socioeconomic, behavioral, and anthropometric risk factors for traumatic dental injuries in...

Socioeconomic, behavioral, and anthropometric risk factorsfor traumatic dental injuries in childhood: a cohort study

CARLOS ALBERTO FELDENS1, PAULO FLORIANI KRAMER1, ELIANE GERSON FELDENS1,LUANA MORAES PACHECO2 & MARCIA REGINA VITOLO3

1Department of Pediatric Dentistry, Universidade Luterana do Brasil, Canoas, RS, Brazil, 2Graduate Program in Dentistry,

Universidade Luterana do Brasil, Canoas, RS, Brazil, and 3Department of Nutrition, Universidade Federal de Ciencias da

Sa�ude de Porto Alegre, Porto Alegre, RS, Brazil

International Journal of Paediatric Dentistry 2014; 24:

234–243

Aim. To investigate risk factors for the occurrence

of traumatic dental injuries (TDI) at 4 years of age.

Design. Prospective cohort study.

Methods. A birth cohort (n = 500) was recruited

from the public healthcare system in São Leopoldo,

Brazil. Demographic, socioeconomic, anthropomet-

ric, and behavioral variables were collected at

6 months, 1 year, and 4 years of age. Clinical

examinations at 4 years of age were carried out by

a single examiner using the Andreasen classifica-

tion. Poisson regression was used to determine risk

factors for the occurrence of TDI at 4 years of age.

Results. A total of 23.7% of the children (80/

337) exhibited TDI at 4 years of age. The risk of

TDI was 35% lower among children who had

been breastfeed for ≥6 months relative risk (RR

0.65; 95% CI 0.43-0.97) and more than twofold

higher among those who were bottle fed ≥ three

times a day (RR 2.37; 95% CI 1.10–5.11) at

12 months of age. Higher household income in

the first year of life and greater height at 4 years

of age were significantly associated with the

outcome.

Conclusions. The identification of behavioral,

socioeconomic, and anthropometric risk factors for

TDI in early childhood can contribute to the elab-

oration of prevention strategies.

Introduction

Traumatic dental injury (TDI) is among the

most prevalent oral health problems and has

physical, emotional, and economic conse-

quences for the affected individual and his/

her family1–5. There is, however, insufficient

scientific evidence on which to base public

health interventions in the primary dentition.

Nearly, all investigations into the association

between potential risk factors and TDI in the

primary dentition are cross-sectional studies,

which have inherent limitations regarding the

demonstration of causality6. Moreover, the

only risk factor that studies have consistently

indicated is overjet, which is difficult to treat

in the first years of life7–10.

A more comprehensive understanding of

the occurrence of TDI in childhood is needed,

with the identification of factors that can be

the target of interventions. The World Health

Organization recommends the reduction in

risk factors that stem from environmental,

economic, social, and behavioral causes to

improve the oral health of populations11.

There is, however, a gap in the scientific liter-

ature on the possible role of behavioral fac-

tors, especially nutritive and non-nutritive

sucking habits, and anthropometric factors.

Moreover, the findings on the relationship

between TDI and socioeconomic factors are

contradictory10,12–15. Longitudinal studies that

identify risk factors and address the intricate

network of associations can contribute to the

development of programs directed at control-

ling TDI11,16 on both the individual and

collective levels.

The aim of this study was to investigate

demographic, socioeconomic, anthropometric,

and behavioral variables that represent poten-

tial risk factors for the occurrence of TDI in a

birth cohort of preschool children in southern

Brazil.

Correspondence to:

Carlos Alberto Feldens, Rua João Telles 185/1301, Porto

Alegre-RS, Brazil 90.035.121.

E-mail: [email protected]

234 © 2013 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

DOI: 10.1111/ipd.12066

Methods

Subjects and study design

The present prospective cohort study was

nested in a randomized trial (registered with

ClinicalTrials.gov, number NCT00629629)

carried out in the city of São Leopoldo, Brazil

(approximate population: 200,000 inhabit-

ants) to investigate the effectiveness of nutri-

tional advice on breastfeeding and healthy

weaning17 based on the recommendations of

the World Health Organization. Five hundred

mothers were recruited from the maternity

clinic of the only publicly funded hospital in

the city, which mainly serves the low-income

population. The overall project also investi-

gated risk factors for general and oral out-

comes.

