close

Вход

Забыли?

вход по аккаунту

?

Correlations between deciduous and permanent tooth morphology in a European American sample.

код для вставкиСкачать
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 133:726–734 (2007)
Correlations Between Deciduous and Permanent Tooth
Morphology in a European American Sample
H.J.H. Edgar1* and L.R. Lease2
1
2
Maxwell Museum of Anthropology and Department of Anthropology, University of New Mexico, Albuquerque, NM 87131
Department of Sociology and Anthropology, Youngstown State University, Youngstown, OH 44555
KEY WORDS
dental morphology; deciduous; permanent; correlation
ABSTRACT
The expression of dental morphological
characteristics is partially genetically controlled, and is
assumed to be similar in deciduous and permanent dentitions. However, there are few published data comparing
normal morphological variation between the two dentitions
in the same individual. For the current study, data were
collected from European Americans (N ¼ 54) whose teeth
were cast both as children and adults. We observed 19 trait
expressions in deciduous and permanent dentitions. Deciduous traits were scored based on Hanihara’s and Sciulli’s
descriptions, while permanent teeth were scored using the
ASU dental anthropology system. The two dentitions’
scores were compared using Goodman–Kruskal’s Gamma
(g) in the original, commonly used systems as well as in a
new, shared scale to which the scores were converted.
Observations were also dichotomized in both formats and
compared using tetrachoric correlation. We expected high
correlations between the two dentitions and for both statistics to yield similar results. For the original scores, g correlations vary from 1.0 to 0.68; tetrachoric correlations vary
from 0.04 to 0.67. For the shared scale scores, g correlations
range from 1.0 to 1.0 and tetrachoric correlations range
between 0.47 and 0.8. Several traits showed no correlation in either test. Overall, categorical data analysis
returned more positive moderate to high correlations than
tetrachoric correlation analysis, and shared scale tests
resulted in more correlations than did tests of data in the
original scoring systems. These results reflect differences
in commonly used scoring systems, variation in rarely
occurring traits, different strengths of trait expression, and
complex genetic/environmental interactions. Am J Phys
Anthropol 133:726–734, 2007. V 2007 Wiley-Liss, Inc.
Many normally occurring occlusal and tooth crown
morphological variables have been identified and quantified in human populations in both the deciduous and
permanent dentitions (Dahlberg, 1951; Jørgensen, 1956;
Hanihara, 1960, 1967, 1969; Turner, 1990; Zubov, 1992;
Irish, 1997). Anthropologists use expression frequencies
of morphological characteristics of both the permanent
(Scott, 1980; Kieser and Preston, 1981; Turner, 1990;
Hanihara, 1992; Guatelli-Steinberg et al., 2001; Manabe
et al., 2003; Irish, 2006) and deciduous teeth (Hanihara,
1960, 1967, 1969; Grine, 1986; Kitagawa et al., 1995;
Sciulli, 1998; Lease and Sciulli, 2005; Lukacs and
Walimbe, 2005) to examine relationships between populations. This is possible because expression of these
traits is genetically modulated (Garn et al., 1963,
1966a,b; Bader, 1965; Sofaer, 1970; Goose and Lee, 1971;
Biggerstaff, 1975; Corruccini et al., 1986; Scott and
Turner, 1997). Usually, results of population studies
based on permanent and deciduous morphology resemble
each other (Hanihara, 1960; Saunders and Mayhall,
1982; Lease, 2003). However, the proportions of trait
expression that are due to genetic and/or environmental
effects are not known.
The field theory of tooth development proposes that for
each tooth class there is a gradient of variation, with the
key tooth being the least variable and the teeth farther
way from the key tooth being more variable (Butler,
1939; Townsend and Brown, 1981). Butler (1939) identified three fields in the permanent dentition: the incisor
field with maxillary central incisor and mandibular lateral incisor as key teeth; the canine field; and the molar
field (consisting of both the premolars and molars) with
the first molar as the key tooth. Dalhberg (1945) divided
Butler’s molar field into a premolar field and a molar
field. Previous findings (Margetts and Brown, 1978;
Farmer and Townsend, 1993; Liversidge and Molleson,
1999) have found that the second deciduous molar (dm2)
is less variable in size and morphology in comparison to
the deciduous first molar (dm1), suggesting that the second deciduous molar is the key tooth of the deciduous
molar field.1
As predicted by dental field theory, previous research
has shown that despite size and shape differences there
is a marked morphological similarity between the dm2
and the first permanent molar (M1) (Dahlberg, 1963;
Smith, 1977; Saunders and Mayhall, 1982). Observed
frequencies of morphological traits, however, are not the
same in the two teeth. Some traits, including protostylid
and hypocone development, have been shown to occur at
higher frequencies in dm2 than in M1 (Dalhberg, 1950;
Hanihara, 1960; Smith et al., 1987). Other traits, such
C 2007
V
WILEY-LISS, INC.
C
1
The deciduous postcanine teeth are premolars, but they are usually referred to as molars in the literature, and we refer to them as
deciduous molars.
Grant sponsor: National Science Foundation; Grant number:
0087400; Grant sponsor: Ohio State University.
*Correspondence to: Heather Edgar, Laboratory of Human Osteology, Maxwell Museum of Anthropology, MSC01 1050, 1 University of
New Mexico, Albuquerque, NM 87131. E-mail: hjhedgar@unm.edu
Received 10 January 2006; accepted 7 December 2006
DOI 10.1002/ajpa.20564
Published online 12 February 2007 in Wiley InterScience
(www.interscience.wiley.com).
DECIDUOUS AND PERMANENT TOOTH MORPHOLOGY
as deflecting wrinkle, may show no difference in frequency of appearance between dm2 and M1 (Hanihara,
1960) or have greater expression in M1 (Smith et al.,
1987). Finally, some traits, such as distal trigonid crest,
have higher frequencies in permanent molars than in
the deciduous molars (Hanihara, 1960). Unlike molar
morphology, few studies have examined the relationship
of morphological expressions in the anterior dentitions.
