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Congenital absence and impaction of the third molar in the Eskimo mandible.

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C O S G E S I T A L SBSENCE AKD IMPACTION O F THE
T H I R D MOLSR I N THE ESKIMO MANDIBLE
MARCUS S . GOLDSTEIN
Division of Physical Anthropology, 17. S. National Museum
A. COXGENITAL ABSENCE
The incidence of the absence of the lower third molar in
the Eskimo, compared with other peoples, should prove of
interest. HrdliEka (’11, p. 407) states that “the tendency
toward the loss of the third molar is evidently a n evolutiona r y feature of the human teeth that belongs to the present
era, and in some races of man has as yet scarcely begun to
be manifest.’’ Some work on the congenital absence of M Jin
the Eskimo has already been done. Leigh (’25b, p. 888)
states that in fifteen of 324 (4.6 per cent) modern Eskimo
crania (U. S. Kational Museum) the third molars had apparently never erupted; it is not clear, however, whether the
third molars of the upper, lower, or both jaws a r e meant.
Hellmaii (’28) notes 28 per cent congenitally missing third
molars in the lower jaws of thirty male Eskimo. My own
observations a r e tabulated in table 1.
The method of determining congenital absence was as follows. Every mandible was examined f or third-molar absence.
When missing, very careful attention was given to any signs
of alveolar absorption o r other conditions that would indicate
the possibility that the third molar may have once been present. Every case i n which such a suspicion existed, or where
the tooth might yet have erupted, was eliminated from the
series. The uncertainty arose, however, occasionally when
the molar was missing, whether o r not the tooth was impacted
o r completely suppressed. Fortunately, Dr. Sterling V.
Mead, of Georgetown University, had recently utilized t h e
381
AMERICAN JOURNAL OF P H Y S I C A L AKTHROPOLOGY, VOL. I V I , NO.
J AN UA RY - M AR CH , 1932
3
382
MARCUS S. GOLDSTEIK
mandibular collections in the C. S. Xational Museum, among
which was the Eskimo, in a research on the incidence of impacted teeth, and an x-ray machine had been used in the
determinations.
Doctor Mead informed me that very rarely was a third
molar so completely impacted that i t would not be visible to
the eye; so rarely, in fact, that these statistics on the congenital absence of the third molar should not be affected.
The d a t a here presented should be, therefore, a faithful representation of the frequency of congenital absence of the
lower third molar as observable in the adult Eskimo.
TABLE 1
Congrnital absence of $he lower thzrd molar in adult Eskimo
__
____
________
-
I
M A MISSING
O N O N E SIDE
I ~ C , MISSING1
SEX
I _. .__
ONBOTH
I
Males ( 3 6 3 )
Females (380)
Totals
Per cent of total adult
mandibles (759)'
~
' Sixteen
'
Right
I,
-_ _
Loft
I
j
PEE CENT
OFMA
TOTAL
'PERCENT
w1-m
OF J A W S
MIssrx(:
, CONQENICON I
TO Y..
- ' TALLY
GENITALLY
THAT
[HISSING M JY I S S I I G M:i S H O U L D B E
lJ.tws
I
IWITH
~-
~
I
18
GO
I
16.50
12.67
~-
JrO
-
1
126
21
'1.8
I
3.8
I
~.
16.G
I
i
13.31
_.
~
mandibles included in t.his total were unsexed.
I t is seen that in 16.6 per cent of all the adult Eskimo mandibles the third molar is missing on one or both sides; too,
tlie third molar is missing in 13.31 per cent of all the third
molars that should normally be present. The absence of the
Ma too appears considerably more symmetrical, i.e., occurring on both sides of the jaw, than not. There seems t o be a
tendency f o r the absence to occur somewhat more often on
the left than on the right side of the mandible. Finally, the
third molar is somewhat more frequently missing, absolutely
and relatively, in the females than in the males.
I n table 2 is recorded the congenital absence of the lower
third molar with reference to geographical locality of the
individuals represented. The Eskimo a r e divided into the
three main subgroups according to HrdliEka's classification
( '30).
383
THIRD MOLAR I N ESKIMO MANDIBLE
TABLE 2
Congenital absence of lower third molar of the Eskimo according t o locality
_
_ ____
~
I
I.OC.4I.ITY
I
-- .;--
Southwest and miclwest :
Total
HISSINQ Ids
Both sides
.-
1
’
46
i
Rightside
- .- -
7
I
Left side
.--I
I
I (mzJ&s)
-.
-
I
18
!
71
Distinct differences in the extent of mandibular thirdmolar absence appear to exist in the three main groups of
the Eskimo. A coiisisteiit percental increase of individuals
lacking one or more lower third molars is noted from the
southwest to the northwest to the north-northeast ; in other
words, with respect t,o third-molar absence, a phenomenon
said to indicate progressive involution in the dentition, the
southwest Eskimo appear appreciably more primitive than
the northwest-north-northeast Eskimo. This is an unexpected showing which stands i n concordance with the results
of the preceding study on the cusps of the lower molars.
