1. Background
Early acquisition of mutans streptococci is a major risk factor in the occurrence of Early Childhood Caries (ECC) (1). The mother-to-child transmission of mutans streptococci is called vertical transmission (2). It is said that neonatal factors are effective in the possibility of early acquisition of these bacteria through vertical transmission (3). A study showed that there is a significant relationship between early acquisition of the aforementioned bacteria and mode of delivery, level of the bacteria in the mother’s mouth, and also the oral hygiene of the mother, i.e., children delivered by caesarean section are afflicted with mutans streptococci a few months earlier than those delivered by normal vaginal delivery. The researchers of the study propose that caesarean section accelerates the acquisition of mutans streptococci, since in this type of delivery, carried out in aseptic conditions, the infant is less exposed to maternal microbiota while in a normal vaginal delivery, the infant is exposed to more variety of the bacteria present in the mother’s vaginal and anal regions (4).
2. Objectives
The present study conducted as a longitudinal study in order to evaluate the effect of the mode of delivery on the extent of occurrence of ECC in two groups of full-term and healthy infants delivered through caesarian section or normal vaginal birth. The effect of factors such as amount of mutans streptococci in the mother’s mouth, and the status of mother’s oral hygiene on the occurrence of the caries is studied as well. Furthermore, considering the lack of information concerning the effect of blood group types on the possibility of occurrence of ECC, and also reports highlighting the role of blood group types in affliction with some diseases such as certain cancers, Ischemic Heart Disease (IHD), and gastro-intestinal disorders (5-7), the present study deals with the above mentioned issue as well.
3. Patients and Methods
The study was conducted as a longitudinal study but at the end of study, data analysis was performed in the same manner as a cross-sectional study. This was done because there was no observed macroscopic sign of caries on erupted teeth surfaces at 6th, 12th and 18th month of life of the babies and the signs were observed only at their 2nd birthday.
3.1. Ethical Consideration
A written consent was obtained from every mother. This took the form of an explanatory information sheet and a consent form. The procedure was approved by Ethics Committee of Kerman University of Medical Science (with Ethical code K/86/20).
4. Results
There was no observed macroscopic sign of caries on erupted teeth surfaces at 6th, 12th and 18th month of life of the babies and the signs were observed only at their 2nd birthday. Therefore, analysis and statistical method was used similar to a cross-sectional study.
- The occurrence of ECC and the children‘s gender relationship:
It was observed that there is a statistically significant relationship between these variables. (P<0.05), 28.2% of the children had caries of their primary maxillary incisors by 24 months of age (Table 1).
- The occurrence of ECC and the mode of delivery relationship:
There was no significant relationship between the occurrence of ECC and the mode of delivery (P>0.05), (Table 1)
Table 1.Distribution of the 2-year-old Children with or without Carious Max. Incisors in Relation to their Gender and in Relation to Mode of Birth
| Children With Carious Teeth, No. (%) | Children With Healthy Teeth, No. (%) | Total, No. (%) | |
|---|---|---|---|
| Female | 9 (13.20) | 59 (86.80) | 68 (100.00) |
| Male | 24 (49.00) | 25 (51.00) | 49 (100.00) |
| Total | 33 (28.20) | 84 (71.80) | 117 (100.00) |
| Caesarean | 19 (32.20) | 40 (67.80) | 59 (100.00) |
| Normal | 14 (24.10) | 44 (75.90) | 58 (100.00) |
| Total | 33 (28.20) | 84 (71.80) | 117 (100.00) |
-Status of oral hygiene of mothers, the amount of mutans streptococci, and the extent of children’s caries relationship:
The instances of ECC in children of mothers who had poor oral hygiene and higher amount of mutans streptococci were higher (Table 2). There were 24 mothers scored as 0 and 4% of their children had caries; 65 mothers were scored as group 1 and 7.7% of their children had caries; 28 mothers were scored as group 2 and 96.4% of children had caries.
Table 2.Distribution of the 2-year-old Children with or without Carious Max. Incisors in Relation to Salivary Level of Strep. Mutans (SM) in their Mothers and in Relation Mother's Oral Hygiene (S-OHI)
| Children with Carious Teeth, No. (%) | Children with Healthy Teeth, No. (%) | Total, No. (%) | |
|---|---|---|---|
| Score0 a | 1 (3.00) | 23 (27.40) | 24 (20.50) |
| Score1 a | 5 (15.20) | 60 (71.40) | 65 (55.60) |
| Score2 a | 27 (81.80) | 1 (1.20) | 28 (23.90) |
| Total a | 33 (100.00) | 84 (100.00) | 117 (100.00) |
| Score0 b | 0 (0.00) | 0 (0.00) | 0 (0.00) |
| Score1 b | 0 (0.00) | 42 (50.00) | 42 (35.90) |
| Score2 b | 2 (6.10) | 40 (47.60) | 42 (35.90) |
| Score3 b | 31 (93.90) | 2 (2.40) | 33 (28.20) |
| Total b | 33 (100.00) | 84 (100.00) | 117 (100.00) |
a Level of the S.M
b S-OHI
-The occurrence of ECC and the birth weight relationship:
There was a statistically significant relationship between the occurrence of ECC and the birth weight of the children (P<0.05), (Table 3).