Trait presence or absence is the result of the ontogenetic history of the teeth in question. The development
of dm2 occurs earlier and more rapidly than that of M1,
with dm2 mineralization of the mesial cusps commencing prior to the soft tissue development of the distal
cusps (Butler, 1967). In M1, calcification does not occur
until all cusps are formed, and proceeds at a slower rate
(Butler, 1967; Shellis, 1984). This observation of the morphogenesis and calcification of the two molars relates to
the generally accepted idea that traits (and teeth) that
develop early are the most conservative in nature
(Sofaer, 1973; Alberch et al., 1979; Alberch, 1980; Smith
et al., 1997).
If trait expressions in the deciduous and succedaneous
dentitions share the same genetic basis for growth and
development as reflected in dental phenotypes, then the
level of expression in both dentitions should be similar
for an individual (Scott and Turner, 1997). However, it is
likely that variation due to the environmental component of trait expression will be more apparent in the
postnatally developing permanent dentition than in deciduous teeth. We observed trait expressions in both dentitions from the same individuals from a sample of European Americans to determine the concordance between
trait expressions. Our null hypothesis is that there is no
correlation between trait expression in the deciduous
and permanent teeth.
727
(Hillson, 1996). There are different scoring procedures
for the deciduous and permanent dentitions described in
the literature and in common use. Deciduous morphological observations were all made by Lease following written standards by Sciulli (1998), which supplement the
photographs and descriptions of Hanihara (1960), Grine
(1986), Irish and Morris (1996), and Turner et al. (1991).
Due to time constraints, characteristics of the permanent
dentition were observed by Edgar following the Arizona
State University Dental Anthropology System (Turner et al.,
1991). This scoring procedure reflects the experience of each
author with the morphology of the two dentitions.
Inter-observer tests
We performed tests of inter-observer error for scores of
both deciduous and permanent morphology. The mean
grade error (MGE, average of absolute differences
between two observations) was computed for each trait
as well as for overall trait scores. For the deciduous
traits, MGEs ranged from 0.05 (UCMR) to 0.81(UMCB).
The overall error was 0.40. With one exception (UMCB,
1.50), permanent trait MGEs ranged from 0.02 (UCMR)
to 0.71(UI2TD). The overall error was 0.40. We attribute
the high error associated with UMCB to the high number of grades available for scoring this trait. In no case
would inter-observer error have affected the dichotomized value of a trait observation.
Intra-observer tests
Each author performed tests of intra-observer error for
the dentition they observed. Lease’s MGEs for the deciduous dentition ranged from 0.0 (UMCB) to 0.17 (LMGP)
and Edgar’s MGEs for the permanent dentition ranged
from 0.09 (LMC7) to 0.85 (LMGP).
MATERIALS AND METHODS
Statistical analysis
Observations were made on dental casts from 54 European Americans (28 female, 26 male) born in Cuyahoga
County, Ohio, between 1920 and 1945 (Behrents and
Broadbent, 1984). The casts are part of the large collection of the Bolton-Brush Longitudinal Growth Study,
housed at Case Western Reserve University. Subjects
had been chosen to represent the growth of healthy children with good access to nutrition and health care (Bailey, 1992). The standard protocol for subject visits was:
four visits between birth and 1 year (every 3 months);
two visits per year between 1 year old and 5 years old
(every 6 months); and one visit per year after the age of
5 through adolescence. During each visit, a cast was
taken of the subject as part of a battery of 20 tests (Behrents and Broadbent, 1984). Intraindividual comparisons
were made of the 19 observations (13 traits recorded on
19 teeth), listed in Table 1, along with their abbreviations, expressed in both the deciduous and permanent
dentitions. Each individual had traits observed on several casts taken at different ages, in order to gather the
most observations possible.
Traits were scored according to standardized, hierarchical descriptions of expressions. Each level of expression
is described in text and/or illustrated by plaques with
casts of individual teeth. Expressions of morphology on
the dentition were compared with these descriptions and
plaques, and a categorical observation was assigned.
This is a standard method of gathering data in anthropological studies of population variation and relations
Trait expressions were compared as both categorical
observations and dichotomized variables. This approach
allows for examination of the complex variation observable in categorical variables (Mayhall, 1999) as well as
future comparisons with studies in which variation is
dichotomized to allow for statistical analyses and/or to
reflect morphological thresholds. To test for correlations
between expressions in the two dentitions, traits were
compared in four statistical analyses:
1. Goodman–Kruskal’s Gamma (g) (Knoke and Bohrnstedt, 1991) was performed using scores in their original forms, based on Sciulli (1998) for deciduous teeth
and Turner et al. (1991) for permanent teeth. z-scores
were calculated to test the significance of g.
2. Tetrachoric correlation (Brown, 1977) was calculated
for dichotomized scores. Breakpoints were based on
Lease (2003) for deciduous teeth and Scott and
Turner (1997) for permanent teeth.
3. It was thought that differences in the two scoring procedures might cause underestimation of between-dentition correlations, so scoring methods were compared
to find equivalent scores in the deciduous and permanent trait scoring methods. These equivalencies were
determined by comparing casts and descriptions of
each trait described in both of the scoring systems.
For example, for the expressions of Carabelli’s trait,
deciduous and permanent scores 0, 1, and 2 were
found to be equivalent. Deciduous score 3 encom-
American Journal of Physical Anthropology—DOI 10.1002/ajpa
728
H.J.H. EDGAR AND L.R. LEASE
TABLE 1. Traits used, with shared-scoring system conversions
Trait
Shovel shape (SS)
Teeth
Mesial ridge (MR)
Distal accessory ridge (DAR)
Ui1/UI1
Ui2/UI2
Uc/UC
Li1/LI1
Li2/LI2
Ui1/UI1
Ui2/UI2
Uc/UC
Uc/UC
Uc/UC
Metaconule (C5)
Um2/UM1
Carabelli’s (CB)
Um2/UM1
Hypocone (H) (HC)
Um2/UM1
Groove pattern (GP)
Lm2/LM1
Cusp number (CN)
Lm2/LM1
Deflecting wrinkle (DW)
Lm2/LM1
Tuberculum dentale (TD)
Protostylid (PS)
Lm2/LM1
Cusp 6 (C6)
Cusp 7 (C7)
Lm2/LM1
Lm2/LM1
Deciduous scores
passed the variation described by permanent scores 3
and 4. The description of deciduous scores 4 and 5 are
the same as permanent scores 5 and 6, respectively.
