Osteoporosis is a bone disease that causes both the loss of bone and the inability to grow new bone tissue. The condition is most common in women over the age of 60, but it can strike men or women at any age. Researchers at the National Osteoporosis Foundation (NOF) estimate that approximately 54 million Americans have osteoporosis, and that number is only going up. In fact, the NOF believes that by the year 2025, osteoporosis will cause an estimated 3 million fractures a year.   Now, a study from the University at Buffalo has found that in addition to helping to increase bone density and decrease bone breakage, treating osteoporosis has another surprising benefit: preventing periodontitis. In fact, researchers found that patients undergoing estrogen therapy for osteoporosis had a 44 percent lower chance of developing periodontitis than women who did not treat their osteoporosis.