chronologies of human dentition-printweb1.dent.cmu.ac.th/mis/dentelearning/uploads/... ·...

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


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.


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


• 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


• The human dentitions are usually categorized

as being

– Primary dentitions

– Mixed (transitional) dentitions

– Permanent dentitions


P.Boonyawong 3


• 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


• 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


P.Boonyawong 4


• 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.


• 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.



• 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.


• 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



P.Boonyawong 5


• 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.


• Usually at birth, no teeth are visible in the

mouth; however, occasionally, infants are born

with erupted mandibular incisors.



• Primary tooth crown formation takes only

some 2 to 3 years from initial calcification to

root completion.


• 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.



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


• 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.



• Dental development can be considered to

have 2 components:

– (1) the formation of crowns and roots

– (2) the 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.



P.Boonyawong 7


• 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.


• 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).



• 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.




P.Boonyawong 8


• 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


• 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


P.Boonyawong 9


• 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.


• 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.



• The follicles of the developing incisors and

canines are in a position lingual to the

deciduous roots.


• The developing premolars, which eventually

take the place of deciduous molars, are within

the bifurcation of primary molar roots.



P.Boonyawong 10


• 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).


• 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.



• 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.


• 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


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.



• 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.




P.Boonyawong 12


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



• 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



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



• 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.


• to avoid treatment that can damage

developing teeth

• to assess patient's age

• to avoid malformation of the teeth and occlusion


P.Boonyawong 14


• 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


• 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


P.Boonyawong 15


• 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


• 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



P.Boonyawong 16


• Dental problem

– Excessive received of some drug and material in

wrong period cause tooth discolorized in

sequence of development


Dental fluorosis Tetracycline stain

chronologies of human dentition-printweb1.dent.cmu.ac.th/mis/dentelearning/uploads/... ·...

Documents