Finally, deciduous score descriptions 6 and 7 are both
similar to the description for permanent score 7. Categories matched in this way were assigned a new,
shared score. All observations were then converted to
the shared system. Deciduous and permanent original
scores and their equivalencies in the new, shared
scoring are listed in Table 1. g tests were performed
to test for correlations of these modified scores, and zscores of these correlations were calculated.
4. Tetrachoric correlations were determined for dichotomized expressions of the trait scores in the modified
scoring system.
Goodman–Kruskal g tests were performed on the categorical trait expression data (tests 1 and 3, mentioned
earlier). The statistic is defined as (Con Dis)/(Con þ
Dis), where Con is a case where both variables agree in
rank (higher or lower) when compared with another case
(concordance), and Dis is a case where the rank orders
0
1
2
3
0
1, 2, 3
4
0
1
2
3
4
0
1
0
1
2
3
4
5
6, 7
3þA
3þB
4
4
1¼þ
2¼X
3¼Y
1
2
3
0
1
2
3
0
1, 2
3
4
5
6
Permanent scores
0
1, 2
3, 4
5, 6
7 ¼ barrel, not included
0
1, 2, 3, 4
5, 6
Equivalent 0–3 scale
0
1
2
3
4, 5
0
1, 2, 3, 4, 5
0
1
2
3, 4
5
6
7
1
2
3
4, 5
1¼Y
2¼X
3¼þ
4
5
6
0
Do not match
2
3
0
1, 2
3
4
5
6, 7
Equivalent 0–3 scale
Equivalent 0–5 scale
New score
0
1
2
3
0
1
2
0
1
2
3
4
0
1
0
1
2
3
4
5
6
1
2
3
4
1¼Y
2¼X
3¼þ
1
2
3
0
1
2
0
1
2
3
4
5
of the two variables are different (for example, deciduous
scores higher and permanent scores lower) when compared with another case (discordance). To test for significance of the g correlations, z is calculated as:
z¼G
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
NCon þ NDis =Nð1 G2 Þ
where G is g, N is the sample size for the trait, NCon is
the total number of agreements in rank for the trait,
and NDis is the total number of disagreements in rank
for the trait (Knoke and Bohrnstedt, 1991).
In addition to g analyses of categorical data and in
order to allow for comparison with other studies, the
data were dichotomized (tests 2 and 4, breakpoints are
in Tables 3 and 5) and analyzed by tetrachoric correlation (Brown, 1977). This statistic is appropriate when
dichotomized observations are used to describe variables
with continuous, normal distributions. Dichotomization
from categorical data into absence or presence observations is a standard technique in dental morphology studies, as it can facilitate statistical analysis. Both g and
American Journal of Physical Anthropology—DOI 10.1002/ajpa
729
DECIDUOUS AND PERMANENT TOOTH MORPHOLOGY
TABLE 2. Frequencies and counts of scores for original scoring procedures (in percent)
Frequency of score
Trait
UI1SS
UI2SS
UCSS
UI1TD
UI2TD
UCTD
UCMR
UCDAR
UMC5
UMCB
UMHC
LI1SS
LI2SS
LMCN
LMGP
LMDW
LMPS
LMC6
LMC7
Dentition
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
1
2
0.32
0.25
0.13
0.37
0.18
0.49
0.76
0.56
0.95
0.51
0.44
0.51
0.98
0.98
0.90
0.63
0.87
0.87
0.17
0.40
0.40
0.53
0.42
0.48
0.31
0.39
0.20
0.06
0.05
0.12
0.33
0.09
0.02
0.19
0.21
0.19
0.15
0.33
0.12
0.04
0.16
0.09
0.02
0.25
0.12
0.06
0.12
0.21
0.26
0.09
0.02
0.07
0.05
0.05
0.05
0.02
0.07
0.26 (Y)
0.88 (Y)
0.51
0.80
0.88
0.92
0.94
0.87
0.28
0.78
4
5
6
7
8
0.18
0.04
0.07
0.02
0.08
0.16
0.13
0.07
0.30
0.23
0.90
0.77
0.60
0.91
3
Scored
0
0.04
0.23
0.30
0.09
0.98
0.80
0.02 (X)
0.12 (X)
0.24
0.14
0.02
0.08
0.04
0.04
0.26
0.18
0.02
0.02
0.20
0.07
0.15
0.04
0.36
0.11
0.18
0.06
0.11
0.23
1.00
0.06
0.09
0.02
0.13
0.71(þ)
0.18
0.06
0.04
0.02
0.08
0.18
0.02
0.06
0.06
0.02
0.26
0.02
tetrachoric correlations can range from 1.0 to 1.0. A
score of 1.0 indicates that there is no discordance, 0.0
indicates the same number of concordant and discordant
observations, and 1.0 indicates that there is no concordance (Knoke and Bohrnstedt, 1991).
RESULTS
Original scoring expressions and correlations
Table 2 provides the frequencies for each level of expression in the deciduous and permanent dentitions for
the traits studied. Additionally, to indicate where differences in results may lie, the table provides percentages
of cases in which the deciduous tooth’s expression was
greater than the permanent, vice versa, and the percentage in which the two scores were equivalent. For 10
traits, scores are the same in both dentitions for more
than 50% of individuals. In the remaining cases, deciduous morphology had more complex expressions than permanent only once (UI1TD); permanent teeth were more
commonly scored higher than deciduous in six cases
(UI2SS, UCSS, UMCB, UMHC, and LMGP). Scoring
was evenly distributed in UI1SS and UCTD.
