Prevalence and Age at Development of Enamel Hypoplasias in Mexican Children
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 72:7-19 (1987)
Prevalence and Age at Development of Enamel Hypoplasias in Mexican Children
ALAN H. GOODMAN, LINDSAY H. ALLEN, GABRIELA P. HERNANDEZ, ALICIA AMADOR, LUIS V. ARRIOLA, ADOLFO CHAVEZ, AND GRETEL H. PELT0 Natural Sciences, Hampshire College, Amherst, Massachusetts 01002 (A.H.G., L. VA.J; Department of Nutritional Sciences, University of Connecticut, Storm, Connecticut 06268 (A. H. G., L. H.A., G.H.P.);Instituto National de la Nutricidn, Division de Nutricirin de Comrnunidad Tlalpan, Mexico D.F, Mexico 14000 (G.RH., A.A.,A. C.) KEY WORDS Dentition, Nutrition, Neonatal and infancy stress, Enamel hypoplasis, Mexico
ABSTRACT Enamel hypoplasias, deficiencies in enamel thickness resul- ting from disturbances during the secretory phase of enamel development, are generally believed to result from nonspecific metabolic and nutritional disrup- tions. However, data are scarce on the prevalence and chronological distribu- tion of hypoplasias in populations experiencing mild to moderate malnutrition. The purpose of this article is to present baseline data on the prevalences and chronological distributions of enamel hypoplasias, by sex and for all deciduous and permanent anterior teeth, in 300 5 to 15-year-old rural Mexican children. Identification of hypoplasias was aided by comparison to a published stan- dard (Federation Dentaire Internationale: Int. Dent. J. 32(2):159-167, 1982). The location of defects, by transverse sixths of tooth crowns, was used to construct distributions of defects by age at development. One or more hypoplasias were detected in 46.7% (95% CI= 40.9-52.5%) of children. Among the unworn and completely erupted teeth, the highest preva- lence of defects was found on the permanent maxillary central incisors (44.4% with one or more hypoplasias), followed by the permanent maxillary canine (28.0%) and the remaining permanent teeth (26.2 to 22.2%) Only 6.1% of the completely erupted and unworn deciduous teeth were hypoplastic. The preva- lence of enamel defects on the permanent teeth was up to tenfold greater than that found in studies of less marginal populations that used the FDI method. The prevalence of defects in transverse zones suggests a peak frequency of' hypoplasias during the second and third years for the permanent teeth, corre- sponding to the age at weaning in this group. In the deciduous teeth, a smaller peak occurs between 30 and 40 weeks post gestation. The frequency of defects after three years of age is slightly higher in females than males, suggesting a sex difference in access to critical resources.
Dental enamel hypoplasias have long been tious agents (Kreshover et al., 1953, 1954), considered to result from periods of general and under- and overnutrition (Becks and physiological disruption (Kreshover, 1960) Furata, 19% Mellanby, 1929; Wolbach and and to reflect the chronological pattern of How, 19331, may cause enamel defects. stress during periods of enamel development The applicability of tbw studies to hu- (Sarnat and Schour, 1941). Laboratory re- mans is supported by the rewq of early search designed to induce defects in experi- ______mental animals has demonstrated that a Received February 6, 1986, accepted May 29,1986 wide variety of noxious stimuli, including Scientific contrlbutlon No 1162, Agrlcultural Experlrnent Sta fever (Kreshover and Clough, 19531, infec- tion, University of Connecticut. Storrs, CT 06268
0 1987 ALAN R. LISS, INC. 8 A.H. GOODMAN ET AL. clinical studies on the association between 1961), conclude that “further studies of its enamel defects and diseases in utero and dur- etiology and public health consequences seem ing infancy (Evans, 1947; Grahnen and Se- overdue” (1971:893). However, we are aware lander, 1954). In summarizing the results of of only one study published after 1974 on these early studies, Kreshover (1960:166) enamel defects in a marginal population. states that This study (Sawyer and Kwoku, 1985) of 45 malnourished children supports the results ample clinical and experimental of Sweeney et al. (1971). evidence exists to suggest that de- While a handful of studies exist on the velopmental tooth disturbances prevalence of enamel defects in marginal are generally nonspecific in na- populations, it is rare to find studies of the ture and can be related to a wide age at development or chronology of enamel variety of systemic disturbances, defects in any group. The first chronology of any of which, depending upon enamel defects was constructed by Sarnat their degree of severity and de- and Schour (1941), based on 60 children from gree of tissue response, might re- the greater Chicago area. They found that sult in defective enamel... . two thirds of defects developed during the first year and all but 2% of the remaining This conclusion is supported by more re- defects developed after 35 months. Since this cent reviews of the epidemiology of dental time, analyses of enamel hypoplasias in per- enamel defects (Cutress and Suckling, 1982; manent teeth of skeletal series have estab- Pindborg, 1982). Cutress and Suckling (1982) lished peak frequencies of defects between 2 note that nearly 100 factors have now been and 5 years of age (Goodman et al., 1984; reported to be associated with enamel de- Schulz and McHenry, 1975; Swardstedt, fects. Since a wide variety of insults may 1966), and Cook and Buikstra (1979) and cause hypopiastic defects and their appear- Blakey and Armelagos (1985) have showed ance seems to be unrelated to the type of that enamel defects of deciduous teeth in pre- causal agent (Suckling and Thurley, 1984), historic Amerindians tend to occur during enamel hypoplasias are best considered to be the third trimester and perinatally. We are nonspecific indicators of metabolic and nutri- aware of only one description of the chronol- tional disruption (Cutress and Suckling, ogy of defects in contemporary populations. 