Every time I go to the dentist, I'm told I need to be flossing more. We always go over the techniques, etc, and I always get a Stern Talking To about not flossing once or twice a day. If I go to the dentist regularly (every 4-6 months), then aren't they cleaning everything out anyway?
Anecdotally, I only got cavities after not going to the dentist for three years, and even then, just two little ones. Prior to that, for 30 years, no cavities, and no flossing.
Here's one example of the claim, from http://www.saveyoursmile.com/healtharticles/flossing.html:
If you do not floss and allow plaque to remain in between teeth it eventually hardens into a substance known as tartar. Unlike plaque which can be easily removed by brushing, tartar can only be removed by your dentist. Over time, levels of more dangerous types of bacteria build up within tartar. Mean and vengeful, these bacteria produce toxins which irritate and inflame the gums. This condition is known as gingivitis. If gingivitis is left untreated it can progress to periodontal disease - a condition where bacteria and their toxins invade not only the gums but also the bones and the structures supporting the teeth. This can lead to bone loss, loose teeth, and teeth which fall out.
However, the scientific articles I can find use small sample sizes (N=4, for http://ukpmc.ac.uk/abstract/MED/6937641, to first establish that flossing reduces bacterial buildup, and N=119 for http://ukpmc.ac.uk/abstract/MED/2786959, taking patients who already have gingivitis to see if flossing helps).
Has there been a large, longitudinal study that compares the effectiveness of flossing to regular dentist visits for plaque reduction and avoidance of gingivitis?