Table 3 presents the outcomes from both the g and tetrachoric correlation tests for scores from the original
scoring methods. g scores vary widely, from 1.00 to
0.02
0.06
0.17
0.15
0.08
0.04
0.09
0.08
Higher
Same
N
0.37
0.35
0.12
0.55
0.10
0.66
0.44
0.12
0.47
0.00
0.34
0.32
0.00
0.05
0.38
0.10
0.14
0.11
0.31
0.44
0.00
0.77
0.22
0.03
0.02
0.31
0.13
0.09
0.02
0.76
0.04
0.33
0.08
0.10
0.14
0.06
0.04
0.64
0.29
53
0.33
52
0.24
51
0.44
50
0.53
43
0.34
43
0.95
44
0.52
51
0.75
45
0.25
53
0.23
44
0.73
52
0.67
53
0.77
54
0.22
42
0.63
49
0.82
52
0.80
52
0.32
50
0.68. Four traits show moderate or better positive correlations over 0.36 (Knoke and Bohrnstedt, 1991), while
four show strong negative correlations of 1.00. Ten
traits show virtually no correlation, with scores ranging
between 0.30 and 0.30. For z-scores, the critical value
for z is >1.96, though z cannot be calculated for g results
of 1.0 or 1.0. The null hypothesis, no correlation
between deciduous trait expression and permanent trait
expression, is rejected for only two of 14 testable traits,
UMCB and LMDW. Tetrachoric correlations were calculable for six of the 18 traits studied. All the correlations
are positive, though expression of only one, UMCB, is
strongly correlated between the two dentitions.
Shared scale expressions and correlations
Table 4 lists frequencies of deciduous and permanent
trait expressions along with the summary scoring differences for the shared scoring system. It was expected
that similarities between scores would be greater for
these results given that the original scores have been
converted to representations on a shared scale. For 12
traits, scores are the same in both dentitions for more
than 50% of individuals, supporting this expectation.
However, deciduous morphology showed greater expressions than permanent twice (UI2SS, UCSS), and permanent scores were greater than deciduous in three cases
American Journal of Physical Anthropology—DOI 10.1002/ajpa
730
H.J.H. EDGAR AND L.R. LEASE
TABLE 3. g and tetrachoric results for original data
Breakpoints
Trait
N
g
ASE
z
UI1SS
UI2SS
UCSS
UI1TD
UI2TD
UCTD
UCMR
UCDAR
UMC5
UMCB
UMHC
LI1SS
LI2SS
LMCN
LMGP
LMDW
LMPS
LMC6
LMC7
53
52
51
50
43
42
44
51
45
53
0.30
0.18
0.19
0.25
0.23
0.00
1.00a
1.00a
0.19
0.68a
0.14
0.18
0.19
0.25
0.23
0.19
0.00
0.00
0.57
0.08
1.07
0.63
0.77
0.71
0.24
0.00
52
53
53
42
49
52
52
50
0.13
0.65a
0.27
0.24
0.66a
1.00a
1.00a
0.37
0.55
0.22
0.29
0.55
0.13
0.00
0.00
0.22
0.17
1.52c
0.08
0.32
2.24b
0.23
3.86b
1.03
Tet
ASE
D
P
0.12
0.24
0/1–4
0–2/3–6
0.04
0.24
0/1–4
0/1
0.09
0.67a
0.36
0.15
0/1
0–1/2–6
0/1–5
0–4/5–7
0.12
0.34
X, þ/Y
X, þ/Y
0.23
0.26
0/1–5
0/1
ASE, asymptotic error.
a
Significant correlation.
b
Significant z-score.
c
Nearly significant z-score.
TABLE 4. Frequencies and counts of scores for shared scoring procedure (in percent)
Frequency of score
Trait
UI1SS
UI2SS
UCSS
UI1TD
UI2TD
UCTD
UCMR
UCDAR
UMC5
UMCB
UMHC
LI1SS
LI2SS
LMCN
LMGP
LMDW
LMPS
LMC6
LMC7
Dentition
0
1
2
3
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
D
P
0.30
0.25
0.12
0.37
0.16
0.51
0.78
0.56
0.93
0.52
0.47
0.53
0.94
0.90
0.84
0.64
0.82
0.87
0.40
0.51
0.02
0.42
0.53
0.42
0.48
0.31
0.39
0.22
0.40
0.07
0.36
0.51
0.41
0.04
0.02
0.12
0.16
0.13
0.13
0.30
0.09
0.24
0.19
0.21
0.21
0.15
0.35
0.10
0.09
0.02
0.25
0.82
0.82
0.57
0.85
0.08
0.18
0.30
0.11
0.08
0.73
0.93
0.84
0.92
0.92
0.90
0.27
0.78
0.07
0.34
0.95
0.18
0.07
0.12
0.06
0.04
0.02
0.45
0.20
Scored
4
5
6
0.18
0.04
0.11
0.02
0.06
0.02
0.06
0.02
0.04
0.18
0.02
0.20
0.02
0.36
0.13
0.04
0.96
0.80
0.02
0.05
0.09
0.02
0.02
0.03
0.22
0.22
0.02
0.02
0.04
0.13
0.63
0.04
0.02
0.04
0.06
0.27
0.02
0.02
0.02
American Journal of Physical Anthropology—DOI 10.1002/ajpa
0.08
0.16
0.16
0.98
0.06
0.08
0.19
0.08
Higher
Same
N
0.26
0.40
0.66
0.08
0.75
0.06
0.36
0.12
0.44
0.00
0.26
0.30
0.00
0.08
0.35
0.15
0.11
0.13
0.28
0.47
0.00
0.82
0.21
0.12
0.02
0.34
0.06
0.06
0.02
0.34
0.00
0.26
0.06
0.15
0.10
0.08
0.04
0.63
0.34
53
0.26
52
0.19
51
0.52
50
0.56
44
0.44
49
0.92
48
0.50
50
0.76
45
0.25
53
0.18
45
0.89
51
0.64
47
0.88
54
0.74
41
0.74
45
0.80
51
0.83
52
0.33
49
731
DECIDUOUS AND PERMANENT TOOTH MORPHOLOGY
TABLE 5. g and tetrachoric results for data on shared scale
Trait
N
g
ASE
UI1SS
UI2SS
UCSS
UI1TD
UI2TD
UCTD
UCMR
UCDAR
UMC5
UMCB
UMHC
LI1SS
LI2SS
LMCN
LMGP
LMDW
LMPS
LMC6
LMC7
53
43
42
41
35
40
39
41
45
40
44
42
45
54
41
37
42
43
40
0.09
0.00
0.18
0.08
0.24
0.08
1.00a
0.42a
0.07
0.61a
0.56a
0.19
0.65a
0.27
0.3
0.45a
1.00a
1.00a
0.61a
0.21
0.21
0.20
0.33
0.45
0.28
0.00
0.42
0.56
0.14
0.10
0.54
0.22
0.29
0.66
0.32
0.00
0.00
0.23
z
0.17
0.29
0.19
0.70
0.09
3.00b
0.52
0.11
0.31
0.68
1.71c
N
Tet
ASE
Breakpoint
53
52
51
50
0.01
0.20
0.02
0.03
0.25
0.28
0.27
0.25
0/1–3
0/1–3
0/1–3
0/1–2
43
0.03
0.24
0/1–2
51
45
53
a
0.47
0.03
0.80a
0.25
0.35
0.11
0/1–4
0/1
0–2/3–6
52
53
0.20
0.55a
0.31
0.24
0/1–3
0/1–3
41
47
51
0.15
0.71a
0.23
0.35
0.17
0.36
X, þ/Y
0/1–2
0/1–5
49
0.24
0.26
0/1–3
ASE, asymptotic error.
