What is adult tooth decay? Learn more in our patient education articles. At Elmbrook Family Dental, we know that the best patient is one who understands how to achieve and maintain optimal oral health and feel % confident in their treatment options. Tooth decay is one of the world’s more common problems with health. This is particularly common in teenagers, children as well as older adults. An insight into what causes tooth decay, adults, gum line, under crown, bacteria, food, children and treatment. What causes tooth decay in adults What causes tooth decay?