1982; Guita, 1984; Pinborg, 1982; Shafer et In a pilot study of Jordanian children from al., 1983; Yaeger, 1980). two villages and a nomadic group, Alcorn Although enamel defects are generally and Goodman (1985) found a peak period of agreed to reflect a period of metabolic andor hypoplastic defects between 1 and 3 years of nutritional disruption, few studies have been age. designed to assess the utility of enamel de- The decline in studies of enamel defects in fects as supplemental indicators of adverse marginal populations may be attributed to a living conditions. In the 1960s and early series of methodological problems and an in- 1970s a series of investigators noted high adequate understanding of intratooth varia- frequencies of enamel hypoplasias and other tions in susceptibility to defects. Fortunately, enamel defects in populations from underde- three issues that had not been addressed in veloped regions (Arkle, 1962; Baume and the 1970s have now been resolved, at least to Meyer, 1966; Enwonwu, 1973; Infante, 1974; a degree: 1)establishment of a replicable ty- Infante and Gillespie, 1974; Moller et al., pology of enamel defects, 2) establishment of 1972; Sweeney and Guzman, 1966; Sweeney a method for assessing the age of individuals et al., 1969, 1971). For example, Sweeney et at the time of development of defects, and 3) al. (1971) noted that 73% of Guatemalan chil- development of understanding of the degree dren with third-degree malnutrition and 43% of differential susceptibility of teeth to de- of children with second-degree malnutrilion fects and the role of these differences in ex- had hypoplasias in enamel formed prior to plaining previous research findings. the diagnosis of malniitritlon. Jelliffe and In 1977 a working group of the Federation Jelliffe, in commenting on the studies of Dentaire Internationale (FDD proposed a sys- Sweeney nn\l others and citing their own data tem for the coding of dental defects suitable on pllamel hypoplasias and circular caries for epidemiological study CFDI, 1982). The (hypoplastic defects with caries formation at key feature of this report is the inclusion of the site of the defect) in the Caribbean (Jel- a series of high quality color prints of dental liffe and Jelliffe, 1961; Jelliffe et al. 1954, defects to be used as standards (FDI, ENAMEL HYPOPLASIAS IN MEXICAN CHILDREN 9
1982:162-163).The authors of this report note fects. Based on recent advances in our under- that the lack of a well-defined and accepted standing of these issues, the potential use of classification of defects has inhibited both enamel defects in studies of marginal groups the comparability and replicability of re- should be reconsidered. sults. Two epidemiological studies of dental In this article we present results of a study defects using FDI coding have included in- of the prevalence and time of development of traobserver reliability estimates. Murray et enamel defects in children from five commu- al. (1984) noted an 82% agreement in the nities in the Solis Valley, Mexico. The spe- recording of opacities, and Suckling and cific purposes are 1) to test the interobserver Pearce (1984) and noted a 95% agreement on and intraobserver reliability of these meth- the presence of a defect of any type. ods in a field situation, 2) to establish the Establishing the age of an individual at the frequency of defects in children by sex and time of defect development requires the use toothtype, 3) to establish the age of these of a tooth development standard and a children at time of defect development, and method for locating defects on tooth crowns. 4) to consider the meaning of the above data For most purposes, the calcification standard in relationship to preliminary data on the of Massler et al. (1941) has been used. The current health and anthropometric status of location of defects in skeletal samples has these children and the socioeconomic level of been achieved by measurement of the dis- their families and villages. tance of a defect from a landmark such as the cementoenamel junction. Such a method, however, is impractical in epidemiological MATERIALS AND METHODS studies of living subjects. In a pilot study with low-birthweight in- The sample consists of 300 Ladino chil- fants, it was noted that a trained observer dren, 5 to 15 years old, from five communi- could reliably locate defects by transverse ties in the Solis Valley, Mexico. These sixths of tooth crowns without use of a mea- communities are being studied by the Collab- orative Research Support Program (CRSP) surement device (Goodman, unpublished ob- marginal malnutrition and function project. i servations). Division of crowns into sixths yields chronological zones of approximately The Solis Valley is located approximately 170 2 to 3 months duration in the deciduous an- km northwest of Mexico City. These commu- terior dentition