a
Significant correlation.
b
Significant z-score.
c
Nearly significant z-score.
(UMCB, UMHC, and LMC7). As with the original scoring procedures, scores were relatively evenly distributed
in UI1SS and UCTD.
Table 5 summarizes outcomes from the g and tetrachoric correlation tests for scores based in the shared
scoring system. In this analysis, 10 of 19 observations
show moderate or better g correlations of at least
|0.36|. Of these 10 correlations, 6 are positive (UCSS,
UCMR, UMCB, LI2SS, LMDW, and LMC7) and 4 are
negative (UCDAR, UMHC, UMPS, and LMC6). Two zscores indicate significant positive correlation (UMCB,
LI2SS) although z-scores cannot be computed for three
of the correlated traits, as their correlations are 1.0 or
1.0. Of tetrachoric results, three correlations are moderate to strongly positive (UMCB, LI2SS, and LMDW).
Only UCDAR is moderately negatively correlated.
DISCUSSION
Results show no significant correlation between dentitions in any test for shovel shaping or tuberculum dentale
of the maxillary dentition. However, shoveling is highly
positively correlated in the mandibular lateral incisor, perhaps a reflection of that tooth’s greater likelihood (compared with the mandibular central incisor) for expression.
On the other hand, in all possible tests, maxillary canine
mesial and distal accessory ridges show a significant relationship between the two dentitions. Unfortunately, these
relationships are not straightforward. While canine distal
accessory ridge is negatively correlated in all possible
tests, canine mesial ridge is negatively correlated in the g
test of the original data and positively correlated in the
same test of the shared scale data. Clearly, the difference
here is a function of the analysis scale and not the morphology. We feel that the shared scale more accurately
reflects the relationship between the deciduous and permanent expressions of this characteristic.
Tables 2 and 4 support previously reported findings
(Saunders and Mayhall, 1982; Smith et al., 1987) regarding correlations of certain molar traits of the deciduous
and permanent dentitions. Smith et al. (1987) found that
dm2 was more likely to have reduced expressions of
hypocone, Carabelli’s trait, oblique ridges, Y molar pattern, and mandibular molar cusps 5 and 7 when compared with the M1. Marginal ridges, occlusal tubercles,
and wrinkling were more commonly seen on the permanent dentition (Smith et al., 1987). Considering the same
teeth in the present study, using original scoring procedures, maxillary dm2 is more likely to express some
form of the Carabelli’s trait than M1 (84 and 60%,
respectively), and mandibular dm2 more frequently
shows cusp 7 (72%) than does M1 (22%). These results
agree with those found by Smith et al. (1987). However,
other results disagree. Maxillary M1 more often has a
large hypocone (100% in permanent molars versus 23%
in deciduous molars), and mandibular M1 is more likely
to express the Y molar pattern (88%) than is dm2 (26%).
As can be seen from Table 3, the majority of correlations among data in the original scoring formats are
weak to moderate, supporting the null hypothesis. However, these correlations again seem both to support and
contradict previous studies (Saunders and Mayhall,
1982; Smith et al., 1987). Smith et al. (1987) did not find
strong positive correlations between the two dentitions
for traits seen on dm2 and M1. In the present study,
there are significant positive g correlations between the
dentitions for two traits (Carabelli’s and deflecting wrinkle) and a correlation close to significance for one trait,
mandibular lateral incisor shoveling, which was not
examined by Smith et al. (1987). Carabelli’s trait retains
its significance when the data is dichotomized.
An examination of the frequencies of expressions using
the shared-scale scoring system shows some similarities
with as well as some differences from the original trait
score results. For two of the molar traits examined by
Smith et al. (1987), Carabelli’s trait and cusp 7, the dm2
expresses the trait more frequently than M1 (91 and
74% in comparison to 65 and 22%, respectively). However, Y groove is much more common in M1 (95%) than
in dm2 (34%). In this study, g correlations are positive
and significant for Carabelli’s trait and for mandibular
lateral incisor shoveling, negating the null hypothesis
American Journal of Physical Anthropology—DOI 10.1002/ajpa
732
H.J.H. EDGAR AND L.R. LEASE
for these traits. The correlation for cusp 7 is close to significance as well. There are three significant tetrachoric
correlations for the results in the shared scoring system;
both mandibular lateral incisor shoveling and Carabelli’s
trait retain strong positive correlations, while deflecting
wrinkle shows a strong negative correlation between the
two dentitions. Differences between original format and
shared-scale results most likely reflect the fact that different researchers working relatively independently
developed the two original scales. Another possible explanation may be imperfect development of the shared
scale used in this paper. At this point, it is unclear
which series of results presented here more accurately
reflects the relationship of the deciduous and permanent
dentitions. It should be noted that expression of Carabelli’s trait is significantly correlated between the deciduous
and succedaneous dentitions in all four analyses, as is
mandibular second incisor shoveling for the three analyses for which correlations can be calculated.
