Re: Where dental deposit comes from?
The actual term is "calculus" and is common on the inside of the lower front teeth. Some people just seem to develop faster than others. The salivary glands under the tongue empty right onto the incisors and contributes to it.
Brushing better won't help with it at this point. You have to have it physically removed (instrumented) by a hygienist/dentist and then increase your brushing and flossing regimen to keep it off.