Table 3.Distribution of the 2-year-old Children with or without Carious Max.Incisors in Relation to Their Weight at Time of Birth (g).
| Children with Carious Teeth, No. (%) | Children with Healthy Teeth, No. (%) | Total, No. (%) | |
|---|---|---|---|
| < 2700 | 11 (33.30) | 0 (0.00) | 11 (9.40) |
| 2700<>3000 | 4 (12.10) | 16 (19.00) | 20 (17.10) |
| 3000 < | 8 (24.20) | 36 (42.90) | 44 (37.60) |
| Non registered | 10 (30.30) | 32 (38.10) | 42 (35.90) |
| Total | 33 (100.00) | 84 (100.00) | 117 (100.00) |
-The occurrence of ECC and the blood groups relationship:
There was no statistically significant relationship between the occurrence of ECC among the children and specific blood groups (Table 4).
Table 4.Distribution of the 2-year-old Children with or without Carious Max.Incisors in Relation to Type of Blood Group.
| Children with Carious Teeth, No. (%) | Children with Healthy Teeth, No. (%) | Total, No. (%) | |
|---|---|---|---|
| A | 11 (33.30) | 8 (9.50) | 19 (16.20) |
| B | 7 (21.20) | 8 (9.50) | 15 (12.80) |
| AB | 3 (9.10) | 4 (4.80) | 7 (6.00) |
| O | 2 (6.10) | 7 (8.30) | 9 (7.70) |
| Non registered | 10 (30.30) | 57 (67.90) | 67 (57.30) |
| Total | 33 (100.00) | 84 (100.00) | 117 (100.00) |
5. Discussion
There have been a limited number of studies to explore the possibility of a relationship between gender and occurrence of Early Childhood Caries (ECC). In a pilot study done in Canada, it was observed that the instances of ECC in boys were higher than in girls; however, the difference was not significant (10). A similar study in Kerman, Iran among 500 children, reported that the instances of ECC in boys under the age of 3 were significantly higher than that of girls of the same age (11). In the present study, there was a significant difference; a high incidence of dental caries among male in comparison to the female group. This difference may be related to Follicle Stimulating Hormone (FSH) which is higher in female. This hormone is secreted by the anterior portion of pituitary gland and has an important role in the development, body growth, puberty and reproductive processes (12). So, it may work as a probable factor for increasing Secretary IgA (S-IgA) in female babies given the low prevalence of dental caries among them. A study showed that the mean saliva concentration of S-IgA in female toddlers with ECC was higher than that in female toddlers without ECC (P <0.05) (13).
The present study showed that there is no statistically significant agreement between types of delivery and the occurrence of caries in the newly-erupted teeth of the child while Li et al. maintained that there was a significant relationship between caesarean deliveries and the early acquisition of mutans streptococci (4). Furthermore, Li et al. as well as Lai et al. had previously showed that there is a significant relationship between early colonization of mutans streptococci and higher and more severe incidences of caries in children (14, 15). Also, Li and colleagues concluded that caesarean section causes a higher incidence of risk of ECC in children (4). However, the present study showed the opposite (Table 1). The amount of streptococci in the mouths of children in the two groups was not investigated in this study. There is a possibility that the acquisition of the bacteria occurs sooner in children born by caesarean section but the occurrence of caries did not show a significant difference between the two groups. This may be due to the numerous factors in the complicated process of occurrence and development of caries.
The present study showed that those mothers who had higher amounts of streptococci in their mouths and lower oral hygiene had children with higher chance of ECC (Table 2). This is indicative of the fact that the aforementioned mothers probably transmitted more bacteria to their children, which is similar to the findings of Berkowitz’s studies (1, 2).
In this study, a significant relationship between child’s birth weight and occurrence of ECC was also found (Table 3). There was a higher occurrence of ECC observed in infants with lower birth weights. It seems that infants with lower birth weights are more likely to progress teeth with hypocalcified and hypoplastic enamels which provide better environments for accumulation of mutans streptococci. Furthermore, the low resistance of developmentally disordered enamel against destructive acids may lead to accelerated caries. These instances were also mentioned in studies carried out by Milgram, Wan and Law (3, 16, 17).
Through the analysis of blood group types of children, the hypothesis that certain genetic factors may be effective in the occurrence of ECC was proposed and investigated. The results showed that although children with blood group of ‘A’ had a higher occurrence of caries compared to other blood group types, the difference was not significant (Table 4). No study on the relationship of incidence of ECC and blood group types has been conducted yet. However, numerous studies showed that among patients suffering from Ischemic Heart Disease, most of the patients without risk factors had the blood group of ‘A’. (6, 18, 19).A study showed that the blood group of Louis is effective in breast cancer (5) and the effect of blood group of ‘O’ in the occurrence of peptic ulcer is clear (7). Nevertheless the identification of mechanisms under which blood group types affect diseases needs further analytical and case-control studies. A limitation of the study was lack of patients’ cooperation. In this two-year follow-up study, we didn`t observe any significant association between method of delivery and occurrence of ECC, despite the positive correlationbetween occurrence of ECC and gender.