Racial survey
Table 3 considers i n brief a racial survey of the incidence
of congenitally missing lower third molars. It is interesting
to note that the percentages of Hellman and the writer on
the Eskimo a re remarkably close.
384
MARCUS S. GOLDSTEIN
TABLE 3
9 l u m l survey of the tnctdence of congenitally massang mandbbular third molar8
~
RACLAL G R O U P ALID AUTHOB
Chiuese :
Hellmail ( '28)
Eskimo :
Hellniaii ( '28)
Goldstein
~-
'
19'
30
!
363 males
380 females
759 total'
j
I
I
!
i
i
I
I
Australian Aboriginal :
Hellmau ( '28)
I
I
i
!
I
i
~
_
_
_
3.9
28
25.3
88.9
26.6
i
I
i
I
!
I
20
lo.s
17.5
13.8
15.9
17
i
1s
i
20
i
13
119
I
i
11
i
!
I
I
55
I
i
Ancient Egyptians :
Ruffer ('20)
____.
21
I
American iiegroes :
Hellman ( '28)
___
80 males
58 females
138 total
I
Anisrieaii Indian:
Hellmau ( '28)
West African iiegroes:
Hellman ( '28)
61
2112a
!
Mougoloid Buriats
Hellmau ( '28)
P E R CENT MISSING YQ
.
-!-
I
European :
Hellmau ( '28)
Golbirscli ( '30)
Hawaiians :
Chappel ( '27)
,
NUMBER OF J A W S
156'
3.2
I
-
I
49
_
0
_
Hellman's figures throughout table are f o r males only.
The total includes sixteen unsexed mandibles.
Combined males and females.
' N o sex given.
The hlongoloid peoples as a whole appear to be most advanced with respect to congenitally missing lower third
molars; the whites, browns, and Australians follow, and the
negroes, it seems, a r e the least advanced. Curiously enough,
the ancient Egyptians appear to present almost no congenitally absent third molars in the mandible.
~
THIRD iMOLAR IX ESKIMO MAh-DIBLE
385
It is noted that congenital absence of the mandibular M:;,
presumably a n advanced stage in the evolution of the human
dentition, occurs in a relatively high percentage of the
Eskimo mandibles, according either to Hellman o r the writer.
It seems, therefore, since the Eskimo use their teeth more
than most peoples, a n d as much as any, mere use or function
has no large correlation with the loss of the mandibular third
molar.
Some authorities have proposed a s the cause for the absence of the third molar (Tomes, Chappel, Darwin), in the
words of Tomes ( ’23, p. 530), “ a consequence of want of
space during its formative period.” The writer, on the other
hand, agrees with Hellman, who well sums up the sitnation
thus ( ’28, p. 173) :
The argument, favoring the idea that the congenital absence of the
third molar is due to the reduction in size of the jaw and the crowding of dentition, cannot be corroborated. The American Negro, the
Eskimo, the Buriat and the Australian Aboriginal do not show any
lack of room due to diniinution in size of the jaw, and yet they all
present a very high percent of congenitally missing third molars.
Vestigial lower third molars
A note may be added on the occurrence of vestigial lower
third molars. I n a few cases, four males and two females,
the third molar was found to be merely a stump. I n one
case where the right third molar was diminished the left was
congenitally missing.
B. I Y P A C T I O N S O F T H E MANDIBULAR NOLARS I N T H E
ADULT ESKIMO
The third molar only was found impacted in the mandibles
of adult Eskim0.l Table 4 presents the tabulated results.
The incidence of impactions is noted to be 5.4 per cent.
Hellman (’28) gives the incidence of M3 impactions in
thirty Eskimo lower jaws, also examined in the U. S. National
Museum, as 9 p e r cent. Mead (’30), using a n x-ray ma-
’
There were three adolescents with five impacted third molars, not iiicluded in
the table.
386
MARCUS S. GOLDSTEIN
chine on the Eskimo material in the U. S. National Museum,
found in 11872 mandibles 4.04 per cent impacted t,hird
molars.
TABLE 4
Iiicidence of impacted lower third molars in adult Eskimo
-.
- -.
Yale
23
~-
1 6 . 9 .
4
- .. -.
.-
Total
..
,
-
I
13____
I 10
-
2
I
41
--
:T--
lIncludes twice the numbers under the ‘Both sides’ eolumn; i.e., oue f o r each
side.