A sample size of 300 four-year-old children

was calculated in the larger study to detect a

difference of 35% in the occurrence of dental

caries between the intervention and control

groups18. This sample size was compatible

with the size required to estimate the associa-

tion between TDI and family structure at

4 years of age (n = 296) employing a 95%

confidence level, 80% statistical power, and

prevalence rates 24% and 11% for TDI

among exposed and non-exposed individuals,

respectively11.

Mothers who gave birth to a single child at

full term (≥37 weeks) with normal birth

weight (≥2500 g) and who had no impedi-

ment to breastfeeding (HIV/AIDS) were

invited to take part in the larger study until

the required sample size for the cohort was

reached. After being informed of the research

procedures, 90% of mothers agreed to partici-

pate. The potential risk factors (demographic,

socioeconomic, and behavioral variables)

were collected through interviews and

anthropometric measures. The outcome (TDI)

was determined through a clinical dental

examination at 4 years of age.

Six-month evaluation – demographic and socioeco-

nomic data collection. When the children were

6 months of age, trained fieldworkers held

face-to-face structured interviews with the

mothers. The questionnaire was previously

tested in a pilot study involving 16 mothers

of children aged 12 months attending primary

care services. The following demographic and

socioeconomic variables were investigated:

child’s gender, mother’s schooling (number of

years of study), monthly household income

per capita, mother’s occupation status, family

structure, and number of residents in the

home. Family structure was considered

nuclear (child living with mother and father)

or non-nuclear (child not living with both

parents). Household income per capita was

calculated by dividing the monthly income of

the family by the current Brazilian minimum

monthly wage at the time of the study

(approximately US $100).

Twelve-month evaluation – anthropometric, behav-

ioral, and clinical data collection. When the

children had completed 12 months of life,

dietary behavior was assessed at a municipal

health center using structured interviews

addressing the onset, duration, and frequency

of feeding practices in the previous 6 months.

For this study, total duration of breastfeeding

and number of bottle feedings per day at

12 months of age were analyzed. Parents

were also asked whether the child had used a

pacifier in the first year of life. Anthropomet-

ric variables (weight and height) were col-

lected by trained students from the nutrition

department using standardized methods for

the calculation of weight for age, height for

age, and body mass index (BMI), which were

subsequently categorized in tertiles. A clinical

dental examination was also performed at the

health center by a single experienced pediat-

ric dentist for the determination of the num-

ber of erupted teeth and the occurrence of

early childhood caries (ECC). The dental

examination was conducted with the child

lying on a stretcher and with the aid of a

mouth mirror. The teeth were previously

brushed and dried with gauze. ECC was

assessed based on case definitions of the

National Institutes of Health (NIH)19: the

presence of one or more decayed (d1+), miss-

ing, or filled tooth surfaces in any primary

tooth (d1+mfs ≥ 1). Intra-examiner reproduc-

ibility was previously assessed with 35 chil-

dren aged 10–18 months in two dental

Risk factors of dental trauma in childhood 235

© 2013 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

examinations spaced 10 days apart (kappa

score = 0.88).

Four-year evaluation – anthropometric, behav-

ioral, and clinical data collection. Between 48

and 53 months of age, the children were

again submitted to the anthropometric evalu-

ation using the same procedures as those

employed at twelve months of age, with the

calculation of weight for age, height for age,

and BMI, subsequently categorized in tertiles.

On the same day as the anthropometric

examinations, the mothers were interviewed

for the collection of behavioral data on

whether the child practiced regular physical

activity during the week (soccer, ballet, swim-

ming, judo, etc.), the mean number of hours

the child spent watching television per day

and whether the child attended a daycare

center (at least one shift per day).

Dental examinations were conducted at a

municipal health center at the 4-year evalua-

tion by the same pediatric dentist who per-

formed the 12-month assessment. The

examiner was blinded to the children’s base-

line variables. The teeth were inspected with

the aid of a mouth mirror, with the child

seated in an ordinary chair. ECC was

assessed following the same criterion used at

the 12-month assessment19. TDI was

recorded based on the descriptions proposed

by Andreasen20: crown discoloration, enamel

fracture, enamel/dentin fracture with or

without pulp exposure, subluxation, lateral

luxation, extrusive luxation, intrusive luxa-

tion, and avulsion. Because none of the chil-

dren were affected at the outset of the

cohort, the frequency of children presenting

TDI at the 4-year evaluation represented the

cumulative incidence in the first 4 years of

life, defined as the proportion of a fixed pop-

ulation that becomes affected with a particu-

lar health condition within a given period of

time6.

