Can infants catch caries? A review of the current evidence on the infectious nature of dental caries in infants.

INTRODUCTION Despite a decline in its prevalence worldwide, dental caries remains one of the most common chronic diseases in childhood (Mouradian, 2001). Moreover, its distribution has become more polar with most of the disease being experienced by certain vulnerable groups, such as pre-school-aged children, for whom reductions in caries experience have not been as marked as in other age groups (Pitts and Palmer, 1994). There is strong evidence to indicate that the experiences and health status of young children directly influence their health, development and wellbeing throughout life (Weinstein, 1998). Dental problems in early childhood have been shown not only to be predictive of future dental problems but also to impact upon general growth and cognitive development by interfering with sleep, appetite, eating patterns, poor school behaviour and negative self-esteem (Ayhan et al, 1996; Acs et al, 1999; Low et al, 1999; Edelstein, 2000; Thomas & Primosch 2002). It is important to understand why very young children develop dental caries, to be able to identify those most at risk, and to instigate effective preventive strategies. Although dental caries is a complex chronic disease with a wide range of biological, environmental and behavioural determinants that complicate its aetiology, its pathogenesis is relatively well understood. There are three essential factors in its aetiology: the host or susceptible tooth, the plaque or oral microflora and the frequent presence of a fermentable carbohydrate. The development and progression of dental caries depend on the presence of cariogenic micro-organisms to metabolise fermentable carbohydrates and produce organic acids that in turn demineralise dental hard tissues (Seow, 1998). The microbiology of dental caries in humans has been well described elsewhere (Loesch, 1986; van Houte, 1994; Tanzer et al, 2001; Kleinberg, 2002). The principal group of bacteria responsible for dental caries has been identified as being mutans streptococci (van Houte et al, 1982; Milnes and Bowden, 1985). Mutans streptococci (MS) possess many characteristics that facilitate caries development, including the ability to adhere to tooth surfaces and to synthesize certain glucans from sucrose (Freedman et al, 1978). MS are also able to synthesize intracellular polysaccharides, which supports continual acid production, which in turn fosters demineralization of the dental hard tissues (Spatafora et al, 1995). Early Childhood Caries or ECC (historically also referred to as nursing bottle caries, baby bottle decay and many other terms) is a particular form of dental caries affecting pre-schoolaged children. It has been defined in many different ways over the years, however currently the American Academy of Pediatric Dentistry defines ECC as “the presence of one or more decayed (non-cavitated or cavitated lesions), missing (due to caries) or filled tooth surfaces in any primary tooth in a child 71 months of age or younger. In children younger than three years of age, any sign of smooth-surface caries is indicative of severe early childhood caries. From ages three through five, one or more cavitated, missing (due to caries), or filled smooth surfaces in primary maxillary anterior teeth, or a decayed, missing, or filled score of equal or more than 4 (age three), equal or more than 5 (age four), or equal or more than 6 (age five) surfaces, constitutes severe early childhood caries” (American Academy of Pediatric Dentistry, 2003). It can affect children as soon as their teeth erupt. Although there is strong evidence that MS cause dental caries, MS are not found in the mouths of newborn babies (Berkowitz et al, 1975). This implies that MS have to be acquired from elsewhere, therefore dental caries can be considered to be a transmissible disease. The aim of this paper is to review the current literature in order to answer the following questions: 1. What is the evidence that MS are associated with caries in infants? 2. When do infants acquire MS? 3. From where or from whom do infants acquire MS? 4. What factors influence the risk of infection with MS in infants? Finally, we will speculate on some potential methods for preventing the initiation and development of dental caries in this young age group.