Article critique

Prenatal Vitamin D and Dental Caries in Infants

WHAT’S KNOWN ON THIS SUBJECT: Many young children are at risk for caries, which is the most common chronic disease of childhood. As primary teeth begin to develop in utero, prenatal influences are believed to affect the integrity of enamel and subsequent resistance to decay.

WHAT THIS STUDY ADDS: This study shows, for the first time, that maternal prenatal 25-hydroxyvitamin D levels may have an influence on the primary dentition and the development of early childhood caries. Specifically, lower levels are associated with increased risk of caries in infants.

abstract OBJECTIVES: Inadequate maternal vitamin D (assessed by using 25- hydroxyvitamin D [25OHD]) levels during pregnancy may affect tooth calcification, predisposing enamel hypoplasia and early childhood car- ies (ECC). The purpose of this study was to determine the relationship between prenatal 25OHD concentrations and dental caries among off- spring during the first year of life.

METHODS: This prospective cohort study recruited expectant mothers from an economically disadvantaged urban area. A prenatal question- naire was completed and serum sample drawn for 25OHD. Dental examinations were completed at 1 year of age while the parent/ caregiver completed a questionnaire. The examiner was blinded to mothers’ 25OHD levels. A P value # .05 was considered significant.

RESULTS: Overall, 207 women were enrolled (mean age: 19 6 5 years). The mean 25OHD level was 48 6 24 nmol/L, and 33% had deficient levels. Enamel hypoplasia was identified in 22% of infants; 23% had cavitated ECC, and 36% had ECC when white spot lesions were included in the assessment. Mothers of children with ECC had significantly lower 25OHD levels than those whose children were caries-free (41 6 20 vs 52 6 27 nmol/L; P = .05). Univariate Poisson regression analysis for the amount of untreated decay revealed an inverse relationship with maternal 25OHD. Logistic regression revealed that enamel hypoplasia (P , .001), infant age (P = .002), and lower prenatal 25OHD levels (P = .02) were significantly associated with ECC.

CONCLUSIONS: This study found that maternal prenatal 25OHD levels may have an influence on the primary dentition and the development of ECC. Pediatrics 2014;133:e1277–e1284

AUTHORS: Robert J. Schroth, DMD, MSc, PhD,a,b,c

Christopher Lavelle, DDS, PhD, DSc, MBA, FRCPath,d Robert Tate, PhD,e Sharon Bruce, BN, MA, PhD,e Ronald J. Billings, DDS, MSD,f and Michael E.K. Moffatt, MD, MSc, FRCPCc,e

Departments of aPreventive Dental Science, Faculty of Dentistry, bPediatrics and Child Health, Faculty of Medicine, dOral Biology, Faculty of Dentistry, eCommunity Health Sciences, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada; cThe Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada; fDivision of Community Dentistry and Oral Disease Prevention, Eastman Institute for Oral Health, School of Medicine and Dentistry, University of Rochester, Rochester, New York

KEY WORDS early childhood caries, enamel hypoplasia, infant, vitamin D

ABBREVIATIONS DT—decayed teeth ECC—early childhood caries S-ECC—severe early childhood caries 25OHD—25-hydroxyvitamin D

Dr Schroth was responsible for conception and design, acquisition of data, analysis and interpretation of data, drafting of the article, and revising the article critically for important intellectual content; Drs Lavelle, Tate, Bruce, and Billings were responsible for analysis and interpretation of data and revising the article critically for important intellectual content; Dr Moffatt was responsible for conception and design, analysis and interpretation of data, and revising the article critically for important intellectual content; and all authors approved the final version to be published.

www.pediatrics.org/cgi/doi/10.1542/peds.2013-2215

doi:10.1542/peds.2013-2215

Accepted for publication Jan 30, 2014

Address correspondence to Robert J. Schroth, DMD, MSc, PhD, Department of Preventive Dental Science (Faculty of Dentistry), Department of Pediatrics and Child Health (Faculty of Medicine), University of Manitoba, 507–715 McDermot Ave, Winnipeg, Manitoba, R3E 3P4. E-mail: [email protected]

PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).