and approximately 7 to 12 nities were selected by the CRSP because months duration in the permanent anterior they met the following criteria: Previous re- dentition. search in these agricultural communities in- Finally, Goodman and Armelagos (1985a,b) dicated that they would be receptive to an have noted up to eightfold differences in the intensive research effort, diets were rela- prevalence of enamel hypoplasias among dif- tively stable, outmigration was minimal, and ferent teeth types. It is therefore very likely a diversity of economic and nutritional sta- that this source of variation has confounded tus existed. many prior studies and confused comparison The sample was derived from a list of fam- of studies that relied on dissimilar teeth. This ilies who were directly involved in the CRSP source of variation may be accounted for by project by virtue of their having a “target” presenting tooth-specific rates. school-aged child (7 to 9 years old). Each of In summary, a review of the literature sug- these children is followed intensively for a 1- gests that such defects have great potential year period, during which measurements are as indicators of stress during development made of health, anthropometry, food intake, and that they may provide a uni uely time- psychosocial and behavioral development, specific indication of stress. Stu1 ies- the and socioeconomic and environmental condi- 1960s and early 1970s have established that- tions. Selection of target individuals ensured these defects are frequent in marginal popu- tlio+vailability of a wide array of supple- lations and often anteceded the clinical ap- mental chta for later comparison with the pearance of malnutrition. However, further dental data. Additional measures were made study of the utility of these defects may have on the family unit kg., qocial and economic been hindered by a lack of a reliable typology and method for estimating the age at devel- opment of these defects and a poor under- .. ‘Supported in part by Collaborative Research Support Grant standing of the confounding effects of No. Dan 1309-G 55-1070-00 from the United States Agency for intratooth differences in susceptibility to de- International Development 10 A.H. GOODMAN ET AL conditions) or were performed on other fam- gingival zone. Since many permanent teeth ily members (e.g., morbidity and anthropo- had not completely erupted, a portion of the metry) at less frequent intervals. Thus, the gingival end of these teeth was frequently list of potential candidates for the present missing. Similarly, many teeth exhibited se- study included both CRSP “target” individ- vere attrition, thus eliminating a portion of uals and their school-aged siblings. the incisal border. In these cases one or more The recruitment of students and the obser- zones was recorded as missing. If any portion vation and recording of dental conditions of a zone was judged to be missing, the entire were performed at the five community zone was scored as missing. schools. Students were recruited from the Defects were recorded by either an anthro- above list by the headmasters of each school. pologist (A.H.G.) or a dentist (G.P.H.). After The original list contained 474 possible stu- a training and standardization period, in- dents (112 “target” children and 362 sib- traobserver and interobserver reliability lings). Target children were called first and were assessed. Reliability data are presented 98 (87.5%)were found and examined. At the on the number of enamel zones lost to study one school where we were able to see all because of incomplete eruption and attrition, listed children, 74 out of 81 (91.3%) were ex- presence or absence of enamel hypoplasias, amined. The high rate of matching of chil- and location of enamel hypoplasias. dren on our list to those attending school In this study we consider two types of hy- lends support to the community social work- poplastic defects: pitting hypoplasias (FDI ers’ view that almost all school-aged children type 3) and horizontal grooves or lines (com- attend their community schools. A possible bined FDI types 4 and 6). Type 6 defects bias exists in this sample toward healthier (missing enamel) have been combined with children (attending schools on the study days) type 4 defects (grooves) because they could and from better-off families (able to keep not be reliably distinguished. Enamel hypo- their children in school). However, given the calcifications (FDI defect types 1 and 2) will high response rate, it is likely that this bias be considered elsewhere. Type 5 defects (ver- is minimal. tical grooves) have not been considered be- Defects were recorded on the anterior den- cause of low reliability (this is the only defect tition (upper and lower canines and incisors) for which the FDI has not provided a because these teeth are the easiest to exam- standard). ine, have been most often studied by other The frequency of hypoplastic defects by researchers, and have relatively high defect transverse zone is converted to ages at time rates (Cutress and Suckling, 1982; Goodman of development of enamel defects. This pro- and Armelagos, 1985b). As most individuals cedure involves estimating times of initia- in this sample had mixed dentitions, data tion and ending of enamel crown calcification have been recorded for both deciduous and and then dividing the crown into six equal- permanent anterior teeth, depending on width zones. The