Tooth decay is the most prevalent global disease caused by acid demineralisation that exceeds remineralisation where food with carbohydrate like sugar rich chocolate or confection is left caught on teeth.
Sugar rich chocolate like some other carb foods, is usually used regularly especially at Easter, Christmas, birthdays and thousands of other occasions causing a little episodes of acid demineralisation that sooner or later develop into cavities where demineralisation exceeds remineralisation.