Copyright © 2014 by the American Academy of Pediatrics

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.

FUNDING: Grant funding for this research was provided by the Manitoba Medical Service Foundation, the Manitoba Institute of Child Health, Dentistry Canada Fund, and the Faculty of Dentistry, University of Manitoba. Dr Schroth received postdoctoral funding from the Children’s Hospital Foundation of Manitoba and was a Canadian Institutes of Health Research Strategic Training Fellow in the Canadian Child Health Clinician Scientist Program. He presently holds a Clinical Research Professorship in Population Medicine from the Manitoba Medical Service Foundation and the Manitoba Health Research Council.

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

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Tooth decay in infants and preschool- aged children is called early childhood caries (ECC). Although dental caries is the most common chronic disease of childhood,1 it is declining in the general population. This finding, however, is not the case for certain groups such as Aboriginal children. For many at-risk groups, the rampant extent of decay exhibited is called severe early child- hood caries (S-ECC).

ECC and S-ECC are multifactorial in origin and are influenced by biomedical factors (microorganisms, diet, and tooth re- sistance) and the social determinants of health.2 Oneproposedexplanationfor the burden of S-ECC in some children is hypoplasia-associated S-ECC.3 Enamel hypoplasia results from defective amelogenesis and is clinically identi- fied by the absence of enamel and by pitting, grooves, or irregularities of enamel.4,5 These defects increase the risk of early colonization by cariogenic bacteria, resulting in caries.3,6,7 There- fore, the period when enamel forms is crucial to understanding the signifi- cance of enamel hypoplasia and risk for ECC. The primary maxillary anterior teeth begin to calcify during the second trimester (specifically, 13–17 weeks) and continue until 3 months’ post- natal.8 It is therefore important to in- vestigate possible factors that can disrupt enamel formation and increase the risk of caries.

Enamel defects have been correlated with factors ranging from genetic dis- orders to problems during prenatal and early postnatal periods.9 Vitamin D de- ficiency in utero is believed to be asso- ciated with enamel hypoplasia because ofthemetabolicinsulttoameloblasts.10–12

Vitamin D plays a central role in cal- cium and phosphorus homeostasis, which is needed for the calcification of hard tissues.13

ThepioneeringeffortsofMellanby14,15gave credence to the belief that the critical pe- riod for influencing the development of

the primary dentition is in utero. Because the duration of primary tooth calcification is short and begins during the second trimester, prenatal nutrition has a tre- mendous influence on the formation of dental tissues.16

Although some clinicians are unfamiliar with research on vitamin D in caries and enamel hypoplasia, several historical studies have reported that vitamin D supplementation may prevent caries in children.17–20 A recent meta-analysis of these studies confirmed the early findings.21 New research suggests that vitamin D plays a role in the human immune response22 and may reduce host resistance to cariogenic bacteria.

Thepurposeofthepresentstudywastotest the hypothesis of an association between lowermaternalprenatal25-hydroxyvitamin D(25OHD)statusandthepresenceofECCin the infant.

METHODS

Aprospectivecohortstudywasdesignedto investigate the association between pre- natal vitamin D concentrations and dental caries in infants in a vulnerable urban population. Participants were recruited during the second or early third trimester after providing written informed consent. The target population was expectant women presenting for prenatal care in Winnipeg, Canada (latitude 49°539N).

A serum sample was collected as part of a prenatal visit during the second or early third trimester, as the primary maxillary incisorsbegintocalcifyduringweeks13to 17 in utero and continue to do so throughoutpregnancy.Serumanalysis was conducted at Winnipeg’s Health Sciences Centre. Samples were analyzed for levels of 25OHD, total calcium, in- organic phosphorus, and alkaline phos- phatase (elevated levels indicate vitamin D insufficiency14). 25OHD, a reliable mea- sure of overall vitamin D status,23 was assessed via radioimmunoassay by using a DiaSorin kit (DiaSorin, Inc, Stillwater, MN). 25OHD concentrations ,35 nmol/L

were considered deficient and those $75 nmol/L were optimal.