Intra-examiner reliability regarding the

diagnosis of TDI and ECC was previously

assessed in two dental examinations con-

ducted 14 days apart involving 20 children

aged three to 5 years. The mean Kappa index

for intra-examiner agreement was 0.94 for

TDI and 0.90 for ECC.

Statistical analysis

Statistical analyses were performed using the

PASW program version 17.0. Unadjusted and

adjusted relative risks of exhibiting TDI were

estimated using Poisson regression models

with robust variance. The multivariable

model followed a hierarchical approach21

from distal to proximal determinants per-

formed on three levels: (i) demographic and

socioeconomic variables; (ii) anthropometric

and behavioral variables at 12 months; (iii)

anthropometric and behavioral variables at

4 years; (iv) and TDI. The backward stepwise

procedure was used to select covariates on

each level. Therefore, the final model esti-

mates relative risks of the selected variables

after adjusting for variables on the same level

or higher levels. A hierarchical approach pre-

vents distal factors from being improperly

adjusted for proximal factors, with a conse-

quent reduction in or elimination of the

effects of the former21. Explanatory variables

with a P-value < 0.15 in the adjusted assess-

ment of risk factors were maintained in the

final regression model. Interactions between

risk factors in the final model were tested

using the Wald test for heterogeneity. An

additional analysis was performed to investi-

gate the possibility that the occurrence of

ECC may have confounded the reported asso-

ciations. Figure 1 summarizes the theoretical

model adopted in this study. Comparisons of

baseline variables (weight and length at birth,

mother’s schooling, and household income)

between children who were lost to follow-up

and those who remained in the cohort were

performed using the chi-squared test and

t-test for independent samples. A two-tailed

P-value of <0.05 was considered statistically

significant.

Ethical considerations

This study received approval from the

Human Research Ethics Committee of the

Federal University of Rio Grande do Sul (Bra-

zil). The procedures, possible discomfort, and

possible benefits of the study were fully

explained to parents, and informed consent

was obtained prior to the investigation.

236 C. A. Feldens et al.


Children with TDI or caries requiring

professional intervention were referred for

treatment at the Pediatric Dental Clinic of

the Lutheran University of Brazil. At the 12-

month and 4-year evaluations, all children

underwent nutritional and development

assessments. Children with anemia, over-

weight, wasting syndrome, stunting, or

developmental problems were referred to

their primary care pediatricians for further

assessment and treatment.

Results

Dental examinations were carried out on

68% (340/500) of the children recruited at

birth. The following were the reasons for

losses between birth and the 4-year evalua-

tion: family moved to another city (n = 67),

refusal to participate (n = 45), address not

found (n = 41), infant given up for adoption

(n = 1), genetic disease (n = 2), death of child

(n = 2), severe illness of mother (n = 1), and

death of mother (n = 1). Three children were

excluded from the analysis of TDI at 4 years

of age due to crown destruction or tooth loss

stemming from dental caries, resulting in a

final sample of 337 children.

Age at the time of examination ranged from

48 to 53 months (mean: 50.5 months; stan-

dard deviation: 1.7 months). The male gender

accounted for 57.0% of the sample. Mother’s

schooling ranged from 1 to 13 years; 71.5%

of mothers had eight or fewer years of formal

education. Nearly 85% of the families earned

an income per capita below the national mini-

mum wage. At 12 months of age, most chil-

dren had more than six teeth and were bottle

fed once to twice per day; half of the children

used a pacifier. At 4 years of age, a great vari-

ation in height was observed, ranging from

92.0 to 117.2 cm (mean 103.1 cm); only 1/5

of the children attended preschool and only

7.3% performed regular physical activity; the

time spent watching television ranged from 0

to 13 h per day (mean: 2.4 h; standard devia-

tion: 2.1 h) (Table 1).