calcification chronology is which were present. Information on defects based on the data from Massler et al. (1941) was derived from the most complete side. for the permanent teeth and on Lunt and The method used for identification and re- Law’s revision (1974) of Massler and cowork- cording of enamel defects is a modification of ers’ data (1941) for the deciduous dentition. the FDI method (FDI, 1982). The FDI sug- Thus, for example, the permanent mandibu- gests the recording of the following types of lar incisors are estimated to begin crown cal- defects: 1) opacity, whitekream; 2) opacity, cification at birth and end crown calcification yellowhrown; 3) hypoplasia, pits; 4) hypopla- at 4 years of age. The 48-month period of sia, horizontal grooves; 5) hypoplasia, verti- development is then divided into six time cal grooves; 6) hypoplasia, missing enamel; periods of8 months, with midpoints at 4, 12, 7) discolored enamel, not associated with 20, 28, 36, and 44 months. Finally, sex-spe- opacity; 8) other defects; and 9) combinaclons cific frequencies of defects are presented for of defects. Before recording we modified the all teeth and by developmental zones of per- FDI method so that combination defects were manent incisors. described in terms of the specific type of de- fects that they incorporated. The FDI method was further modified to RESULTS take into account the time of development of Interobserver and intrmbserver reliability defects. The anterior tooth crowns were di- Dental defect data were scored by both ob- vided into six transverse zones of approxi- servers for the same 30 individuals, yielding mately equal width, from an incisal to a 177 teeth for study. Ten individuals, with a ENAMEL HYPOPLASIAS IN MEXICAN CHILDREN 11 total of 59 teeth, were observed twice by the While the prevalence of hypoplastic defects same investigator (A.H.G.) per child is high, there is great variation in In the interobserver study, there was prevalence by tooth (Table 2). Among the agreement on the precise number of zones permanent teeth, the highest prevalence of having attrition or being unerupted in 145 of hypoplastic pits, hypopiastic -grooves, and 177 (81.9%) teeth (Table 1). A disagreement combined hvpodastic defects is found on the on one zone was found in 29 (16.4%), and a maxillary ;e-n
TABLE 1. Inter- and intraobserver agreement in number of zones present (based on variation in agreement on the degree of attrition and eruption), location of enamel hypoplasias, and presence or absence of enamel hypoplasias Interobserver Intraobserver Agree me n t No. % No. % No. of zones present 145 81.9 51 86.4 Location of enamel 30 81.1 16 88.9 hypoplasia Presence or absence of 143 80.8 51 86.4 enamel hypoplasia
TABLE 2. The prevalence (%) of enamel hypoplasias by tooth for teeth with all zones present and teeth with one or more zones present Tvoe No. 3 4-5 3-5 Complete teeth Perm. max. I1 162 8.6 37.7 44.4 Perm. max. I2 65 6.2 20.0 26.2 Perm. max. canine 25 0.0 28.0 28.0 Perm. man. I1 206 4.9 19.4 23.3 Perm. man. I2 124 4.0 21.0 24.2 Perm. man. canine 36 2.8 19.4 22.2 One or more zones present Perm. max. I1 249 8.4 34.5 40.6 Perm. max. I2 190 6.8 16.8 23.7 Perm. max. canine 61 1.6 18.0 19.7 Perm. man. I1 279 5.4 16.1 20.8 Perm. man. I2 238 2.5 14.3 16.4 Perm. man. canine 84 2.3 13.1 14.3 Decid. max. I1 50 8.0 6.0 14.0 Decid. max. I2 89 3.4 3.4 6.7 Decid. max. canine 228 2.6 1.7 3.9 Decid. man. I1 19 0.0 0.0 0.0 Decid. man. I2 56 0.0 0.0 0.0 Decid. man. canine 210 2.3 0.5 2.9 Type 3, hypoplastic pits; type 4-5, hypoplastic grooves or missing enamel. Note: The frequency of type 3 plus types 4 and 5 defects may be greater than the frequency of combined defects because both types may be present on the same tooth.
TABLE 3. Prevalence (%) of enamel hypoplasias by developmental zones for the permanent anterior teeth Developmental zones Permanent 1 2 3 4 5 6 Maxillary I1 1.37 27.1 28.3 27.3 13.0 11.1 (249) (247) (24.1) (238) (2 14) (162) I2 10.0 14.9 15.7 11.8 6.3 7.5 (189) (18W (184) (161) (127) (67) 16.1 Canine 14.3 20.8 18.3 17.5 23.3 (56) (56) (53) (49) (40) (30) Mandibular I1 6.9 14.1 12.4 9.2 4.5 3.8 (276) (279) (276) (273) (246) (211) 12 8.4 13.0 11.2 8.3 4.8 6.5 (238) (237) (233) (217) (166) (124) Canine 12.0 11.1 14.6 13.4 13.2 12.8 (83) (81) (75) (67) (53) (39)- Values in parentheses are numbers of teeth. ENAMEL HYPOPLASIAS IN MEXICAN CHILDREN 13 30 -* 28 ------* 26 - I \, *----*Mxll I \ O----OMx12 24 - I \ * ...... * Mn I1 h I 22 / 0 ...... 0 Mn 12 K - '\ ./ I m 20 - \ c I \ u I c 18 - 8 L 16 - x 14 - C 3 12 - U -* e 10 - L 8- ,-o 6- 4-
2/ I I I I I I I I I I 0 10 20 30 40 50 developmental age (months) Fig. 1. The chronological distribution of enamel hypoplasias on the permanent dentition. MxI1, maxillary central incisor; MxI2 maxillary lateral incisor. Data are based on frequencies of enamel defects by transverse sixths CTable 3). second and third years, and lower rates again ception of the mandibular central incisor, after 36 months. where the male frequency is 3%greater (24.8 Among these teeth the highest frequency v 21.8%; = -x2 0.25; Table 5). The female of enamel hypoplasias at all ages is found in rate is over twice as high (33.3 v 15.3%) on the maxillary central incisor. The other three the mandibular lateral incisor (x2= 4.90, P incisors have comparable frequencies of =0.03). enamel hypoplasias, with rates equivalent to Based on an analysis of sex differences in about one