Participants completed a questionnaire proctoredbytheprincipal investigator(Dr Schroth) or clinic staff. This instrument was based on a tool that assessed nutri- tional deficiencies in northern Manitoba.24

The questionnaire was modified with in- put from researchers and clinicians, in- cluding a dietitian. Information was collected on demographic characteristics (eg, age, ethnicity, education level), preg- nancy (eg, prenatal health status, parity, use of prenatal vitamins), health con- ditions, nutrition (eg, intake of milk, dairy, fish, eggs, meat), and awareness of ECC (eg, heard of ECC, older children had ECC, what causes ECC). Exposure to sunlight (eg, time spent in sunshine in summer), family composition (eg, relational status, family size), finances, and employment were also assessed.

The final component of the study was an assessmentoftheprimarydentition,with the examiner (Dr Schroth) blinded to the prenatal 25OHD level of each infant’s mother. Infants’ teeth were assessed for caries by using established recom- mendations.25 ECC and S-ECC were de- finedaccordingtorecognizeddefinitions.25

Incipient and noncavitated caries of enamel (white spot lesions) were recorded. Individual cumulative totals of the number of decayed, extracted, and filled primary teeth and cumulative totals of the number of decayed pri- mary teeth (decayed teeth [dt] score) weredetermined.Developmentaldefects of enamel were assessed according to an established index for recording enamel defects such as hypoplasia and opacities.5

A follow-up questionnaire collecting in- formation on demographic character- istics (eg, child’s gender, age), household finances, birth weight, prematurity, feeding practices (eg, breastfeeding, bottle-feeding, introduction of solids), and infant health status was admin- istered at the time of the infant’s

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examination. Caregiverswere also asked about the age of the eruption of the first tooth,oralhygienepractices,andwhether their child had visited the dentist.

The estimated sample size was reviewed byabiostatisticianandvalidatedbyusing PASS version 6.0 (NCSS, Kaysville, UT) based on prevalence data of prenatal vitamin D status in Manitoba.24 The minimum sample size was doubled to allow for some loss while maintaining an adequate sample size.

Clinical and questionnaire data were en- tered into a Microsoft Office Access data- base (Microsoft Corporation, Redmond, WA) and analyzed by using NCSS version 2007 (Kaysville, UT) and SPSS version 17.0 (IBM SPSS Statistics, IBM Corporation, Armonk,NY).Analysisincludeddescriptive statistics (frequencies and mean 6 SD values). Bivariate analysis included x2

analysis, t tests, correlation, Poisson re- gression, and analysis of variance. Multi- ple logistic regression for ECC and Poisson regression for dt scores were used. Poisson regression is appropri- ate for count data, such as caries scores in infants.

SeparateregressionmodelsforECCwere fit to identify important independent variables within sets of 5 themes, in- cluding serum metabolites (eg, 25OHD, calcium, alkaline phosphatase, phospho- rus), factors influencing vitamin D status (eg, milk intake, margarine use, prenatal vitamin use, season, vitamin D drops), infantfeedingpractices(eg,bottle-feeding, breastfeeding, use of sippy cup), so- cioeconomic factors (eg, income, em- ploymentstatus),and dentalstatusand dental behaviors (eg, siblings with ECC, tooth brushing, dental problem, age at dental examination, believing ECC is preventable). A final model was con- structed, including independent vari- ables significantly associated or approximating the threshold of signif- icance with ECC in these separate models, in addition to variables rou- tinely reported to be associated with

ECC in the literature. For continuous variables, odds ratios and confidence intervals were calculated to reflect a change in 1 SDunit of the variable. For example, the odds ratio for 25OHD reflected a 1 SD unit change. A P value #.05 was considered significant.