According to locality
T h e Eskimo again a r e divided into three main groups, according to HrdliGka ( ’30), and the incidence of impacted
molars noted.for each. I n t.able 5 is seen a rather small, yet
consistent, decrease in impacted third molars from the southand midwest to the northwest and norbh-northeast.
Mead ( ’30, p. 4), in summarizing a study of dental conditions among the Eskimo by Wahl, states that “in the younger
generation [of the Eskimo] where . . . . diet consists of, o r
is interfered with by the use of, carbohydrates, candies, etc.,
. . . . caries has become apparent as we!I a s have malocclusion, a n d impactions.”
I t would seem from the above that a positive correlation
exists between the incidence of caries and that of impactions.
To be sure, the order of increase of impactions among the
three main groups of Eskimo is identical with that of the incidence of caries in the three groups, as will be indicated in
study 111.
Hellman (’28, p. 173) comments on the cause of thirdmolar impaction as seeming “ t o have no relation to lack of
space [in the mandible]. They [impacted Ms’s] seem to be
a The discrepancy between the figures of Mead and the writer with reference
to number of mandibles observed is probably due to the f a c t t h a t the former,
noting impactions in the whole mandibular dentition, included in his series a
considerable number of jaws which the present writer necessarily excluded because
of a lack of molar teeth.
387
THIRD MOLAR IN ESKIMO MAKDIBLE
associated rather with the position of the tooth crown during
the formation period than the room needed for its accommodation.” Very certainly in the Eskimo lower jaws, where
impaction of the third molar occurred, there was no lack of
space or room.
TABLE 5
Zaczdence of ampnctpd l o w ~ rtkard molars in the adult Eskimo accordang t o thew
geographacal localtly
- -__ _ _ - X U H R E R OF J A W 6
LOCALITY
-
__
South-midwest :
Nuiiirak
St. Laareiiee Island
Yukon Ricer
Tanunuk
St. hfichel Islaiid
Rocky Point
Golofiiin Bay
Pastolik
Hooper Ray
Total
Per cent of mandibles ( 4 7 7 )
Korthwest :
Point Hope
Wales
Shishmaref
Total
P e r cent of inaiidibles (832)
Korth-northeast :
Greenland
-,I
AFFECTED
I
_--
NUMBER OF
INPACTIOKS
_ _ .
--
I
I
I
i
I
I
12
5
7
4
4
3
2
2
1
1
1
1
1
1
1
1
1
1
-.
21
28
5.9
5
3
-
5
3
2
-
9
10
I
1
4.3
I
11
-3.5
2
1
1
Total
Per cent of mandibles (40)
Miscellaneous Alaska’
1
._ - __
‘There were tell adult iiiaiidibles from Alaska with
tioiied.
I
110
_ - --__
precise locallty men-
SUMMARY
1. The third molar never appeared on one or both sides of
the mandible in 16.6 per cent of adult Eskimo. The absence
was usually on both sides of the jaw.
2. The lower third molar is more frequently missing in the
females than in the males.
388
MARCUS S. GOLDSTEIS
3. Congeiiitally missing lower third molars occur appreciably less frequently in the south-midwest Eskimo than in
the northwest-north-northeast Eskimo, the former group,
therefore, being more primitive in this character than the
latter.
4. Racially, the Eskimo appear among the most advanced
with respect to congenitally missing lower third molars.
5. Impacted lower third molars occurred in 5.3 per cent of
759 adult Eskimo.
6. The lower third molar of the male is slightly more frequently impacted than in the female.
7. A consistent decrease in mandibular third-molar impactions occurs from the south- and midwest to the northwest
and nor th-no r t h east Eskimo.
BIBLIOGR.4PHT
19.7
Jaws and teeth of ancient IIawaiians. Yem. Bishop
MUS., Hollolulu, I X , 251-268.
DARWIN, C . 1881 The descent of man. New York.
GOLBIRSCH,
A. W. 1930 A study of third molar teeth. J. Am. Dent. Assoc.,
X V I I , 1849-1854.
HELLXAX,M. 1928 Racial characters in human dentition. Proc. Amer. Philos.
Soc., L X T I I , 2.
HRDLICKA, A. 1911 Human dentition and teeth from the evolutionary and
racial standpoint. Domin. Dent. J., X X I I I , 9.
1930 Anthropological survey i n Alaska. 46th Ann. Rept. Bur.
Am. Ethnol., Washington.
LEIGH,R. W. 1925 Dental pathology of the Eskimo. Dent. Cosmos, LXVIT,
884-898.
MEAD,S. V. 1930 Incidence of impacted teeth. Internat. J. Orthod., XVI, 3-8.
RUFFER,A. 1920 Study of abnormalities and pntliology of ancient Egyptian
teeth. Am. J. Phys. Anthrop., 111, 3.
TOMES,C. S. 1923 Dental anatomy. Kew Tork.
CHAPPEL, 11. G .
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