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Chronology of dentition
P.Boonyawong 1
Chronologies of Human
Dentition
P.Boonyawong
Aims of study
After studying this topic, everyone
must describe about
Development and eruption of the teeth
Chronology of dentition
Clinical considerations
Introduction
• Chronology is defined as "a study which deals with the timing of various stages of tooth development, starting with the initiation of the first dental tissue laid down to the emergence of tooth in the oral cavity and its completion of calcification“
• Chronology of human dentition is based upon data of Logan and Kronfeld reported in 1933
• Slightly modified by
– McCall and Schour in 1941
– Kraus and Jordan 1965
– Nystrom in 1977
Introduction
• It must be kept in mind that
– The dental practitioner sees in a "normal" healthy
mouth not only the clinical crowns of the teeth
surrounded by the gingival tissues, but also the
hidden part of the teeth that are covered by the
gingiva can be visualized radiographically.
Chronology of dentition
P.Boonyawong 2
Introduction
• It must be kept in mind that
– Most of the data on tooth morphology are derived
from studies of samples of population of
European-American ancestry and, for example, as
indicated in the section on Tooth Formation
Standards in this topic, a variety of sequences in
eruption of the teeth exist depending on the
population sampled.
Development
and eruption of the teeth
Development and eruption of the teeth
• the term emergence was used to denote the
raising out of a tooth through the gingiva
• the term eruption was used to define
continuous tooth movement from the dental bud to occlusal contact
Development and eruption of the teeth
• The human dentitions are usually categorized
as being
– Primary dentitions
– Mixed (transitional) dentitions
– Permanent dentitions
Chronology of dentition
P.Boonyawong 3
Development and eruption of the teeth
• Emergence of the primary dentition takes
place between the 6th and 30th months of
postnatal life.
• It takes from 2 to 3 years for the primary
dentition to be completed, beginning with the
initial calcification of the primary central
incisor to the completion of the roots of the primary second molar
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Development and eruption of the teeth
• The emergence of the primary dentition
through the alveolar mucous membrane is an
important time for the development of oral
motor behavior and the acquisition of masticator skills.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Chronology of dentition
P.Boonyawong 4
Development and eruption of the teeth
• Tooth do not all develop at the same rate;
some teeth are completed before others are
formed, which results in different times of eruption for different groups of teeth.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
• Some of the primary/deciduous teeth are
undergoing resorption while the roots of
others are still forming.
• Not all the primary teeth are lost at the same
time; some (e.g., central incisors) are lost 6 years before the primary canines.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Development and eruption of the teeth
• Groups of teeth develop at specific rates so
that the sequence of eruption and emergence
of the primary/ deciduous teeth is well
defined with few deviations.
• Even so, for the individual child, considerable
variation in the times of emergence of the
primary dentition may occur.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
• The primary dentition is completely formed by
about age 3 and functions for a relatively
short period of time before it is lost
completely at about age 11.
• Permanent dentition is completed by about
age 25 if the third molars are included
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Chronology of dentition
P.Boonyawong 5
Development and eruption of the teeth
• Calcification of the primary teeth begins in
utero from 13 to 16 weeks post fertilization.
• By 18 to 20 weeks, all the primary teeth have
begun to calcify.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
• Usually at birth, no teeth are visible in the
mouth; however, occasionally, infants are born
with erupted mandibular incisors.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Development and eruption of the teeth
• Primary tooth crown formation takes only
some 2 to 3 years from initial calcification to
root completion.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
• However, mineralization of the permanent
dentition is entirely postnatal, and the
formation of each tooth takes about 8 to 12
years.
• The variability in permanent tooth
development is similar to that for eruption,
sexual maturity, and other similar growth
indicators.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Chronology of dentition
P.Boonyawong 6
• Crown formation of the primary teeth continues after birth for
– about 3 months for the central incisor
– about 4 months for the lateral incisor
– about 7 months for the primary first molar
– about 8.5 months for the canine
– about 10.5 months for the second primary molar.
Development and eruption of the teethPrimary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Development and eruption of the teeth
• After the crown of the tooth is formed,
development of the root portion begins.
• At the cervical border of the enamel (the
cervix of the crown), cementum starts to form
as a root covering of the dentin.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Development and eruption of the teeth
• Dental development can be considered to
have 2 components:
– (1) the formation of crowns and roots
– (2) the eruption of the teeth
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
• After the crown and part of the root are
formed, the tooth penetrates the alveolar
gingiva and makes its entry (emergence) into
the mouth.
• Teeth do not begin to emergence until crown
formation is complete, their emergence rate
does not closely correlate with root
elongation.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Chronology of dentition
P.Boonyawong 7
Development and eruption of the teeth
• The process of eruption of the tooth is
completed when most of the crown is in
evidence and when it has made contact with
its antagonists in the opposing jaw.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
• The primary/deciduous dentition is considered
to be completed by about 30 months or when
the second primary molars are in occlusion.