RESULTS

Atotalof207womenwereenrolled(mean age: 19 6 5 years). The majority (82%) were recruited from the Health Sciences Centre, and 93% resided in Winnipeg. Although 71% reportedly took vitamins during pregnancy, only 37% did so daily. Characteristics of participants and their offspring are given in Table 1.

Complete laboratory results were avail- able for 200 participants (Table 2). The mean 25OHD level was 48 6 24 nmol/L (median: 43 nmol/L); 65 (32.5%) partic- ipants had deficient concentrations (,35 nmol/L), and 24 (12%) had optimal levels ($75 nmol/L). Participants undergoing blood draws during winter months (November–April) had significantly lower levels than those sampled during sum- mer periods (May–October): 38 6 22 versus 55 6 24 nmol/L (P , .001). When stratified according to season, there was no significant difference in 25OHD con- centrations between those who spent time outside in the sunshine and those who did not (Table 1).

Despite losses to follow-up, 64% (n = 133) of the cohort returned for the infant follow-up visit. There were no differences inage(P=.24), levelofeducation(P=.74), or ethnic heritage (P = .24) between women lost to follow-up and those remaining in the study. Furthermore, there was no difference in the 25OHD lev- els between these 2 groups (50 6 26 vs 45 6 20 nmol/L; P = .08). A total of 135 infants(2setsoftwins)withameanageof 16 6 7 months (median: 13 months) returned. Overall, 56% of infants were male.

Enamel hypoplasia was identified in 22% of the cohort (29 of 134), the main

forms being pits and missing enamel. Thirty-one infants (23%) had ECC when caries was restricted to cavitated enamel lesions. However, when white spot lesions of enamel were included, 49 infants (36%) had ECC. The mean dt score was 1.2 6 2.1 (range: 0–10), whereas the mean score for the num- ber of decayed, extracted, and filled teeth was 1.5 6 2.8 (range: 0–17). When white spot incipiencies were in- cluded, the dt score was 3.4 6 2.0.

Table 3 shows the relationship between mean 25OHD levels and ECC. Mothers of infants with ECC, based on the pres- ence of cavitated caries lesions, had significantly lower prenatal concen- trations of 25OHD than those whose children were caries-free (P = .05). However, when white spot lesions were included, there was no difference be- tween groups. No significant associations were found between mothers’ 25OHD concentrations and ECC in their infants when the deficient (,35 nmol/L) or optimal ($75 nmol/L) thresholds were applied(P = .36 and P= .38, respectively).

Poissonregressionrevealedasignificant inverserelationshipbetweentheaverage number of decayed teeth (dt score) and prenatal 25OHD levels (P = .0002) (Fig 1). Infants of mothers with lower 25OHD concentrations during pregnancy had significantly higher dt scores. The t test analyses were undertaken to assess the relationship between the number of dt scores with 25OHD thresholds for de- ficientandoptimal concentrations.There was nosignificant differenceinthemean number of primary teeth with decay among infants of mothers with 25OHD concentrations #35 nmol/L or .35 nmol/L (Table 4). Interestingly, infants of mothers who had optimal 25OHD levels ($75 nmol/L) had a statistically lower mean dt score than those with moth- ers who had levels below this threshold (P = .03).

Mothers of infants with ECC were sig- nificantly more likely to be Aboriginal

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(P = .02), rate their own health as aver- age or poor (P = .01), have otherchildren with ECC (P , .005), and consume milk less frequently during pregnancy (P = .01). Furthermore, they were more likely to use food banks and have low incomes (P , .005).