The two statistics used present somewhat different
results for the two different data sets, original scoring
system data and the shared scoring system data. The g
statistic, as it is calculated on all possible scores, may be
more sensitive to small fluctuations in trait grade. The
tetrachoric correlation might be thought of as filtering
out \noise" and more clearly presenting the actual correlations between dentitions, regardless of the strength of
the trait expression. In fact, while there are about the
same number of positive and negative g results (9 and 10,
respectively), the tetrachoric correlations are generally
positive (11 positive results versus 5 negative g results).
The results presented here are equivocal in their agreement with previous research regarding deciduous and
permanent molar characteristics. The strong positive correlations of the molar traits in the Bolton-Brush sample
may suggest that traits that appear early in morphogenesis (e.g., reduced hypocone and Carabelli’s trait) may be
more likely to be present in both the deciduous and the
permanent dentition of the same individual. Several
authors (Kraus and Jordan, 1965; Saunders and Mayhall,
1982; Kieser, 1984; Smith et al., 1987) found that earlierforming characteristics with a dentin component (e.g.,
Carabelli’s trait, Y groove pattern, mandibular cusps 5
and 7, and reduced hypocone) were more likely to be
found in the dm2s than in M1s of the same individual.
Previous research has indicated that morphological characteristics visible at the dentin–enamel junction such as
these may have developed earlier in our phylogeny and
show more conservative variation (Kraus and Jordan,
1965; Smith et al. 1997; Corruccini, 1998). Later-forming
traits (e.g., marginal ridges and cusps and occlusal
tubercles) are more likely to be found on M1s. In general,
the present research confirms these observations. Results
in both the original and shared scoring systems show that
Carabelli’s trait, mandibular molar cusp 7, and reduced
hypocone, all early developing traits, are more common in
dm2 than in M1. However, current results for the expression of Y groove, supposedly another early developing
trait, is more common in M1 than in dm2. Results also
show that two later-developing molar traits, deflecting
wrinkle and protostylid, occur more commonly on dm2
than M1, contrary to expectations.
There are several possible explanations for the differences between the current research and previous work:
1. The sample consists of European Americans dentitions. Members of this group rarely have strong phe-
notypic expressions of most dental traits (Saunders
and Mayhall, 1982). The occasional expression of
some traits may be due to stochastic variation in
genes or to environmental influences rather than to
any predictable patterns of heritability. This explanation is supported by the fact that several of the traits
with high correlations between the two dentitions,
such as Carabelli’s trait and mandibular lateral incisor shoveling, are those that have been previously
shown to occur in at least moderate levels in European-derived populations.
2. Methodological problems may also confound results.
The sample is small, 54 individuals. Also, construction of the shared scoring system may have introduced errors in the data, confounding the analysis.
3. Another possible explanation is that these results
accurately reflect reality, and genetic control, as well
as environmental influences, over the expression of
dental traits is not always as expected in the two dentitions. This phenomenon may be due to a multitude
of factors, including pleiotropic, epistatic, and developmental effects.
It is presumed that the dentition has a high genetic component in regard to the determination of size, morphology,
and number of teeth present. There have been several studies conducted on the heritability of morphological traits
(Bader, 1965; Garn et al., 1963, 1966a,b; Sofaer, 1970;
Goose and Lee, 1971; Biggerstaff, 1975; Corruccini et al.,
1986). While previous studies show that there is a degree of
heritability in regards to tooth size and morphology, the information from these studies is, at times, contradictory
(Alvesalo and Tigerstedt, 1974; Potter et al., 1983; Harzer,
1987; Dempsey et al., 1999). In recent years, the impact of
environmental influences, both in utero and post utero,
highlight the fact that size and morphology of the dentition
are not just genetically controlled (Moller, 1967; Garn et al.,
1979, 1980; Fearne and Brook, 1993; Heikkinen et al.,
1994). It should not be forgotten that there is a high correlation between tooth morphology and crown size, which
may also be important (Kangas et al., 2004; Kondo and
Townsend, 2006). Studies using mice as models (Kangas et
al., 2004) provide evidence that minute changes in genetic
signaling in regard to crown size and shape influence the
expression of morphological characteristics.
CONCLUSIONS
Most studies do not discuss data regarding the morphology of the anterior dentition. This is likely because,
in most cases, the only deciduous and permanent analogs to be observable in a dentition at the same time are
the dm2 and M1. Results presented here indicate that
correlations of trait expression in deciduous and permanent incisors and canines are generally weak. It is possible that, due to extrapolations based on previous studies
that considered only molar trait expressions, the significance of correlations for the entire dentition has been
overestimated.
The majority of comparisons presented here did not
allow rejection of the null hypothesis, that there are no
correlations between expressions of morphological characteristics in the deciduous and permanent dentitions of
the same individual. The strong exceptions to this are
with regard to Carabelli’s cusp, mandibular lateral incisor shoveling, and deflecting wrinkle. One of these traits,
Carabelli’s trait, develops early in dental ontogeny,
American Journal of Physical Anthropology—DOI 10.1002/ajpa
DECIDUOUS AND PERMANENT TOOTH MORPHOLOGY
which may lead to the expectation that it will occur at
the same or greater frequency in dm2 and M1. Deflecting wrinkle, however, is thought to be a late ontogenetic
development, so the correlation shown here serves to
obscure the meaning of these results. Again, previous
studies have not considered correlations of incisor shoveling between dentitions of the same individual.
Before any real conclusions can be drawn, additional
studies similar to the present one, comparing morphological traits from several teeth in both dentitions of the
same individual, should be conducted with sample subjects drawn from other, non-European-derived populations with overall higher expressions of numerous traits.