A total of 23.7% (80/337) of the children

exhibited TDI at 4 years of age; 65 of whom

had only one tooth affected, 13 had two teeth

affected, and two had more than two teeth

affected. In the overall sample, 98 teeth had

suffered TDI. Maxillary central incisors were

the most frequently affected by TDI (85.7%),

followed by maxillary lateral incisors

(10.2%), and mandibular central incisors

(4.1%). The most common type of injury was

enamel fracture (n = 44; 44.9%), followed by

crown discoloration (n = 34; 34.7%), and

enamel/dentin fracture (n = 11; 11.2%). The

other types of TDI encountered were lateral

luxation (n = 4), avulsion (n = 4), and intru-

sive luxation (n = 1).

The unadjusted model (Table 2) demon-

strates that the frequency of TDI was signifi-

cantly greater among children whose families

had a higher household income, those with a

shorter period of breastfeeding in the first

year of life, and those who bottle fed more

often at 12 months. A greater height for age

at 12 months and 4 years was also associated

with the occurrence of TDI.

The multivariable analysis (Table 3) demon-

strated that the risk of TDI was significantly

greater among children whose families had a

higher household income and those with a

greater number of teeth erupted at 12 months

of age. Children having been breastfed for at

least 6 months had a 35% lower risk of TDI

at 4 years of age, whereas bottle feeding three

or more times a day at 12 months of age was

associated with a greater than twofold

increased risk of TDI at 4 years of age. More-

over, children with a greater height for age at

Demographic variablesSex

Family structureNumber of residents in home

Socioeconomic variablesMother’s schooling

Mother’s work statusIncome per capita

Anthropometric variables(12 months)

Weight for ageHeight for age

Body mass indexNumber of teeth

Behavioral variables(12 months)

Breastfeeding durationNumber of bottles/day

Pacifier use

Anthropometric variables(4 years)

Weight for ageHeight for age

Body mass index

Behavioral variables(4 years)

Daycare attendanceWeekly physical activityHours watching TV/day

Traumatic dental injuries

Figure 1. Conceptual hierarchical framework for traumatic

dental injuries (TDI).



4 years had an 80% greater risk of TDI. No

interactions were found among the variables

in the final model. The adjusted relative risks

of TDI were virtually unchanged after adjust-

ing for ECC at 1 year of age: income ≥ 1

BMW (1.66, 95% CI: 1.08–2.55; P = 0.021),

total breastfeeding duration ≥6 months (0.65,

95% CI 0.43-0.97; P = 0.035), and number of

bottles/day at 12 months ≥ 3 (2.37, 95% CI

1.10-5.10, P = 0.027). The relative risk and

P-value remained the same for the 3rd tertile

of height for age. Similarly, no significant

change in the estimates was observed after

adjustment for ECC at 4 years of age.

No difference was found between the chil-

dren lost to follow-up and those who remained

in the cohort at 4 years of age regarding poten-

tial risk factors for childhood outcomes: weight

at birth (P = 0.871), length at birth

(P = 0.122), mother’s schooling (P = 0.423),

and household income (P = 0.477).

Discussion

This is the first cohort study to investigate risk

factors associated with TDI in the first 4 years

of life based on socioeconomic, anthropo-

metric, and behavioral variables. Approxi-

mately 25% of the children had clinical signs

of TDI, demonstrating the high frequency of

this outcome in the early years of life. Most

studies investigating the prevalence of TDI in

different populations report rates ranging

from 20 to 40% among preschoolers7–9,22,23.

Differences in the distribution of potential risk

factors in different communities may lead to

divergent degrees of susceptibility. Moreover,

the variation in the prevalence of TDI among

children and adolescents has been attributed

to the different diagnostic criteria and exami-

nation methods employed12,24,25.

Previous studies found that breastfeeding

and non-nutritive sucking habits were associ-

ated with malocclusion8,26,27, whereas accen-

tuated overjet and open bite were associated

with the occurrence of TDI7,9,10. No previous

longitudinal study has, however, investigated

the relationship of early feeding practices and

non-nutritive sucking habits with TDI in the

primary dentition. In the present investiga-

tion, breastfeeding for 6 months or more was

a protection factor and a high frequency of

bottle feeding at 12 months of age was a risk

factor for the occurrence of TDI. Moreover,

these findings remained significant even after

controlling for confounding factors and the

adjustment of the final model, indicating an

independent effect on the occurrence of the

outcome.

It is plausible that both breastfeeding

and non-nutritive sucking habits exert an

influence on the facial pattern of children,

Table 1. Demographic, socioeconomic, and behavioralcharacteristics of sampled children.

