Formation of the permanent dentition in Arikara Indians Timing differences that affect dental age assessments.код для вставкиСкачать
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 61:467-471(1983) Formation of the Permanent Dentition in Arikara Indians: Timing Differences That Affect Dental Age Assessments DOUGLAS W. OWSLEY AND RICHARD L. JANTZ Department of Geography and Anthropology, Louisiana State Uniuersity, Baton Rouge, Louisiana 70803 (0.W 0.)and Department ofAnthropology, University of Tennessee, Knoxuille, Tennessee (R.L.J.) KEY WORDS Arikara Indians, White standards, Dental ages ABSTRACT This report concerns one problem encountered with application of American white dental formation standards to age assessment of subadults of archaeological context. Dental ages for eight mandibular permanent teeth and maxillary central and lateral incisors of Arikara Indian immature skeletons were determined according to degree of crown or root mineralization. Ages assigned to the various teeth of the same individual were compared. They showed similarities as well as patterned differences. First premolar, second premolar, and mandibular incisor ages closely approximated one another. In relation to this complex, dental ages for maxillary incisors and mandibular second molars were older by 0.5 to 1.1 years. Developmental ages assigned to individuals on the basis of third molars showed relative advancement by more than 2 years. The systematic occurrence of these observations reflects more than just individual variability; it shows the presence of population differences in tooth-formation timing. Timing differences complicate assessment of dental ages needed for growth or demographic studies. Dental ages of preadults of forensic science or archaeological context may be determined by examining the degree of dental calcification. Dental calcification standards generally used are those of Moorrees et al. (19631, although others are available (Anderson et al., 1976; Demirjian et al., 1973; Gleiser and Hunt, 1955; Nolla, 1960).The Moorrees et al. (1963)research provided norms detailing the formation of permanent dentitions of North American white children of the middle-socioeconomic group. Application of these standards to groups other than the population for which the charts were designed is a significant factor that introduces possible error “[In] another population, the children may pass through these stages of dental development in the same sequences . . . but consistently earlier or later” (Moorrees et al., 1963:1500). Tooth calcification standards for other populations are generally not available. Also of note is evidence that certain teeth emerge at slightly different ages in different populations or racial groups (Bean, 1914; Dahlberg and Me- 0 1983 ALAN R. LISS, INC negaz-Bock, 1958; Eveleth, 1966; Friedlaender and Bailit, 1969; Hrdlicka, 1908; Mayhall et al., 1977, 1978; Moorrees, 1957; Suk, 1919). Dental eruption schedules of American Indian, Eskimo, and Aleut populations show differences when contrasted with normative data for whites (Dahlberg and Menegaz-Bock, 1958; Garn and Moorrees, 1951; Hrdlicka, 1908; Mayhall et al., 1977, 1978; Moorrees, 1957; Steggerda and Hill, 1942). Dahlberg and Menegaz-Bock (1958)have reported that Pima Indian children are relatively advanced in eruption of the posterior teeth but have later eruption of the anterior teeth. Others similarly provide evidence that Indian and Aleut posterior teeth erupt earlier (Garn and Moorrees, 1951; Moorrees, 1957; Steggerda and Hill, 1942). This research evaluated the application of the Moorrees et al. (1963) standards to archaeological collections using a n Arikara InReceived June 28, 1982; accepted April 21, 1983 468 D.W. OWSLEY AND R.L. JANTZ dian skeletal sample. Our objective was to show how age assessments based on differing teeth can in fact vary. This variation was demonstrated by determining dental ages for each tooth and then comparing within individual values. The principle applied was as follows: The standards allow a dental age to be determined for each tooth according to the degree of crown or root formation. An age determined for one tooth should, on average, be similar to ages derived for other teeth if developmental schedules parallel the pattern described in whites. If, relative to this population, certain teeth displayed age advancement or retardation, pairwise contrasts of the ages assigned should reveal systematic differences. T A B L E I. Tooth-formation stages and corresponding svmbolsl Stage Symbol Initial cusp formation Coalescence of cusps Cusp