Certainly, finding samples in which data from both dentitions in the same individual can be studied will be
problematic.
ACKNOWLEDGMENTS
We thank two anonymous reviewers of a previous
draft, Paul Sciulli, Joe Powell, and Michael Mahaney for
statistical advice, and the Bolton-Brush Longitudinal
Growth Study for access to their collections.
LITERATURE CITED
Alberch P. 1980. Ontogenesis and morphological diversity. Am
Zool 20:653–657.
Alberch P, Gould SJ, Osyter GF, Wake DB. 1979. Size and shape
in ontogeny and phylogeny. Paleobiology 5:296–317.
Alvesalo L, Tigerstedt PMA. 1974. Heritabilities of human tooth
dimension. Hereditas 77:311–318.
Bader RS. 1965. Heritability of dental characters in house
mouse. Evolution 19:378–384.
Bailey J. 1992. The long view of health. Case Western Reserve
University Newsletter. February. p 1–7.
Behrents RG, Broadbent BH. 1984. In search of truth for the
greater good of man: a chronological account of the BoltonBrush Growth Studies. Cleveland: The Bolton-Brush Growth
Study Center, Case Western Reserve University School of
Dentistry.
Biggerstaff RH. 1975. Cusp size, sexual dimorphism, and heritability of cusp size in twins. Am J Phys Anthropol 42:127–
140.
Brown MB. 1977. The tetrachoric correlation and its asymptotic
standard error. Appl Stat 26:343–351.
Butler PM. 1939. Studies of the mammalian dentition-differentiation of the post-canine dentition. Proc Zool Soc Lond B
109:1–36.
Butler PM. 1967. Comparison of the development of the second
deciduous molar and first permanent molar in man. Arch
Oral Biol 12:1245–1260.
Corruccini RS. 1998. The dentino-enamel junction in primate
mandibular molars. In: Lukacs JR, editor. Human dental development, morphology, and pathology: a tribute to Albert A.
Dahlberg. Eugene: University of Oregon Press. p 1–16.
Corruccini RS, Sharma K, Potter RHY. 1986. Occlusal genetic
variance and heritability in twins. Am J Phys Anthropol
70:293–299.
Dahlberg AA. 1945. The changing dentition of man. J Am Dent
Assoc 32:676–690.
Dahlberg AA. 1950. The evolutionary significance of the protostylid. Am J Phys Anthropol 8:15–25.
Dahlberg AA. 1951. The dentition of the American Indian. In:
Laughlin WS, editor. Papers on the physical anthropology of
the American Indian. New York: Viking Fund. p 138–176.
Dahlberg AA. 1963. Analysis of the American Indian dentition.
In: Brothwell DR, editor. Dental anthropology. Oxford: Pergamon. p 149–177.
733
Dempsey PJ, Townsend GC, Martin NG. 1999. Insights into the
genetic basis of human dental variation from statistical modeling analyses. Perspect Hum Biol 4:9–17.
Farmer V, Townsend GC. 1993. Crown size variability in the deciduous dentition of South Australian children. Am J Hum
Biol 5:681–690.
Fearne JM, Brook AH. 1993. Small primary tooth-crown size in
low birthweight children. Early Hum Dev 33:81–90.
Garn SM, Lewis AB, Kerewsky RS. 1963. Interaction between
relative molar size and relative number of cusps. Science
142:1060.
Garn SM, Lewis AB, Kerewsky RS. 1966a. Extent of sex influence on Carabelli’s polymorphism. J Dent Res 45:1823.
Garn SM, Lewis AB, Kerewsky RS, Dahlberg AA. 1966b. Genetic independence of Carabelli’s trait from tooth size or
crown morphology. Arch Oral Biol 11:745–747.
Garn SM, Osborne RH, Alvesalo L, Horowitz SL. 1980. Maternal and gestational influences on the deciduous and permanent tooth size. J Dent Res 59:142–143.
Garn SM, Osborne RH, McCabe KD. 1979. The effect of prenatal factors on crown dimensions. Am J Phys Anthropol 51:
665–678.
Goose DH, Lee GTR. 1971. The mode of inheritance of Carabelli’s trait. Hum Biol 43:64–69.
Grine FE. 1986. Anthropological aspects of the deciduous teeth
of South African blacks. In: Singer R, Lundy JK, editors.
Variation, culture and evolution in African populations.
Johannesburg: Witwatersrand University Press. p 47–83.
Guatelli-Steinberg D, Irish JD, Lukacs JR. 2001. Canary islandNorth Africa biological affinities: measure of divergence based
on dental morphology. Homo 52:173–188.
Hanihara K. 1960. Criteria for classification of crown characters
of the human deciduous dentition. J Anthropol Soc Nippon
68:27–44.
Hanihara K. 1967. Racial characteristics of the dentition.
J Dent Res 46:923–926.
Hanihara K. 1969. Mongoloid dental complex in the permanent
dentition. In: Proceedings of the Eighth International Congress of Anthropological and Ethnological Sciences, Tokyo and
Kyoto. p 298–300.
Hanihara T. 1992. Dental and cranial affinities among populations of East Asia and the Pacific: the basic populations in
East Asia, IV. Am J Phys Anthropol 88:163–182.
Harzer W. 1987. A hypothetical model of genetic control of
tooth-crown growth in man. Arch Oral Biol 32:159–162.
Heikkinen T, Alvesalo L, Osborne RH, Tienari J. 1994. Maternal
smoking and tooth formation in the foetus. II. Tooth crown
size in the permanent dentition. Early Hum Dev 40:73–86.
Hillson S. 1996. Dental anthropology. Cambridge: Cambridge
University Press.
Irish JD. 1997. Characteristic high- and low-frequency dental
traits in sub-Saharan African populations. Am J Phys Anthropol 102:455–467.
Irish JD. 2006. Who were the ancient Egyptians? Dental affinities among Neolithic through postdynastic peoples. Am J
Phys Anthropol 129:529–543.
