In this context, the similarity in baseline characteristics between those lost and those not, between the treatment groups analyzed, including their use of dental services, and the similar proportion of overall losses in each group (30% of the intervention group, 34% of controls) suggest that selection bias is unlikely to be a major problem. The greater initial loss of controls can be seen as part of this process, being most likely attributable to the somewhat longer period between hospital discharge and their first home contact. It is reassuring that even our worst-case analysis, in which all lost were assumed to have caries, demonstrated a statistically significant reduction not too different from that of our main analysis.