half of the maxillary central inci- the rate of enamel hypoplasias by develop- sor rate (Fig. 1). mental zone (Table 61, it is unlikely that the increased frequency of defects in females is Age at development of defects: Deciduous due to differential attrition or eruption. Fe- dentition male rates are significantly greater than Low frequencies (less than 10%)of enamel male rates (P < 0.05) for six of 24 zones, four hypoplasias are generally found per trans- on the lateral mandibular incisor and two on verse zone in the deciduous anterior teeth the lateral maxillary incisor. Females re- (Table 4). The highest frequency of hypopla- main at high risk for enamel defects in the sias is found in the fourth zone of the maxil- third year, while the male rate drops by this lary central incisor (9.4%). No defects were time. As an example of this phenomenon, the found in 18 of 54 zones (33.3%),including all male rate of hypoplasia falls to below 10%at of the first developing (incisal) zones of all all time periods in the mandibular lateral teeth. incisor. However, the female rate hovers near The age at development of enamel hypopla- or above 10% for all zones. Differences are sias has been plotted for four deciduous teeth, significant during the first zone (birth to 8 maxillary lateral and central incisors, and months), third zone (16 to 24 months), and both canines (Fig. 2). The highest frequency fifth and sixth zones (32 to 48 months). of enamel hypoplasias occurs during the last half of pregnancy. Moderately high frequen- cies are found during the middle trimester DISCUSSION and around birth (or 42 weeks gestation), Reliability and methodological implications while low frequencies are found postnatally. If there is a high prevalence of premature This study of dental deft- in a mild to births then the peak in the maxillary central moderately undernourished pOpUIttt;on in- incisor might be near the actual time of birth. corporates several unique aspects: 1) enatrk defects were assessed in a field situation in a Male-female differences nonwestern country using the FDI standard, Females have a higher frequency of hypo- 2) tooth-specific prevalence rates were col- plasias on all permanent teeth, with the ex- lected for a population experiencing mild to 14 A H GOODMAN ET AL
TABLE 4 Prevalence (%I of enaniel hypoplascas by developmental zones for the deciduous antenor teeth Developmental zones Deciduous 1 2 3 4 5 6 Maxillary I1 0.0 6.3 3.1 9.4 0.0 0.0 (9) (16) (32) (43) (50) (50) 12 0.0 4.5 2.0 2.6 3.4 4.4 (5) (22) (51) (78) (88) (89) Canine 0.0 1.9 2.0 1.7 1.7 0.9 (3) (53) (191) (225) (228) (228) Mandibular I1 0.0 0.0 0.0 0.0 0.0 0.0 (5) (10) (17) (18) (18) (18) I2 0.0 0.0 0.0 0.0 0.0 0.0 (4) (17) (44) (55) (55) (55) Canine 0.0 1.2 1.5 1.0 0.5 0.5 (13) (83) (194) (209) (210) (208) Values in parentheses are numbers of teeth.
-30 -10 10 30 developmental age (weeks from birth) Fig. 2. The chronological distribution of enamal hypoplasias on the deciduous dentition. MxI1, maxillary central incisor; MxI2, maxillary lateral incisor; MxC, maxillary canine; MnC, mandibu- lar canine. Data are oased on frequencies of enamel defects by transverse sixths (Table 4). Birth is based on those carried to full term.
TABLE 5. Comparison of the frequency of enamel hypoplasias found on thc permanent dentition of males and females Males Femdles Sample % Sample % size Defects size Defects x2 P Max. I1 81 42.0 81 46.9 0.40 NS Max. I2 31 19.4 34 33.4 1.42 NS Max. cilnille 8 12.5 17 35.3 1.40 NS Man. I1 105 24.8 101 21.8 0.25 NS Man. I2 59 15.3 65 33.3 4.90 0.03 Man. canine 12 16.7 24 25.0 0.32 NS x2 values are without continuity correction; P values are two-tailed. ENAMEL HYPOPLASIAS IN MEXICAN CHILDREN 15
TABLE 6. Comparison of the frequency of enamel hypoplasias by developmental zones on the permanent incisors of males and females Males Females Tooth and Sample % Sample % zone size Defects size Defects x2 P Max. I1 1 121 11.6 128 15.6 0.86 NS 2 121 24.8 126 29.4 0.65 NS 3 118 26.3 126 30.2 0.45 NS 4 117 27.4 121 27.3 0.01 NS 5 104 13.5 110 12.7 0.02 NS 6 81 7.4 81 14.8 2.25 NS Max. I2 1 89 7.9 100 12.0 0.89 NS 2 89 11.2 99 18.2 1.78 NS 3 87 12.6 97 18.6 1.20 NS 4 77 10.4 84 13.1 0.28 NS 5 62 1.6 65 10.8 4.51 0.03 6 33 0.0 34 14.7 5.24 0.02 Man. I1 1 136 4.4 140 9.3 2.56 NS 2 137 15.3 142 12.7 0.40 NS 3 137 11.7 139 12.9 0.10 NS 4 136 8.1 137 10.2 0.37 NS 5 122 3.3 124 5.6 0.80 NS 6 106 1.9 105 5.7 2.12 NS Man. I2 1 117 4.3 121 12.4 5.10 0.02 2 116 9.5 121 16.5 2.58 0.10 3 114 6.1 119 16.0 5.67 0.01 4 106 6.6 111 9.9 0.78 NS 5 82 1.2 84 8.3 4.58 0.03 6 59 1.7 65 10.8 4.22 0.04 i’ values are uncorrected; P values are two-tailed moderate malnutrition, 3) individual’s ages liability. Furthermore, this standard may be at time of development of defects were as- used by someone trained in dentistry, but sessed in a field situation, and 4) a training with only limited (less than 2 weeks) training session has been adopted to improve intraob- in the evaluation of dental defects. One po- server and interobserver reliability. tential use of enamel hypoplasias is that they The FDI typology of defects showed rela- may provide a relatively quick and inexpen- tively high intraobserver agreement in two sive indication of the degree of stress experi- other studies, both involving children stud- enced during tooth development. However, ied in schools with the aid of a dental chair this potential will not be reached, and