Dental embryology:Development of Teeth, Lecture notes of Dental Anatomy

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Development of Teeth Dr. Khaldoun Darwich Specialist in Oral and Maxillo-Facial Surgery – Hamburg UniversityPhD – Hamburg UniversityAcademic Teacher - Department of OMF Surgery in Damascus UniversityInstructor and Academic Advisor in IUST

^ Overview
^ Initiation of Toothdevelopment
^ Stages of toothdevelopment
^ Development of thedental papilla

^ Dentinogenesis
^ Amelogenesis
^ Crown Maturation
^ Development of theTooth Root
^ Development ofsupporting structures

^ Each of us began life as a single cell, a

zygote.

^ The zygote produces a ball of cells (the

morula)

which in turn produces the

Human embryo

.

^ However, the

actual^ development of Teeth

starts

at approximately

6-7 weeks

after conception.

^ In the human

20 primary

and^32

permanent

teeth develop from the

interaction of the oral

epithelial

cells and

the underlying

mesenchymal

cells.

Each tooth develops through three successiveearly stages : 1. Bud stage.2. Cap stage.3. Bell stage.

^ During these early stages the

tooth germs

grow^ and

expand^

and the^ cells

that are to

form the hard tissues of the teeth differentiate

.

^ Differentiation

takes place in the

bell

stage^ setting the stage for

enamel^ and

dentin^ formation

^ As the

crowns^

are formed and

mineralized

the roots

of the teeth begin

to form
After the roots calcify

the supporting

tissues^ of the teeth (the

cementum

,

periodontal ligament

, and^ alveolar bone

)

begin to develop
Subsequently the completed tooth crown erupts^ into the oral cavity

^ Root formation

and^ cementogenesis

continue until a

functional tooth

and its

supporting structures are fullydeveloped

^ Developmentally missing

permanent

teeth^ can be a result of a

genetic

abnormality

.

^ When fewer than 6 teeth are missing it is^ termed

Hypodontia

^ When more than 6 teeth are missing it is^ oligodontia

Oligodontia

Severe dental agenesis (oligodontia). In this case lack of most permanentteeth (indicated by arrows

^ Teeth develop from 2 types of cells: 1-^ oral epithelial cells

form the^ enamel organ

2-^ mesenchymal cells

form the^ dental papilla

in addition the

neural crest cells

contribute to

tooth development

^ The first sign of tooth formation is thedevelopment of

dental lamina

rising from the

oral epithelium

^ Dental lamina ^ Bud ^ Cap ^ Bell ^ Appositional ^ ….

^ The Dental lamina

develops into a sheet of epithelial cells

that pushes into the underlying mesenchyme

around the perimeter of both the maxillary and mandibular jaws.

^ At the leading edge of the

lamina^ 20 areas

of

enlargement appear which form tooth buds forthe^ 20 primary teeth

.

^ After^ primary teeth

develop from the buds the leading edge of the lamina continues to grow todevelop^ the permanent teeth

, which succeed

the 20 primary teeth. This part of the lamina iscalled the

successional lamina

^ The lamina

continues

posteriorly

into the

elongating jaw and from it come the

posterior

teeth^ , which form behind the primary teeth.  In this manner

20 of the permanent teeth replace the 20 primary teeth and

12 posterior

permanent molars

develop behind the primary dentition  The last teeth to develop are the

rd^3 molars

,

which develop about 15 years after birth

^ The lamina

continues

posteriorly

into the

elongating jaw and from it come the

posterior

teeth^ , which form behind the primary teeth.  In this manner

20 of the permanent teeth replace the 20 primary teeth and

12 posterior

permanent molars

develop behind the primary dentition  The last teeth to develop are the

rd^3 molars

,

which develop about 15 years after birth

^ the primary teeth and permanent molars formfrom the

general lamina ^ The anterior permanent teeth which succeed theprimary teeth form from

the successional lamina ^ The^ initiating dental lamina

that forms both the

successional and general lamina begins tofunction in

th^ the 6prenatal week

and continues

to function until

th^ the 15year producing all 52

teeth

Each tooth develops through three successiveearly stages : 1. Bud stage.2. Cap stage.3. Bell stage.^ Each stage is defined according to

the shape^

of

the epithelial enamel organ

which is a part of the developing tooth