The x2 analysis revealed that infants with enamel hypoplasia were significantly more likely to have ECC (73% vs 27%; P , .001). Children with ECC were significantly older thanthosewhowerecaries-free(19 610vs1464months;P=.001).ECCwas not significantly associated with bottle- feeding (P = .86) or breastfeeding (P = .35). Among the 21 infants who were reported to have stopped bottle-feeding, there was no difference between the presence and absence of ECC and wean- ing age (P = .051). However, those who were still using sippy cups were signifi- cantly less likely to have ECC (P = .001).

Asignificantlysmallerproportionofthe 117 children whose teeth were being cleaned had ECC (P = .02). However, there was no significant difference between groups in the mean age when caregivers began to clean their infants’ teeth (P = .07).

Regression analyses were performed to assessrelationshipsbetweenindependent variables and the dependent outcomes of ECCanddtscores.Thesemodelsaddressed the themes of prenatal serum metabolite concentrations,factorsinfluencingvitamin D attainment, infant feeding practices, familycharacteristicsandfinances,enamel hypoplasia and family dental history and awareness (models not shown). An overall final logistic regressionmodel for ECCwas constructed incorporating 12 different variables (Table 5). Some were signifi- cantly associated with ECC in earlier models or approximated the threshold of significance, whereas others were either significant at the bivariate level or were commonly identifiable contributors to ECC risk in the literature. Some other vari- ables that influence vitamin D status were also included. Results revealed

TABLE 1 Maternal and Infant Characteristics and Associations With Maternal Prenatal 25OHD Levels

Variable Total No. in Cohorta

Prenatal 25OHD Levels, Mean 6 SD (nmol/L)

P

Maternal characteristics Mean age, y 19 6 5 – – Resided in Winnipeg .42 Yes 190 (93) 48 6 25 No 15 (7) 50 6 23

Canadian Aboriginal (First Nations, Métis, or Inuit) ,.001 Yes 186 (90) 46 6 22 No 20 (10) 69 6 33

Self-rated prenatal health statusb .03 Good 130 (64) 52 6 24c

Average 70 (34) 42 6 24 Poor 5 (2) 46 6 19

Primigravid .87 Yes 125 (61) 48 6 24 No 81 (39) 49 6 26

Drink milkb ,.001 Often (daily) 103 (50) 56 6 26d

Sometimes (.1 time per week) 68 (33) 42 6 21 Rarely (,1 time per week) 20 (10) 34 6 16 Never 15 (7) 43 6 23

Daily vitamin use ,.001 Yes 74 (37) 57 6 26 No 125 (63) 44 6 22

Identified food(s) containing vitamin Db .50 Yes 44 (22) 52 6 32 No 28 (14) 49 6 25 Do not know 130 (64) 47 6 21

Education level .02 ,High school 190 (92) 47 6 24 $High school 16 (8) 62 6 31

Annual income, $ .30 #18 000 196 (95) 48 6 23 .18 000 10 (5) 61 6 40

Had heard of ECC or antecedent term(s) .07 Yes 159 (77) 47 6 24 No 47 (23) 53 6 25

Self-rating of dental healthb .01 Good 79 (38) 55 6 29e

Fair 100 (49) 44 6 20 Poor 26 (13) 47 6 21

Sun exposure (May–October) .23 Spent time outside in sunshine 9 (7) 64 6 34 Did not spend time outside in sunshine 117 (93) 54 6 23

Infant characteristics Gender .24 Male 75 (56) 52 6 28 Female 60 (44) 47 6 24

Premature .43 Yes 17 (13) 54 6 33 No 117 (87) 49 6 25

Low birth weight .96 Yes 6 (5) 49 6 25 No 124 (95) 49 6 26

Mean birth weight, g 3490 6 561 / / Breastfed .15 Yes 97 (74) 51 6 25 No 35 (26) 44 6 29

Bottle-fed .29 Yes 130 (96) 49 6 25 No 5 (4) 83 6 54

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that the presence of enamel hypoplasia (P = .001) and the age of infants at the time of the dental examination (P = .01) were significantly associated with ECC, with those aged $14 months at the time of their examination being more likely to have ECC. Furthermore, 25OHD levels during pregnancy were found to be significantly associated with ECC (P = .05). Backward logistic regression analysis was also performed, with the final iteration revealing that enamel hypoplasia (P , .001), infant age (P = .001), and lower 25OHD levels (P = .02) were significantly and independently

associated with ECC after controlling for income and employment status, infant feeding methods, season, and infant oral hygiene practice.