a large and artificial lights (Murray et al., 1984; body of comparative data will be slow to de- Suckling and Pearce, 1984). Our intra- and velop, if the method can not be learned in a interobserver agreement scores for identifi- short amount of time. cation of hypoplastic defects suggest that Relatively high agreement was reached in these defects may be scored under most field both the intra- and interobserver studies on conditions with only minimal dental equip- the number of zones present for assessment ment (probes, mirrors), a chair, and natural of defects and the location of defects. The lighting. high interobserver rates, which almost equal Interobserver agreement on the presence the intraobserver rates, were reached only or absence of an enamel hypoplasia was after an initial training period, again sug- reached on 80.8%of 177 teeth (Table 1).This gesting the importance of adequate training. rate of agreement is comparable with the To assess an individual’s age at the time of intraobserver rate found in this study (86.4%) defect development in Jordanian children, and rates noted by Murray et al. (1984) and Alcorn and Goodman (1985) noted the degree Suckling and Pearce (1984) for all enamel of attrition and gingival emergence in the defects. These results suggest that the publi- field and then took photographs of the ante- cation of the FDI standard has increased re- rior teeth. Defects were identified from pho- 16 A.H. GOODMAN ET AL tographs, and chronologies were constructed The frequency of enamel defects by measurement of the relative distance of defects from the gingiva and occlusal surface. The 46.7% prevalence of enamel hypopla- This technique, however, is limited, since ex- sias in this study is greater than that found tensive time, expense, and expertise is re- in four of five other studies that have used quired to take adequate photographs of a the FDI method. Enamel hypoplasia rates of large sample. In general, the high degree of less than 5% have been noted by Murray et agreement on the location of defects by trans- al. (1984) in a study of English children, by verse sixths of enamel crowns suggests that De Liefde and Herbison (1985) in New Zea- this may be the method of choice in situa- land children, and by Cutress et al. (1985) in tions that do not allow for more objective another study of New Zealand children. In a techniques. third study in New Zealand, Cutress and It is difficult to estimate the variation be- Pierce (1984) report that less than 10% of tween the estimation of an individual’s ages children have either missing enamel, hypo- at the times of development of defects and plastic pits, or horizontal lines. On the other his chronological ages. The standard of Mas- hand, King and Brook (1984) note that 63.9% sler and coworkers has been justified as the of dental students in Hong Kong have an best available for studies of most anthropol- enamel hypoplasia on at least one tooth. In- ogical populations (Goodman and Armela- terestingly, no individual had a defect on gos, 1985a). Both individual and population more than seven teeth, suggesting local and variations surely exist, especially under ad- nonsystemic causes. verse living conditions. However, these vari- Variation in prevalence of enamel hypopla- ations may be relatively minor considering sias among these studies suggests the need the high degree of genetic control over the to consider differences in environmental and time of tooth calcification (Garn et al., 1965; genetic factors that may account for these Garn, 1977). Longitudinal studies of dental rate differences. The high rate of hypoplasias calcification and defect development under found in our study is unlikely to be due to adverse living conditions will certainly help high fluoride concentrations in water. Two to improve the validity of methods for water samples were taken from the source estimating an individual’s age at defect serving the valley and were found to contain formation. 0.20 ppm fluoride (Dr. N. Tinnanoff, personal The recoding of defects by location on tooth communication), well below the level consid- crowns is the most important innovation of ered to cause enamel defects. It is also un- this study. The primary purpose in collecting likely that genetic factors, local traumas, 01 data in this manner has been to estimate the drug toxicities are important causes- The individual’s age at development of defects. high rate of hypoplastic defects found in this mile this procedure is not enor-free, it may region suggests the need to test for the exis- provide essential data. First, taking advan- tence of a gradient of increased frequency of tage of the chronological nature of dental hYPoPlasias with decreased dietary adequacy defects provides a time-specific indication of and increased infant-childhood stress. stress. In many situations this may be the The increased prevalence of enamel defects only method for estimation of the degree of on the permanent central incisors (Table 2) stress by individual’s age. Second, in a lon- supports the results of prior studies of the gitudinal study, location information may pattern of defects among permanent teeth help in establishing both the cause of defects (Goodman and Armelagos, 1985b; Cutress and the timing of dental calcification. Third, and Suckling, 1982). These results specifi- location information can help in understand- cally support the view that teeth that are