Variables n (%)

GenderMale 192 (57.0)Female 145 (43.0)

Mother’s schooling≤4 years 66 (19.6)5–8 years 175 (51.9)>8 years 96 (28.5)

Income per capita<1 BMW 277 (84.7)≥BMW 50 (15.3)

Mother’s work status (child aged 6 months)Yes 115 (37.1)No 195 (62.9)

Family structureNuclear 236 (70.4)Non-nuclear 99 (29.6)

Number of residents in home<4 87 (26.0)4–5 180 (53.7)>5 68 (20.3)

Number of teeth at 12 months≤6 136 (40.6)>6 199 (59.4)

Total breastfeeding duration<6 months 125 (37.3)≥6 months 210 (62.7)

Number of bottles/day at 12 monthsNone 85 (25.2)1–2 201 (59.6)≥3 51 (15.2)

Pacifier use at 12 monthsNo 167 (49.7)Yes 169 (50.3)

Daycare attendanceYes 62 (18.6)No 272 (81.4)

Weekly physical activity at 4 yearsYes 24 (7.3)No 307 (92.7)

Hour watching TV/day at 4 years<2 141 (43.0)2–4 129 (39.3)>4 58 (17.7)

*1 BMW = Brazilian monthly minimum wage (R$ 180 or US$ 80).



Table 2. Unadjusted relative risk (RR) and 95% confidence interval (95% CI) of exhibiting traumatic dental injuries (TDI) at4 years of age.

Variables NWith TDI

P* RR (95% CI) Pn (%)

Socio-demographic variables in first year of lifeGenderMale 192 52 (27.1) 0.097 1.40 (0.94–2.10) 0.102Female 145 28 (19.3) 1.00

Family structureNuclear 236 56 (23.7) 0.920 0.98 (0.64–1.48) 0.979Non-nuclear 99 24 (24.2) 1.00

Number of residents in home<4 87 18 (20.7) 0.504 1.004–5 180 45 (25.0) 1.21 (0.74–1.96) 0.443>5 68 17 (25.0) 1.21 (0.67–2.16) 0.524

Mother’s schooling (years)≤4 66 10 (15.2) 0.143 1.005–8 175 45 (25.7) 1.70 (0.91–3.17) 0.097>8 96 25 (26.0) 1.72 (0.89–3.33) 0.109

Mother’s work statusYes 115 31 (27.0) 0.443 1.17 (0.79–1.73) 0.441No 195 45 (23.1) 1.00

Income per capita<1 BMW 277 60 (21.7) 0.029 1.00≥BMW 50 18 (36.0) 1.66 (1.08–2.56) 0.021

Anthropometric and behavioral variables at 12 months of ageWeight for age (at 12 months)1st tertile 111 22 (19.8) 0.209 1.002nd tertile 112 28 (25.0) 1.26 (0.77–2.06) 0.3563rd tertile 111 30 (27.0) 1.36 (0.84–2.21) 0.208

Height for age (at 12 months)1st tertile 111 19 (17.1) 0.017 1.002nd tertile 110 26 (23.6) 1.38 (0.81–2.34) 0.2323rd tertile 114 35 (30.7) 1.79 (1.10–2.94) 0.020

BMI (at 12 months)1st tertile 112 28 (25.0) 0.940 1.002nd tertile 112 24 (21.4) 0.86 (0.53–1.38) 0.8573rd tertile 110 28 (25.5) 1.02 (0.65–1.60) 0.938

Number of teeth at 12 months≤6 136 22 (16.2) 0.006 1.00>6 199 58 (29.1) 1.80 (1.16–2.80) 0.009

Total breastfeeding duration<6 months 125 43 (34.4) 0.001 1.00≥6 months 210 37 (17.6) 0.51 (0.35–0.75) 0.001

Number of bottles/day at 12 monthsNone 85 9 (10.6) 0.001 1.001–2 201 54 (26.9) 2.54 (1.31–4.91) 0.006≥3 51 17 (33.3) 3.15 (1.52–6.53) 0.002

Pacifier use at 12 monthsNo 167 39 (23.4) 0.845 1.00Yes 169 41 (24.3) 1.04 (0.71–1.52) 0.845

