The Effect of Breast Feeding on Eruption of First Primary Tooth in a Group of 6-12 Month Saudi Children

Eruption of primary teeth is a very important indicator to assess growth and development of the children. Aim: The present research studied the possible influence of the breast feeding on eruption time of first primary tooth. Also, number of erupting primary teeth in both males and females up to 12 month in relation to type of feeding has been studied. Study Design: This is an analytic cross sectional study. Place and Study: The present sample was selected from 4 June 2015. Methodology: A total of 100 healthy children aged between 6-12 month with mean age of (9.26±2.90) month were selected according to cluster random sampling. A questionnaire was completed by direct interview of the children's Mothers. They were asked about the type of feeding (Breast or bottle feeding) they practiced for their children, the eruption age of the first appearing primary tooth in the oral cavity for their children as well as the number of erupted primary teeth. Results: In breast feeding children the mean time of eruption for first primary tooth was (7.48±1.64) month, while it was (7.17±1.34) month for bottle feeding with no significant difference, p=0.477. The mean number of erupting primary incisors teeth was lower in group of breast feeding (1.72±1.84) than those in bottle feeding (3.12±2.82) with statistical significant difference (p=0.005). For the whole sample, the mean number of erupting teeth was not affected by the gender. It was (1.98±2.09) for males and (2.15±2.29) for females with no significant difference, p=0.706. Multivariable linear regression analysis demonstrated that Increase in age and bottle feeding were predicators of number of erupted teeth. Conclusion: In this group of Saudi Children, breast feeding had no influence on eruption time of first primary tooth. The number of erupting primary incisors teeth was significantly lower in the group of breast feeding than those in bottle feeding. Eruption of primary teeth was not affected by gender.


INTRODUCTION
Primary teeth, which known as (milk teeth, baby teeth, and temporary teeth), are the first set of teeth in the growth development of humans. They form and develop during the embryonic stage of development. The eruption of these teeth begins at the age of six months and continues until twenty-five to thirty-three months of age [1].
Although eruption of primary teeth is a physiological process, it is affected by climate, race, diet, nutrition, and disease. Consequently, primary teeth emergence has been used to assess growth and development and for age estimation in children [2].
Milk is the major nutritional source in the first years of child life. It is beneficial for the development of teeth and bone [3,4].
Breast milk is an essential nutrients for the healthy teeth development. It includes calcium, phosphorus, and vitamins A, C, and D. Calcium and phosphorus are needed to properly form the hydroxyapatite crystals, and their levels in the blood are maintained by Vitamin D. Vitamin A is necessary for the formation of keratin, and Vitamin C is for collagen. So the deficiencies of these nutrients can have a wide range of effects on tooth development [5]. For these reasons, different health care workers such as dentists, dietitians and nursing professionals have been known to give recommendations to the public, for breast feeding and weaning (3,4). Moreover, the World Health Organization (WHO) recommends to maintain breast feeding up to the second year of the life or even longer [6].
Considering breastfeeding status as a possible source of variation in the timing of emergence of primary teeth, several researches had been conducted with different results. Some reported delayed eruption of teeth in children who were not breast fed [2,5], and earlier eruption in children with exclusive breast fed compared to those partially breast fed [14]. Appreciable associations between breastfeeding status and emergence timing and patterns of eruptions of first primary teeth was recently reported [15]. On the other hand, some other researchers found that breast feeding did not alter the eruption time of primary teeth [16][17][18][19].
For this inconsistent results, the present research studied the possible influence of the breast feeding on eruption time of first primary tooth. Also, number of erupting primary teeth in both males and females up to 12 month in relation to type of feeding has been studied.

MATERIALS AND METHODS
A cross sectional study for a sample of 100 children (55 females and 45 males) aged 6-12 months who came for child's vaccination into four primary health care centers in, Al-Madinah Al-Monorah, KSA were selected according to cluster random sampling. Inclusion criteria were: Saudi nationality as verified by identity cards of parents ,clinically healthy, free from any diseases or disorders and not receiving any medication and normal full term born child as indicated by child medical record.
Ethical approval was sought from the research committee, Faculty of Dentistry, Taibah University, KSA before starting the study. Verbal consent was obtained from the mother of every child after explaining the purpose of the research and before collecting data. A questionnaire was completed by direct interview of the mother by the first researcher. The mother was asked about the sex and type of feeding of her child (breast or bottle). Also, she was asked about the time and place of erupting first primary tooth. The number of the erupting teeth in the child mouth was recorded as self reported by the mother.

Data Analysis
Descriptive statistics was undertaken to report children characteristics. Continuous data (e.g. age of children) was reported as mean±SD. The categorical data (e.g. children's gender) was reported as number (N) with percentages. The independent t-test was used to compare the means of continuous variables across categorical variables (e.g. number of teeth erupted for both gender). Pearson product -moment correlation coefficient was run to explore the relationship between age and number of erupted teeth. Finally, multivariable linear regression analysis was run to find the significant predictors of number of erupted teeth in a group of Saudi children (aged 6-12 months). Only predictors with significant level of P≤.05 considered to enter the regression model. For all analyses, a P≤.05 was considered statistically significant. Data was analyzed using the statistical package IBM SPSS software, version 20.