Poissonregressionfor thedtscorewas performed including the same in- dependent variables that appeared in the expanded logistic regression model for ECC. Similarly, results revealed that infant age, the presence of enamel hy- poplasia, and maternal 25OHD levels during pregnancy were significantly associated with dt score (Table 6). Lower 25OHD levels and lower ratings

of childhood health were associated with higher dt scores (P = .04).

DISCUSSION

Although some studies have reported associations between vitamin D status and dental caries,10–12,26 no previous study, to the best of our knowledge, has prospectively examined the relation- ship between prenatal 25OHD levels during periods of tooth development and caries in offspring. Many women had suboptimal 25OHD levels; nearly 90% had levels below the threshold for adequacy. Suboptimal levels are asso- ciated with increased risk for many chronic diseases, including osteopo- rosis, cardiovascular disease, and periodontal disease.27–29 Unfortu- nately, most women in this study would need to take .2000 IU of vita- min D daily to raise their levels to 80 nmol/L.30 Daily doses of 400 IU of vitamin D3 for 8 weeks results in an increase of only 11 nmol/L.29

Mothers of children with ECC had sig- nificantly lower levels of 25OHD than mothers of caries-free children. In ad- dition, there was an inverse relation- shipbetweenprenatal25OHDandthedt score, with lower concentrations pre- dicting higher scores of decayed pri- mary teeth. Infants whose mothers had optimal prenatal 25OHDconcentrations ($75 nmol/L) had significantly lower dt scores.

Several early studies identified a connection between vitamin D–fortified diets and sun exposure, a lower in- cidence and extent of caries, and a decrease in the prevalence of enamel hypoplasia in permanent teeth.31,32 A recent meta-analysis revealed that supplementation with vitamin D2, vitamin D3, or ultraviolet light lowered the risk for caries.21

It has also been suggested that 25OHD concentrations between 75 and 100 nmol/L offer protection against caries.33

TABLE 1 Continued

Variable Total No. in Cohorta

Prenatal 25OHD Levels, Mean 6 SD (nmol/L)

P

Mean age at eruption of first tooth, mo 6 6 2 – – Health rating by caregiverb .90 Very good 75 (56) 50 6 24 Good 51 (38) 49 6 30 Fair 8 (6) 46 6 21

a Unless otherwise noted, data are no. in cohort (% if applicable). b Analysis of variance. c Significantly differs from average. d Significantly differs from sometimes and rarely. e Significantly differs from fair.

TABLE 2 Prenatal Serum Concentrations of 25OHD and Related Metabolites

Assay Range of Normala Values N Mean 6 SD Range

25OHD, nmol/L 35–105 (winter), 37–200 (summer)

200 48 6 24 5–145

25OHD deficiency, nmol/L ,35 65 25 6 6 5–34 $35 135 59 6 22 35–145

Calcium, mmol/L 2.10–2.60 198 2.25 6 0.10 2.01–2.57 Phosphate, mmol/L 1.29–2.26 (,17 y) 200 1.15 6 0.19 0.69–2.28

0.81–1.45 (.16 y) Alkaline phosphatase, U/L 59–422 (#17 y) 200 98 6 52 34–372

30–120 (.17 y) a Department of Biochemistry and Genetics Laboratory reference values.

TABLE 3 Relationship Between Oral Health Outcomes and Maternal 25OHD

Caries Status Maternal 25OHD P

N Mean 6 SD Median

ECC (cavitated lesions) .05 Yes 30 41 6 20 39 No 103 52 6 27 47

ECC (including white spot lesions) .18 Yes 48 46 6 24 41 No 85 52 6 28 46

Based on t test analysis.

