Recent news about this small-scale, yet highly interesting, study performed at the University of Dunedin has been published internationally. Researchers measured pH levels of participants at night and forced them to breathe through their mouths. They found that on average pH level became a mildly acidic at 6.6. Sometimes, the levels reached a pH of 3.6 which is fairly acidic and comparable to drinking a fizzy drink or orange juice. The critical pH threshold at which tooth enamel starts to erode is 5.5. Bathing your teeth in acid for several hours at night is a short cut to caries and other problems.
However, mouth breathing at night can cause many other problems in addition to tooth decay. Another Dunedin study published last year showed a connection between mouth breathing during sleep and lower academic performance in children as well as behaviour problems. The reason is that mouthbreathing causes an increase in breathing volume, which leads to reduced carbon dioxide levels in the blood. Low CO2 can be directly attributed to low oxygen availability to cells due to vasoconstriction (tightening of blood vessels) and the Bohr effect.
The question becomes what can we do about this? Breathing retraining – not more drugs – is the sensible answer.