Sir, in a letter J. Hartley wonders where the evidence for 'spit don't rinse' after toothbrushing originates (BDJ 2014; 217: 206). A previous article in the BDJ explains this well.1 As long ago as 1992 there was evidence of caries reduction if fluoride toothpaste was not rinsed off.2 In this study a 6% reduction in caries incidence was found and later studies have shown a larger reduction of up to 16%. Dr Hartley mentions a case in America where ingestion of excess fluoride was a problem. This is easily avoided by using only a pea-sized blob of toothpaste. It has been recommended to rinse with a small amount of water,3 but the most widely accepted advice is indeed to 'spit not rinse'. Delivering better oral health states that there is grade 4 evidence to support it, ie evidence from well-designed, non-experimental studies from more than one centre or research group.4 This has been taught to many dental nurses on fluoride varnish courses and to avoid confusing our patients it is important that our advice is evidence based, and consistent. I hope that this helps.