Dental caries can also cause defects in your tooth enamel and, eventually, dentin as well as in the cementum. You may know this as ‘tooth decay’ or cavities. Unlike erosive tooth wear, defects caused by dental caries may be only very small on the enamel surface, but much larger inside the enamel, like a cave with a small entrance
The main difference between dental caries and erosive tooth wear is that erosive tooth wear affects the exposed surfaces of the teeth, gradually wearing down layers. Dental caries tends to affect areas which are not brushed/flossed and the defects can go very deep
Whereas erosive tooth wear is caused by acids and mechanical wear, dental caries is a disease caused by the interaction between sugar and some types of bacteria in your mouth
There are many types of oral bacteria, everyone has them, they are a normal part of your mouth.
Problems can occur when there is too much sugar in the mouth, some bacteria over-feed on this sugar and produce acid, leading to ‘demineralisation’ (as happens in erosion), but in this case with mineral loss starting from below the tooth surface.
Too much sugar may not just be due to eating too much but also if you don’t have enough saliva to wash it away or you don’t clean your teeth often enough.
This means that consuming sugary, acidic food or drink can contribute to both erosive tooth wear and dental caries, but they are different conditions and caries occurs in sites frequently covered by bacterial plaque (or biofilm)
Selwitz RH, Ismail AI, Pitts NB. Dental Caries. Lancet 2007;369:51–59.