ing prevalence differences among teeth. For under greatest genetic control, such as max- example, higher defect rates in a canine ver- illary central incisors, may be the most sus- sus an incisor may be due to defect formation ceptibile to enamel hypoplasias (Goodman after the incisor crown has formed. This and Armelagos, 1985a,b). method has been presented as a first effort to The implication of these intratooth varia- provide information on the chronology of de- tions in susceptibility to defects for future fects in a less-developed country. It is ex- studies is that tooth-specific rates must be pected that future studies will refine this reported. Comparisons of results from stud- procedure. ies based on different teeth are highly prob- ENAMEL HYPOPLASIAS IN MEXICAN CHILDREN 17 lematic. Whole mouth or individual rates, 12 and 36 months (Fig. 2). This peak period based on some combination of teeth, are is earlier than that which has been found in equally difficult to interpret. Finally, differ- studies of archaeological populations (Good- ences within studies in the complement of man et al., 1984; Schulz and McHenry, 1975; teeth studied and their degree of attrition Swardstedt, 1966) and occurs after the first and eruption may influence rates and con- year, which has long been proposed to be the found within-study comparisons. time during which defects are most likely to The rate of defects on deciduous teeth is occur (Sarnat and Schour, 1941). The peak considerably lower than the rate of defects period of hypoplasias is in accord with the found on permanent teeth (Table 3). Among Jordanian study of Alcorn and Goodman deciduous teeth, the maxillary central inci- (1985). The high rate of hypoplasias during sor is most often hypoplastic. A similar pat- the second and third years suggests in- tern of defects has been found by both creased susceptibility with the loss of mater- Funakoshi et al. (1981) and Johnsen et al. nal antibodies from the decline and ending (1984) in studies of low-birthweight infants. of breastfeeding. Women in the Solis Valley This increased susceptibility might also have usually wean between the first and second been long-realized by others as this tooth has years. Future studies of the chronology of been the one most frequently included in defects in individuals now being studied dur- studies of dental defects on primary teeth ing weaning may help to clarify the relation- (e.g., Infante, 1974; Infante and Gillespie, ship between weaning, infant stress, and 1974; Sweeney and Guzman, 1966; Sweeney dental defect formation. et al., 1969, 1971). Finally, the increased fre- The peak for enamel hypoplasias in the quency of defects on the deciduous anteced- deciduous dentition occurs during the last ent of the maxillary central incisor indicates trimester and near birth (Fig. 2). This peak that the field of genetic control over develop- is near in timing to the peak frequency of ment of the deciduous teeth is similar to the hypoplastic defects found by Blakey and Ar- permanent dentition’s field. melagos (1985). Dental defects have a long Comparison of the prevalence of hypopla- history of association with the birth process sias on the deciduous maxillary central inci- (Kronfield and Schour, 1939; Via and sor with the rates and description of defects Churchill, 1959). reported by Infante (1974;Infante and Gilles- pie, 1974) and Sweeney (Sweeney and Guz- Male- female differences man, 1966; Sweeney et al., 1969, 1971) A review of the literature on sex differ- suggests that the defects found in this study ences in the frequency of enamel defects are not as prevalent or as severe as those failed to reveal a consistent pattern. No sig- found in either Apache or Highland Guate- nificant sex differences in total defects were malan children. These differences may be due found by Sucking and Pearce (1984) or for to better pre- and perinatal conditions for linear hypoplasias by Infante and Gillespie Mexican children. (1974). However, Arkle (1962) noted a higher Transverse groove hypoplasias are far more frequency of opacities and hypoplasias among common than pitting defects. However, this- Tasmanian girls than boys, while El-Najar pattern was not consistent between denti- et al. (1978) identified more hypoplastic de- tions. Permanent teeth had more hypoplastic fects among males than females in the Ham- grooves but deciduous teeth had slightly mon-Todd osteological collection (comprised more pitting defects. The cause of these pat- of skeletons of lower-class individuals from tern differences is unknown. However, if hy- the Cleveland area who died during the early poplastic grooves are the result of disruptions 1900s). in secretion of a complete front of amelo- In this study, females had a higher rate of blasts and pitting defects are the results of enamel hypoplasias. Females were at a disruptions to sporadic sections of the secre- slightly increased risk for hypoplasias dur- tory front, then hypoplastic grooves may in- ing the first 2 years and at a particularly dicate a more severe stress. high relative risk of defects during the third and fourth years. After 2 years, male rates Age at development of defects dropped while female rates remained ele- In the permanent dentition, enamel hypo- vated. Data now being analyzed on the nutri- plasias appear to develop most often between tional, anthropometric, and health status of 18 A.H. GOODMAN ET AL. children in