Irish JD, Morris DH. 1996. Technical note: canine mesial ridge
(Bushman canine) dental trait definition. Am J Phys Anthropol 99:357–359.
Jørgensen KD. 1956. The deciduous dentition: a descriptive and
comparative anatomical study. Acta Odontol Scand 14:1–202.
Kangas AT, Evans AR, Thesleff I, Jernvall J. 2004. Nonindependence of mammalian dental characters. Nature 432:211–214.
Kieser JA. 1984. An analysis of the Carabelli trait in the mixed
deciduous and permanent human dentition. Arch Oral Biol
29:403–406.
Kieser JA, Preston CB. 1981. The dentition of the Lengua Indians of Paraguay. Am J Phys Anthropol 55:458–490.
Kitagawa Y, Manabe Y, Oyamada J, Rokutanda A. 1995. Deciduous dental morphology of the prehistoric Jomon people of Japan: comparison of nonmetric characters. Am J Phys Anthropol 97:101–111.
Knoke D, Bohrnstedt GW. 1991. Basic social statistics. Itesche,
IL: Peacock.
American Journal of Physical Anthropology—DOI 10.1002/ajpa
734
H.J.H. EDGAR AND L.R. LEASE
Kondo S, Townsend GC. 2006. Associations between Carabelli
trait and cusp areas in human permanent maxillary first
molars. Am J Phys Anthropol 129:196–203.
Korenhof CAW. 1982. Evolutionary trends of the inner enamel
anatomy of deciduous molars from Sangiran (Java, Indonesia). In: Kurten B, editor. Teeth: form, function and evolution.
New York: Columbia University Press. p 350–355.
Kraus BS, Jordan RE. 1965. The human dentition before birth.
Philadelphia: Lea and Febiger.
Lease LR. 2003. Ancestral determination of African American and
European American deciduous dentition using metric and nonmetric analysis. Ph.D. Dissertation, Ohio State University, OH.
Lease LR, Sciulli PW. 2005. Discrimination between EuropeanAmerican and African-American children based on deciduous
dental metrics and morphology: brief communication. Am J
Phys Anthropol 126:56–60.
Liversidge HM, Molleson TI. 1999. Deciduous tooth size and
morphogenetic fields in children from Christ Church, Spitalfields. Arch Oral Biol 44:7–13.
Lukacs JR, Walimbe SR. 2005. Deciduous dental morphology
and the biological affinities of a late Chalcolithic skeletal series from western India. Am J Phys Anthropol 65:23–30.
Manabe Y, Oyamada J, Kitagawa Y, Rokutanda A, Kato K,
Matsushita T. 2003. Dental morphology of the Dawenkou Neolithic population in North China: implications for the origin
and distribution of Sinodonty. J Hum Evol 45:369–380.
Margetts B, Brown T. 1978. Crown diameters of the deciduous
teeth in Australian aboriginals. Am J Phys Anthropol 48:493–
502.
Mayhall JT. 1999. Dichotomy in human dental morphology: a
plea for complexity. In: Mayhall JT, Heikkenen, editors. Dental morphology ’98. Oulu: Oulu University Press. p 43–47.
Moller IJ. 1967. Influence of microelements on the morphology
of teeth. J Dent Res 46:933–937.
Potter RHY, Rice JP, Dahlberg AA Dahlberg T. 1983. Dental
size traits within families: path analysis for first molar and
lateral incisor. Am J Phys Anthropol 61:283–289.
Saunders SR, Mayhall JT. 1982. Fluctuating asymmetry of dental morphological traits: new interpretations. Hum Biol 54:
789–799.
Sciulli PW. 1998. Evolution of the dentition in prehistoric Ohio
Valley Native Americans. II. Morphology of the deciduous
dentition. Am J Phys Anthropol 106:189–205.
Scott GR. 1980. Population variation of Carabelli’s trait. Hum
Biol 52:63–78.
Scott GR, Turner CG II. 1997. The anthropology of modern
human teeth: Dental morphology and its variation in recent
human populations. Cambridge: Cambridge University Press.
Shellis RP. 1984. Variation in growth of the enamel crown in
human teeth and a possible relationship between growth and
enamel structure. Arch Oral Biol 29:697–705.
Smith P. 1977. Variations in dental traits within populations.
In: Dahlberg AA, Graber TM, editors. Orofacial growth and
development. Amsterdam: Mouton Press. p 171–182.
Smith P, Gomorri JM, Spitz S, Becker J. 1997. Model for the examination of evolutionary trends in tooth development. Am J
Phys Anthropol 102:283–294.
Smith P, Koyoumonsky-Kaye E, Kaldaron W, Stern D. 1987.
Directionality of dental trait frequency between human second deciduous and first permanent molars. Arch Oral Biol 32:
5–9.
Sofaer JA. 1970. Dental morphological variation and the
Hardy–Weinberg law. J Dent Res 49:1505–1508.
Sofaer JA. 1973. A model relating developmental interaction
and differential evolutionary reduction of tooth size. Evolution
27:427–434.
Townsend GC, Brown T. 1981. Morphogenetic fields within the
dentition. Aust Orthod J 7:3–10.
Turner CG II. 1990. Major features of Sundadonty and
Sinodonty, including suggestions about East Asia microevolution, population history, and late Pleistocene relationships
with Australian Aboriginals. Am J Phys Anthropol 82:295–
318.
Turner CG II, Nichol CR, Scott GR. 1991. Scoring procedures
for key morphological traits of the permanent dentition: the
Arizona State University dental anthropology system. In:
Kelley MA, Larsen CS, editors. Advances in dental anthropology. New York: Wiley-Liss. p 13–32.
Zubov AA. 1992. The epicristid or middle trigonid crest defined.
Dent Anthropol Newslett 6:9–10.
American Journal of Physical Anthropology—DOI 10.1002/ajpa
Документ
Категория
Без категории
Просмотров
0
Размер файла
130 Кб
Теги
correlation, morphology, deciduous, toots, samples, american, permanent, european
1/--страниц
Пожаловаться на содержимое документа