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A recent case-control study reported significantly lower 25OHD levels in childrenwithS-ECC.34 Morerecently,we have also reported similar findings in a larger sample of an association be- tween S-ECC and 25OHD, even after controlling for season, milk intake, use of vitamins, and household income.35

Although these 2 studies do not estab- lish causation, they provide further evidence of an association between caries in early life and lower 25OHD concentrations.

This study highlights the incidence of ECC in a sample predominantly

comprising Canadian Aboriginal chil- dren. Nearly one-quarter had ECC when cavitated lesions were considered and more than one-third when incipient lesions were included, far higher than urban-dwelling children of similar ages.36 This finding is comparable to the 30.4% of Manitoba infants ,24 months of age reported to have ECC.37

Unfortunately, 23% of the infants in this study met the criteria for S-ECC.25

Regression modeling was necessary to control for the influence of confound- ers to determine whether prenatal 25OHD levels were associated with ECC.

Because finances, poverty, and employ- ment can influence the risk of caries, the final model incorporated several related variables.Ageisarecognizedpredictorof ECC, and it was therefore also included in the model.37 Those children examined at $14 months of age were at increased odds of having ECC. The model also accounted for infant feeding practices, oral hygiene, season, and milk intake. After controlling for these influences, 3 variables were significantly and in- dependently associated with ECC: enamel hypoplasia, infant age ($14 months), and25OHD levels.Enamel hypoplasia was a strong predictor of ECC in our cohort (odds ratio .8), providing further cre- dence to the theory of hypoplasia- associated S-ECC.3,7

The Poisson regression model for the untreatedprimarytoothdecay score(dt) includedthesameindependentvariables incorporated in the expanded logistic regression model for ECC. Enamel hypo- plasia, infant age, and 25OHD levels were again identified as independent pre- dictors of caries scores. This blinded prospectivestudysuggeststhatinfantsof mothers with lower 25OHD levels are

TABLE 4 Relationship Between dt Score and Maternal 25OHD Levels in Pregnancy

25OHD dt Score P

N Mean 6 SD (Range)

25OHD threshold, deficiency .20 ,35 nmol/L 44 1.6 6 2.3 (0–10) $35 nmol/L 88 1.1 6 1.9 (0–9)

25OHD threshold, Institute of Medicine .32 ,50 nmol/L 57 1.0 6 1.9 (0–10) $50 nmol/L 75 1.4 6 2.1 (0–9)

25OHD threshold, optimal .03a

$75 nmol/L 19 0.6 6 1.2 (0–4) ,75 nmol/L 113 1.4 6 2.2 (0–10)

a Aspin-Welch unequal-variance test.

FIGURE 1 Predicted number of decayed primary teeth (dt score) according to 25OHD level.

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significantly more likely to develop ECC. The exact mechanism is unclear, but it is likelythatlowerlevelsofvitaminDduring tooth development result in enamel that is less resistant to caries.

Naturally, there were some limitations to the present study. Attrition of the cohort was expected, considering the life challenges faced by many of its participants. The cohort size restricted our ability to develop complex multi- variate models. Although there were several losses to follow-up, there was nosignificantdifferencein25OHDlevels between those who remained in the study and those lost to follow-up. The

questionnaires were also limited. In hindsight, they did not fully explore certain potential confounders that may have had an influence on infant oral health status, particularly caries risk.

The generalizability of our findings may also be limited. This study was not a random sample but rather one of convenience. However, the study pro- vides insight into the nutritional status of expectant women and the oral health of their infants. We purposely targeted a high-risk population for both low vi- tamin D level and ECC, allowing this study to be generalizable to this urban Aboriginal population.