RESULTS AND ANALYSIS
This study was taking over 2 months, June and July 2015. Table 1 shows the characteristics of the present participated children.
Lower central incisor is reported by all the mothers as the first appeared tooth in the mouth of their children.
Of the whole sample, 64 children were with erupted teeth (Table 1). Regarding the influence of type of feeding on the time of eruption of first primary tooth, statistical analysis showed no significant difference between breast and bottle feeding. For breast feeding children the mean time of eruption for first primary tooth was7.48±1.64 month, while it was 7.17±1.34 month for bottle feeding, P=.48 as shown in Table 2.

N (%) = Number and percentages
In respect of the number of erupting teeth in both breast and bottle feeding children, bottle feeding group showed higher number of erupting teeth than breast feeding with statistical significant difference. The mean number of erupting teeth in bottle fed children was 3.12±2.82 compared to 1.72±1.84 for breastfed children, P=.005 as shown in Table 2. This differences was prominent among children aged 12 months where bottle-fed children were more likely to have more erupted teeth 4.20±2.39 than breastfed children 1.18±1.63, P=.001.
As for gender differences, with respect to erupted teeth for the whole sample (aged 6-12 months), there was no significant differences between male children 1.98±2.09 and female children 2.15±2.29, P=0.71 and likewise at age 12 for males 4.08±1.85 and females children 4.71±2.58, P=0.47 (Table 2).
Finally, it was found a strong, positive correlation between increase in age and number of erupted teeth (r=0.690, P=0.0001). As the child getting older, the number of erupted teeth increased.
Multivariable linear regression analysis demonstrated in (Table 3) that Increase in age and bottle feeding were predicators of number of erupted teeth. These two variables contributed by 49% of the variance (R=0.71, R 2 =0.49, N=100, P=0.001).

DISCUSSION
The emergence of first primary tooth in the oral cavity of the child is of great importance to assess child growth and development [20,21].  Nutrition is considered one of multiple factors affecting the timing and pattern of tooth eruption [14,17].

Variable †N (%) Mean±SD t P-value First tooth eruption time/month
Milk in different forms either breast or bottle formula is considered the major source of nutrition in the first 12 month of children's life [3,4]. Within this period of life breast feeding may be terminated, so its effect may be more important during this period as shown by Martin, [22].
For the aforementioned reasons the present study adopted the age of 6-12 month. Moreover, the first primary tooth is suggested to erupt within this age range [10,16,23].
Opinion is still unresolved regarding the role of nutritional status in dental development [15,23,24] so, this study is carried out to clarify the influence of the breast feeding on eruption time of first primary tooth. Also, number of erupting primary teeth in both males and females up to 12 month in relation to type of feeding has been investigated.
Present study showed that the time of eruption of first primary tooth was not influenced by the type of feeding (breast or milk) as shown in Table 2.
This result is running with several studies who did not show effect of breast feeding on the time of eruption and pattern of teeth eruption within the first 12 month of children life [13,16,[17][18][19].
On the other hand, it contradicts the results of Holman and Yamaguchi [2] who showed that children who were not breastfed at all showed delay emergence of the central incisors. However, Aziz [11] found that the lower central incisors erupted earlier in beast-fed group than bottle-fed group with significant difference. He attributed his results to the nutritional advantages of the breast feeding. Moreover, Oziegbe et al. [14], reported that exclusively breast fed children had earlier erupting primary teeth in comparison to those who were partially breast fed.
In respect of the number of erupting teeth in both breast and bottle feeding children, bottle feeding group showed higher number of erupting teeth than breast feeding with statistical significant difference as shown in Table 2.
This result is surprising. Although 75% of the mothers positively responded to breast feeding as social desirability, they maybe actually practiced partial breast feeding with short durations and frequencies. Meanwhile, the presence of enriched formula of bottle milk as well as the change in life style with increased consumption of junk food which is not healthy and lacking a lots of vitamins and minerals may justify this result. This result contradicts other investigators who found that the number of erupting teeth is greater in exclusively breast fed children [11,14,18]. At the same time, Folayan and et al. [17] failed to find relation between breast feeding and number of teeth erupted within the first 12 month of life. Recently, Kohli and et al. [15] reported that only breastfeeding frequencies had significant impact on timings and patterns of eruption than durations of breast feeding.
Similar to previous study [17], age seems to play an important role in number of erupting teeth. The differences in erupted teeth was prominent among children aged 12 months where bottle-fed were more likely to have more erupted teeth as shown in Table 2.
Contrary to others (17) who found age as the only factor significantly influence the number of erupted teeth, current study showed that age and bottle feeding were predictors of number of erupted teeth as shown in Table 3.
Statistical analysis showed that eruption of primary teeth in the present study was not affected by gender as shown in Table 2. This result is in agreement with Hollman study [2] who did not find significant sex differences in eruption of primary teeth. On contrary, other studies for different children populations reported earlier eruption of primary teeth in males compared to females in Sudanese children [13] and Saudi children [8]. Nepalese [25] and Indian children [11,15] showed an earlier emergence of primary teeth in females compared to males. The inconsistent results may be related to different study populations, sample size, study designs, nutritional, climatic and racial background.

CONCLUSION AND RECOMMENDA-TIONS
Within the limitations of this cross sectional study (small sample's number and self reported answers by the mothers), we can come to the following conclusions: Breast feeding had no influence on the time of eruption of first primary tooth. Number of erupting teeth within the age range of 6-12 month was lower in breast fed children rather than bottle fed children. Eruption of primary teeth was not affected by gender. There was a strong positive correlation between increase in age and number of erupted teeth.
Further study using a larger sample size including different districts in KSA is recommended. This study would prove a useful basis of comparison with other future researches.