Prevalence of dental caries among a cohort of preschool children living in Gampaha district, Sri Lanka: A descriptive cross sectional study

Scant attention is generally paid towards protecting primary teeth, although they have many important functions. Apart from their role in feeding and phonation, they provide protection and space for permanent teeth[1]. Lack of care towards primary teeth, leads to poor oral hygiene and dental caries among preschool children. There are many well established public health programmes in Sri Lanka, but there is no such programme to promote oral health in preschool children.

Early childhood caries are a global public health problem. The American Academy of Paediatric Dentistry defines early childhood caries (ECC) as ‘the presence of caries in one or more primary teeth (cavitated or non-cavitated) in a child 71 months of age or younger’. ECC prevalence in England and USA is 6.8 - 12% and 11–53.1% respectively[2]. Highest prevalence of caries in maxillary anterior teeth is reported from Africa and South-East Asia[2]. In India, ECC prevalence among children between 8–48 months was reported as 44%[3].

Early stages of dental caries appear as white, chalky areas on the enamel close to the gum margin (enamel caries). As decaying process progresses to involve the dentine a visible cavity (dentinal caries) will develop. Once dental pulp is involved it becomes painful. Enamel caries are difficult to pick up, especially in uncooperative children. A mouth mirror and a good light source are needed to identify enamel caries. Mouth mirrors need sterilization in between patients and the main limiting factor in conducting dental research in a field setting is having adequate number of mouth mirrors. In contrast dentinal caries are easy to detect even without a mouth mirror.

Wrong feeding practices such as overnight feeding, adding sugar to formula milk and excessive consumption of sweets promote ECC[4, 5]. In Sri Lanka a significant number of children are fed overnight, beyond the age of two years[6]. We often observe poor oral hygiene among preschool children, admitted to Teaching Hospital Ragama. Only few published reports are available on ECC among preschool children in Sri Lanka. Prevalence of ECC among 1–2 year olds was reported as 23% by one study[7], while the National Oral Health Survey 2002/03 reported a prevalence of 65% among 5 year olds[8]. Kumarihamy et al. (2011), reported an ECC prevalence of 32.19% in children aged 1–2 years[9].

This study was conducted with a view of describing the prevalence of dental caries among a cohort of Sri Lankan preschool children, living in Gampaha district, Sri Lanka.

Sri Lanka is a low moderate income country, which has impressive health statistics. Maternal mortality rate (33.4 per 100,000) and infant mortality rate (10.1 per 1000 live births) in Sri Lanka, are among lowest in the region[10]. Ragama is situated in the Gampaha district, about 25 Km north of the capital, Colombo. In socio-economic standards, Gampaha is only second to Colombo district[11]. Ragama consists of a mixture of urban and suburban areas. The area belonging to Ragama Medical Officer of Health (MOH) extends over 25 Km², and consists of a socio-economically mixed population. Child welfare clinics (CWC) are held twice a week within the Ragama MOH area. Immunization, nutritional assessment and growth monitoring are carried out at these clinics. According to Ragama MOH office, about 95% of children living in the area utilise facilities of these clinics.

A descriptive cross sectional study was carried out from August to October 2010, at CWCs held in Ragama MOH area. Reasons for selecting this area were the socioeconomically mixed population and easy accessibility. The study was based on guidelines from World Health Organization (WHO) on conducting dental research, with few modifications due to limitation in resources.

Although the primary dentition has many important functions, due to lack of care prevalence of dental caries is high among preschool children. According to American Academy of Dentistry, the first visit to a dentist should be at one year of age and all children should have at least two routine visits to a dentist each year. In this study population a large percentage of children had never been to a dentist. Few children have visited a dentist to get treatment for a dental problem. This confirms that preschool children in Sri Lanka do not get adequate dental care. This is in stark contrast to other impressive health indices of Sri Lanka. Results of this study emphasize the importance of strengthening community based dental care services for preschool children in Sri Lanka.

Prevalence of dental caries showed a gradual increase with age to reach 68.8%, by the age of five years. This is high compared to western countries like England (6.8 -12%) and USA (11–53.1%). According to Kumarihamy et al. (2011) prevalence of dental caries among Sri Lankan children between 1–2 years was 32.19% and the mean deft was 2.01. In our study we included only children between two to five years, as we were studying only dentinal caries. Inclusion of early stages of caries (enamel caries) by Kumarihamy et al., explains the higher deft score observed by them compared to us. Results of Sri Lanka National Oral Health Survey 2002/03, also revealed a high prevalence of caries (65%) at 5 year of age. Absence of a programme to promote oral hygiene among preschool children and wrong feeding practices may be contributing for the high prevalence of caries observed. Unfortunately no action is taken up to now, to promote oral hygiene among preschool children in Sri Lanka[8].

