Key words: Deciduous dentition, Enamel-hypoplasia, IUGR.

The eruption of teeth in infants is an important event. This initiates neuro-behavioral mechanisms underlying infant development and learning of feeding behavior, particularly masticatory skills. While eruption chronology of primary dentition has been studied in some populations(1-6), only limited studies have been reported from India(7-10).

Enamel hypoplasia is a defect of enamel matrix formation caused by an insult to ameloblasts (enamel forming cells). Clinically the defect appears as opacities, coalesced deep pits, grooves or missing enamel. The enamel defects are seen in genetic disorders e.g., Ehlers Danlos syndrome, chromosomal anomalies and inborn errors of metabolism. Nutritional deprivation and chronic illness are important causes of enamel hypoplasia(11-13). Further, the degree of prematurity, mineral imbalance, duration of breast feeding’, racial factors, etc. have been studied in relation to enamel hypoplasia with variable results(14-16). The present study was carried out to collect data on the pattern of deciduous dentition and prevalence of enamel hypoplasia in wellnourished, malnourished and intrauterine growth retarded (IUGR) children.

A total of 280 children, born in the Guru Teg Bahadur Hospital, Delhi having complete records and receiving regular immunizations were selected every Monday from January 1999 to April 2000. The calculated sample size was 233 for 30% prevalence of enamel hypoplasia, when the type I and II errors are 5% and 20% respectively. To compare wellnourished and malnourished infants for primary dental eruption and prevalence of enamel hypoplasia, 40 consecutive children each in age groups of <1, 1-2 and 2-3 years in both nutritional categories were studied.

Forty infants with IUGR were also selected. IUGR infants consisted of term (37-41 completed weeks) born, with birth weight less than tenth percentile for gestational age(17). Children with congenital malformation or metabolic disorders e.g., diabetes, inborn errors of metabolism were excluded.

Length was measured on an infantometer (Sahani & Sons, Delhi) with 0.2 cm accuracy and weight on a weighing scale (Chattilon, USA) with accuracy of 10 g, using methods described previously(18). Children were taken as normally nourished if their length and weight were more than 90% of the expected for age, taking 50th centile of Indian affluent children as standard(18, 19). For this age group Indian affluents correspond to NCHS reference. Children with length <90% (stunted) and weight <75% (stunted-wasted) taking 50th centile value of the standard as 100%(19,20). The examined children had nutrition status distribution as normally nourished 32%, malnutrition grade I - 37% and remaining 31 % were in grades II and III.

The number of erupted teeth was recorded, the age of eruption was inquired from the mother, and tooth was considered erupted if any part of the crown had pierced the gum.

The teeth were examined in bright light with the help of dental probe and mirror (initially by SN and KNA and confirmed by NK). All surfaces of each tooth were examined and the most severe lesion on each surface was recorded. Enamel defect was scored by modified DDE (Development Defects of Enamel) Index(13) as described below.

Enamel defect score =

EHP Code × Number defective tooth surface × 10*

—–———————————————————

Total number of tooth surface at risk

* An arbitrary factor to obtain fewer decimals.

Statistical analysis: Mean, standard deviation and ANOVA tests were used on SSPS package.

Dental eruption: In wellnourished children the earliest teeth to erupt were lower central incisors at mean age of 8.2 ± 1.8 months (range 5-14 months). The eruption in malnourished group was at 8.7 ± 1.7 months (range 6-14 months). Upper central incisors were the next teeth to erupt at mean age of 9.6 ± 1.9 and 9.8 ± 1.9 months in wellnourished and malnourished groups, respectively. Similarly canine and molars showed delayed eruption in malnourished children (Table I) . In the IUGR infants, mean age of eruption was similar to the wellnourished children below 1 year of age (Table I). In Table II number of erupted deciduous teeth are lower in malnourished as compared to well nourished children. The difference was significant at 12-15 months of age (P < 0.01).

Table I__	Deciduous Teeth Eruption (months) in Wellnourished and 
Malnorished Children and Infants with IUGR

