In a perfect world everyone would brush and floss twice a day. Plaque builds up over time and this sticky bacterial film can solidify and turn into calculus or tartar. This cement-like substance is removed by the hygienist at your regular cleaning visits. A six-month interval not only serves to keep your mouth healthy and clean, it allows potential problems to be found and diagnosed earlier. In some instances a six-month schedule in not enough. Based on your dental history, rate of calculus buildup, and pattern of decay a 3 or 4 month interval may be needed. Your dentist can work with you to determine what will be best for you.