outline complete Crown 112 complete Crown 314 complete Crown complete Initial root formation Initial cleft formation Rooth length 114 Root length 112 Rooth length 314 Root length complete Apex 112 closed Apical closure complete ‘From Moorrees et al. (1963). MATERIALS AND METHODS The skeletal collections analyzed in this report represent Arikara Indian populations of South Dakota during the time span A.D. 1600-1835. The archaeological sites included are the following: Four Bear (39DW2), Larson (39WW2), Leavenworth (39C09), Mobridge (39WW11, Rygh (39CA41, Sully (39SL4), and Swan Creek (39WW7). Sources that may be consulted for information about these sites, Arikara history, settlement, or subsistence patterns are Bass et al. (19711, Holder (19701, Hurt (1957,19691, Hurt et al. (19621, Krause (19721, Lehmer (19711, and Lehmer and Jones (1968). Periapical dental x-rays (generally Kodak size DF42) were taken for subadults to allow dental maturity scores to be obtained. Ratings for loose teeth recovered from damaged mandibles were scored by visual inspection. Standards for two maxillary (I1,12)and eight mandibular (I1-M3) permanent teeth were applied. Moorrees et al. (1963) defined 13 or 14 formation stages for the permanent teeth, depending on whether they are single-rooted teeth or molars (Table 1).The reliability of distinguishing betweeen two stages of crown or root development was enhanced by double determination for many specimens on separate occasions. All scores were obtained by Owsley. Differences that occurred never exceeded one stage. Scores were transformed into dental ages for analysis. Tooth-specific mean ages (sexes pooled) relating to each stage of formation (given in Moorrees et al., 1963; Figs. 3-6) were assigned. Pooling was necessary since subadults cannot be sexed on a reliable basis. Sexual dimorphism is present in the ages at which the permanent teeth attain various stages of mineralization (Bailit and Hunt, 1964; Demirjian and Levesque, 1980; Fanning, 1961; Garn et al., 1958; Moorrees et al., 1963; Nola, 1960; Samoka and Demirjian, 1971; Thompson et al., 1975).This uncontrolled source of variation should not radically affect results. First and second premolars were used as reference points. Pairwise contrasts were completed by comparing the age assigned to each tooth with the premolar ages. This choice was based on the following: (1) Premolar developmental periods overlap substantially with all permanent teeth; (2) sexrelated calcification timing differences are less than for mandibular canines (Demirjian and Levesque, 1980; Fanning, 1961; Moorrees et al., 1963; Nolla, 1960; Thompson et al., 1975);(3)the Moorrees et al. (1963)standards are most complete for the posterior dentition. Ages were reported for final stages of incisor crown development and for root development, but not for the initial stages. Limited comparisons were also completed using the molars (MI and Ma, Mz with M3). Mean differences were tested for significance using a paired t test program (Helwig and Council, 1979). RESULTS Table 2 presents for each paired contrast the observed overlap in developmental stages, sample sizes, resulting positive or negative mean differences, and corresponding paired t values. The majority of tests revealed differences that achieved statistical significance a t the 0.01 level or better. Several differences were statistically significant AGE ASSESSMENT IN ARIKARA INDIAN DENTITION 469 TABLE 2. Tooth pair contrasts, deuelopmental stages shared in common, mean differences, and paired t values D-:I a,, N (A-B) I' - P, I' - P2 12 - P1 I2 - Pz 11 -PI I1 - P z 12 - P] 12 - p2 c-P, c - Pz P, -P, PI - M1 P2 - MI Pi - Mz P2 - Mz P i - M3 P2 - M3 M1- M2 M2 - M:3 100 90 95 88 68 68 70 71 188 159 166 153 Developmental stages overlaaaing ._ A B 118 Cr, - A w Cr, - AjlL Crc-ALh Cr, - Ak,$ R%,-AyA Ry-RR, RIA- Ath RIM- AH CrllA- AIlA Cr., Crch- Ajh Cj - Rv2 Cj - Rih 161 171 53 65 116 75 R>y/,-AiyL R~A-A,/~ Rj Cli- A, c,,,- Alh cc, - A, Difference /.,-.