What is a “cavity”? It is a weakening of the outer enamel layer caused by acids in dental plaque. The acids break down the enamel minerals and cause them to leach out. At the start the change is not noticeable. In this stage the cavity is called an incipient lesion, and it is reversible. The minerals can be reabsorbed into the enamel if the plaque is kept off the surface.
On the other hand, if the plaque remains on the tooth and acids continue to work on the enamel, an incipient lesion will become a cavitation, or hole through the enamel. A filling is needed to treat cavitation.
Risk factors include frequent intake of sugars/carbohydrates, carbonated drinks (acidity), lack of flossing and thorough brushing, dry mouth, due to medications that decrease saliva flow, or post radiation cancer treatment.
Prevention is simple. Brushing, especially with bristles touching the gum line, in short strokes or a circular motion removes the soft plaque. Flossing cleans between teeth, inaccessible to a toothbrush.
Using fluoride toothpaste is essential if you are prone to tooth decay, along with fluoride rinses which are over the counter, non-prescription.
In office prevention includes dental sealants to protect deep grooves in molar teeth (no drilling) and a concentrated fluoride varnish applied after cleanings.