AGE ESTIMATION from Oral and Dental Structures

external environment

The timing and pattern of tooth eruption are fairly well buffered from the

primary or mixed dentition

recording tooth eruption status can be a rapid, useful, and convenient way to estimate a person's age if the subject is in the

Tooth eruption

the process of a tooth's migration from its initial position in its bony crypt into occlusion

• appearance of some portion of the tooth's crown piercing the gingival mucosa (gingival eruption)

• the most occlusal portion of the crown emerging above the alveolar bone (alveolar emergence)

• when the tooth is fully erupted, so it is in functional occlusion with its antagonist in the opposing arch

Tooth emergence has at least 3 operational definitions in literature:

five years of age

Obvious evidence of root tissue destruction (i.e., loss of a quarter of root length) occurs by _______ IN girls, and a bit later in boys.

sexual dimorphism

Emergence of the permanent teeth exhibits fairly consistent _________ across groups

Girls' teeth

erupt earlier at chronological ages than boys'

tooth emergence

fleeting event that occurs at an instant in time—a tooth can only be unemerged or emerged

6 years

permanent tooth eruption occurs within a span of only about

Tooth Mineralization

the development of a tooth's hard tissues

Tooth Mineralization

spans a much longer age range than eruption, making it more broadly applicable than emergence

(1) the age at initiation of cusp mineralization,

(2) how much of the tooth crown is mineralized at term

(3) the age after birth when the crown has finished mineralization

(4) the age when the root is complete (root apexification)

Primary Tooth Formation Four development landmarks for each tooth

• there are few distinguishable grades

• there are "gaps" between one stage and the next

• it is evident that crown-root mineralization is a continuous, seamless process

Problems with the use of formation stages are

• the extent of crown-root development of the seven teeth is scored

• a table of values is used to weight each tooth's score

• these weights are summed

• the sum is checked against another table that provides the person's dental age.

Four steps in the Demirjian system:

Gustafson Method

One of the most broadly referenced studies in forensic odontology and made multifaceted attack on this subject by assessing six age-progressive changes

OCCLUSAL ATTRITION

wearing down of the occlusal surface, predominantly from grit in the diet

PERIODONTOSIS

Destruction of the gingival, periodontal, and alveolar tissues may develop due to pathogens-acute infectious diseases.

PERIODONTOSIS

These often rapid destructive processes have to be distinguished from "continued eruption," in which teeth continue to erupt, albeit slowly, throughout much of life.

SECONDARY DENTIN

diminishes and ultimately occludes the pulp chamber.

SECONDARY DENTIN

needs to be distinguished from tertiary dentin that is thought to accumulate in response to caries and trauma.

roots

The thickness of cementum often increases on _____ with age

CEJ

cementum generally is thinnest near the

apical third of the root

cementum generally is thickest on the

tree rings

Recent attention has focused on cementum annulations-the deposition of a new layer of cementum onto roots in a manner analogous to the growth of

cementum is thicker

impacted teeth

periodontally involved teeth

Johanson

claimed that "extensive attrition is always followed by extensive increase in thickness of the cementum."

xternal apical root resorption (EARR)

occasionally is seen to be age progressive (older-aged groups).

ROOT RESORPTION

the least dependable predictor of those suggested by Gustafson.

orthodontic treatment.

In modern populations, a very common cause of EARR is

ROOT TRANSPARENCY

due to the age-progressive occlusion of dentin tubules leading to sclerotic dentin.

ROOT TRANSPARENCY

commences in the apical region, progressing coronally with age.

third molar

most variable tooth in the dentition with respect to developmental chronology

Aspartic Acid Racemization

conversion of the L-isomer to the D-isomer toward equilibrium

Aspartic Acid Racemization

proceeds slowly throughout lire, continues at a markedly reduced rate after death, so it is also useful for aging archaeological samples

Aspartic Acid Racemization

has been demonstrated in a variety of proteins such as those in the eye lens, brain, vertebral discs, and dental tissues

radioactive carbon-14 isotope (14C)

Nuclear testing from 1955 to 1963 produced greatly increased atmospheric levels of the

Enamel Uptake of Radioactive Carbon-14

The technique is useful only for individuals born after 1943 since the formation of the enamel of the third molars is completed at approximately age twelve.

Enamel Uptake of Radioactive Carbon-14

Estimates the date of birth