Overall, the study was of moderate size and deliberately involved a high-risk population of mostly urban Aboriginal subjects, with limited education levels and incomes. The prospective design allowed the natural history of caries to be observed and permitted multiple outcomes to be assessed for a single exposure (ie, 25OHD status). In addi- tion, a temporal sequence was estab- lished, spanning pregnancy through infancy. Cohort studies also have the advantage of reduced bias. Another notable strength was that dental assessments were made while re- searchers were blinded to maternal 25OHD levels.

Findings from this study may have implications for early childhood oral health policy. Attempts to improve nu- trition during tooth formation in utero and early childhood should be exam- ined as a potential strategy to reduce the risk of caries. Prevention efforts should begin during pregnancy by bolstering maternal nutrition, either through improved dietary intake or supplementation with vitamin D.

CONCLUSIONS

This study shows, for the first time, that prenatal 25OHD levels may have an in- fluenceontheprimarydentitionandthe development of ECC. Specifically, lower levels were associated with increased risk for dental caries in infants. Pre- natal 25OHD levels, enamel hypoplasia, and infant age were independent pre- dictors for caries.

ACKNOWLEDGMENTS The authors thank the staff at the Health Sciences Centre’s Women’s Hos- pital, the Health Action Centre, and Mount Carmel Clinic for their assis- tance in the recruitment of partici- pants, especially Donna Duncan, Cheryl Fainman, Linda Uhrich, Sheelagh Smith, Kathi Christenson, and Dr Margaret Morris.

TABLE 5 Logistic Regression for ECC (Excluding White Spot Lesions): Final Expanded Model

Variable Regression Coefficient(b) (SE)

Adjusted Odds Ratio (95% CI)

P

Low annual income (reference: .$18 000) 22.47 (1.49) 0.085 (0.005–1.57) .1 Child health (reference: less than very good to good) 20.61 (0.60) 0.55 (0.17–1.76) .31 Infant’s teeth being cleaned or brushed (reference: no) 1.29 (1.04) 3.63 (0.47–28.07) .22 Drink milk (reference: not often) 20.36 (0.60) 0.70 (0.21–2.29) .55 Enamel hypoplasia (reference: no) 2.18 (0.67) 8.89 (2.40–32.87) .001 No one with full-time employment in household (reference: no) 0.99 (0.91) 2.70 (0.45–16.24) .28 Government assistance (reference: no) 20.48 (0.60) 0.62 (0.19–1.99) .42 Infant age at time of dental examination (reference: $14 mo) 21.60 (0.62) 0.20 (0.06–0.68) .01 Infant feeding (bottle) (reference: mixed) 0.25 (0.64) 1.28 (0.36–4.51) .70 Infant feeding (breast) (reference: mixed) 20.14 (1.62) 0.87 (0.04–20.63) .93 Season (reference: summer) 20.40 (0.62) 0.67 (0.20–2.27) .52 25OHD levela 20.029 (0.015) 2.02 (1.00–4.08) .05

ECC reference = yes; R2 = 32.9%. CI, confidence interval. a SD in sample = 24.44.

TABLE 6 Poisson Regression for dt (Caries Tooth Score)

Variable Regression Coefficient

695% Confidence Interval

P

Intercept 1.68 Low annual income (reference: ,$18 000) 20.28 0.73 .45 Child health (reference: less than very good to good) 20.35 0.33 .04 Infant’s teeth being cleaned or brushed (reference: no) 20.13 0.51 .60 Drink milk (reference: not often) 0.054 0.36 .77 Enamel hypoplasia (reference: no) 1.02 0.37 ,.001 No one with full-time employment in household

(reference: no) 0.39 0.59 .20

Government assistance (reference: no) 0.13 0.38 .50 Infant age at time of dental examination (reference:

$14 mo) 21.03 0.38 ,.001

Infant feeding (bottle-fed) (reference: mixed) 0.031 0.37 .87 Infant feeding (breastfed) (reference: mixed) 20.53 0.81 .20 Season (reference: summer) 20.32 0.42 .13 25OHD level 20.013 0.0085 .002

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