Question

My six-year-old grandchild attends kindergarten in the canton of Obwalden. There, the children were told by a dentist and a dental hygienist that they should not rinse their teeth after brushing, but only spit them out so that the fluoride toothpaste has a more lasting effect. I think that's absurd and harmful. What does your specialist say? D. E. in L. 

Short answer

Most importantly, children should not be discouraged from cleaning their teeth with a fluoride toothpaste. Those who wish to rinse lightly with water after brushing should do so. Those whose personal comfort in the mouth allows them to rinse only may receive a small prophylactic benefit. The difference of higher fluoride concentrations in the mouth without rinsing is so small that not rinsing after brushing is absolutely harmless.

The prophylactic measures successfully introduced by the Swiss dental profession and supported for decades in Switzerland are based on three pillars: 1. regular and correct tooth brushing, 2. regular fluoride application, 3. a low-sugar diet and avoidance of sugary snacks and drinks. 

Unique in the world 

These measures have led to a reduction in tooth decay of up to 90% in Swiss adolescents today! This result is unique worldwide. As part of Swiss school dental care, these prophylactic measures are now taught to all children and young people and supplemented with toothbrushing exercises, check-ups and any necessary dental treatment. 

Regular fluoride toothpaste

Your question relates to point 2. In principle, it is useful to allow the fluoride to remain in the oral cavity for as long as possible, where it strengthens the enamel, reverses incipient caries and reduces the formation of caries-causing acids. The question is therefore whether the benefit is sufficiently high that the unpleasant feeling in the mouth when not rinsing should be tolerated. The fluoride concentration in toothpastes is between 1000 and 1500 ppm (parts per million). When brushing without rinsing, only spitting out, about 400 ppm fluoride remains in the mouth. When brushing with a light rinse, around 250 ppm fluoride also remains in the mouth. Incidentally, 250 ppm corresponds to the concentration of fluoride-containing mouthwash. Whether the 150 ppm higher fluoride concentration (as is present without rinsing) has a greater benefit is scientifically controversial. 

Do not demotivate children 

Most importantly, children should not be discouraged from cleaning their teeth with a fluoride toothpaste. Those who wish to rinse lightly with water after brushing should do so. Those whose personal comfort in the mouth allows them to spit only may receive a small prophylaxis benefit. 

Absolutely harmless 

When brushing teeth, about 0.4% of the amount of toothpaste used is usually swallowed anyway. The difference of 0.015% (150 ppm) higher fluoride concentration in the mouth without rinsing is so small that not rinsing after brushing is absolutely harmless. 

Author: Dr. med. dent. Jürg Eppenberger
Published in: Neue Luzerner Zeitung on May 30, 2007