Anthropometric and behavioral variables at 4 yearsWeight for age (4 years)1st tertile 111 22 (19.8) 0.222 1.002nd tertile 111 27 (24.3) 1.23 (0.75–2.02) 0.4203rd tertile 112 30 (26.8) 1.35 (0.83–2.19) 0.222

Height for age (4 years)1st tertile 112 16 (14.3) 0.002 1.002nd tertile 110 27 (24.5) 1.72 (0.98–3.01) 0.0583rd tertile 112 36 (32.1) 2.25 (1.33–3.81) 0.003

(Continued)



especially anterior open bite and maxillary

overjet8, making them more or less susceptible

to TDI. Clarification regarding the network

of associations involving feeding practices,

non-nutritive sucking habits, and TDI can

contribute to the development of prevention

strategies directed at preschoolers. In this pop-

ulation, pacifier use and bottle feeding in the

first month of life have been associated with a

shorter period of breastfeeding28. Moreover,

advising new mothers about breastfeeding

is reported to reduce pacifier use in the first

year of life and other outcomes29, which

demonstrates the feasibility of this type of

intervention.

Associations between TDI and anthropo-

metric variables have been increasingly inves-

tigated in recent years. A number of studies

suggest that obesity is a risk factor for TDI in

both schoolchildren24,30 and preschoolers15.

In this study, TDI was more frequent among

children in the highest tertile for height for

age at 4 years, and this finding has no obvi-

ous explanation. It is plausible that a child’s

height may be related to deficits in balance

and muscle strength, which are two impor-

tant intrinsic risk factors for falls and injuries

that were not evaluated in this study31. A

systematic review found that the height of a

fall is a major risk factor for the incidence

and severity of injuries in children32. In a

study involving American children, each one-

unit increase in fall height increased the risk

of injury by a factor of 2.333. In this study,

the considerable variation in height among

the children may have contributed to the

results. It is also possible that taller children

are more exposed to activities of greater risk.

The frequency of TDI in the three categories

of height for age indicates some degree of a

dose–response effect, with little chance that

Table 2 (Contd.)

Variables NWith TDI

P* RR (95% CI) Pn (%)

BMI (4 years)1st tertile 111 27 (24.3) 0.483 1.002nd tertile 110 29 (26.4) 1.08 (0.69–1.71) 0.7283rd tertile 113 23 (20.4) 0.84 (0.51–1.37) 0.477

Daycare attendanceYes 62 15 (24.2) 0.862 1.04 (0.64–1.71)No 272 63 (23.2) 1.00 0.862

Weekly physical activityYes 24 8 (33.3) 0.225 1.48 (0.81–2.71)No 307 69 (22.5) 1.00 0.200

Hours watching TV/day<2 141 31 (22.0) 0.661 0.91 (0.52–1.58) 0.7402–4 129 32 (24.8) 1.03 (0.59–1.77) 0.922>4 58 14 (24.1) 1.00

BMW, Brazilian monthly minimum wage.*Chi-squared test.

Table 3. Final multivariable model: adjusted relative risks(RR) and 95% confidence interval (95% CI) of exhibitingtraumatic dental injuries at 4 years of age.

Variables RR (95% CI) P

GenderMale 1.39 (0.93–2.08) 0.111Female 1.00

Income per capita<1 BMW 1.00≥1 BMW 1.66 (1.08–2.56) 0.021

Number of teeth at 12 months≤6 1.00>6 1.74 (1.13–2.67) 0.011

Total breastfeeding duration<6 months 1.00≥6 months 0.65 (0.43–0.97) 0.034

Number of bottles/day at 12 monthsNone 1.001–2 1.79 (0.90–3.57) 0.099≥3 2.37 (1.10–5.11) 0.027

Height for age at 4 years1st tertile 1.002nd tertile 1.47 (0.83–2.60) 0.1863rd tertile 1.79 (1.03–3.11) 0.039

BMW, Brazilian monthly minimum wage.



the association was found by chance. The

inclusion of anthropometric variables in mul-

tivariable models in future studies investigat-

ing the causality of TDI in children could

contribute to the clarification of this issue.

