I recently noticed dents on my nails.?
It depends on the type of ridges. Lengthwise ridges could be due to onychorrhexis (brittle nail syndrome) or due to age. (more details here: Jessica Lynne's answer to What do vertical lines on fingernails indicate?) Horizontal ridges can be due to a recent systemic disease that affect the nail growth (called Beaus lines), including malnutrition, heart attack, severe infections, and metabolic disturbances, including poorly controlled diabetes. If your fingernails change color or you develop horizontal nail ridges on all nails, consult your doctor. These changes could indicate an underlying health condition. Either type of ridge can be due to nail trauma (damage) including vigorous rubbing and picking at the base of the nail as a habit (called a habit tic disorder).