Teath	Wellnourished            (n = 120)     n         Mean ± SD		Wellnourished      (n = 120)   n        Mean ± SD		IUGR       (n = 40)   n        Mean ± SD
Right upper central incisor	93	9.6±1.9	93	9.8±1.9	13	9.4±1.4
Right upper lateral incisor	79	11.6±1.9	74	12.0±1.8
Right upper canine	61	20.6±1.6	60	21.2±1.5
Right upper Ist molar	57	16.0±0.9	69	16.2±1.3
Right upper IInd molar	16	28.8±0.9	12	28.5±0.9
Left upper central incisor	96	9.3±1.9	87	9.9±2.0	13	9.1±1.4
Left upper lateral incisor	68	11.6±1.9	72	12.0±1.8
Left upper canine	61	19.9±2.7	43	21.1±1.5
Left upper Ist molar	68	16.0±0.9	60	16.2±1.3
Left upper IInd molar	16	28.5±1.9	11	28.0±2.0
Left lower central incisor	115	8.2±1.8	112	8.8±1.8	37	8.4±1.3
Left lower lateral incisor	59	12.3±2.5	55	13.2±2.8
Left lower canine	50	20.4±1.7	61	21.7±1.5
Left lower Ist molar	54	16.3±0.5	49	17.2±0.4
Left lower IInd molar	5	27±1.8	2	27.5±0.9
Right lower central incisor	115	8.2±1.8	111	8.7±1.7	37	8.3±1.4
Right lower lateral incisor	59	12.3±2.5	55	13.2±2.8
Right lower canine	50	20.0±1.8	50	21.7±1.5
Right lower Ist molar	49	16.3±0.4	50	17.3±1.5
Right lower IInd molar	49	27.0±1.8	15	27.6±0.8

IUGR = Intrauterine growth retardation

Table II - Number of Teeth (mean ± SD) in Wellnourished and malnourished children in realtion
to Age

Enamel hypoplasia: The prevalence of enamel hypoplasia was higher in well-nourished girls as compared to boys; which was significant for the age group 1-2 years (P <0.02). The relative risk of enamel hypoplasia in girls was 1.38 (P <0.03). The prevalence was more in malnourished children of both sexes (Table III) in the first year of life. However, the differences were not significant.

TABLE III - Enamel Hypoplasia in relation to sex

EDS enamel defect score
*F=6.81; P<0.002.

The enamel defect score was higher in 12-24 months wellnourished children as compared to other age groups. In mal-nourished group, the score was higher in children <12 months of age as compared to wellnourished. However, these differences were not significant (Table III).

Enamel hypoplasia was seen in 30% infants. The mean values for teeth, eruption and enamel defect score were similar to wellnourished children (Tables I and III). The prevalence of enamel hypoplasia was 20.5% in breast fed as compared to 37.1% in those receiving animal or commercial milk (F = 10.56; P <0.005). This influence of breast feeding was also significant (F = 11.53; P <0.03).

The sequence of eruption of primary dentition was as follows: lower central incisors (8.2 months), upper central incisors (9.3 months), upper lateral incisors (11.6 months), lower lateral incisors (12.3 months), upper first molars (16.0 months), lower first molars (16.3 months), lower canines (20.4 months), upper canines (20.6 months), lower second molars (27.0 months) and upper second molars (28.5 months). These findings are similar to other Indian studies(7-10). The eruption of teeth as compared to studies from other countries was marginally delayed in Indian children(1-6). The malnourished children in the present study had delayed dental eruption that was evident in the first year of life.

Prevalence of enamel defects was more common in malnourished children within the first year of life as compared to wellnourished; combined as well as in males and females, separately. This suggests that malnutrition in children <3 years old may be an etiological factor for enamel hypoplasia. Infants with IUGR also showed marginally higher enamel hypoplasia than the wellnourished. Interestingly, Lai, et al.(16) had reported enamel hypoplasia in 96% very low birth weight babies.

Breast-feeding was significantly asso-ciated with decreased incidence of enamel hypoplasia. The prevalence of enamel hypo-plasia was higher in females in both wellnourished and malnourished groups, which did not show relationship to breast-feeding. Feeding pattern, mouth cleaning and other possible morbidity factors need to be studied to find the causes of enamel hypoplasias.

It may be recalled that during laying down of the enamel, at first the ameloblasts secrete a enamel protein and a matrix is formed which is later degraded and removed. This is followed by rapid influx of calcium and phosphate ions. In malnourished children, relative protein and mineral imbalance may be responsible for enamel hypoplasia either at the level of protein synthesis or during rapid influx of calcium and phosphate ions or both. Synergism between undernutrition and infection may also lead to generalized defect in growth and development.

Our observations show that lower central incisors are the first teeth to erupt. Dentition sequence of appearance was similar in mal-nourished as well as wellnourished children. However eruption was marginally delayed in the malnourished children. Enamel hypoplasia was more common in girls. Malnourished children had higher prevalence of enamel hypoplasia and enamel defect score. Breast-feeding possibly decreased the incidence of enamel hypoplasia.

Contributors: KNA, SN, NK collected and verified data. All the authors planned study. MMAF helped in discussions.

Competing interests: None stated.

Funding: None.