Community Dental Health (2004) 21 (Supplement), 71–85 © BASCD 2004 Risk factors for dental caries in young children: a systematic review of the literature Rebecca Harris 1 , Alison D Nicoll 1 , Pauline M Adair 2 and Cynthia M Pine 1 1 WHO Collaborating Centre on Oral Health in Deprived Communities, University of Liverpool Dental School, England; 2 Department of Clinical Psychology, The Royal Hospitals, Belfast, Northern Ireland Correspondence to: Dr R.V. Harris, 5 th Floor, The University of Liverpool, School of Dentistry, Pembroke Place, Liverpool L3 5PS, UK. E-mail: harrisrv@liverpool.ac.uk Objective To conduct a systematic review of the literature on risk factors for dental caries in deciduous teeth of children aged six years and under, to give a scientific framework for the international collaborative studies on inequalities in childhood caries. Method Accepted guidelines were followed. Studies were identified by electronic searching and reviewed on the basis of key words, title and abstract by two reviewers to assess whether inclusion criteria were met. Copies of all articles were obtained and assessed for quality according to the study design. Results 1029 papers were identified from the electronic search, 260 met the prima facie inclusion criteria. 183 were excluded once full copies of these papers were obtained. Of the 77 studies included, 43 were cross sectional, 19 cohort studies, 8 case control studies and 7 interventional studies. Few obtained the highest quality scores. 106 risk factors were significantly related to the prevalence or incidence of caries. Conclusion There is a shortage of high quality studies using the optimum study design, i.e. a longitudinal study. The evidence suggests that children are most likely to develop caries if Streptococcus Mutans is acquired at an early age, although this may be partly compensated by other factors such as good oral hygiene and a non- cariogenic diet. Diet and oral hygiene may interact so that if there is a balance of ‘good’ habits by way of maintaining good plaque control and ‘bad’ habits by way of having a cariogenic diet, the development of caries may be controlled. Key words: risk factors; dental caries; early childhood caries Introduction Dental caries is widely recognised as an infectious disease induced by diet. The main players in the aetiol- ogy of the disease are; a) cariogenic bacteria, b) fermentable carbohydrates, c) a susceptible tooth and host and d) time. However, in young children bacterial flora and host defence systems are in the process of being developed, tooth surfaces are newly erupted and may show hypoplastic defects, and their parents must negotiate the dietary transition through breast/bottle feed- ing, first solids and childhood tastes. Thus it is thought that there may be unique risk factors for caries in infants and young children (Seow, 1998). It is disconcerting to see rampant caries in young children (Fass, 1962). The pattern of decay is typically that many teeth are affected, with caries developing rapidly, often soon after the teeth have erupted. Surfaces usually at low risk of developing caries are affected such as the buccal surfaces of maxillary incisors with the obvious consequence of affecting the child’s facial appearance. It is this pattern of caries that has been labelled variously as ‘baby bottle tooth decay’, ‘nursing caries’ and ‘night bottle mouth’. However, since these terms suggest that the prime cause of such caries is inappropriate bottle feeding and current evidence sug- gests that although use of a sugar-containing liquid in a bottle at night-time may be an important aetiological factor, it may not be the only or the most important factor, it is now recommended that the term ‘early child- hood caries’ be used when describing any form of caries in infants and pre-school children (Reisine and Douglass, 1998). The answer to the question ‘What causes early child- hood caries?’ is an important, if a complex one. It concerns those in both developed (Holt et al., 1996; Wendt et al., 1996) and developing countries (Matee et al., 1994; Ye et al., 1999) where many children experience this pattern of disease. Understanding the aetiology of the disease has a direct influence on public policy. In the United Kingdom, the British Society of Paediatric Dentistry recommend a reduction in sugar intake by the whole child population in the country. The policy recom- mended by the equivalent professional society in America, on the other hand is that sugar restrictions can be relaxed in a society where fluoride is used frequently, particularly for children who have low or no caries (although this is not a universally held view amongst dentists in America), (British Society of Paediatric Dentistry, 1992; American Academy of Pediatric Dentistry, 1989). How aetiology is interpreted also influences the design of interventional programmes set up to prevent the disease. Factors that may be implicated in giving rise to caries in young children have been described in a number of review papers (Federation Dentaire Internationale, 1988; Horowitz, 1998; Moss, 1996; Reisine and Douglass, 1998; Seow, 1998). However none of these have employed a systematic methodology. The body of evidence in this area is large, and without a systematic approach where strategies for identifying and selecting information are