mechanism of tooth movements :■ Root formation :

– Proliferating root impinges on a fixed base, thus converting an apically directed force of the tooth into occlusal movement

– Fallacies :■ Rootless teeth do erupt (most obvious in cases of

dentin dysplasia type I & following irradiation)■ Teeth do NOT erupt after completion of root

formation■ Some teeth erupt a distance > total length of the

rootTherefore, root formation is accommodated during tooth eruption & is a consequence, NOT a cause of

eruption process

Marks and Schroeder; Tooth eruption: theories and facts. Anat Rec 1996; June; 245(2):374-93

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Mechanism of tooth movements :■ Vascular pressure theory :

– Present in pulpal tissues as well as PDL– The pressure exerted by the blood vessels at the apex of

the tooth help in tooth eruption– Fallacies :

■ Question marks remain if the pressure exerted is enough to help in eruption

■ Teeth erupt even when vascular supply is cut


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Mechanism of tooth movements :■ Ligament traction theory :


Contractile elements – collagen in fibroblasts

Constriction

Force initiation

by Fibroblasts

Transmitted to

extracellular

compartments by

fibronexus and

collagen bundles by

root formation

ERUPTION

Fallacies :• Examples of

PDL being present but tooth not

erupting and vice versa have been reported

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DEFECTS :

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Natal teeth : Eruption :

■ These are extra teeth that are present at birth.■ Maybe considered an example of pre deciduous dentition■ The most common natal teeth are lower incisors.■ Clinical aspects :

– Clinically, in the majority of cases, both natal and neonatal teeth are characterized by small immature conical dental structures, of a brown-yellowish color, with an undeveloped root

– These anomalous aspects permit great mobility, facilitating spontaneous loss or exfoliation, with gingival edema and inflammation, and some bleeding areas

■ Treatment: – These teeth are defective and their removal is generally

recommended, particularly if mobility poses a threat of aspiration.

– These teeth also make feeding difficult

Fátima Andrélo GONÇALVES et al; Natal Teeth: Review of the Literature andReport of an Unusual Case; Braz Dent J (1998) 9(1): 53-56

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Neo Natal teeth : Eruption :

■ Neonatal teeth are teeth that emerge through the gingiva during the first month of life (the neonatal period)

Guidelines prior to extraction :• Mandatory protection of airways by placing a gauze on the

back of the mouth• Checking medical history for infantile jaundice

• Hypoprothrombinemia contra indicates extraction

Syndromes associated with presence of natal and pre natal teeth :

• Chondroectodermal dysplasia• Pierre- Robin syndrome

• Ellis van creveld syndrome• Sotos syndrome• Rigafede disease

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Eruption cyst / hematoma : Eruption :

■ The cyst develops as a result of separation of the dental follicle from around the crown of an erupting tooth that is within the soft tissues overlying the alveolar bone

■ The epithelial lining of eruption cyst is similar to that of the dentigerous cyst (non-keratinized stratified squamous epithelium), so the eruption cyst is considered a superficial dentigerous cyst

■ Appears as a soft, often translucent swelling in the gingival mucosa overlying crown of an erupting deciduous or permanent tooth

■ Most commonly associated with deciduous mandibular centrals, 1st permanent molars and the deciduous maxillary incisors

This soft gingival swelling contains considerable blood and can also be designated as an eruption hematoma

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Impaction : Eruption :

■ Teeth that cease to erupt before emergence are impacted ■ Causes:

– Crowding– Insufficient maxillofacial development– Overlying cysts and tumours– Trauma– Reconstructive surgery– Systemic disorders and syndromes

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Ankylosis : Eruption :

■ The cessation of eruption after emergence is termed ankylosis and occurs from anatomic fusion of tooth cementum or dentin with the alveolar bone

■ Causes :– Trauma– Local failure from bone growth– Abnormal pressure form the tongue

■ PDL acts as a barrier that prevents osteoblasts from applying bone directly into the cementum

■ Ankylosis arises from a variety of factors that result in a deficiency of this natural barrier

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Eruption sequestrum : Eruption :

■ A small spicule of non vital bone may be seen radiographically or clinically overlying the crown of partially erupted permanent posterior tooth.

■ The process is termed an eruption sequestrum■ It’s occurs when the osseous fragment becomes separated from

the contiguous bone during eruption of the associated tooth

A radiopaque fragment of sequestrating bone can be seen overlying an impacted third molar.

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Timeline of tooth development:

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Summary of tooth development:

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Conclusion :■ As an oral diagnostician it is imperative we know about the

normal developmental stages and morphology so as to differentiate it from abnormal

■ Syndromic association may also be deduced by learning about tooth abnormalities

■ Learning about the timeline of tooth development will help us in avoiding unnecessary panic to the patient guardian in cases where we suspect early exfoliation and/or delayed eruption

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References :■ Oral and Maxillofacial Pathology; Neville, Allen, Bouquot,; 2nd

edition, pages 52 – 100■ Orban’s Oral Histology and Embryology ; GS Kumar; 12th

edition; pages 22 - 43 ■ Tencate’s Oral Histology; Antonio Nanci; SE Asia Edition; 79 –

107 ■ Mokhtari et al; Christ-Siemens-Touraine Syndrome: A Case

Report and Review of the Literature; Case Reports in Dentistry ; Hindawi Publishing Corporation; Article ID 586418

■ M. Hülsmann, “Dens invaginatus: aetiology, classification, prevalence, diagnosis, and treatment considerations,” International Endodontic Journal, vol. 30, no. 2, 79–90, 1997.

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Health & Medicine

Tooth development, eruption & applied aspects