The observation that behavioral variables at

4 years of age, such as frequency of attending

a daycare center, practice of physical activity,

and number of hours spent watching televi-

sion, were not associated with the outcome

does not necessarily mean that these forms of

behavior exert no influence on the occur-

rence of TDI. Because these variables were

collected at 4 years of age, it is plausible that

the time in which the children were exposed

was much lower in comparison with the

behavioral variables collected in the first year

of life. Studies involving schoolchildren indi-

cate that a significant number of cases of TDI

occur in and around schools, with little or no

interference from teachers with regard to

either prevention or immediate care28,29. In

contrast, the characteristics of activities devel-

oped in the preschool phase and the greater

monitoring of supervisors at daycare centers

may have contributed toward a similar fre-

quency of TDI among children attending day-

care centers at 4 years of age. Moreover, the

low frequency of children who practiced

physical activity may also account for the lack

of an association with the outcome. This

notion is supported by the difference in the

frequency of TDI between children who prac-

ticed physical activities (33.3%) and those

who did not practice such activities (22.5%).

As the associations between TDI and these

forms of behavior in early childhood are

examined for the first time in this study, simi-

lar investigations should be carried out in

populations with different characteristics.

Conflicting findings are reported regarding

the influence of socioeconomic factors on the

occurrence of TDI in different populations.

Although a number of studies report higher

rates of TDI among children with a lower

socioeconomic status12,13,34, other investigations

report an association with a higher socioeco-

nomic status10,14,15, which is in line with the

present findings. This divergence may be par-

tially explained by the use of different socio-

economic indicators. Family income, social

class, parents’ level of education, parents’

occupation, and type of school measure dif-

ferent aspects and have different meanings in

different communities, which may affect the

findings and conclusions35. Moreover, it is

possible that socioeconomic status exerts an

influence in different ways, depending on

cultural aspects and issues related to access to

safe environments, protective equipment for

the avoidance of TDI, and healthcare services

in each country. It has been suggested that

the greater occurrence of TDI among children

with a higher socioeconomic status in devel-

oping countries (as in the present case) is due

to the greater exposure of such children to

situations of risk without the existence of safe

environments1,10,14.

This study has limitations that should be

addressed. Firstly, a considerable number of

children were lost to follow-up, which is a

common problem in cohort studies, mainly in

populations with a high degree of mobility.

To minimize this problem, identification data

were collected in detail by the researchers at

the outset of the study. Selection bias,

however, is unlikely to be a major problem,

considering the similarity in baseline charac-

teristics between those lost to follow-up and

those who remained in the cohort. Secondly,

the lack of assessment of TDI at different ages

may have led to the misclassification of the

outcome, especially luxation, which can heal

and may not be detected in a subsequent

evaluation. Although some lesions may have

received restorative treatment and hindered

the diagnosis at 4 years of age, this is not

believed to have distorted the results, as a

very small number of children had visited the

dentist and the filled component represented

only 2.3% of the dmft �ındex17. Thirdly,

malocclusion was not collected in this

investigation. The inclusion of overjet in the

analysis, however, would possibly not have

altered the findings, as this variable would

serve as a mediator between the observed

behavior and outcome, which is a condition

that a confounding variable cannot conceptu-

ally assume6. Even if overjet mediates the

relationship between associated behaviors and

TDI, it seems much more advisable to concen-

trate efforts on the encouragement of ade-



quate breastfeeding and a reduction in bottle

feeding than the use of orthodontic appli-

ances for the correction of malocclusion at

this age.

In conclusion, a shorter breastfeeding period

and high frequency of bottle feeding in the

first year of life are risk factors for the occur-

rence of TDI in early childhood. With regard

to the implications for clinical practice, man-

agement, and public policies, advising mothers

about early feeding practices should be consid-

ered in the development and implementation

of prevention strategies directed at caries,

malocclusion, and TDI in childhood. This

represents a common risk approach, which

appears to be the most effective strategy for

disease prevention36. A higher socioeconomic

status and greater height for age were also

associated with the outcome and should be

investigated in depth in further studies.

Why this paper is important to pediatric dentists

● There are few cohort studies concerning TDI in pri-

mary dentition

● This paper provides information about behavioral,

socioeconomic, and anthropometric risk factors for

the occurrence of TDI in preschool children.

● These findings can help pediatric dentists in clinical

practice, contributing to the advising of parents and

elaboration of prevention strategies of TDI at the pop-

ulation level.

Conflicts of interest

The authors declare that they do not have

any conflict of interest.

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