• The dentition period includes the time when no
apparent changes occur intraorally (i.e., from
about 30 months to about 6 years of age).
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Development and eruption of the teeth
• The form of the dental arch remains relatively
constant without significant changes in depth
or width.
• A slight increase in arch width occurs about the
time the primary incisors are lost, and an
increase in size in both jaws in a sagittal
direction is consistent with the space needed to
accommodate the succedaneous teeth.
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionDevelopment and eruption of the teeth
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Chronology of dentition
P.Boonyawong 8
Development and eruption of the teeth
• The first transition dentition begins with the
emergence and eruption of the mandibular first
permanent molars and ends with the loss of
the last primary tooth, which usually occurs at
about age 11 to 12.
• The permanent teeth do not begin eruptive
movements until after the crown is completed.
Mixed dentitionMixed dentitionMixed dentitionMixed dentition Mixed dentitionMixed dentitionMixed dentitionMixed dentition
Development and eruption of the teeth
• The initial phase of the transition period lasts
about 2 years, during which time the
permanent first molars erupt, the primary
incisors are shed, and the permanent incisors
emerge and erupt into position.
Mixed dentitionMixed dentitionMixed dentitionMixed dentitionDevelopment and eruption of the teeth
• During eruption, the permanent mandibular
first molar is guided by the distal surface of the
second primary molar.
Mixed dentitionMixed dentitionMixed dentitionMixed dentition
Chronology of dentition
P.Boonyawong 9
Development and eruption of the teeth
• Before the permanent tooth can come into
position, the primary tooth must be exfoliated.
• This is brought about by the resorption of the
deciduous roots.
• The permanent tooth in its follicle attempts to
move into the position held by its predecessor.
Mixed dentitionMixed dentitionMixed dentitionMixed dentitionDevelopment and eruption of the teeth
• Its influence on the primary root evidently
causes resorption of the root, which continues
until the primary crown has lost its anchorage,
becomes loose, and is finally exfoliated.
Mixed dentitionMixed dentitionMixed dentitionMixed dentition
Development and eruption of the teeth
• The follicles of the developing incisors and
canines are in a position lingual to the
deciduous roots.
Mixed dentitionMixed dentitionMixed dentitionMixed dentitionDevelopment and eruption of the teeth
• The developing premolars, which eventually
take the place of deciduous molars, are within
the bifurcation of primary molar roots.
Mixed dentitionMixed dentitionMixed dentitionMixed dentition
Chronology of dentition
P.Boonyawong 10
Development and eruption of the teeth
• The permanent incisors, canines, and premolars
are called succedaneous teeth because they
take the place of their primary predecessors.
• The central incisor is the second permanent
tooth to emerge into the oral cavity.
• Eruption time is quite close to that of the first
molar (i.e., tooth emergence occurs between 6
and 7 years).
Mixed dentitionMixed dentitionMixed dentitionMixed dentitionDevelopment and eruption of the teeth
• As with the first molar, at 6 years 50% of
individuals have reached the stage considered
to be the age of attainment of the stage or,
more specifically, the age of emergence for the
central incisor.
• The mandibular permanent teeth tend to erupt
before maxillary teeth.
Mixed dentitionMixed dentitionMixed dentitionMixed dentition
Development and eruption of the teeth
• The mandibular central incisor usually erupts
before the maxillary central incisor and may
erupt simultaneously with or even before the
mandibular first molar.
• The mandibular lateral incisor may erupt along
with the central incisor.
Mixed dentitionMixed dentitionMixed dentitionMixed dentitionDevelopment and eruption of the teeth
• The permanent dentition consisting of 32 teeth is completed from 18 to 25 years of age if the third molar is included.
• The permanent dentition begins with the emergence and eruption of the second molars.
• Usually, the second molars come in when the individual is about 12 years of age; they are posterior to the first molars and are commonly called 12-year molars.
Permanent dentitionPermanent dentitionPermanent dentitionPermanent dentition
Chronology of dentition
P.Boonyawong 11
Permanent dentitionPermanent dentitionPermanent dentitionPermanent dentitionDevelopment and eruption of the teeth
• The third molars do not come in until the age
17 or later, they are commonly called wisdom
tooth.
• Considerable posterior jaw growth is required
after the age of 12 to allow room for these
teeth.
• Third molars are subject to many anomalies
and variations of form.
Permanent dentitionPermanent dentitionPermanent dentitionPermanent dentition
Development and eruption of the teeth
• Insufficient jaw development for their
accommodation complicates matters in the
majority of cases.
• Individuals who have properly developed third
molars in good alignment are very much in the
minority.
