“ANGER’S like a battery that leaks acid right out…” wrote Criss Jami in his poetry collection Venus in Arms (2012).

Dental education, even as far back as our elementary school years, points at food acidity as one thing to watch out for to avoid tooth injury. For instance, enamel, the outer covering of the teeth, consists primarily (around 96 percent) of hydroxyapatite, which is calcium phosphate in crystalline form.

Sugary foods such as candies, fruit juices and soft drinks unwashed from the mouth feed the normal bacterial population in the mouth, which converts these into lactic acid and acidifies the environment of the mouth. When acidification occurs, the hydroxyapatite component of the enamel weakens (demineralizes). This weakening enamel structure allows bacteria to invade the deeper parts of the tooth, increasing acidity there, resulting to further demineralization of enamel.

The cycle repeats again and again if the bacteria inside the enamel are not removed, until the teeth decay.

However, acidity is not the only threat to the mouth. Alkalinity too is a threat to the mouth. It induces inflammation and erosions in the skin and the epithelium.

Temporary alkalinity of the oral cavity may be brought by tobacco products, bicarbonate toothpaste, calcium chloride in deep cavities and pulp filling materials and sodium hydrochlorite used in root canal treatment. Tobacco, for instance, is the leading cause of oral cancer. In fact, in Taiwan, it is the most common site of oral cancer in the buccal lining due to the common use of the betel quid, which contains alkaline slaked lime. In Japan, it commonly causes cancer in the tongue. It has been established that nicotine absorbs easily through the mouth lining in free form. A study in Japan, published in Acta Histochemica et Cytochemica in 2014, confirmed this buccal damage from alkaline chemicals, which resulted to wound repair within a week. However, the study cannot establish the mechanism of buccal cancer formation resulting from alkaline chemical attack, especially from such compounds as nicotine.

This again is another situation where balance is crucial, where a tip toward the right can be as bad as a tip toward the left. Confucius said in Analects (1990): “To go beyond is as wrong as to fall short.”