\ ly CSI 3 1 X C,, - Atpi Cj - R:% c,, - Rc Cj - R:, Cr:, - R E Cco RIA Cr:, - R:, - Rlh Ci -Ash Cj - A , Ci - A>h Cr, - AyA Ri Cco - A ~ A C," - Alh C,,, - Rw C,, - RY, C,, - RIA R% 0.77 0.52 1.08 0.79 -0.12 -0.25 0.24 0.06 -0.24 -0.55 0.17 0.27 0.51 -0.81 -0.55 -2.30 -2.00 - -1.11 - 1.52 t 10.65*** 6.13*** 12.84""" 8.87"** -1.67"" -3.38"" 2.85"* 0.80"" -4.20*"* * * - 7.84 :k -3.29"" 4.84 1: *X: 8.412:1: " -13.37""" -9.08""" 17.10"1: " -16.67""" 15,88;k:k * -15.13""" *P < 0.05. **P < 0.01.. **.XP < 0.001. "'Not significant. without being substantively important ( < 0.25 years). Mandibular incisor ages, for example, showed no appreciable differences from corresponding premolar ages. The first and second premolar test revealed consistency in ages assigned to them. Minor differences were generally of little consequence in the analysis of forensic or archaeological cases. Of note, however, were differences of greater magnitude. Maxillary incisor ages were 0.5 to 1.1years advanced relative to both premolars. Mandibular canines were assigned younger ages by 0.2-0.6 years as were the first molars. Second molars were ahead of the premolars by 0.6 to 0.8 years. Third molars were advanced by more than 2.0-2.3 years. This directional trend was corroborated by comparison of dental ages of first and second, and second and third molars. Distal molars were assigned older ages. DISCUSSION Accurate assessment of chronological ages of preadult skeletal remains is important in many fields of investigation, including medicolegal and skeletal biology research. Whenever possible, ages are determined by examination of the dentition with usual reference to standards for white children. Normative data are not available for most other populations. This lack of information represents a potential source of error when standards for one population are, out of necessity, applied to another (Merchant and Ubelaker, 1977). This research has defined one problem encountered with application of the Moorrees et al. (1963) standards to Indian children. Ages assigned to different teeth of the same individual often vary. As a result, the task of skeleton age determination is complicated because of differing dental age assessments for the same subadult. Aging a n Arikara child by the third molars, for instance, on average results in a n age assignment older by more than 2 years than a n estimate from the premolars or mandibular incisors. This difference is large for certain types of studies (e.g., long bone growth) that are normally based on yearly increments. The Arikara pattern of variation was determined by means of within individual comparisons. Application to archaeological samples was permissible because knowledge of chronological ages was not required. The Moorrees et al. (1963) standards simply provided a baseline for analysis by describing rates and timing of development for Ameri- 470 D.W. OWSLEY AND R.L. JANTZ can whites. Resulting nonrandom age assessment differences presumably reflect population variation in tooth calcification schedules. If these standards were applied to another American white series, between tooth differences might occur, due to variation among groups in relative calcification rates. But the differences within whites should be less than when the standards are applied to nonwhite groups. Application to a nonwhite sample produces patterns such as the one observed. The developmental timing of specific teeth appeared advanced or delayed relative to the others, as older or younger ages were assigned. Of particular note were the older ages given to posterior molars. Such results seem compatible with previous studies of living children that document advanced eruption timing in American Indians or other nonwhite populations for second and third molars (Dahlberg and Menegaz-Bock, 1958;Fanning, 1962; Friedlaender and Bailit, 1969). In summary, we have reported on a developmental process that varies in its timing relative to American whites. Pairwise contrasts of dental ages for various teeth revealed systematic differences. Some of the differences were sufficiently large that they could complicate the process of age assessment. Under these circumstances, a practical solution toward achieving consistency in age determinations would be to emphasize observations for selected subsets of teeth. We, for example, place greatest emphasis on premolar ratings in ongoing demographic and growth studies. At the very least, it is important to be aware of the types of differences that exist. ACKNOWLEDGMENTS Special thanks are given to Drs. William Bass and Douglas Ubelaker for permission to examine skeletal material recovered under their direction. Excavation of the Plains skeletal material was made possible by grants from the National Science Foundation (GS 837, GS 1653, GS 2717) and the National Geographic Society (699, 912). Data recovery was supported by grants from the Southern Regional Education Board and the National Science Foundation (BNS-8102650). Valuable assistance was provided by Dr. P. Willey, Cleone Hawkinson, and Steve Symes. Dr. Reuben Pelot kindly made available his dental x-ray facilities. 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