Permanent dentitionPermanent dentitionPermanent dentitionPermanent dentition
Chronology of dentition
Chronology of dentition
P.Boonyawong 12
Chronology of dentition
Tooth 1st evidence of
calcificication
(week in utero)
Crown
completed
(months)
Eruption (months) Root
complete
(years)
Emergence
sequence
U i1 14 11/2 10 (8-12) 11/2 2
U i2 16 21/2 11 (9-13) 2 3
U c 17 9 19 (16-22) 31/4 7
U m1 15 6 16 (13-19�) (14-18�) 21/2 5
U m2 19 11 29 (25-33) 3 10
L i1 14 21/2 8 (6-10) 11/2 1
L i2 16 3 13 (10-16) 11/2 4
L c 17 9 20 (17-23) 31/4 8
L m1 151/2 51/2 16 (14-18) 21/4 6
L m2 18 10 27 (23-31�) (24-30�) 3 9
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionChronology of dentition
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentition
Chronology of dentition
• Sequence of emergence of primary teeth
– The predominant sequence of eruption of the
primary teeth in the individual jaw is central
incisor (A), lateral incisor (B), first molar (D),
canine (C), and second molar (E).
Primary dentitionPrimary dentitionPrimary dentitionPrimary dentitionChronology of dentition
Tooth 1st evidence of
calcificication
Crown completed
(years)
Eruption
(years)
Root complete
(years)
Emergence
sequence
U I1 3-4 mo 4-5 7-8 10 4
U I2 10-12 mo 4-5 8-9 11 6
U C 4-5 mo 6-7 11-12 13-15 12
U P1 11/2 - 13/4 yr 5-6 10-11 12-13 8
U P2 2 – 21/4 yr 6-7 10-12 12-14 10
U M1 At birth 21/2 - 3 6-7 9-10 2
U M2 21/2 - 3 yr 7-8 12-13 14-16 14
U M3 7-9 yr 12-16 17-21 18-25 16
L I1 3-4 mo 4-5 6-7 9 3
L I2 3-4 mo 4-5 7-8 10 5
L C 4-5 mo 6-7 9-10 12-14 7
L P1 11/4 - 2 yr 5-6 10-12 12-13 9
L P2 21/4 - 21/2 yr 6-7 11-12 13-14 11
L M1 At birth 21/2 - 3 6-7 9-10 1
L M2 21/2 - 3 yr 7-8 11-13 14-15 13
L M3 8-10 yr 12-16 17-21 18-25 15
Permanent dentitionPermanent dentitionPermanent dentitionPermanent dentition
Chronology of dentition
P.Boonyawong 13
Years 6 8 10 12 13 18 20
6 1 2 4 5 3 7 8
6 1 2 3 4 5 7 8
Chronology of dentitionPermanent dentitionPermanent dentitionPermanent dentitionPermanent dentition
• Sequence of emergence of permanent teeth
Clinical considerations
Clinical considerations
• Knowledge of the development of the teeth
and their emergence into the oral cavity is
applicable to clinical practice, anthropology,
demography, forensics, and paleontology.
• However, dental applications are considered primarily.
Clinical considerations
• to avoid treatment that can damage
developing teeth
• to assess patient's age
• to avoid malformation of the teeth and occlusion
Chronology of dentition
P.Boonyawong 14
Clinical considerations
• More precise information was needed to
avoid injury to developing teeth during surgery on young children
To avoid injuryTo avoid injuryTo avoid injuryTo avoid injuryClinical considerations
• Dental Age
– Dental age has been assessed on the basis of the
number of teeth at each chronological age or on
stages of the formation of crowns and roots of the
teeth or eruption of the teeth.
– Estimation of juvenile age is more precise than that of adult age.
To ae atient ageTo ae atient ageTo ae atient ageTo ae atient age
Clinical considerations
• Dental Age
– Chronologies of prenatal tooth formation are
based generally on dissected fetal material;
postnatal development chronologies are most
often based on radiological data and clinical.
To ae atient ageTo ae atient ageTo ae atient ageTo ae atient ageClinical considerations
To ae atient ageTo ae atient ageTo ae atient ageTo ae atient age
Chronology of dentition
P.Boonyawong 15
Clinical considerations
• Dental problem
– Misunderstanding of parents on permanent first
molar is deciduous tooth!!
To To To To avoid malformationavoid malformationavoid malformationavoid malformationClinical considerations
• Dental problem
– Disease of periapical area in primary tooth cause
enamel hypoplasia in permanent tooth
To To To To avoid malformationavoid malformationavoid malformationavoid malformation
Clinical considerations
• Dental problem
– Early loss of primary dentition cause malocclusion
in permanent dentition
To To To To avoid malformationavoid malformationavoid malformationavoid malformationClinical considerations
• Dental problem
– The failure of the root to resorb may bring about
prolonged retention of the primary tooth.
– Although permanent teeth can not move to
normal position, and cause malocclusion problem
To To To To avoid malformationavoid malformationavoid malformationavoid malformation
Chronology of dentition
P.Boonyawong 16
Clinical considerations
• Dental problem
– Excessive received of some drug and material in
wrong period cause tooth discolorized in
sequence of development
To To To To avoid malformationavoid malformationavoid malformationavoid malformation
Dental fluorosis Tetracycline stain