these communities may help to ACKNOWLEDGMENTS explain the meaning of this sex difference in We thank George Armelagos, University of frequency of enamel hypoplasias. At present, Massachusetts, and Sam Weinstein, Univer- these data suggest the possibility that male sity of Connecticut, for commenting on an children may be obtaining greater access to earlier version of this article. Norman Tin- basic resources such as food, shelter, and nanoff, University of Connecticut Dental health care. School, analyzed the fluoride content of the Solis Valley water supply. Edward Stanick, CONCLUSIONS University of Massachusetts, provided statis- The following conclusions are derived from tical expertise. Many members of the Solis a study of the prevalence and chronological Valley project contributed invaluable advice distribution of enamel defects in 300 children and assistance in the field. We especially from five rural agricultural communities. thank the people of the Solis Valley who par- 1. Based on the FDI method for classifica- ticipated in and encouraged this project. This tion of defects, 46.7% of children have at least project was partly supported by an NIDR one enamel hypoplasia on their anterior postdoctoral fellowship (T-32-DE07049). teeth. This high rate, relative to other stud- IJI1'EIZATURE CITED ies with similar methods o€ assessment, sug- gests that aspects of their marginal living Alcorn, MC, and Goodman, AH (19851 Dental enamel conditions might be implicated. defects among contcmporary nomadic and sedentary Jordanians. Am. J. Phys. Anthrop. fifil2):139. 2. The highest frequency of defects is found Arkle, PW (1962) Prevalence of enamel opacities and on the maxillary central incisors (44.4%).The hypoplasias in the permanent teeth of school children. increased frequency of defects on this tooth J. Dent. Res. 41131:511-512. is consistent with prior studies in suggesting Baume, LJ, and Meyer, J (1966) Dental dysplasia related a field effect controlling susceptibility to den- to malnutrition, with special reference to melanodon- tia and odontoclasia. J. Dent. Res. 455'26-741. tal defects. Tooth differences in susceptibility Becks, H, and Furata, W (1941) EKect of magnesium to defects may explain some of the inconsist- deficient diets on oral and dental tissues. 11. Changes encies in the results of prior studies. Future in enamel structure. J. Am. Dent. Assw. 28:1083-1088. studies should report tooth-specific rates. Blakey, ML and Armelagos, GJ (1985) Deciduous enamel 3. Enamel hypoplasias are relatively rare defects in prehistoric Americans from Dickson Mounds: Prenatal and postnatal stress. Am. J. Phys. Anthropol. on deciduous teeth. Most deciduous tooth de- 66:37 1-380. fects appear to have developed during the Cook, DC, and Buikstra, JE (1979) Health and differen- last trimester of pregnancy and neonatally. tial survival in prehistoric populations: Prenatal den- 4. The highest frequency of enamel hypo- tal defects. Am. J. Phys. Anthropol. 51 549-664. plasias occurs during the second and third Cutress, TW, and Suckling, GW (1982) The assessment of noncarious defects of enamel. Int. Dent. J. 32(2):117- years, suggesting a casual role for stress as- 122. sociated with weaning. Cutress, TW, Suckling, GW, Pearce, EIF, and Ball, ME 5. Females have a significant excess of (1985) Defects of tooth enamel in children in fluori- hypoplastic defects. This sex difference may dated and non-fluoridated water areas of the Auckland result from differential access to basic re- Region. N.Z. Dent. J. 81:12-19. De Liefde, B, and Herbison, GP (1985) Prevalence of sources. developmental defects of enamel and dental caries in 6. High intraobserver and interobserver re- New Zealand children receiving differing fluoride sup- liability scores suggest that training for the plementation. Comm. Dent. Oral Epidemiol. 13:164- identification and scoring of defects can be 167. El-Najjar, MY, DeSanti, MV, and Ozebek, L (1978) Prev- achieved in a relatively short period of time. alence and possible etiology of dental enamel hypopla- 7. Future studies should aim at improving sias. Am. J. Phys. Anthropol. 48:185-192. methods for the identification of defects. Most Enwonwu, CO (1973) Influence of socio-economic condi- importantly, however, efforts should be di- tions on dental development in Nigerian children. rected toward understanding the conditions Arch. Oral Biol. 18:95-107. Evans, MW (1974) Further observations on dental de- associated with and causative of enamel de- fects in infants subsequent to maternal rubella during fects. As methods for nutritional assessment pregnancy. Med. J. Aust. 1:780-785. are few and generally inexact, development Federation Dentaire lnternationale (FDI) (1982) An epi- of assessment methods should be a research demiologic index of developmental defects of dental priority. Fifteen years after Jelliffe and Jel- enamel (DDE Index). Technical Report No. 15. Int. Dent. J. 32l2i: 159-167. liffe (1971) concluded that research on the Fleiss, JL (1973) Statistical Methods for Rates and Pro- etiology and public health consequences of portions. New York John Wiley & Sons. enamel hypoplasias is overdue. Researchers Funakoshi, Y, Kushida, Y, and Hieda, T (1981) Dental are now in a position to go ahead with this observations of low birth weight infants. Pediatr. Dent. research. 3(1):21-25. ENAMEL HYPOPLASIAS IN MEXICAN CHILDREN 19
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