Although the SIC index for the total sample was 4.09, SIC index for children between 4 – 5 years was 5.84. WHO has a set a goal that globally the SIC index should be less than three, at 12 years of age, by year 2015[12]. Although no target is set for preschool children, SIC index for Sri Lankan preschool children is nearly double the expected figure. When enamel caries are also included actual figures will be much higher than this.

In contrast to the findings of the United States National Health and Nutrition Examination Survey 1999–2004[14], boys in this population had a lower prevalence of dental caries and a low mean deft score than girls. High individual deft scores were also recorded from girls than from boys. As there is no gender discrimination against female children in Sri Lanka, there must be other factors responsible for this gender difference in dental caries. Effect of gender on prevalence of dental caries is probably an important area for future research.

Not only primary prevention of caries was unsatisfactory, but the care for carious teeth was also unsatisfactory. Majority of the carious teeth were left unattended, allowing children subjected to pain, discomfort and premature loss of primary teeth. Very low care index (1.55) proves this fact. Our findings are compatible with findings of Kumarihamy et al., which revealed 95% of carious teeth were left unattended. Primary teeth are not generally extracted unless they cause significant discomfort and pain, as they keep space for the permanent teeth. In this study we found some children who had multiple tooth extractions, which is a terrifying and fearful experience for a child of this age.

Previous studies have shown children living in poverty have higher prevalence of caries (14), but a clear association between family income and dental caries was not observed in this study. Though the highest income group had lowest prevalence of caries, the middle income group had higher prevalence than the lower income group. The discrepancy may due to other confounding factors like feeding practices. Children of mothers with a low educational level had high prevalence caries and children of mothers with highest educational level had lowest prevalence. However, a reverse pattern was observed in the middle educational categories.

This study was conducted in a district with higher socio-economic standards compared to most of the districts in the country (11). Therefore, it is reasonable to postulate the situation in other parts of the country may be worse than this. There are effective programmes in Sri Lanka for promoting breast feeding, family planning, immunization, growth monitoring and school dental hygiene, but there is no programme to promote oral hygiene in preschool children. Even at child welfare clinics no attention is paid to oral hygiene. According to this study and the study by Kumarihamy et al., the process of dental decay commences at a very early age. Any educational or interventional programme aimed at promoting oral hygiene should be introduced around latter part of infancy.

Brushing teeth twice a day is an important mode of preventing dental caries. Effective brushing will remove dental plaques, which is the first step in dental decay. Using a tooth paste containing fluoride reduces decay by making enamel more resistant. In contrast to very high prevalence of dental caries in this population, tooth brushing was commenced at very young age and nearly all children were using a tooth paste containing fluoride. High prevalence of dental caries in the presence of good oral hygiene practices, points towards wrong feeding practices as the cause. A study conducted in the same area revealed a high prevalence of wrong feeding practices, like overnight feeding beyond two years of age and adding sugar to formula milk[6].

Pattern of dental decay described by this study is similar to findings of earlier studies[9]. Most commonly involved teeth were the maxillary incisors and these accounted for nearly half of the carious teeth. When children are fed at night, milk tends to pool between the upper lip and maxillary incisors. Carbohydrates in milk are fermented by bacteria leading to dental caries[15]. In contrast incisors of the lower jaw had a very low prevalence of caries, probably because tongue and lower lip cover them from pooled milk. In the lower jaw, molars in both quadrants had high prevalence of caries. In the upper jaw first molars had high prevalence of caries but second molars had relatively low prevalence, which may be due to late eruption. Canines were the least involved, probably because their shape providing some protection from caries.

Prevalence of dental caries among preschool children in this population is very high. Majority of decayed tooth are left unattended, indicating poor dental care facilities for preschool children. Process of dental caries begins at very early age and progress steadily thereafter. An interventional program aimed at improving oral hygiene among preschool children is needed urgently. Although the prevalence of dental caries was high, practices related to tooth brushing were satisfactory, indicating wrong feeding practices as the possible cause.